Willsenton R8: Final Power Supply Mods.

In this video I am replacing the power choke, the grid power resistor and answering some questions asked about the previous video.
This is a video series about the popular Willsenton R8 KT88 EL34 Push Pull tube audio amplifier. We will go through the repair this amp needs, testing and reviews of the amp as delivered, and then work on modifications to improve the sound quality and durability.
A great book for DIY amp building info!
Morgan Jones: Building Valve Amplifiers.
amzn.to/3X2hKfk
You can buy this amplifier here
amzn.to/3Q3Ynjr
The tools I use in this video include:
Hakko FX888D-23BY Digital Soldering Station
amzn.to/3WUf7MP
Hakko-CHP-170 Micro Cutter - Red
amzn.to/3Gk5YGh
Hakko CHP CSP-30-7 Wire Stripper
amzn.to/3GL19Hd
Long needle nose pliers
amzn.to/3VRvhoO

[@R3dFiv3.]

I enjoy the brutal honesty. All you hear left and right is glowing reviews or scathing reviews from others, so this content and delivery is, I think, outstanding. Thank you!

[@SkunkieDesignsElectronics]

I appreciate that!

[@toddhupp]

Skunkie is a terrific teacher.Gifted.

[@joeamos5877]

Love your presentations and frankness. Agree that someone who has no knowledge of electronics / electricity could have a problem making all these modifications. It would be great if after all the changes are done, you could provide a shopping list of stage 1 through stage 5 options including parts, labor and verified test data for those who would prefer to pay someone who knows what they are doing implement the changes. The problem with this could be you would be so overwhelmed with orders you would have to teach your dog how to solder.

[@SkunkieDesignsElectronics]

HA!

[@bobbysparky4299]

ROFLMAO

[@peterziegler6359]

Incredible content. Just found the channel. Have been looking for something this deep in audio equipment for a long time. Thank you.

[@SkunkieDesignsElectronics]

Awesome, thank you!

[@marklohnes6313]

I agree!

[@Nosferatufatum]

Loving your content. Not planning on doing any work to the amp myself but just enjoy the way you show and explain things. Great stuff 👍

[@BobTyldsley]

I am enjoying your willsenton R8 videos. I bought one about 2 years ago and last year it started blowing fuses. With china audio's help I was able to diagnose that the B+ bridge rectifier failed. I replaced it with a higher amp version and have had no problems since. No idea if it was a bad part or a design problem. They did send me a version of the circuit diagram that is like the Australian site one but much larger and clearer. For instance the choke is marked 4H 300ma. The pdf is marked "do not share on web" so I am reluctant to post it but if I will send it to anyone who wants it

[@SkunkieDesignsElectronics]

That is baffling, the sticker on the choke says 180ma? Maybe it is a 300ma? Who knows! The diagram online, is not how the amp is wired though.

[@robertdiffin9136]

Telling it like it is! Love it ❤😂

[@anhdangduc1061]

Thank you so much for answering my question. Really appreciate your honest concern. I will definitely take my time and do more research before tackling any of the mods.

[@SkunkieDesignsElectronics]

Thanks for understanding and I'm sure with some study you will be able to do this stuff :)

[@cobar5342]

Thank you Stephe. The project seems to be going very well

[@mike212916]

7:35 that was my question haha. Thanks for showing me. No offense, I understand you're just looking out for my safety but I just want to upgrade my amp and not buy an electrical engineering book. This isnt something I plan to do again anytime soon. And because your videos are so straightforward I feel confident to do the job. As long as my R8 model has the same layout as yours then I'll be fine. Mostly because I am very good at soldering. Long ago I had a big ebay store where I soldered 0603 leds to consoles/gaming controllers. Since they were so small I became a surgeon like solderer. And I still got all my high end tools. PS: I bet there will be some good youtube videos I can watch in under and hour that will give me all the basic electrical knowledge. I'll just start watching some now. If anyone knows of any good somewhat short videos that helped you in the past post them.

[@samb3706]

You are so correct and honest---A little knowledge is beyond dangerous!

[@manliveful]

Very informative and we would like to thank you for all the detiled information baout the mods, if possible can you please provide a list of all the important modifications that would have to be done and verified if they are on the New R8 Mod II when someone purchases the unit, in other words a complete list of modifictions from a A to Z so one can verify if they have been done on the newer units, thank you Skunkie...!

[@SkunkieDesignsElectronics]

I did that in the video series...

[@HerrFinsternis]

This was really relaxing to watch after a long long week at work, thx 😊 I like what you said about being bothered by some of the questions you got about basic electronics. For someone like me who doesn't know anything about all this but is interested learning, do you have any advice on where to start? Any books on the basics you found particularly good. Would be cool to build something like a headphone amp. Seems easier to do then an entire integrated.

