I think we went through this but I will bring it up again. If you use a Variac to lower the voltage you get that "brown sound". In America, at Niagara Falls where we built a huge electric power generating facility, sometimes because of overuse (too many people using electricity at the same time of day) they could not meet the standard power requirements of 110VAC and only sent out 90Vac. So we designed electrical appliances to function from 90Vac to 127vac. So in America if you wish you can run a guitar amplifier at 90 Vac and starve the power tubes a little and that's how you get the 'brown sound". To your readers here. The brown sound sounds very much like tube sag, if you are not familiar with these terms. In Europe you run at 220VAC and a brown out perhaps would be down around 180 VAC. I know Johan has made a video showing how this affects a MARSHALL AMPLIFIER (of course). -Peter Johan has taught more people about guitar amplifiers than perhaps anyone else-ever! What a tremendous gift to all of us Johan is.
220V? That's a bit lacklustre. 240ish volts and 50Hz is what a Marshall is supposed to run off of. "230v" kit is supposed to run anywhere in yerp, but it's variable pretty much street to street with distance from a substation. The magic recording studio in the middle of nowhere might just be doing it's magic because the supply voltage is rock bottom.
UK mains is 230V +10%/-6% so 216V-253Vac. My house is 253V all the time so I use a variac to give 230Vac when setting the bias on any UK amp. I set 1987x bias to 35mA cathode current, which is nearly 32mA plate current. Plate V=460Vdc so the EL34s are running around 15W or at 60%.
our voltage here (Boscombe,Dorset,U.K) goes right down at peak times, even as low as 190 at the weekends., I think 187 is the lowest I seen so far, been doing it for years, same in my neighbours ,
Living in the U.S.A. we were brought up hearing 220VAC as the reference AC voltage in Europe, I'm 69 and the voltage like the times have changed. So forgive my nominal usage of 220 VAC for your Europe voltage. Really, I live here in America and I only know what I was taught 45 years ago. Ha ha. But also even this year I have read many times 220VAC from a European person!
This is a very helpful video, Johan. I have kept my 1969 head as close to 30mA as possible and of course any change is much effort. I think I like the colder settings you show here. I have been working on a circuit to select bias on the fly with my beloved 1987, showing no mod at the front panel. Panel mount test probe points on the rear panel right beside a discrete 3 or 4 position switch. After hearing your presentation, I’d go with 3 settings. Thanks for this.
The beautiful thing about these NMV Marshall’s is their output sections are always balls to the wall all the time unless you’re playing clean, so the bias can be set significantly lower without much adverse affect on tone. If you tried this on a 2204, in particular at lower volume settings, the difference between hot and cold would be much more pronounced
I like the harmonic content at around 33ma, but I would also add that an overdrive pedal could approximate that for lower values. Maybe not perfectly, but the audience could not tell. Great video, as always Johan!
In person bias differences are very perceivable. Know your bias! Know what bias works with your tubes best. It's ok to mess with it until you get it right as long as your safe. It's like how changing string gauges makes you need to reintonate. If you change tubes even to the same kind but newer. I also highly recommend rebiasing every few months or at least making sure it's still where you want it as it can have a tendency to drift. Doing regular bias checks are much easier with external bias points. So it's something to consider when buying a new all tube head. For example my new DSL100HR has external bias points that you can get to by just removing the back panel of the head and it makes biasing much much safer and much much much more convenient!
@@Emplexador In my experience that is 100% true. I think a lot of people only dislike their new tube amp cause they don't know that their bias is unstable at first an needs to be set until it settles.
18ma is unexpectedly useful. Thought it would be "starved," but actually lends itself to have leaner, more agile sound. I could see 33ma as "bloated" in comparison
I thought I’d hear more difference.....but to my ears 33ma wins followed by 26ma. 18ma sounded a little lifeless like an excellent solid state amp recreating the tube amp sound.
I can agree with that. If I had to pick one, it would be 33. A pretty perfect amount of crunch for hard rock. All of the settings sounded great. Point is, there is audible difference. Those not picking up on it are not paying attention to the saturation and sustain in say 18 vs 42. Also notice when he’s up the neck playing single notes on 18, the texture and dynamics, vs 42, where they are a little less.
NOW TEST PLAYING CLEAN! HOTTER BIAS MEANS CLEARER ....VERSUS COLD, MORE FUZZIER. 41 milliamps and 18 milliamps sounded ALMOST the same to me listening on my phone's speaker playing distorted, but hotter better! THANK YOU FOR ALL YOUR VIDEO'S! LOVE THEM!
Angus tech said in an interview they bias his Super Leads as hot as he wants them to be to sound good - even though they blow tubes regularly this way… part of the magic
Thanks Johan for another informative video. I was honestly expecting to hear a much more dramatic difference between hot and cold biased, but the only major difference I heard was that hot biased went into harmonic feedback more quickly. The tone and amount of actual gain sounded pretty similar down the line. Very unexpected. Thanks again.
hardest video ever.. to my ears, higher bias tends to compress more and the mids are more present and it has an impact on the harmonics too.. awesome video!!
One hand in the pocket!!!! Great advice, and PLEASE dont attempt this if you have never worked inside the chassis... I bias all my pwn amps. On my Marshall's I tend to Bias just a bit to the hotter side, but not by much. Just a small amount past optimal. My Hiwatts and my Sound City, I Bias even slightly more hotter. Its hell on the tubes but really does warm things up and saturates a bit more. I like this on clean amps. ( Hiwatts are kinda hard to get the power section to saturation, Dave Reeves whole point of the design I think...clean headroom for miles... ) I do have a Hiwatt OL version, the only amp I bias on the colder side, but just by a small amount. I "percieve" that it sounds a bit better this way. I have always kept my Fenders at about optimal ( middle range ). My Silvertone doesnt seem to make much difference either way. I think mostly because the 1484 has such a very under-powered tranny, that it really doesnt do much to bias it hot. The 1484 is said to be 60W, but its no where near that in reality....
