Dear Stephe, you're the best! Some of the Chinese producers make good tube amplifiers, but if they had a designer like you probably they could become very competitive
Stephe, million thank for this latest vid. You do an amazing work and you helps us to understand how this stuff works and you help all the R300 owners! Absolutely highly appreciate that🙏🏻👏🏻
Thanks for posting a video on this modification. One day this shop will revisit some audio amps " too many vintage tv's in the repair line". Keep up the good work!!!
Thanks, Stephe. Fantastic work as usual. I’ve been working on tube amps and occasionally SS amps for decades, which has even become my profession at this point, but I always learn stuff from you. People need to open up their minds to never stop learning, and stop pretending they’re “experts” cuz they did a sim or whatever. That’s for the ignorant. Thanks again…🔊😊🎶
A video that offers clear, simple advice and modifications that even I can understand. Waouuuhh ! Thanks a lot Stephe :) You help a lot of people like me.
Nice mod Stephe! 👌Since the delay board is ditched and some space is created for a second choke, are you considering to update the power supply to dual rail? That might be a cool upgrade 🙂🤞
@@SkunkieDesignsElectronics It makes sense since there are two 5AR4's and it will minimise cross talk between the two 300B's. So please give it a shot 🤩
Hi Stephe! Great video. Thank you for digging into this amp. The qualitative reviews seem great but the quantitative tells a different story. On the verge of pulling the trigger on getting one. Does anyone know if Willsenton is still putting the delay boards in them?
We appreciate your videos. I help Young people that are going to school. And I think it would be a blessing if people making videos would please stop saying B+. It just confuses the heck out of new people trying to learn.
Or how about they learn what the term we all use means? Saying "B+" is so much easier than saying "The filtered high voltage DC on the output of the power supply"...
Good precaution on the lesser 300B's. 100 ohms would provide enough voltage drop for JJ's. In that case I would add the 3 H Hammond choke and 50 ohms instead.
Stephe, Wouldn't you need to solder 1- Vishay wire wound 50 ohm 5W, for the left and right rectifier tube sockets? On your video above, I noticed you only added your spare resistors to one rectifier tube socket. I'm about to order them from mouser. I'm ready to place a order for both my Willsenton R300 amps. I was going to order 4 of them. Although I may hold off until, I see more on your modification series, and save on shipping cost. In the event I need to order more parts, for other area's you notice part changes-reconfiguring. It would be nice, if you could also mention in your series, performance mod's, beyound the basics of reliability issues your correcting as well. Since Willsenton hasn't did a good job on these particular reliability issues. I personally would like to take the amp, to a higher performance level within reason, based on your suggestions, that wouldn't be overkill. For example Mundorf caps, Hammond chokes, as well as any other suggestions you may find beneficial. I know new iron would definately help, but at what expense does one have to say their is a resonable stopping point. Your suggestions are certainly welcomed. I followed your guidelines, removing my delay board and performed all your reconfiguration suggestions on rewiring. Very easy to do by the way, FYI R300 owners. I reattached new zip ties to the original lay out. After i finish one of them correcting all the issues, one will be for sale. Thank you for helping R300 community Stephe
You only need this resistor on the one side, it's attached on one side where the two rectifier tubes are connected together after the diodes, and the other side to the wire going to the choke. Look at the schematic. If you are worried about the $7 of parts shipping costs, wait till I am finished.
Thanks for the advice Stephe. I have an older model without the delay board. When you say bias 1 click to the left, is it the small hashes or the large hash?
Did you measure the total resistance of the HV secondary? Is it a 350-0-350 secondary? I’m guessing the 2 10R + 50R are enough limiting resistance for the 5AR4s granted each of them has their plates tied together. Now the question is: Would it survive a turn-on a few seconds after a turn-off, i.e. a hot start. Also, remember to check if that fixed the huge frequency hole around 11kH.
These mods would allow a single (NOS quality) 5AR4 to survive. A pair will be coasting. Given we needed to bleed off some HV, adding the 50R serves both purposes and I doubt this fixes the other issues I found. more to come.
