Willsenton R8: Power Supply and Output Resistor Upgrade

[@justinbarker871]

These are great videos and i'm really looking forward to learning and making some mods myself. I ordered my R8 back in December 2022 and have just opened it up today to have a look at what parts I need. Interestingly the filter caps in my amp are in fact rated at 500v, so it looks like even prior to the mk2 they have been making some revisions. A bit of money saved at least : )

[@heshoh2]

Very nice close-up shots and camera angles that show your work on the amp.

[@Mark-rw3kw]

Not sure if this is mentioned by others or in the video, but probably a good idea to make sure the existing large capacitors are discharged before messing with them.

[@SkunkieDesignsElectronics]

Which is why I post that warning at the start of every video. I seriously can't cover all the safety considerations in every video or each one would be over an hour, with the same information repeated for 30+ minutes of each one.

[@augustonorona9717]

Hi there, again. I just sent my first reply 10 minutes ago...now I'm watching your r* power supply mods. Will watch it's entirety & definitely get back to you. Thank you again.

[@edverbeek6292]

Nice close ups, very instructive, thanks for you patience and endurance with your channel.

[@tubeman1355]

Thank you for sharing your knowledge and experience with us noob. I really do appreciate it.

[@crimsonghost6454]

I'm interested in how the coupling caps will affect the sound. This entire series on this amp has been great. You always do great work and I'm excited for more on this one. I too bought one of these maybe a year or more ago. I'm very happy with mine but I'm always game to improvements. Anyways great content

[@SkunkieDesignsElectronics]

Thanks!

[@mikekelly8805]

I replaced the coupling caps in my R8 with nice Audio Note copper foil in oil caps. Big improvement. I replaced the coupling caps in my Reisong A10 with inexpensive Clarity Caps (after the Skunkie mods) and that a HUGE improvement.

[@dmhnc07]

Very good information you are providing! You are a gem! I'm currently researching different tube integrated amps and whatever I end up buying I aim to get the most from it as possible. I have no issues doing all the work myself and already have the tools to do any mods. The skills I have but not your knowledge. I really enjoy all your videos!

[@cdbeen123]

Awesome , I also have an R8 which i love , I was considering paying someone to do these upgrades but your excellent easy to follow instructions have encouraged me to try it myself . After a bit of soldering practice that is . Cheers 👍

[@axlincasuma]

This series is amazing! It is such a gift for us that live mostly indoors due to wild winter. Thanks!

[@cobar5342]

Great progress so far, Stephe

[@shodan6401]

Upgrading the filter capacitor is a MUST. ElPaso TubeAmps built a nice little stereo amp that he used as his main driver in his shop. After a year it cut out, took the cap, resistor that split in half, the fuse, and I don't remember if it took out a tube. Same problem - at power on, the in rush of voltage over drove the cap and eventually led to catastrophic failure. You can either upgrade the cap, or install a thermistor to limit the voltage just long enough for the tubes to start drawing current and bringing the voltage down. I prefer the thermistor route, as it also prevents that big thump in your speakers, and just adds another layer of protection for the amp.

[@mike212916]

This is a great video. Thank you! I’m buying an r8 in a couple of weeks for my focal aria 906 speakers.

[@brycejeannotte7699]

I am really enjoying this series. I hope that you will produce a list of the components that you use to upgrade the amp. The shot of the Mouser bag was great for the 10 ohm resistors.

[@SkunkieDesignsElectronics]

Yes, I plan on it. Possibly make up a kit of the low cost passives.

[@uttaranchakrabarti5712]

@@SkunkieDesignsElectronics - you are awesome.. we are learning so much from you

[@uttaranchakrabarti5712]

@@SkunkieDesignsElectronics pls make a pkg with coupling caps and resistors and sell.. i want to put an order

[@arvindgoudar1586]

Too Good a Video ! Gives me a lot of confidence to even open up an amp ! Thank You !!

[@SkunkieDesignsElectronics]

Rock on!

[@scaryperson27]

I assume you already have your caps but I have had really good luck with REL film caps in a tube amps signal path. Silmic II's are nice for electrolytics. I listened to that Elton John song. It has a nice center image. It was nice to listen to.