Very interesting. You always hear about biasing hot or cold, but it's good to have some examples. Generally confirms what I've read. I think I liked it a bit warmer at 33.
The colder settings seem to have clearer note separation and less compression. It probably would do really well with an OD in the front to bridge the gap if more dirt was needed. The hotter it was, the darker and more compressed it sounded, which isn’t bad, but I think it then gets shoved into a hole and not as versatile.
Its because of the voltage sag due to higher screen current of the output tubes. Less voltage = more drive and compression for the preamp tubes. And less high end.
It's not easy to "feel" the differences just by hearing it. You need to feel it. But Johan Segeborn, Master in TONE Sciences, always sounds massive through any piece of gear. Even with 0mA tube idle current. :P Nailed it.
Very useful info here! Great video. Would love to see more stuff like this. Please consider doing a follow-up video exclusively with clean tones on the same amp. Clean tones would reveal the differences in tone much more easily.
Johan, you can measure the plate voltage and use that to calculate the actual dissipation. These mA values dont give you much information by themselves. For example: Two marshalls can have a 50v difference between their plate voltages. So setting both amps to "34mA" wont give the same result. But setting both to 70% dissipation will make both amps biased the same.
@@migueldelatorre9475 I wouldnt recommend working on a live amp if you dont have an electronics background. There are important safety rules to follow. Those amplifiers have about 500 volts DC inside, which will kill you instantly.
@@migueldelatorre9475 500 DC volts setting on multimeter. Ground probe clipped to chassis, live probe to pin 3 using right hand. Left hand stays in your trouser pocket during measurement. This is to avoid a current path between the hands trough the heart. Obviously with shoes on and standing on non-conductive floor. (Concrete floors can conduct to ground.) You got this.
Great job! It sounded very similar and most people can differentiate between 18 & 41 mA. Now little suggestion: 1987x has cca 370V on plates (?), if so, you could go with max anode dissipation giving 67mA (25/370) and that would be HOT. Yours 41mA is only 60%
Great video Johan as always, I don't think enough people realize how much of a role bias plays in tone. If your not in control of your bias your not in control of your tone.
First of all, that amp sounds just flat out wicked at any bias. My personal favourite was 41.followed by 18 then 33 and finally in last place, 26. I liked the all out roar of the hot bias then I also liked the thickness of the and give of the 18. Kinda weird but hey, I'm a weirdo!
My tech is reckons it’s a myth that hot bias improves tone in any major way, he says it just reduces tube life. I think this proves him right, medium and hot are indistinguishable to me, and I can only hear a very slight difference with cold. Cheers
Interesting vid, as always. I prefer to listen to your demo completely and submit my comments before I listen to your comments or read the other comments so I don't start off "biased" in what I'm hearing. To me, the biasing at 33mA sounded better in every way. Lower biasing sounded anemic like the amp needed new tubes and the higher bias sounded like the tubes were microphonic.
I hear the hot bias as more open and dynamic, the cold bias as smoother and more polite, and the intermediate values as compromises between the two. I could see using either of the extremes for particular sounds, but I think on the whole I'd go for 33. I can't see the point of very cold biasing for everyday use, as you can get that compressed, muted effect in other ways. The hot bias, while exciting, is approaching the edge of unusable, and can't be doing the valves much good. I assume that's why Marshall bias their amps the way they do: the best sound consistent with decent valve life. I thought the differences were more audible on rhythm parts than single notes.
I've been telling people for years there is no advantage to biasing your amp hot. All it does is wear your tubes out faster. The video proves there is very little to no difference at all in tone. Don't watch the video, just listen to it. Bias your amp in the medium to cold/medium range, your tubes will last much longer.
Are you serious? Normally I think most of the tone voodoo crap is bullshit, but this is absolutely not that. Theres a VERY clear difference between 18 and 42. The highs are MUCH more pronounced on the "hot" setting... Are you listening on a cell phone??? That said, I think 33mA was the money spot; but youre out of your mind if you think 18 and 42 "sound the same". Just.. no
I agree with the higher bias number for Fender. When I first bought my Fender HR Deville I checked the bias settings and it showed between 48-50 so I adjusted to around 68-70 and it made a noticeable difference for the better.
@@davidcaro8217 a hotter bias works wonders for fenders I have found at least with the fender amps that I've owned through the years that they usually come slightly cold or neutral from the factory all those harmonics really shine through once biased hotter I once owned a 73 quad reverb that I had blackfaced and biased hot and the difference was night and day can't recommend it enough Cheers
i reckoned to prefer the hot bias, but 26mA seems to be the sweet spot for me. really nice comparison johan, a good reminder to always keep an open mind/ear.
Nice comparison Johan. There's a lot of debate on correct settings for even what manufacturers specify their bias to be. As you've shown, the lower the bias the less bottom end and the longer the tubes will last. The higher the bias, the more distorted it gets but you'll burn the tubes out quicker. The happy medium is in between those two. Best way I've found is get it in the ball park from the manufacturer, then play and tweak it a bit. All tubes respond a little different even between same species. BTW. You can get a setting screw driver that has a metal tip and the shaft is HV insulated plastic. Get them from most electronics stores and only cost a few bucks. A lot safer than using just an insulated screw driver even though the bias pots are on the low voltage side of the tube. There's enough HV around the rest of the board as you've said!
The age of the valves will impact on the sound and not to mention the valve brand. My experience is that newer the valves the cleaner the sound. They start to breakup more when they're old. I guess that's why the bias function is there, to try and get a sound given the age of the valves?