[@SkunkieDesignsElectronics]

kzbin.info/aero/PLtEhh3UpOsiDdHABS0q5byT2gAQ5z31Hk That is one playlist, here is another video on suggested reading: kzbin.info/www/bejne/haaWZKN8bsaMmM0

[@HerrFinsternis]

@@SkunkieDesignsElectronics oh that's amazing, my thanks 😄

[@PaulMoorfoot]

Fantastic content Skunkie. Thankyou

[@Loggiebeat]

Some great and sound advice there Stephe 👍 Also when upgrading / modding don't do it all at once. Check and double the amp after each step. It seems now this is a good amp to start with that only can get better. I've now started to read a 300+ thread about this amp on the Stereonet website to get an idea what other people think of this amp and its possibilities. My only other tube build experience is a Bottlehead Crack tube OTL headphone amp. Such a fun build.

[@mddawson1]

Once again, many thanks for your clear and concise instructions and warnings 🙂. I was one of those who asked about the wiring for 230/240v countries. I am positive I could easily work it out but I do prefer to follow the advice of someone with vast experience like yourself. So far I haven't removed the base plate to look so I don't know what other differences, if any, the 240v version may have lurking inside it.

[@SkunkieDesignsElectronics]

No worries

[@mddawson1]

@@SkunkieDesignsElectronics FYI, I found a H4 250ma shielded choke on Aliexpress that seems to be close to the originals size but then it is from Aliexpress so who knows how close it is to advertised specs.

[@PGHJR002]

Incredible, it all sounds dangerous Thank you for your safety conscious lessons

[@SkunkieDesignsElectronics]

Thank you for recognizing this!

[@MichaelPuente]

Cool video. I like the friendly attitude.

[@dannyc4501]

Yeah .. good catch on the choke- I noticed that too. Come to think of it I am really starting to wonder what the PT is rated at?? It did run a little warm after a few hours with the 6550's - I'd be interested to see if it's much cooler with the EL34's- it is pushing over 200ma but what is the rating? got me wondering now- and why a 180ma choke? The positive is that the R8 has been out for awhile already and haven't heard of 1 PT melting down. And I also removed the headphone jack wiring on mine also .. just clipped the 2 wires on the outputs that ran to the headphone jack and ran the 2 grounds to the ground that were removed from the headphone jack as I never use headphones anyway and when I tested it with a headphone plugged I still had sound to the speakers so instead of troubleshooting - it was removed. My Skunkie 300B amp runs much much cooler and sounds much better. I really don't think you'll ever get it to sound as good as your 300B- not that the R8 sounds bad -it's just not a 300B.

[@SkunkieDesignsElectronics]

Not it's not and I'm a big fan of single ended amps anyway.

[@GREGBT69]

You're the best!!!

[@crazylikeafox1000]

Thank you for what you do, it gives me confidence!

[@joesapereira5539]

Well done Stephe. Also, I can only assume that the people asking for the parts list are new to the channel and do not know this is not a kit you have already put together, but a possible kit you may end up with after going through the amp to fix an issue your friend had with it. Keep up the good work and looking forward to what is next on this build/upgrade.

[@dmhnc07]

Great info, thank you for sharing your knowledge! I have the skills and all the tools to perform these types of mods. But my experience is with communication and relay protection equipment. Similar though. It's been decades since I was into audiophile equipment. I got into other hobbies that are also expensive and I can't afford them all, sadly. But I've been considering a tube based system for a while and I'm just beginning to do my research. I've always wanted a tube mono block setup but I must be more realistic. Maybe after I retire, lol. But for now I am thinking about something like the Willsenton R800i 300B 845 /805 Tube Single-Ended Class A integrated amp. I'm surprised to see a Chinese company that's delivering a product that's affordable, well, more affordable and also of decent or good quality. I've been looking at some American based companies and what they offer is over twice or 3 times as much at the least. That and how many of their parts are made in China? I heard that Willsenton has moved into a new place and are going to step up on the quality of their parts and build to what ships to the US. Also at only a small price increase. I'd like to see you examine an R300 as well as a R800i. That would be great! Thanks again!

[@jonshimamoto2710]

Hi Stephe, again, I love your videos, very informative... According to Zed Zed at Stereonet Willsenton R8 forum (on page 63), when you set the bias for the KT88 with the bias meter in the center position, he measured the bias at

[@SkunkieDesignsElectronics]

On this amp, it's showing 52ma with the meter centered set for KT88 tubes, which is still pretty cool. That's over 200ma just for the output tubes and that is at only 63% of their rated wattage, with the amp at idle. 42 ma would be more where an EL34 tube would be run. I'm not sure how he calculated what he posted. and that isn't even adding in the power used by the input tubes, which isn't a lot, but it's there.