Steph, great work. I have an early version with the 220uf cap and only one 10 ohm resister. China HiFi sent me a delay board which was installed but of course it didn’t prevent the 274B’s from arcing. I intend on replicating your mods by first eliminating the delay board, adding a 5watt 50 ohm resister, adding the new choke and then adding the ‘missing’ diode. Can you provide the correct spec for the diode?
Do you think keeping the 5U4GB EH (I already received from the producer) plus adding an inrush current limiter like CL-60 in the primaries of traffo and adjusting the 50 Ohm resistor to reach the correct plate voltage could be a solutions as well? Thanks
@@SkunkieDesignsElectronics This amp PSU is a nightmare. I disassembled it and the first Cap is 330uF then choke and last is 220uF (opposite order to yours). In my amp there is zero resistors in the PSU... Just one extra diode before 330uF cap. The latest tubes I received from China Audio (5U4GBEH) are rated max 40uF. My amp was sent without the delay board - it was delivered few weeks later to solve all the issues...
You can, it's MUCH more likely to survive than a 274b tube is, but this amp design still FAR exceeds the max capacitance specification for any rectifier tube ever made.
Hi Stephe, I changed the 5U4G, and I fell a bit different with willsenton 274b tube. Now, another question is could I use 5AR4 into same amp? Again, thanks another for your help.
@@SkunkieDesignsElectronics Hi Stephe, I changed the 5U4G, and I fell a bit different with willsenton 274b tube. Now, another question is could I use 5AR4 into same amp? Again, thanks another for your help
Yes, but would require more wiring changes for that to work and starts to push that 100uf first caps being OK. Then you would need a better quality choke to keep the AC ripple at the same level.
Hi Steph. Genuinely before you said it i was thinking it looks nicer with the 5ar4's, the 300's stand out more now. A few questions though, if you can possibly find the time it would be appreciated. Why keep the diodes in the B+ psu circuit? Sorry I don't understand the purpose of this, and also what is the purpose of the 10r resistor before the rectifier on the AC, is this just a dropping resistor, also the purpose of keeping the 50r after the diodes in your design. Is this just to add extra filtering.
The diodes protect the rectifier tube in case of a hat restart and I've read can also help suppress a flash over. Mainly leaving the 10R in because they are already there + adds a bit of voltage drop resistance without generating a lot of localized heat. The 50R after the diodes is the main thing protecting the cap on start up as those really big caps fill up. The amp needs the voltage drop from going to a more efficient rectifier anyway so is a win/win.
@@SkunkieDesignsElectronics so one of my amps was built into a small box that my father gave me (sentimental). I have 47uf 1st cap, 200uf film cap (2nd cap), but only one 10H choke in psu, is there an easy way to get any more filtering with resistors rather than adding a second choke that would reduce B+ and I don't have space for in the box. B+ is approx 310v and rectifier is 5r4gy running 2 x el84's. The film caps are huge and were expensive to buy but i thought probably worth the investment.
If the TL iron is good, and the package price is good I may well be building these SE monos, be great if they could run EL34 too, could this be acheived through w switchable cathode resistors rather than a rectifier change.
No, these amps have a lot of issues. I haven't seen the latest "black" version but unless they redesigned the whole driver stage, these still have performance problems.
The problem with using this price as a goal post for a 300B amp is this "list price" isn't realistic. We see the same thing with the Reisong A50. First you have to toss all the tubes, which adds easily $500 to the price. Then in both cases, they require internal modifications and in some cases major parts replaced to perform to the level a 300B amp should be at. Sadly these poorly designed amps have set consumer expectations on what a quality amp should cost so low, it's driven everyone out of the market.
@@SkunkieDesignsElectronics Thank you for your answer! I thought about building your budget 300B design, but I'm a little scared to mess up, if I have to build from scratch. The modifications you did with your videos seems very possible for me. It dont have to be an 300B amp, if I can get a better sounding tube amp for the money. Fokus is on Midrange and highs, bassdriver will driven by Accuphse E303-X which should work good with tube amps. Just saw your Video about R8 MKII, maybe this is an option or maybe even a Musical Paradise MP301 MK3 for the start? (To much videos, forums... not enough time) Im just 30 years old and want to start with tube amps and I like the idea, that they can grow with me. Swap for better tubes, do some modifications or when money is better, buy a better amp.