41 mA sounded a bit brittle to me, 18 mA a bit muddy, and I can't decide if I like 26 mA or 33 mA better, so I'd say split the difference at set it to 30 mA with those tubes. TBPH, if you gave me any of those settings in a blind test, I'd just turn the gain and eq to where it sounded right to me, anyway. I don't worry about bias, ever. I play a fixed-bias two-tube Class AB push-pull Mesa amp, and I buy matched pairs of tubes pre-tested to ensure they are within specification. Currently, I run Groove Tubes KT66HPs (#5 rating) in my Mesa F-50, and they sound amazing, to me. Most of my tubes were bought on clearance sale at GC, and so I have a stash that will probably last decades.
The difference has in the feeling I guess, the cold Bias seens alot "harder" the distortion (no more gain or less) just something "hard". I don't know how to describe it. I prefer Hot BIAS, seens alot easier to play I guess.
They all sound gorgeous!! But it’s 33 for me. Btw your English is fantastic and you know I love your accent, FYI it’s pronounced ‘Byas, ‘ love from England!,
Not so much a difference in tone but compression/bloom for me. That cold setting really limited your dynamics! Thanks for doing this, I always wanted to hear a comparison!
If you bias closer to class A the amp sounds a tad fuller and richer but with a little less crackly crunch. It's generally more pleasant sounding probably because of the lack of crossover distortion. Some power supplies in some amps sag quite a bit when you bias hot. It can reduce the headroom and of course burn up the tubes faster. With very little bias current, it sounds like it's got more headroom but it also has less "life" to it. I've played with the bias myself on lower powered (push-pull) amps I've built and this video seems to reflect my findings. There seems to be a balance somewhere in class AB where the sound is almost the same as total class A. Every amp has a sweet spot you just have to find it.
What this demonstrates, even better than the difference in bias settings, is the power and quality of a power tube distortion over a pre-amp tube distortion. Which is one of my many complaints about many modern tube amps.
Kids , don`t try this at home !!! And if you must , a pair of rubber gloves is highly recommended , - you are dealing with High Voltage Rock`n`Roll !!!
Seemed like the high bias was a bit tighter and sounded like it was easier to get feedback. I like the idea of running it cooler to be easier on the amp and tubes but.. geeeesh now ya got me thinking again :)
Hi, Johan! On my second part I think, the optimal for ME is 31. 26 its I have a lot of time, but for single coils I need some more. But 40+ is to much distorted. May be fun without middles (4-6) range is ok. Maybe will be nice to see a little description about the schema, but for my years its probably 33!:-) See you! Thank you for a video, INTERESTING video! Zigfrid
@@samfosdick9874 Hi Sam! I am OK.:-) Looking for the news. Maybe I will go to visit Detroit soon. There are some realy interesting things to do. Looks like there "rock" means AWESOME! So I was invited to play there with Jake Smith, great guitarist and nice man. If I will be "ok", in the summer I want to go there. I never was in Detroit, but I know probably, there is no danger for those visitings. Must to be interesting trip!:-))
Hi Johan! Wonderful video as always :). Some people say to bias by ear, but I'm more the engineering type, so I set it as hot as I was comfortable with and adjusted cold to see where my ears liked the bias. Turns out my ears liked my blackface bassman around 55-60% of plate dissipation. There was a sweet spot when the harshness seemed lowest. One video idea that's right up your alley might be a tone comparison between a vintage oversize Marshall 1x12 cabinet (like open back Bluesbreaker size) vs a more standard sized 1x12. I ordered a cab on ebay for an Altec 417-8h and didn't check its size first. Oops, it's a big 1x12 with the same dimensions as the Bluesbreaker.
From my experience, cold (positive) bias is darker, more damped, and quieter with higher headroom, whereas hot (negative) bias is brighter, looser, and louder with less headroom. Use cold bias if you like to push the front end with pedals and stack your gain that way. Use hot bias if you get your distortion from the amp itself and want that cranked sound at slightly lower volumes. Both too cold and too hot will shorten tube life and adversely affect tone.
Interestingly, Fender, in the EVH 5150iii 100w head schematic, recommends 20ma per tube (6L6GC) which is super cold. I've tested that and 70% plate voltage (482v), and stayed at 20. I'm assuming Eddie also liked cold biased tubes.
Difference is negligible because the preamp shapes the tone and gives a little distortion, but the bulk of the “power tube distortion” you hear in a Marshall is actually the phase inverter breaking up. Marshall plexi type design simply doesn’t have enough drive past the phase inverter to actually saturate the power tubes (running under normal conditions). This doesn’t mean that the power tubes don’t add their own tone shaping, as they do, but it’s not a big effect on things.
Bias does effect tone a lot … especially in the way notes and chords bloom as they ring and sustain. This especially becomes apparent if you look at players who have a tone all their own and do tricks like getting the thumb of their picking hand involved in their attack. Guys like EVH, Billie Joe, Angus, Billy Gibbons, Brian Setzer … me. The middle to low-hot (26-33) is where all this happens, and it's really only obvious in the tones of players with a lot of finesse in their attack. But what do I know, right-
Johan; I do biasing all the time. It’s actually pronounced By-ass. BTW, your English is incredibly good.! The amp, to my ears, sounds amazing at 26 Ma! Thanks for the comparisons!
the best way to bias is with using a signal gen and a scope, plug the amp into a load, run the amp just before clipping, if the amp is under biased you will get a kink in the wave form in the middle at cross over, that's cross over distortion adjust the bias till the wave is smooth, when you run the amp into clipping crossover distortion will be present anyway, its just getting it clean at full power before distortion
Cool video! I've wondered about this for years. FWIW it's usually pronounced 'bye ass' 'bi - ass' 'by as'. Although I'm constantly impressed by your English considering how hard I failed at learning any nordic language...