[@PeterAMorrone]

I love how you make a change and then test and qualify before moving on. Do you have any videos that show how best to ensure the tube amp is safe to work on after you power down from a test. IE how to ensure capacitors are discharged fully etc?

[@SkunkieDesignsElectronics]

I will in a future video!

[@BMW_108_M]

Watched all the mod videos, how ever I never had a single issue with my R8 and it was dead silent from factory and still is dead silent. I did replace all the Willsenton Caps with Mundorf SGOs and it’s a great improvement. I will carry out the mods that are required such as dual rail mod, safety resistor mod. I have EL34 tubes not KT88s

[@SkunkieDesignsElectronics]

Not sure what to say other than both of the ones I worked on had some hum at mid volume. They were quiet at low volume and at full volume.

[@BMW_108_M]

@@SkunkieDesignsElectronics did you ever get the hum to disappear ?

[@SkunkieDesignsElectronics]

It slowly got better, the final "hum killer" was the volume control rewire.

[@ja8020]

Great content and common sense advice. Taking your time is ok with me.

[@iainford7592]

Great vid, Stephe :)

[@erikjohansson1488]

Really like your content thanks for sharing your knowledge .

[@Willywonkaz]

Thanks a lot ! Excellent teacher !

[@robertwathey1957]

Hi Stephe, I got my 194G choke, and you think going from 4H to 3H in the power supply will not be audibly noticeable? I certainly trust your opinion! Hope you are well, and thanks for all you do for us fellow amp owners!

[@SkunkieDesignsElectronics]

I just measured the choke I pulled out of the amp, it measured 1.4H not 4H. The 194G measured 2.9H. Now the difference in DC resistance makes more sense, the one in the amp is not actually the Henries it's labeled as. I was baffled how the slightly smaller choke had more H at a lower DCR. The fact is, it doesn't.

[@robertwathey1957]

@@SkunkieDesignsElectronics That is great, for everyone who replaces it! It's sad that companies can misrepresent their products like that. Thank you for responding, and thank you for all of your knowledge! Robert

[@UptownReef]

Have you been testing the amp using the preamp inputs and an external preamp? I’m having mixed results in my modding journey. All of the changes I’ve made have positive results besides when I use the preamp inputs and my Freya+. Using the preamp inputs is causing the amp to hum noticeably however, all other inputs work great without issue. I suspect it’s related to a Fruit mod I did switching out the 220k resistor on the preamp power supply with one of greater value. When I used a 300k the amp was not stable and preamp section dropped out intermittently. I drop the value to 287k and I gained stability back but still have a noticeable hum. I’m looking forward to seeing the upcoming rebuild of the preamp power supply. If you don’t mind, please test after using an external preamp and see if you reproduce similar results that I did. Thanks for all your hard work putting this video series out! I’m certain you are helping countless folks gain new knowledge and opening some beginners to the tube amp world. You’re awesome!

[@SkunkieDesignsElectronics]

Changing the voltage on the 6SL7, being a direct coupled setup could cause unexpected things to happen. I will test this and thanks for the suggestion!

[@RnhTechnologic]

many tnx for great video, can i start from choke replace it first without do any change in resistors or caps?

[@SkunkieDesignsElectronics]

Yes, absolutely, it's just a drop in replacement. The other one I HIGHLY recommend is adding some "safety resistors" to the bias boards, I did a video on that too.

[@christopherredfern6472]

wowzers - worries the life out of me that some people can really ask such basic questions too --- i know we all started somewhere BUT ???? i hope they listen to you and understand exactly what 500v DC can do to you !!!!!! sorry to be blunt but this is not for the bloody stupid ones !!

[@SkunkieDesignsElectronics]

Yup, it's why I have that warning before every video.

[@neccron9956]

If possible, when you modify the circuits, it would be nice to have the schematic flash-up, on the screen, to follow along.

[@thomasfi1275]

Many thanks for the amazing videos!!! One stupid question. Is it possible that all the downsides of the R8 were done by purpose, to get a specific sound signature 🤔please don’t shoot me 😂

[@SkunkieDesignsElectronics]

I doubt it, I think it's cost savings.

[@TomFarnsworth]

Apologies but can you kindly provide a link for that 2watt choke resistor?

[@laurenceschnieber5370]

Thank You

[@philipketchum1407]

This is good stuff.

