Comparison between a number of different power tube biasing settings on a Marshall 1987X. I'm using a TAD Bias Master to measure the tube idle current.
@@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'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
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 !!!
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!
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!
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
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
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?
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....
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.
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!
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.
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.
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%
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.
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!
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
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.
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.
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
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.
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.
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.
ive always biased my 800 & 900 heads to around 32-34ma provided they are still within plate voltage spec @60-65% the thing is valve amps need to be turned up to sound best many bedroom players bias them hot cause it makes em sound 'better' at low vol, turn those amps up and biased hot they dont sound as good (mushy / too distorted) as one biased a bit cooler when its turned up it will break up and overdrive much more nicely
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.
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!,
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.
I think all this power tube biasing stuff is B.S.!! :D Good vid Johan, the hot bias was a bit much, the 33 was good, I was surprised that although the low bias setting lacked some "oomph" and dynamics it still sounded pretty darn good.
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!
Johan can you do video on comparing the sound of a tube amplifier before its warmed up and after to show thw differences and reasons to let your amp warm up great playing man its kick ass i live the sg
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!:-))
One needs to know the voltage of the tube in order to get dissipation in watts. The higher the voltage the Lower the current.. you bias a push pull amp so the plate dissipation is around 50% to 70% at idle. This is between a cold 12.5W or a hot 17.5W for an EL34 tube with a max dissipation of 25W. So www.tedweber.com/webervst/tubes1/calcbias.htm I have an amp with a pair of EHX EL34 right now which I play on the clean channel with pedals. But something is not right. I tried so many different EQ settings but the response is not right.. I have not meddles with bias.. You have to open up the chassis,, and read plate voltage and then I read the output transformer taps ohm count and look at the voltage drop over the taps.. I remember setting the bias pot at the highest bias voltage and coldest bias and I think that even this settings was not "cold" ,, but I have to check it again..
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...
Great vid so sorry to be the pednant scientist here, but the signal source (guitar) needs to be the same for EVERY test run to ensure consistancy of approach/comparison. To make this a completely robust test, a dry guitar signal should be recorded and then used as a repeatable sound source to eliminate any variables that could be introduced during the multiple takes...
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?
No tone difference, slight diff in output. Biasing was never meant as a tone control. Plus every time your line voltage goes up or down (which most do depending on air temp and pwr grid load) your bias changes. I do mine around 55%. Gives room for voltage or swapping tubes that bias close without re-biasing. Tubes last long time!
The coolest thing this video clearly proves is that we overthink lots of things and spend way too much time tweaking and not enough time doing what we are supposed to be doing LOL you know, writing and playing music and performing. Be a musician not a tweaker. Cheers
A hotter bias does not mean a better sound, it drives just the tubes much harder. My EL34s are biased at around 25 mA and that's far enough for a Mesa Boogie (as the specs on the schematic are setted for -47 of negative grid bias voltage). I modded mine to get a separate bias for each tube with two potentiometers, that way I can get rid of hum even if the tubes are not properly matched. If you think your amp has no balls, you should rather look at the values of the Long Tail Pair resistors and coupling capacitors. There's a lot of things to do there, to get the sound you want (the Phase Inverter tube is maybe the most important one inside your amp). Setting your bias hot like crazy does not solve your problem, it will only shorten the life of the tubes and turn them into a muddy and noisy sound.
Why people mess around with bias I have no idea. In all class AB amplifiers the output devices must be biased to the point where there is no crossover distortion ... Running the output tubes at higher quiescent currents limits the output peak power, saturates the output transformer and shortens the life expectancy of the tubes .. so stick to the manufacturer's original negative bias voltage ( applied to grid 1 ) Final checking can be done by measuring the voltage across the cathode resistors ( assuming they are identical )
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
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.
Hi Johan great idea for a video! Cool! Thanks for posting :) I think to me it sounds like the higher you go the more aggressive the sound? I got into biasing when I had a Ceriatone Overdrive Special Clone (6L6's) I think were set around 35mA. Compared that to the EL34's in the 100w DSL, they run at about 90mA I think. Those things run seriously hot (set by Marshall themselves no less) I wanted my tubes to last longer and wanted mellower sound so used to run at 74, don't know if it really made much difference though! Love your work man as always!
As the doctors say in France, dites 33!thanks for another great exploration Johan, subtle differences but differences indeed! Are there different humming as well or none?
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.