[@EsotericArctos]

These look like a quite well constructed amplifier. A few little modifications seem to take it from very good to fantastic. :)

[@dougg1075]

I have one and it’s great

[@gshcarter]

Loving this! Looking forward to a BOM 🙂

[@mddawson1]

Have you listened for hum with the R8 using the 'pre-in' input as that bypasses the volume control?

[@SkunkieDesignsElectronics]

I plan to play with this next time I power it up.

[@toddhupp]

very cool.quality parts really do make a difference.perhaps you should offer a parts upgrade kit.there are hundreds of these amps out there.

[@SkunkieDesignsElectronics]

That's the plan!

[@jordantoms4802]

Hello. Thank you for your extremely empowering videos. You take away the intimidating befuddling element of electrical engineering and make one feel they clearly understand what the many items are in a circuit , what they do and why they pose a danger when not connected properly. Furthermore, you illustrate clearly how to rectify the dangers of improper execution of an electrical design. I just bought an R8. Haven’t received it yet so don’t know if it’s a MKII or not . My question is could you post a list off all the capacitors ,resistors . Solid core wiring and any other item so that I could buy all the items needed to complete the mods you’ve outlined in one order? I feel confident with the videos on hand I can complete these procedures . Thank you so much for the videos and I look forward to taking this amp from good to safe and amazing for years to come .

[@SkunkieDesignsElectronics]

First see which version you have! Hopefully they send you the newest "MKII" version is what I call them. I uploaded a video about those, which really don't need much as far as mods to sound good and be reliable.

[@jordantoms4802]

Ok Thank you. I have watched all the r8 videos . I’ll get it soon and get back to you. I’d like to keep the headphone Jack . Shouldn’t be a massive deal breaker right?

[@jaspers49]

Could you do a video on what songs you use for reference when testing?

[@124MPH]

Another great video!

[@VintageStereoCollectorChannel]

Nice progress. How about hooking up a preamp to bypass the volume knob to see if the residual hum is present? I’m one of the subscribers that reported no hum and I use a preamp.

[@SkunkieDesignsElectronics]

I'm going to play with this more.

[@abxaudiophiles]

I can report that with 2 different pre amps into the R8 with the volume knob disabled (PREAMP MODE) that it still humms and actually MORE humm as the pre amp has gain.

[@abxaudiophiles]

Is there a good source for those two main 380LX caps? Having trouble finding that exact one online. THX

[@SkunkieDesignsElectronics]

www.mouser.com/ProductDetail/598-380LX331M550A052

[@abxaudiophiles]

@@SkunkieDesignsElectronics Life saver!!! Figured I would start with these two and the stuff on your first video. I can’t express how much I appreciate the video series and your testimony made me feel comfortable to purchase my R8 from a friend with came with $1000 in upgraded tube included a full quad set of Golden Lion, and Psvane KT88 power tubes and a handful of RCA red base and others. Such a great sounding amp!! And I paid $1400 for the amp and all the tubes included. Looking forward to making my way through the mods. Can you remind me which mod got rid of the small humm? Thx. ABX

[@Whitewolf4869]

I see 2 resisters with chunks out of them in the close up view

[@SkunkieDesignsElectronics]

And honestly, that part of the circuit has almost no current running through it, even if the amp got overvolted. I'm not sure what is making them breakup like that.

[@Whitewolf4869]

@@SkunkieDesignsElectronics Actually 3 with damage. Perhaps it has nothing to do with the amp at all.

[@donaldbryant5295]

This is very very good thank you.

[@CohibaJoe]

Fantastic series thread and I look forward to additional Upgrades on builds and customer gear (quality parts do matter). For the Coupling Caps, Screw Terminals work easer with multiple wires as a solder lug terminal can be used. BTW: DECWARE uses the following parts for their Amps. SIGNAL CAPACITORS: MIFLEX KFPM-01: BYPASS CAPACITORS: MIFLEX KFPM-01: ELECTROLYTIC CAPACITORS: F&T: CATHODE CAPS: NICHICON MUSE, ATOM. Where space is limited, I also use Auricap XO, Mundorf EVO - Aluminum Oil or SilverGold Oil Signal/Bypass replacing the Willsenton Films.

[@abguy4]

I am already wondering IF you have any interest in assembling/selling a complete upgrade kit for this amp. And YES~!, this is a lot of fun to watch. Thank YOU.