[@radicalaudiodesign]

What do you think of screening the choke? I previously had issues in another amp with the choke causing noise when not oriented the right way. (yes it was DC, couldn’t believe why?) I will also try to upgrade the bridge rectifier to 4x Vishay Hexfreds, heard good things about them and heard before they can have really good effect on the sound. Some people say they sound like tuberectifer but acts like a silicon one… interesting. Anyway, about the voltage switch, i guess i got little bit offended since i didn’t right away figured it out. I measured the resistance i had in 230V and checked winding on PT to find similar. You or someone else can call me slow but those switches are throwing me off you can say… Only issue i have with me R8 after extensive upgrade is that i have a slight ”pop” when i turn it off and little afraid to hurt my tweeters. can’t figure out ”why”, I’m Suspecting there is something with those damn relays to do but since i want to go full triode i will later try to remove those and rewire it slightly. I think triode is superior to UL. Any advice on that in your videos later i would really like. Can’t thank you enough and i’m Surprised you haven’t got more subscribers yet.. it’s you and a handful people out there with this level of competence so big kudos to you. God bless you.

[@SkunkieDesignsElectronics]

The pop is likely a bad capacitor on the power switch.

[@radicalaudiodesign]

@@SkunkieDesignsElectronics Funny you say that because i replaced it with a new one a week ago to a RIFA PHE840 / 10nf as orginal but no change…

[@johnkal8403]

A quick question about that 4.7k resistor. Is it rated for 2 watts and 500 volts or less? You said it could be a metal film or Wire wound correct? Great video BTW!

[@SkunkieDesignsElectronics]

Yes it is, not even close to those limites.

[@johnkal8403]

@@SkunkieDesignsElectronics I'm not sure what voltage to use, sorry.

[@SkunkieDesignsElectronics]

@@johnkal8403 There is less than 100V across that resistor.

[@johnkal8403]

@@SkunkieDesignsElectronics Thanks again.

[@thomasfi1275]

Because of the 180mA choke, will there be any problems using KT88 or safety issue? Many thanks.

[@SkunkieDesignsElectronics]

I don't think it's going to catch on fire or anything. They are just really pushing what this component can handle.

[@Warclock07]

Assume the PT is 180mA, what would it does when you replace with 200mA choke? I have seen a lot PP amp without choke since the OT can filter out the noise and my PP amp doesn't choke either. In your experience, does the choke in PP amp would give better sound or reduce the AC ripple? I have been thinking to add the choke to my amp but not sure if it would give out a better sound or improve something else.

[@SkunkieDesignsElectronics]

It reduces ripple, and also allows for a reduction in the DC resistance of the filtering network of the power supply. I have no idea what the PT is rated at, I hope it's large enough to actually power 4 KT88 tubes but who knows?

[@dannyc4501]

I did see the KT88's tubes bias up so the PT is putting out +200ma Forgot how much current each was pulling but was over 200ma for the 4 tubes and that was not using the meter but a tube adaptor with my fluke to read current

[@dannyc4501]

@@SkunkieDesignsElectronics Just off the top of my head - Iam running 6550's in there last time I used it and I believe I have them around 60ma each (if memory serves me correctly) so were already at 240ma. And the PT is doing it - is does run warm after awhile but not crazy hot like my Dynaco ST70- I light my cigars off of that one. I do wonder what it's rated at though- being potted you can't even see it.

[@andresamson7779]

Curious if you tried out the amp since changing the choke. Do you expect any improvement in bass?

[@SkunkieDesignsElectronics]

I haven't yet but plan to tomorrow.

[@andresamson7779]

@@SkunkieDesignsElectronics I was looking at other choke options for fun and found a 4H, 400ma I think would fit, but the DCR is quite a bit lower than the Hammond one you're using--30ohms vs 80ohms. Do you think that could cause an issue somewhere else, like with B+? Any issue with using 5H or more?

[@SkunkieDesignsElectronics]

@@andresamson7779 Link them? And more H isn't an issue, I've run 10H chokes in SE power supplies.

[@andresamson7779]

@@SkunkieDesignsElectronics Sent a pm on Stereonet. Hope that's okay.

[@ברוריהחזן-ח8ה]

Can i know which correct value you replace the green resistor with black in transformer which value that ,Tnx for information

[@SkunkieDesignsElectronics]

I ended up discovering it is NOT a wire wound resistor and while originally it was 5.7K ohm, that is such an oddball value I used a 5.6K and it works fine.

[@RnhTechnologic]

@@SkunkieDesignsElectronics original is 4.7k , gold red violet yellow =4.7k in green resistor

[@stevenpaul3886]

FYI I sent you my info using ur website for the R300b…

[@SkunkieDesignsElectronics]

OK I will go look for it!