And people have to stop listening to these influencers talking about "chocolaty midrange and so much air, it floats to the ceiling" nonsense.. From my experience, most of these designed and made in China amps are junk.
I really don't understand the desire for tube rectification. I can understand the logic behind using a tube in the audio path, because I do it myself to get a little tubey harmonics, but designing an amplifier in 2023 with a tube rectifier when it could be done so much more cleanly and efficiently just seems strange and counter productive to me. I mean, if they're going to design an amp with a tube rectifier, at least make it a cool one like a mercury arc or something. Also, the irony of using diodes across a tube diode.
The diodes aren't across the tube rectifier, they are in series. They only function in the case of a tube failure. The advantage of using an indirectly heated rectifier tube like a 5AR4 is the slow voltage ramp up.
Why do they even bother using a tube rectifier for the power supply? A solid state power supply is not going to take away from the "tube sound" of a 300B power amp.
They had problems with the rectifier tubes !!!......hmmm.......Any blind technician from the tube era looking at the circuit could predict that !!! And the way they designed the HV delay with direct heated rectifiers is a BIG mistake... They have no clue about tube technology but are selling and building tube amplifiers . Good to see that some people today like you are there to correct those thosze errors and solve the problems ... Customers still think that those chinese BS is designed by skilled and experienced technicians .
Agree, shocking to see how Willsenton „designs“ their amps. Absolutely BS. How is it possible to sell this BS and get so many positive „reviews“ from all the youtuber „experts“.
Exactly, Frank! I’m younger and not necessarily from the “tube era”, except for the fact that I’d never not use a tube amp for my guitar amps. But….I work on guitars and tube amps almost everyday, mostly replacing bad parts, retubing, and biasing tried and true designs, and even I can see that the HV design with a delay before a direct heated rectifier is just a bad idea. I don’t know who’s designing these Chinese made tube amps, but you shouldn’t have to immediately repair a design on a brand new amp! Mods and upgrades after listening to and living with it for a bit, and seeing where they’re necessary and will help the amps performance is a different thing, but having to fix the basic design is just wrong. Stephe is such a skilled and knowledgeable person when it comes to trouble shooting these designs.
These companies need to employ your services, if I was building tube amps commercially, couldn't think of anyone better.🙂
Commercial means are their first consideration, and consumers may find it worthwhile to use two 274.
Dear Stephe, you're the best!
Some of the Chinese producers make good tube amplifiers, but if they had a designer like you probably they could become very competitive
Stephe, million thank for this latest vid. You do an amazing work and you helps us to understand how this stuff works and you help all the R300 owners! Absolutely highly appreciate that🙏🏻👏🏻
Thanks for posting a video on this modification. One day this shop will revisit some audio amps " too many vintage tv's in the repair line". Keep up the good work!!!
Congratulations! This has turned out very well and you have no doubt helped a lot of people
Thanks, Stephe. Fantastic work as usual. I’ve been working on tube amps and occasionally SS amps for decades, which has even become my profession at this point, but I always learn stuff from you. People need to open up their minds to never stop learning, and stop pretending they’re “experts” cuz they did a sim or whatever. That’s for the ignorant.
Thanks again…🔊😊🎶
Thanks for digging into this amp even though at first you didn’t want to.
Good video Stephe. Best part at the end. The amp will run cooler and everything will be happier! Wilsenton needs to listen to you.
They are :)
A video that offers clear, simple advice and modifications that even I can understand. Waouuuhh ! Thanks a lot Stephe :) You help a lot of people like me.
Nice mod. 5AR4s are great tubes. I have two Dynaco ST-70s that have their original Mullard 5AR4s.
Yes they are!