[@SkunkieDesignsElectronics]

This is something I might consider.

[@lancepeters9095]

@@SkunkieDesignsElectronics I would be interested as well as would save purchasing from multiple suppliers and happy to support you for all the great work you have done.

[@78sound]

nice work

[@openbafflespeakerbuilder9863]

After replacing the 330Uf caps and the choke (no other power supply mods yet) I had biasing issues on V2. V2 would not reach bias and stayed at minimum on the bias scale while all other tubes biased fine. Switched KT88's to make sure it wasn't a bad tube and the problem persisted at V2. Overall sound out put was low, it seemed on both channels. I turned the amp on and off a few times and then both V1 and V2 bias shot up. Everything biases fine now and continues to hold bias fine on all 4 KT88's.Could this be related to the new cap charging? As a side note, I had no biasing issues after performing the bias board and output resistor mods. Thanks!

[@SkunkieDesignsElectronics]

It has nothing to do with the power supply caps, you likely have a failing bias pot. Keep an eye on that!

[@openbafflespeakerbuilder9863]

Thank you, I’ll keep an eye on it.

[@richardkieran6873]

I have done some of the mods and I'm very happy so far. Did hit a snag though. I can't find the power supply capacitors. The ones I find, using the part number from the ones you put in, are rated at 450v. Any help?

[@SkunkieDesignsElectronics]

search for uf and voltage, then make sure they are the same diameter. Part numbers change and keeping a BOM current is a full time job.

[@anthony2010707]

thanks very much for your video, what is the voltage of the capacitor you replaced?

[@SkunkieDesignsElectronics]

www.skunkiedesigns.com/r8-mods BOM is posted there.

[@avnerbelisha1457]

Grate videos, can you recommend a tube kit that have good instructions for first build (Phono will better for me)

[@SkunkieDesignsElectronics]

The EAR834 ebay kits are easy and sound amazing! I did a video series on building one.

[@avnerbelisha1457]

@@SkunkieDesignsElectronics i will see the video thanks for your videos

[@TheRealAudioDidact]

Skunkie, do you want to try out my R800i 845 SET? It's not in use now and I'd love to see what you can do with it...

[@SkunkieDesignsElectronics]

Sure, contact me at my website www.skunkiedesigns.com/contact

[@JenkinsUSA]

23:30 - did the hum go away when the tubes were swapped? The world wants to know! 😊

[@SkunkieDesignsElectronics]

No, I explain in the video. There was a bad solder joint on a resistor under the power transformer.

[@JenkinsUSA]

@@SkunkieDesignsElectronics I was referring specifically to the slight hum in the middle of the volume.

[@SkunkieDesignsElectronics]

@@JenkinsUSA Nope, it's still there. I don't think this is a tube issue but at this point, not 100% sure what is causing it.

[@mbracerh]

Did the manufacturer use these changes after you send it back, so if i buy one it's the same as the one you was changing ?? sorry for my english

[@SkunkieDesignsElectronics]

They did some of the more important ones.

[@MrGleb1966]

Hi! A question about 10 Ohms resistors: you recommend to put 1W resistors in that position. I have 0.5W 10 Ohms resistors. If it will be OK, or they will burn out?

[@SkunkieDesignsElectronics]

They should be fine, ohms law is showing they should handle 225ma before they exceed their rating. Just make sure they are closely matched so the meter is accurate between the tubes.

[@MrGleb1966]

@@SkunkieDesignsElectronics Thanks. They are rated 0.5%.

[@RnhTechnologic]

tnx for great video , the big caps black here its 550v and 330uf ?

[@SkunkieDesignsElectronics]

Yup!

[@patrickmccrank8414]

I ask because I have one of these. Unpacked but never used due to other problems.

[@1324390]

Have had the R8 with stock KT88s for a year now and no problems so far. Very happy with it still though I'm sure the upgrades you're doing would bring it to another level. Must say as is this amp already represents good value for money. Got one question: I have a pair of Elac Uni-Fi 2.0 UB52 speakers rated at 6 ohms and 85 dB sesitivity. Shall I connect them to the 8-ohm binding posts or the 4-ohm ones rather?

[@SkunkieDesignsElectronics]

I would use the 4 ohms and see if it's loud enough.