33 was the best for sound, the others I couldn't find any reason to justify them based on this recording, even in real life I think reliability is a bigger factor to consider than the minute amount of tone gain you might acquire, I went into this video hoping the hot bias would prevail to justify practices of old, but one important thing we miss as listeners is the direct human to fretboard feel.
I have JCM800 that I've built. Heyboer PT and ClassicTone OT. Long story - short: I bias for full 25W of dissipation for EL34. Under full load my HV sags to about 380V, when w/o signal it's close to 450V. So 17.5W (70%)of bias it's just a rule of thumb... By the way, first set of EL34 by EHX lasted for 8 years :) So no, my amp is not "tube-hungry"
33 ma to my ears. Did my usual thing i do when watching comparison videos. Put on my beyer dt770 and place the phone face down. What ever sound makes me turn the phone around is my favourite. This time 33 ma every time 👍🏼
Thanks! The output volume was basically the same for all settings. The hotter biases felt a lot easier to play though. They kind breathed with the playing a lot more.
Not as much difference as I had anticipated considering the broad range of ma. The higher gain tones reminded me a bit of the difference between affordable solid stat and tube amp comparison videos some people do which was interesting to me. e.g. The latest Andertons discussion video with the guy from BlackStar amps where they tried both a tube and modeling amp head towards the end.
A question, Johan. When often using a hotplate, would it be wise to bias 3-5 mA colder to keep the " living period" of the tube longer? I am especially taking about amplifiers with master volume (JCM 900 4100). I blew an output tube after some days of test of output tube distortion. The HT fuse blew also (of cause), but one of the tubes was way off. Ha' det bra, Steffen
Nice comparison. I heard something special with the 33ma setting. Did you actually physically play each test piece or did you replay each setting through a looper type pedal to remove potential variation?
I couldn't hear much difference, only at the very end of sustained notes, where there's this faint "fizz" that's more present in 33mA, 26mA and 18mA. Makes sense, as that's likely crossover distortion, which is inevitable in push-pull amps, and a hotter bias causes less of that distortion because the tubes are conducting for more of the signal.
@@rikardocarvalho I can ! Well....with non-masters volumes i can give you ballpark values ! The hotter the bias the more crunch when maxed out at 11. But also it will sound more compessed and so, less dynamic.
@@peterverberne2410 as if.... amp design, guitars, pickups, pedals, mics, recordings, etc make no difference. In a band context... will sound like a great tone... nothing else.
I preferred the hot setting, but perhaps I am biased
This is the pun police, let me see your hands!
Ba dum tssss
Lol I see what you did there
Dad, is that you? Hahaha
You win one internet. Use it wisely.
26 and 33 sounded the best to me. Awesome to hear the differences! Thanks for another great video.
Your videos are always fascinating - philosophical, analytical, and flat-out rocking.
I learned about setting bias, and now I need to learn how to set the bee-ass?! The learning never ends!!!
I think we went through this but I will bring it up again. If you use a Variac to lower the voltage you get that "brown sound".
In America, at Niagara Falls where we built a huge electric power generating facility, sometimes because of overuse (too many people using electricity at the same time of day) they could not meet the standard power requirements of 110VAC and only sent out 90Vac. So we designed electrical appliances to function from 90Vac to 127vac. So in America if you wish you can run a guitar amplifier at 90 Vac and starve the power tubes a little and that's how you get the 'brown sound". To your readers here. The brown sound sounds very much like tube sag, if you are not familiar with these terms.
In Europe you run at 220VAC and a brown out perhaps would be down around 180 VAC. I know Johan has made a video showing how this affects a MARSHALL AMPLIFIER (of course).
-Peter
Johan has taught more people about guitar amplifiers than perhaps anyone else-ever! What a tremendous gift to all of us Johan is.
220V? That's a bit lacklustre. 240ish volts and 50Hz is what a Marshall is supposed to run off of. "230v" kit is supposed to run anywhere in yerp, but it's variable pretty much street to street with distance from a substation. The magic recording studio in the middle of nowhere might just be doing it's magic because the supply voltage is rock bottom.
UK mains is 230V +10%/-6% so 216V-253Vac. My house is 253V all the time so I use a variac to give 230Vac when setting the bias on any UK amp. I set 1987x bias to 35mA cathode current, which is nearly 32mA plate current. Plate V=460Vdc so the EL34s are running around 15W or at 60%.
Brown sound is different story...even with 90V you can get hot or cold bias setting and sound...
our voltage here (Boscombe,Dorset,U.K) goes right down at peak times, even as low as 190 at the weekends., I think 187 is the lowest I seen so far, been doing it for years, same in my neighbours ,
Living in the U.S.A. we were brought up hearing 220VAC as the reference AC voltage in Europe, I'm 69 and the voltage like the times have changed. So forgive my nominal usage of 220 VAC for your Europe voltage. Really, I live here in America and I only know what I was taught 45 years ago. Ha ha. But also even this year I have read many times 220VAC from a European person!
This is a very helpful video, Johan. I have kept my 1969 head as close to 30mA as possible and of course any change is much effort. I think I like the colder settings you show here. I have been working on a circuit to select bias on the fly with my beloved 1987, showing no mod at the front panel. Panel mount test probe points on the rear panel right beside a discrete 3 or 4 position switch. After hearing your presentation, I’d go with 3 settings. Thanks for this.
Then..your amp is properly B.S'd."
Your awsome Johan. Thanks for all you do !
The beautiful thing about these NMV Marshall’s is their output sections are always balls to the wall all the time unless you’re playing clean, so the bias can be set significantly lower without much adverse affect on tone. If you tried this on a 2204, in particular at lower volume settings, the difference between hot and cold would be much more pronounced
33 was my favorite. Followed by 18, then the setting in the 20’s. The hottest bias was my least favorite.