Thanks Stephe, you do a great job. Appreciate your efforts to educate us.
Glad it was helpful!
Well that was satisfying to watch! Congratulations on your engineering success.
Thank you very much!
Nice mod Stephe! 👌Since the delay board is ditched and some space is created for a second choke, are you considering to update the power supply to dual rail? That might be a cool upgrade 🙂🤞
That is absolutely a possibility, especially using 5AR4 tubes!
@@SkunkieDesignsElectronics It makes sense since there are two 5AR4's and it will minimise cross talk between the two 300B's. So please give it a shot 🤩
Hi Stephe! Great video. Thank you for digging into this amp. The qualitative reviews seem great but the quantitative tells a different story. On the verge of pulling the trigger on getting one. Does anyone know if Willsenton is still putting the delay boards in them?
The newest one I saw, the "plus" version does not. They now have a smaller first cap and use the 5AR4 tubes I recommended.
Thank you for todays teaching lesson👋
Outstanding!!
Excellent excellent work.
Thank you so much 😀
Great work Stephe!
Great video
oh good, hopefully it's not a complete pewp show 😅 great video! 🙏🏻
We appreciate your videos. I help Young people that are going to school. And I think it would be a blessing if people making videos would please stop saying B+. It just confuses the heck out of new people trying to learn.
Or how about they learn what the term we all use means? Saying "B+" is so much easier than saying "The filtered high voltage DC on the output of the power supply"...
Stephe, What Manufacturer 5AR4 Rectifier tubes do you recommed, for the Willsenton R300?
TAD, Sovtek or Gold Lion for new production.
Good precaution on the lesser 300B's. 100 ohms would provide enough voltage drop for JJ's. In that case I would add the 3 H Hammond choke and 50 ohms instead.
Just be aware raising the resistance also increases the wattage across the resistor.
@@SkunkieDesignsElectronics Ohm's Law, of course. You'd need 10 W capacity for 100 ohms.
Yep. I would just avoid those JJ 5AR4 tubes.
Stephe,
Wouldn't you need to solder 1- Vishay wire wound 50 ohm 5W, for the left and right rectifier tube sockets? On your video above, I noticed you only added your spare resistors to one rectifier tube socket. I'm about to order them from mouser. I'm ready to place a order for both my Willsenton R300 amps. I was going to order 4 of them. Although I may hold off until, I see more on your modification series, and save on shipping cost. In the event I need to order more parts, for other area's you notice part changes-reconfiguring. It would be nice, if you could also mention in your series, performance mod's, beyound the basics of reliability issues your correcting as well. Since Willsenton hasn't did a good job on these particular reliability issues.
I personally would like to take the amp, to a higher performance level within reason, based on your suggestions, that wouldn't be overkill. For example Mundorf caps, Hammond chokes, as well as any other suggestions you may find beneficial. I know new iron would definately help, but at what expense does one have to say their is a resonable stopping point. Your suggestions are certainly welcomed.
I followed your guidelines, removing my delay board and performed all your reconfiguration suggestions on rewiring. Very easy to do by the way, FYI R300 owners. I reattached new zip ties to the original lay out. After i finish one of them correcting all the issues, one will be for sale.
Thank you for helping R300 community Stephe
You only need this resistor on the one side, it's attached on one side where the two rectifier tubes are connected together after the diodes, and the other side to the wire going to the choke. Look at the schematic.
If you are worried about the $7 of parts shipping costs, wait till I am finished.
Thanks for the advice Stephe. I have an older model without the delay board. When you say bias 1 click to the left, is it the small hashes or the large hash?
small hash.
Did you measure the total resistance of the HV secondary? Is it a 350-0-350 secondary?
I’m guessing the 2 10R + 50R are enough limiting resistance for the 5AR4s granted each of them has their plates tied together.
Now the question is: Would it survive a turn-on a few seconds after a turn-off, i.e. a hot start.
Also, remember to check if that fixed the huge frequency hole around 11kH.
These mods would allow a single (NOS quality) 5AR4 to survive. A pair will be coasting. Given we needed to bleed off some HV, adding the 50R serves both purposes and I doubt this fixes the other issues I found. more to come.