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.
interesting video Johan, thanks! When you're into gear and read about it, this subject comes up regularly but I've never seen a direct comparison like this...interestingly, I preferred the cold 18ma bias - it seemed more articulate to me without really giving anything else up (may have been different in the room however), and the 33 was also good and seemed to have a slight bass bump over the other settings, or was that just my ears?
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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.
I learned about setting bias, and now I need to learn how to set the bee-ass?! The learning never ends!!!
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
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 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'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.
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!
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!
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!
Hot 4:49
Cold 5:08
MVP
Then..your amp is properly B.S'd."
Your awsome Johan. Thanks for all you do !
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'm surprised to find that I preferred the colder biases, which seemed more precise and clearer, over the hotter ones.
Beeyasss
Sheeeeeeeeit
B.S.
I preferred 33 but there was very little in it
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
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?
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....
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?
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!
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.
1 x Johan + 1x Gibson + 1 x Marshall = Always sounds GREAT! Regardless of the bias.
That 41ma will get you through about half a set before... uh oh!
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
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!
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.
Could not hear much if any difference
I really can't hear that much of a difference to be honest.
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!
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.
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.
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.
tbh: i dont hear the slightest difference ...
I would LOVE to see comments on a blind test. I would be my life that results would be all over the map.
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.
Your videos are always fascinating - philosophical, analytical, and flat-out rocking.
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
In a clean power amp situation (like a JCM800), with all distortion coming from the preamp, the difference would be a lot more noticeable!
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.
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
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 heard no difference at all in sound , I imagine there could have been a difference in feel though.
ive always biased my 800 & 900 heads to around 32-34ma provided they are still within plate voltage spec @60-65%
the thing is valve amps need to be turned up to sound best
many bedroom players bias them hot cause it makes em sound 'better' at low vol, turn those amps up and biased hot they dont sound as good (mushy / too distorted) as one biased a bit cooler when its turned up it will break up and overdrive much more nicely
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.
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!,
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 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.
I think all this power tube biasing stuff is B.S.!! :D
Good vid Johan, the hot bias was a bit much, the 33 was good, I was surprised that although the low bias setting lacked some "oomph" and dynamics it still sounded pretty darn good.
There's no difference. You'll hear a lot more difference turning one knob from 4 up to 5 so using the eq is your best friend in this scenario.
26 and 33 sounded the best to me. Awesome to hear the differences! Thanks for another great video.
Always intelligent video
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!
Johan can you do video on comparing the sound of a tube amplifier before its warmed up and after to show thw differences and reasons to let your amp warm up great playing man its kick ass i live the sg
Then why do you let amps warm up for like 15 minutes before use? Thats not fast
@@Emplexador what do you mean by oil
@@minibikegarage1577 ...trying to be funny. Again, no need to 'warm up' amp for 15min.
@@Emplexador my amp has oil capacitors
I bought a marshall afd100, the tone changes dramatically after the amp has warmed up for a good 20mins, sounds very thin if not.
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!:-))
What would be the mv equivalent? the same? I just accidentally biased my tsl60 to a total of 35mv and im worried i damaged it
One needs to know the voltage of the tube in order to get dissipation in watts. The higher the voltage the Lower the current.. you bias a push pull amp so the plate dissipation is around 50% to 70% at idle. This is between a cold 12.5W or a hot 17.5W for an EL34 tube with a max dissipation of 25W.
So www.tedweber.com/webervst/tubes1/calcbias.htm
I have an amp with a pair of EHX EL34 right now which I play on the clean channel with pedals. But something is not right. I tried so many different EQ settings but the response is not right.. I have not meddles with bias.. You have to open up the chassis,, and read plate voltage and then I read the output transformer taps ohm count and look at the voltage drop over the taps.. I remember setting the bias pot at the highest bias voltage and coldest bias and I think that even this settings was not "cold" ,, but I have to check it again..
Awesome.Johan..love the S.G sound . I thought Toni immoi was there really..was just great
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...
Great vid so sorry to be the pednant scientist here, but the signal source (guitar) needs to be the same for EVERY test run to ensure consistancy of approach/comparison.
To make this a completely robust test, a dry guitar signal should be recorded and then used as a repeatable sound source to eliminate any variables that could be introduced during the multiple takes...
🎶i got one hand in my pocket and the other one is adjusting the BEE-YAS🎶🎶
I'd be curious to hear the same test without distortion :P
JOHAN SEGEBORN, how do you bias the power tubes compression?
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?
It really seems to depend on the amp - on my JVM I tend to prefer 50+ whereas 40ish sounds best on this one.