33 was clearly the best
I like the harmonic content at around 33ma, but I would also add that an overdrive pedal could approximate that for lower values. Maybe not perfectly, but the audience could not tell. Great video, as always Johan!
In person bias differences are very perceivable. Know your bias! Know what bias works with your tubes best. It's ok to mess with it until you get it right as long as your safe. It's like how changing string gauges makes you need to reintonate. If you change tubes even to the same kind but newer. I also highly recommend rebiasing every few months or at least making sure it's still where you want it as it can have a tendency to drift. Doing regular bias checks are much easier with external bias points. So it's something to consider when buying a new all tube head. For example my new DSL100HR has external bias points that you can get to by just removing the back panel of the head and it makes biasing much much safer and much much much more convenient!
@@Emplexador In my experience that is 100% true. I think a lot of people only dislike their new tube amp cause they don't know that their bias is unstable at first an needs to be set until it settles.
18ma is unexpectedly useful. Thought it would be "starved," but actually lends itself to have leaner, more agile sound. I could see 33ma as "bloated" in comparison
I thought I’d hear more difference.....but to my ears 33ma wins followed by 26ma. 18ma sounded a little lifeless like an excellent solid state amp recreating the tube amp sound.
Thanks Dave, I expected bigger differences too
Same here, 33 sounds best, followd by 26, but 18 and 41 are both not convincing for me.
33 was the sweet spot for me too
I can agree with that. If I had to pick one, it would be 33. A pretty perfect amount of crunch for hard rock. All of the settings sounded great. Point is, there is audible difference. Those not picking up on it are not paying attention to the saturation and sustain in say 18 vs 42. Also notice when he’s up the neck playing single notes on 18, the texture and dynamics, vs 42, where they are a little less.
Great experiment, as usual! Thanks, dr Segeborn!
Couldn't hear much difference, though. I'll think I'll stick to the information in the manual.
NOW TEST PLAYING CLEAN! HOTTER BIAS MEANS CLEARER ....VERSUS COLD, MORE FUZZIER. 41 milliamps and 18 milliamps sounded ALMOST the same to me listening on my phone's speaker playing distorted, but hotter better! THANK YOU FOR ALL YOUR VIDEO'S! LOVE THEM!
26 for Malcolm, 33 for Angus. Whatever extra wear and tear you put on your tubes at 41 isn't worth it.
Not true at all for them
Angus tech said in an interview they bias his Super Leads as hot as he wants them to be to sound good - even though they blow tubes regularly this way… part of the magic
Thanks Johan for another informative video.
I was honestly expecting to hear a much more dramatic difference between hot and cold biased, but the only major difference I heard was that hot biased went into harmonic feedback more quickly. The tone and amount of actual gain sounded pretty similar down the line. Very unexpected. Thanks again.
Thanks I agree, the differences were unexpectedly small. Should probably do this for a couple of more amp models
hardest video ever.. to my ears, higher bias tends to compress more and the mids are more present and it has an impact on the harmonics too.. awesome video!!
Thanks man, glad to hear it!
On my amplifiers, I set bias 35mA ± 2mA for EL34, the hot one is more harmonious, IMHO .
Thank you Johan for a great real demonstration!
One hand in the pocket!!!! Great advice, and PLEASE dont attempt this if you have never worked inside the chassis...
I bias all my pwn amps. On my Marshall's I tend to Bias just a bit to the hotter side, but not by much. Just a small amount past optimal. My Hiwatts and my Sound City, I Bias even slightly more hotter. Its hell on the tubes but really does warm things up and saturates a bit more. I like this on clean amps. ( Hiwatts are kinda hard to get the power section to saturation, Dave Reeves whole point of the design I think...clean headroom for miles... ) I do have a Hiwatt OL version, the only amp I bias on the colder side, but just by a small amount. I "percieve" that it sounds a bit better this way. I have always kept my Fenders at about optimal ( middle range ). My Silvertone doesnt seem to make much difference either way. I think mostly because the 1484 has such a very under-powered tranny, that it really doesnt do much to bias it hot. The 1484 is said to be 60W, but its no where near that in reality....
I would LOVE to see comments on a blind test. I would be my life that results would be all over the map.
Very interesting. You always hear about biasing hot or cold, but it's good to have some examples. Generally confirms what I've read. I think I liked it a bit warmer at 33.
Johan you can never stop making these videos! 🔈🔉🔊🎧🎸🎤👤.....Great work.
1 x Johan + 1x Gibson + 1 x Marshall = Always sounds GREAT! Regardless of the bias.
26 is my fav on all apps, love your playing as always, Johan!
The colder settings seem to have clearer note separation and less compression. It probably would do really well with an OD in the front to bridge the gap if more dirt was needed. The hotter it was, the darker and more compressed it sounded, which isn’t bad, but I think it then gets shoved into a hole and not as versatile.
Its because of the voltage sag due to higher screen current of the output tubes. Less voltage = more drive and compression for the preamp tubes. And less high end.
I'm surprised to find that I preferred the colder biases, which seemed more precise and clearer, over the hotter ones.
i love amps that have bias adjustment on the outside of the amp. makes life so much easier and safer.
It's not easy to "feel" the differences just by hearing it. You need to feel it. But Johan Segeborn, Master in TONE Sciences, always sounds massive through any piece of gear. Even with 0mA tube idle current. :P
Nailed it.
Thanks my friend, the different biases did indeed much more different than they sounded. Hotter biases were easier to play
@@JohanSegeborn How about the longevity of tubes?