[@taniapolnski]

hey dear my amp come with cap 100uf 200v i see you put there 100uf 160v.. this not be a problem put not same value like this came?

[@SkunkieDesignsElectronics]

There is less than 100V at this location, if you want to use a 200V go ahead but a 160V isn't a problem either.

[@sethjohnson1590]

Take that 🎧 jack and wiring out

[@SkunkieDesignsElectronics]

I agree, it's a MESS!

[@sethjohnson1590]

@@SkunkieDesignsElectronics I mentioned in another video that I was going to buy one or two r8s But I have no faith in their products. What if the outputs were a batch of inferior ones like most of the workmanship/engineering, corner cutting tactics they always sell us.

[@jimpeek7967]

I was wondering if it is possible with the power upgrades to run kt120 or is there not enough power thanks

[@SkunkieDesignsElectronics]

Nope. The power transformer nor the output transformers could handle the load

[@frankgeeraerts6243]

@@SkunkieDesignsElectronics Correct .................;;seen amplifiers blow up that way , even with changing rectifiers who draw much higher cuirrent ! Good and fair to warn people to have some experience and know how about electricity >/electronics and HIGH VOLTAGE BEFORE going in a tube amplifier and modify or repair !!!!!!!! thumbs up for the warning !

[@paulconteyoutubesucks2931]

Love ❤️ this program looks absolutely amazing hun

[@CP-qe2ym]

I'm still unsure what the rating is of the 2W wire wound resistor at 16:36 ??

[@SkunkieDesignsElectronics]

4.7K

[@CP-qe2ym]

@@SkunkieDesignsElectronics thanks for the rapid response.

[@toddhupp]

when Skunkie is done this amp will be comparable to the Prima Luna evo 100 @ 2800$

[@FaintSignals]

A whole lot of time and money, maybe fun for the owner, fun for the tech to do a vid, but the mods even if worthy destroy the resale value, might even render it unsellable except at a blow out price to another tweaker who wants it for the tubes, chassis, and iron. Smart decision is to sell it stock, mint in box, and buy something you are happier with. Or have SDE or your fave tech build you something from scratch, cost of this amp plus many hours of service and parts will finance a very decent custom build. Might even be enough to pick up something vintage that appreciates in value like a Radio Craftsman Williamson, Eico 60, Heath W4. My two cents. Nonetheless, I was curious about this thing and enjoying observing the surgery.

[@SkunkieDesignsElectronics]

Honestly these made in China amps don't have much resale value anyway. And just IMHO, to get an amp better than this one will be after some mods, you are probably gonna spend 3X what this amp costs. I know a custom build from me would be!

[@inerlogic]

Some savage takes, but absolutely... If you don't know the basics, don't touch a screwdriver..... Lol... Say "wire-wound resistor" 5 times fast :)

[@SkunkieDesignsElectronics]

Yeah, I had like 4 takes trying to say it even close to right lol.

[@RnhTechnologic]

can use 220uf or must 100uf on power supply?

[@SkunkieDesignsElectronics]

On what part of the power supply are you talking about? If it's the bias supply, no you can't.

[@RnhTechnologic]

@@SkunkieDesignsElectronics on power supply have big cap one that in original came 200v 100uf... can i put 220uf 160v?

[@SkunkieDesignsElectronics]

No you can not, that will delay the negative bias voltage which can cause bad things to happen.

[@davidmaruska1641]

Hi, to your comment about heat and capacitors, you have the one laying on the large wattage resistor that you replaced. over time the heat dissipation will heat the cap and could shorten its life or if the resistor was to fail it will bake the cap. I like your show, and I also agree, if you don't understand basic wiring, don't jump into a tube amp or any high power item that can kill you....

[@SkunkieDesignsElectronics]

Except there would need to be large wattage going through it for it to become hot :)

[@davidmaruska1641]

@@SkunkieDesignsElectronics I dont disagree, but power is power, which is converted to heat via the resistor, which can be calculated ohms law. This is a practice that is taught in my early career, and when I see it I correct it.

[@paulpaulzadeh6172]

why there is a lot of hair inside this amp? I think your dog is curios when you are not working on amp.🤗🤗🐕

[@SkunkieDesignsElectronics]

HA, there is dog hair EVERYWHERE in my life :)

[@mfr58]

I guess this is why Chinese amps are relatively cheap, they are just not finessed and design anomalies, production quality and reliability issues, are left for the consumer to work out....

[@SkunkieDesignsElectronics]

Reminds me of the old soviet film cameras. They were a starting point for a tech to turn into a decent, usable camera.