Steph, great work. I have an early version with the 220uf cap and only one 10 ohm resister. China HiFi sent me a delay board which was installed but of course it didn’t prevent the 274B’s from arcing. I intend on replicating your mods by first eliminating the delay board, adding a 5watt 50 ohm resister, adding the new choke and then adding the ‘missing’ diode. Can you provide the correct spec for the diode?
1N4007 should work.
cheers
I gotta be a sicko. I luv to watch you do those mods. lol
Do you think keeping the 5U4GB EH (I already received from the producer) plus adding an inrush current limiter like CL-60 in the primaries of traffo and adjusting the 50 Ohm resistor to reach the correct plate voltage could be a solutions as well? Thanks
I'm sure there are multiple solutions! There always are. I know sizing the CL-xxxx devices is key so read up on that and that should work.
@@SkunkieDesignsElectronics This amp PSU is a nightmare. I disassembled it and the first Cap is 330uF then choke and last is 220uF (opposite order to yours). In my amp there is zero resistors in the PSU... Just one extra diode before 330uF cap. The latest tubes I received from China Audio (5U4GBEH) are rated max 40uF. My amp was sent without the delay board - it was delivered few weeks later to solve all the issues...
Hi there, I have questions about the 274b rectifier tube: can I change that tube with 5U4G tube without any modification on 300r amp? Thanks
You can, it's MUCH more likely to survive than a 274b tube is, but this amp design still FAR exceeds the max capacitance specification for any rectifier tube ever made.
@@SkunkieDesignsElectronics
Thanks for your help 👍 🙂 🙏
Hi Stephe,
I changed the 5U4G, and I fell a bit different with willsenton 274b tube. Now, another question is could I use 5AR4 into same amp?
Again, thanks another for your help.
@@SkunkieDesignsElectronics
Hi Stephe,
I changed the 5U4G, and I fell a bit different with willsenton 274b tube. Now, another question is could I use 5AR4 into same amp?
Again, thanks another for your help
The working current of 5ar4 is 250ma, is one ok?
Yes, but would require more wiring changes for that to work and starts to push that 100uf first caps being OK. Then you would need a better quality choke to keep the AC ripple at the same level.
Hi Steph. Genuinely before you said it i was thinking it looks nicer with the 5ar4's, the 300's stand out more now. A few questions though, if you can possibly find the time it would be appreciated. Why keep the diodes in the B+ psu circuit? Sorry I don't understand the purpose of this, and also what is the purpose of the 10r resistor before the rectifier on the AC, is this just a dropping resistor, also the purpose of keeping the 50r after the diodes in your design. Is this just to add extra filtering.
The diodes protect the rectifier tube in case of a hat restart and I've read can also help suppress a flash over.
Mainly leaving the 10R in because they are already there + adds a bit of voltage drop resistance without generating a lot of localized heat.
The 50R after the diodes is the main thing protecting the cap on start up as those really big caps fill up. The amp needs the voltage drop from going to a more efficient rectifier anyway so is a win/win.
@@SkunkieDesignsElectronics so one of my amps was built into a small box that my father gave me (sentimental). I have 47uf 1st cap, 200uf film cap (2nd cap), but only one 10H choke in psu, is there an easy way to get any more filtering with resistors rather than adding a second choke that would reduce B+ and I don't have space for in the box. B+ is approx 310v and rectifier is 5r4gy running 2 x el84's. The film caps are huge and were expensive to buy but i thought probably worth the investment.
with a 10H choke, it's probably good as is.
If the TL iron is good, and the package price is good I may well be building these SE monos, be great if they could run EL34 too, could this be acheived through w switchable cathode resistors rather than a rectifier change.
This is a fixed bias amp.
@@SkunkieDesignsElectronics interesting.Thanks Steph.
So if I order one today, this is something I dont have to worry about?
No, these amps have a lot of issues. I haven't seen the latest "black" version but unless they redesigned the whole driver stage, these still have performance problems.