Couldn't tell much if any difference with my eyes closed. I love how you pronounce "Bias"! Have a great day bro and Rock on!!
Thanks Brother, yeah even though they sounded very similar the higher biases was a lot easier to play
Very useful info here! Great video. Would love to see more stuff like this. Please consider doing a follow-up video exclusively with clean tones on the same amp. Clean tones would reveal the differences in tone much more easily.
33 sounds the best... this is a great video explaining the difference in bias settings. Thanks so much
Johan, you can measure the plate voltage and use that to calculate the actual dissipation. These mA values dont give you much information by themselves. For example: Two marshalls can have a 50v difference between their plate voltages. So setting both amps to "34mA" wont give the same result. But setting both to 70% dissipation will make both amps biased the same.
That is very interesting and makes sense. How do you measure the plate voltage? Thanks man!
@@migueldelatorre9475 I wouldnt recommend working on a live amp if you dont have an electronics background. There are important safety rules to follow. Those amplifiers have about 500 volts DC inside, which will kill you instantly.
@@infectionsman thanks for the warning man!! Pin 3.
@@infectionsman thanks for the warning man, appreciate. Pin 3 and ground
@@migueldelatorre9475 500 DC volts setting on multimeter. Ground probe clipped to chassis, live probe to pin 3 using right hand. Left hand stays in your trouser pocket during measurement. This is to avoid a current path between the hands trough the heart. Obviously with shoes on and standing on non-conductive floor. (Concrete floors can conduct to ground.) You got this.
Great job! It sounded very similar and most people can differentiate between 18 & 41 mA.
Now little suggestion: 1987x has cca 370V on plates (?), if so, you could go with max anode dissipation giving 67mA (25/370) and that would be HOT. Yours 41mA is only 60%
Very relevant!
Great video Johan as always, I don't think enough people realize how much of a role bias plays in tone. If your not in control of your bias your not in control of your tone.
First of all, that amp sounds just flat out wicked at any bias. My personal favourite was 41.followed by 18 then 33 and finally in last place, 26. I liked the all out roar of the hot bias then I also liked the thickness of the and give of the 18. Kinda weird but hey, I'm a weirdo!
My tech is reckons it’s a myth that hot bias improves tone in any major way, he says it just reduces tube life. I think this proves him right, medium and hot are indistinguishable to me, and I can only hear a very slight difference with cold. Cheers
Awesome.Johan..love the S.G sound . I thought Toni immoi was there really..was just great
As always - very objective - thank you. Swedish accent - bias - simply perfect!
Interesting vid, as always. I prefer to listen to your demo completely and submit my comments before I listen to your comments or read the other comments so I don't start off "biased" in what I'm hearing. To me, the biasing at 33mA sounded better in every way. Lower biasing sounded anemic like the amp needed new tubes and the higher bias sounded like the tubes were microphonic.
I preferred the 33mA then 26mA 18mA too cold, 41mA too hot. Another great video Johan !!
I hear the hot bias as more open and dynamic, the cold bias as smoother and more polite, and the intermediate values as compromises between the two. I could see using either of the extremes for particular sounds, but I think on the whole I'd go for 33. I can't see the point of very cold biasing for everyday use, as you can get that compressed, muted effect in other ways. The hot bias, while exciting, is approaching the edge of unusable, and can't be doing the valves much good. I assume that's why Marshall bias their amps the way they do: the best sound consistent with decent valve life.
I thought the differences were more audible on rhythm parts than single notes.
I've been telling people for years there is no advantage to biasing your amp hot. All it does is wear your tubes out faster. The video proves there is very little to no difference at all in tone. Don't watch the video, just listen to it. Bias your amp in the medium to cold/medium range, your tubes will last much longer.
Also sounds tighter in the low end
@@LukeCannotSkate Right on.
Are you serious? Normally I think most of the tone voodoo crap is bullshit, but this is absolutely not that. Theres a VERY clear difference between 18 and 42. The highs are MUCH more pronounced on the "hot" setting... Are you listening on a cell phone??? That said, I think 33mA was the money spot; but youre out of your mind if you think 18 and 42 "sound the same". Just.. no
@@JgHaverty Well I guess your ears are superior. I never said to bias at the extreme cold end. Re-read
@@pppaulie73 no, you said theres no difference. There is VERY CLEARLY a difference. Learn to... read your own stuff? Lol.
I actually like the cold bias on that Marshall weird considering on my fender amps I prefer a hot bias
Thanks Greg
I agree with the higher bias number for Fender. When I first bought my Fender HR Deville I checked the bias settings and it showed between 48-50 so I adjusted to around 68-70 and it made a noticeable difference for the better.
@@davidcaro8217 a hotter bias works wonders for fenders I have found at least with the fender amps that I've owned through the years that they usually come slightly cold or neutral from the factory all those harmonics really shine through once biased hotter I once owned a 73 quad reverb that I had blackfaced and biased hot and the difference was night and day can't recommend it enough
Cheers
@@TheGman858 carvin too. Almost twice what carvin recommends and the tubes still last forever.
They sound to similar for my old ears! Lol, Thanks as always my friend :)
Great video. George Lynch said that he used to bias his amps while he played through them and got electrocuted pretty badly a couple times.
In a clean power amp situation (like a JCM800), with all distortion coming from the preamp, the difference would be a lot more noticeable!
i reckoned to prefer the hot bias, but 26mA seems to be the sweet spot for me. really nice comparison johan, a good reminder to always keep an open mind/ear.
Nice comparison Johan. There's a lot of debate on correct settings for even what manufacturers specify their bias to be. As you've shown, the lower the bias the less bottom end and the longer the tubes will last. The higher the bias, the more distorted it gets but you'll burn the tubes out quicker. The happy medium is in between those two. Best way I've found is get it in the ball park from the manufacturer, then play and tweak it a bit. All tubes respond a little different even between same species.