Unless it is on the extremes it doesn't really make that much difference
except hotter will shorten tube life.
No tone difference, slight diff in output. Biasing was never meant as a tone control. Plus every time your line voltage goes up or down (which most do depending on air temp and pwr grid load) your bias changes. I do mine around 55%. Gives room for voltage or swapping tubes that bias close without re-biasing. Tubes last long time!
They sound to similar for my old ears! Lol, Thanks as always my friend :)
Or just get a Mesa Boogie, no bias adjustment. LOL! (I have both Germino and Mesa Boogie). Germino is biased between 30-32 ma at 120 vac.
Surprisingly little difference. If the tubes are mismatched is that noticeable?
The coolest thing this video clearly proves is that we overthink lots of things and spend way too much time tweaking and not enough time doing what we are supposed to be doing LOL you know, writing and playing music and performing. Be a musician not a tweaker. Cheers
A hotter bias does not mean a better sound, it drives just the tubes much harder. My EL34s are biased at around 25 mA and that's far enough for a Mesa Boogie (as the specs on the schematic are setted for -47 of negative grid bias voltage). I modded mine to get a separate bias for each tube with two potentiometers, that way I can get rid of hum even if the tubes are not properly matched. If you think your amp has no balls, you should rather look at the values of the Long Tail Pair resistors and coupling capacitors. There's a lot of things to do there, to get the sound you want (the Phase Inverter tube is maybe the most important one inside your amp). Setting your bias hot like crazy does not solve your problem, it will only shorten the life of the tubes and turn them into a muddy and noisy sound.
Johan, I'm curious... What mA did you leave your 1987 at?
Why people mess around with bias I have no idea. In all class AB amplifiers the output devices must be biased to the point where there is no crossover distortion ... Running the output tubes at higher quiescent currents limits the output peak power, saturates the output transformer and shortens the life expectancy of the tubes .. so stick to the manufacturer's original negative bias voltage ( applied to grid 1 ) Final checking can be done by measuring the voltage across the cathode resistors ( assuming they are identical )
Not really that much difference. I will definitely dial-in for longevity
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
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.
Is it my imagination that the cold biased tubes are fizzy, while the hotter settings are more round and singing?
Didn’t like the hottest or coldest bias. 33mA seems to be a sweet spot
For my taste, the hotter the better. But apparently most guys from the 60s were ala Cream were running cold bias amps. Or is it just me?
I use the amp chassis for the negative probe. which means i only need to use one hand to probe the positive bias point.
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.
Let’s face it, tubes love to be pushed. Hot bias, cranked up volume = tube heaven.
Why is there 2 bias controls in the 1987X?
So, basically, cold bias is darker sounding and hot is brighter and more clear sounding?
Hi Johan great idea for a video! Cool! Thanks for posting :) I think to me it sounds like the higher you go the more aggressive the sound? I got into
biasing when I had a Ceriatone Overdrive Special Clone (6L6's) I think were set around 35mA. Compared that to the EL34's in the 100w DSL, they
run at about 90mA I think. Those things run seriously hot (set by Marshall themselves no less) I wanted my tubes to last longer and wanted mellower sound so used to run at 74, don't know if it really made much difference though! Love your work man as always!
35MA would be my sweet spot. Not too hot or cold but just right 🙂
Ive never heard a guitar make that noise in my life at 3:39 😅 your crazy!!!
Johan you can never stop making these videos! 🔈🔉🔊🎧🎸🎤👤.....Great work.
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.
Bias is dependent on the particular amp... the same bias setting that sounds killer in one amp may sound like shit in another.
As the doctors say in France, dites 33!thanks for another great exploration Johan, subtle differences but differences indeed! Are there different humming as well or none?
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 I first herd the power tube distortion. 37 would work well at n that amp
I always bias my EL34’s a bit colder. Does sound better
clean demo of same tests? I liked the mid to hot BIAS setting(obviously, lol)
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.
interesting video Johan, thanks! When you're into gear and read about it, this subject comes up regularly but I've never seen a direct comparison like this...interestingly, I preferred the cold 18ma bias - it seemed more articulate to me without really giving anything else up (may have been different in the room however), and the 33 was also good and seemed to have a slight bass bump over the other settings, or was that just my ears?
I set my Marshall Jubilee at 35-36 ma 100 watt sounds great
What was the plate voltage of this amp?
Sure, but the hand in the pocket must be the left, so that the current can not run over the heart!