Im thinking about buying a R300 or can somebody recommend something close to the price? Thank you very much for this video!
The problem with using this price as a goal post for a 300B amp is this "list price" isn't realistic. We see the same thing with the Reisong A50. First you have to toss all the tubes, which adds easily $500 to the price. Then in both cases, they require internal modifications and in some cases major parts replaced to perform to the level a 300B amp should be at. Sadly these poorly designed amps have set consumer expectations on what a quality amp should cost so low, it's driven everyone out of the market.
@@SkunkieDesignsElectronics Thank you for your answer! I thought about building your budget 300B design, but I'm a little scared to mess up, if I have to build from scratch. The modifications you did with your videos seems very possible for me.
It dont have to be an 300B amp, if I can get a better sounding tube amp for the money. Fokus is on Midrange and highs, bassdriver will driven by Accuphse E303-X which should work good with tube amps.
Just saw your Video about R8 MKII, maybe this is an option or maybe even a Musical Paradise MP301 MK3 for the start? (To much videos, forums... not enough time)
Im just 30 years old and want to start with tube amps and I like the idea, that they can grow with me. Swap for better tubes, do some modifications or when money is better, buy a better amp.
I am planning to buy this amplifier, but after watching this video, it's better to buy well established brands.
And people have to stop listening to these influencers talking about "chocolaty midrange and so much air, it floats to the ceiling" nonsense.. From my experience, most of these designed and made in China amps are junk.
So how’s it sound now? 🤔
More to come later today.
heaven forbid,but.... what about the solid state rectifiers? cheap ?
And massively change the internal voltages... Especially when the factory supplied rectifiers have a large voltage drop across them.
I really don't understand the desire for tube rectification. I can understand the logic behind using a tube in the audio path, because I do it myself to get a little tubey harmonics, but designing an amplifier in 2023 with a tube rectifier when it could be done so much more cleanly and efficiently just seems strange and counter productive to me.
I mean, if they're going to design an amp with a tube rectifier, at least make it a cool one like a mercury arc or something.
Also, the irony of using diodes across a tube diode.
The diodes aren't across the tube rectifier, they are in series. They only function in the case of a tube failure.
The advantage of using an indirectly heated rectifier tube like a 5AR4 is the slow voltage ramp up.
Why do they even bother using a tube rectifier for the power supply? A solid state power supply is not going to take away from the "tube sound" of a 300B power amp.
GZ34 is a good tube
Do the voltage drop, the first cap meet the requirements of the R300?
I can't definitely say on the early version until I dissect one but tentatively, yes.
They had problems with the rectifier tubes !!!......hmmm.......Any blind technician from the tube era looking at the circuit could predict that !!!
And the way they designed the HV delay with direct heated rectifiers is a BIG mistake...
They have no clue about tube technology but are selling and building tube amplifiers .
Good to see that some people today like you are there to correct those thosze errors and solve the problems ...
Customers still think that those chinese BS is designed by skilled and experienced technicians .
Agree, shocking to see how Willsenton „designs“ their amps. Absolutely BS. How is it possible to sell this BS and get so many positive „reviews“ from all the youtuber „experts“.
Exactly, Frank! I’m younger and not necessarily from the “tube era”, except for the fact that I’d never not use a tube amp for my guitar amps. But….I work on guitars and tube amps almost everyday, mostly replacing bad parts, retubing, and biasing tried and true designs, and even I can see that the HV design with a delay before a direct heated rectifier is just a bad idea.
I don’t know who’s designing these Chinese made tube amps, but you shouldn’t have to immediately repair a design on a brand new amp! Mods and upgrades after listening to and living with it for a bit, and seeing where they’re necessary and will help the amps performance is a different thing, but having to fix the basic design is just wrong.
Stephe is such a skilled and knowledgeable person when it comes to trouble shooting these designs.
If they have the knowledge to make amplifiers ,why do they need to be schooled?! The OPT's must be 2.5 lbs OXYGEN LADEN COPPER....
i wil never buy any willsenton amp,