BTW. You can get a setting screw driver that has a metal tip and the shaft is HV insulated plastic. Get them from most electronics stores and only cost a few bucks. A lot safer than using just an insulated screw driver even though the bias pots are on the low voltage side of the tube. There's enough HV around the rest of the board as you've said!
very good video. gives a really clear comparison. I like it around the 35 mark. she sings but doesn't scream!
Great demonstration Johan !
The age of the valves will impact on the sound and not to mention the valve brand. My experience is that newer the valves the cleaner the sound. They start to breakup more when they're old. I guess that's why the bias function is there, to try and get a sound given the age of the valves?
I preferred 33 but there was very little in it
Very good video ! Thx !
I sometimes even preferd the 18mv :D other times I could not even hear the diffrence,
I was very suprised !
41 mA sounded a bit brittle to me, 18 mA a bit muddy, and I can't decide if I like 26 mA or 33 mA better, so I'd say split the difference at set it to 30 mA with those tubes.
TBPH, if you gave me any of those settings in a blind test, I'd just turn the gain and eq to where it sounded right to me, anyway.
I don't worry about bias, ever. I play a fixed-bias two-tube Class AB push-pull Mesa amp, and I buy matched pairs of tubes pre-tested to ensure they are within specification. Currently, I run Groove Tubes KT66HPs (#5 rating) in my Mesa F-50, and they sound amazing, to me.
Most of my tubes were bought on clearance sale at GC, and so I have a stash that will probably last decades.
The difference has in the feeling I guess, the cold Bias seens alot "harder" the distortion (no more gain or less) just something "hard". I don't know how to describe it. I prefer Hot BIAS, seens alot easier to play I guess.
Presence
They all sound gorgeous!! But it’s 33 for me. Btw your English is fantastic and you know I love your accent, FYI it’s pronounced ‘Byas, ‘ love from England!,
Not so much a difference in tone but compression/bloom for me. That cold setting really limited your dynamics! Thanks for doing this, I always wanted to hear a comparison!
Great idea for a video, well done, again Dr. Segeborn!
If you bias closer to class A the amp sounds a tad fuller and richer but with a little less crackly crunch. It's generally more pleasant sounding probably because of the lack of crossover distortion. Some power supplies in some amps sag quite a bit when you bias hot. It can reduce the headroom and of course burn up the tubes faster. With very little bias current, it sounds like it's got more headroom but it also has less "life" to it. I've played with the bias myself on lower powered (push-pull) amps I've built and this video seems to reflect my findings. There seems to be a balance somewhere in class AB where the sound is almost the same as total class A. Every amp has a sweet spot you just have to find it.
What this demonstrates, even better than the difference in bias settings, is the power and quality of a power tube distortion over a pre-amp tube distortion. Which is one of my many complaints about many modern tube amps.
Kids , don`t try this at home !!! And if you must , a pair of rubber gloves is highly recommended ,
- you are dealing with High Voltage Rock`n`Roll !!!
Cheers Gary! :-)
Always keep one hand in your pocket!
What Sam said and additionally, rubber gloves will not save you
Of course all this not when you play the guitar!
That goes for MOST guitarists. They have NO clue as to how their guitars or amps work anyway!
Seemed like the high bias was a bit tighter and sounded like it was easier to get feedback. I like the idea of running it cooler to be easier on the amp and tubes but.. geeeesh now ya got me thinking again :)
Hi, Johan!
On my second part I think, the optimal for ME is 31. 26 its I have a lot of time, but for single coils I need some more. But 40+ is to much distorted. May be fun without middles (4-6) range is ok. Maybe will be nice to see a little description about the schema, but for my years its probably 33!:-) See you!
Thank you for a video, INTERESTING video!
Zigfrid
Thanks Zigfrid! See you my friend!
I'll jump right in and say BURN THOSE FREAKING TUBES! how's it going Zigmaster?
@@samfosdick9874 Hi Sam! I am OK.:-) Looking for the news. Maybe I will go to visit Detroit soon. There are some realy interesting things to do. Looks like there "rock" means AWESOME! So I was invited to play there with Jake Smith, great guitarist and nice man. If I will be "ok", in the summer I want to go there. I never was in Detroit, but I know probably, there is no danger for those visitings. Must to be interesting trip!:-))
33 sounded great. Lot of harmonic content. I vote warm.
My favorite too
I'd be curious to hear the same test without distortion :P
Hi Johan! Wonderful video as always :). Some people say to bias by ear, but I'm more the engineering type, so I set it as hot as I was comfortable with and adjusted cold to see where my ears liked the bias. Turns out my ears liked my blackface bassman around 55-60% of plate dissipation. There was a sweet spot when the harshness seemed lowest. One video idea that's right up your alley might be a tone comparison between a vintage oversize Marshall 1x12 cabinet (like open back Bluesbreaker size) vs a more standard sized 1x12. I ordered a cab on ebay for an Altec 417-8h and didn't check its size first. Oops, it's a big 1x12 with the same dimensions as the Bluesbreaker.
From my experience, cold (positive) bias is darker, more damped, and quieter with higher headroom, whereas hot (negative) bias is brighter, looser, and louder with less headroom. Use cold bias if you like to push the front end with pedals and stack your gain that way. Use hot bias if you get your distortion from the amp itself and want that cranked sound at slightly lower volumes. Both too cold and too hot will shorten tube life and adversely affect tone.
I think 33 sounded the best, but to me the differences were subtle. However, that really is a great sounding Marshall. Great match for that SG
Interestingly, Fender, in the EVH 5150iii 100w head schematic, recommends 20ma per tube (6L6GC) which is super cold. I've tested that and 70% plate voltage (482v), and stayed at 20. I'm assuming Eddie also liked cold biased tubes.
Difference is negligible because the preamp shapes the tone and gives a little distortion, but the bulk of the “power tube distortion” you hear in a Marshall is actually the phase inverter breaking up. Marshall plexi type design simply doesn’t have enough drive past the phase inverter to actually saturate the power tubes (running under normal conditions). This doesn’t mean that the power tubes don’t add their own tone shaping, as they do, but it’s not a big effect on things.
clean demo of same tests? I liked the mid to hot BIAS setting(obviously, lol)
Bias does effect tone a lot … especially in the way notes and chords bloom as they ring and sustain. This especially becomes apparent if you look at players who have a tone all their own and do tricks like getting the thumb of their picking hand involved in their attack. Guys like EVH, Billie Joe, Angus, Billy Gibbons, Brian Setzer … me. The middle to low-hot (26-33) is where all this happens, and it's really only obvious in the tones of players with a lot of finesse in their attack. But what do I know, right-
Johan; I do biasing all the time. It’s actually pronounced By-ass. BTW, your English is incredibly good.! The amp, to my ears, sounds amazing at 26 Ma! Thanks for the comparisons!
the best way to bias is with using a signal gen and a scope, plug the amp into a load, run the amp just before clipping, if the amp is under biased you will get a kink in the wave form in the middle at cross over, that's cross over distortion adjust the bias till the wave is smooth, when you run the amp into clipping crossover distortion will be present anyway, its just getting it clean at full power before distortion
the cold bias at 18mA sounded best to my ears, but surely, this can vary as the feel has a role when you play the guitar
This is a really cool video Joahn!
They all sounded the same to me, the differences I listen are differences in the playing itself/the performance and not the sound of the amp.
Cool video! I've wondered about this for years.
FWIW it's usually pronounced 'bye ass' 'bi - ass' 'by as'. Although I'm constantly impressed by your English considering how hard I failed at learning any nordic language...
I think 26 was best. Not too cold but not too hot eather. Tone was more clear with little drive. Have to test 26-28 with my amp. Thanks, Johan!
33 was the best for sound, the others I couldn't find any reason to justify them based on this recording, even in real life I think reliability is a bigger factor to consider than the minute amount of tone gain you might acquire, I went into this video hoping the hot bias would prevail to justify practices of old, but one important thing we miss as listeners is the direct human to fretboard feel.
I agree 33 sounded best
I have JCM800 that I've built. Heyboer PT and ClassicTone OT. Long story - short: I bias for full 25W of dissipation for EL34. Under full load my HV sags to about 380V, when w/o signal it's close to 450V.
So 17.5W (70%)of bias it's just a rule of thumb...
By the way, first set of EL34 by EHX lasted for 8 years :) So no, my amp is not "tube-hungry"
33 ma to my ears.
Did my usual thing i do when watching comparison videos.
Put on my beyer dt770 and place the phone face down.
What ever sound makes me turn the phone around is my favourite. This time 33 ma every time 👍🏼
Always intelligent video
its really hard to tell any difference from the tones. was the volume any different? the feel? love your videos
Thanks! The output volume was basically the same for all settings. The hotter biases felt a lot easier to play though. They kind breathed with the playing a lot more.
@@JohanSegeborn yes it sounded like you were feeling it more when the bias was hotter. have a great week man, cheers
Liking 41mA but then again, 31 mA sounds killer too!
Perfect stuff. Thanks for sharing.
I liked the sound of the colder biases. Maybe it’s awkward feeling under the fingertips? If it still feels right dynamically I would run it cold lol
Not as much difference as I had anticipated considering the broad range of ma. The higher gain tones reminded me a bit of the difference between affordable solid stat and tube amp comparison videos some people do which was interesting to me. e.g. The latest Andertons discussion video with the guy from BlackStar amps where they tried both a tube and modeling amp head towards the end.
33mA sounded best. Can't quite put my finger on it, but something about the harmonics sounds amazing and the full tone is all there.
That 41ma will get you through about half a set before... uh oh!
A question, Johan. When often using a hotplate, would it be wise to bias 3-5 mA colder to keep the " living period" of the tube longer? I am especially taking about amplifiers with master volume (JCM 900 4100). I blew an output tube after some days of test of output tube distortion. The HT fuse blew also (of cause), but one of the tubes was way off. Ha' det bra, Steffen
One thing I'm gonna change now for sure is the way I pronounce bias.
Nice comparison. I heard something special with the 33ma setting. Did you actually physically play each test piece or did you replay each setting through a looper type pedal to remove potential variation?
I couldn't hear much difference, only at the very end of sustained notes, where there's this faint "fizz" that's more present in 33mA, 26mA and 18mA. Makes sense, as that's likely crossover distortion, which is inevitable in push-pull amps, and a hotter bias causes less of that distortion because the tubes are conducting for more of the signal.
Yep, the lower was more distinct. The hotter was more saturated, I I liked the colder settings
I'm all for Hot! 🔥
So useful. Thanks a lot Johan! 👍
I couldn’t hear any meaningful difference.
Check the ears! ;-)
@@deHelli The truly important thing is..... check any classic rock song... and then tell us how much current their amps had
@@rikardocarvalho I can ! Well....with non-masters volumes i can give you ballpark values ! The hotter the bias the more crunch when maxed out at 11. But also it will sound more compessed and so, less dynamic.
@@peterverberne2410 as if.... amp design, guitars, pickups, pedals, mics, recordings, etc make no difference. In a band context... will sound like a great tone... nothing else.
@@rikardocarvalho Yes...sure they do influence/matter. Some factor in more than others. But still......
I like the snarl of my 1959 SLP at 35 mA 🙌