[@1324390]

@@SkunkieDesignsElectronics Thanks Skunkie ! Tried both terminals. The 8-ohm posts sound punchier with better defined bass whilst the 4-ohm ones sound softer... In fear of overloading the amp I now stick to my other set of speakers, namely the Triangle Borea BR03 rated at 90 dB sesensitivity with 8 ohm impedance.

[@mdvp123]

Great video! If I wanted to modify the headphone out to deliver more power into lower impedance (32ohm) headphones, would it be as easy as replacing those two 460ohm resistors with lower valued resistors (say 30ohm)?

[@SkunkieDesignsElectronics]

I plan to look at that part of the amp later.

[@cdbeen123]

What soldering iron tip do you recommend for this type of work ? Will the one that comes with the Hakko Iron you recommend do? Thanks for any advice

[@SkunkieDesignsElectronics]

Yeah, that is the tip I use.

[@CP-qe2ym]

Excellent video for a newbie like me, I feel ready to carry out these upgrades myself. Are all the resistors 2W except the 10ohm cathode resistors that are 1W?

[@SkunkieDesignsElectronics]

Pretty much, there are two larger resistors that appear to be 3W

[@mattbonaccio3522]

Try checking for DC on the volume potentiometer, both at the terminals and on its little metal case. That can cause weird, hard to diagnose issues sometimes. And, obviously, if there's DC on output of the pot, then that means there's current flowing in the grid of the first tube. That probably would have made itself obvious by now. Those failing resistors in the power supply ought to be replaced, though some diagnosis ought to be done to figure out why they failed in the first place--too much power? I haven't watched your earlier video about this amp yet, actually, but it sounds like the B+ voltage is too high, so maybe it's just that simple. It's very common to use metal oxide resistors in power supplies as they're cheap and generally suitable, but if it's in the budget I recommend using good quality Ohmite or Vishay wirewound resistors. If you have the time and care to do so, you may want to rewire that whole section. The whole amp seems to have a very high build quality except that section of the power supply. And that's the part that's falling apart, go figure. Are the brown 100uF electrolytic caps on those red PCBs the cathode bypass caps for the output tubes? You may find that your subjective audio nitpicks (bass detail, etc) would be improved by upgrading those in some way. Just my $0.02...

[@SkunkieDesignsElectronics]

I explain all of this in the earlier video and this is a fixed bias amp, there are no cathode bypass caps on the output tubes. And I also explain I am replacing all the resistors in this amp. And to your first point, if there was DC on the pot, the input tube would have melted.

[@frankgeeraerts6243]

Correct Matt !

[@danielthomas3057]

What's in the Ilford box at bottom left?

[@SkunkieDesignsElectronics]

B&W printing paper from years ago :)

[@frankkaufmann9184]

😂

[@BobCvideos]

Saw that too .. being an old matrix guy..

[@Willywonkaz]

Are all the resistors (10, 1k, 39k) 1W and 0.5% ?

[@SkunkieDesignsElectronics]

I'm using 2W 5% except the 10 ohm cathode, those I used 1W 0.5%. There also is a pair of 3 watt ones on the front end of the amp.

[@Willywonkaz]

@@SkunkieDesignsElectronics Thank you. Can you give us the Product Number of the capacitor? Thanks!

[@mike212916]

When you create a parts list for these caps and resistors please use the highest quality parts.

[@SkunkieDesignsElectronics]

Well there is a point of diminishing returns. I am using Vishay Metal film resistors, and a mixture of Audio Note "standard line" caps and Nichicon. I'm sure there are some $$$$ resistors and caps one can use, I don't plan on listing those.

[@mike212916]

@@SkunkieDesignsElectronics That's true. I have no idea how much these parts all cost as well. I know you havent finished the upgrade yet but do you have a general ballpark has to how much $$ this upgrade will cost?

[@SkunkieDesignsElectronics]

@@mike212916 It's hard to say and I'm probably going to do more than many people would be interested in doing. Part of what I plan to do is just my anal retentiveness about lead dress and wiring layout lol.

[@mike212916]

@@SkunkieDesignsElectronics Well if you make good tutorial I will also do the same haha.

[@BobTrainor]

Hi Skunkie! I’m really enjoying this R8 series. I own an R8 and my amp does not turn the speakers off when I plug in my headphones anymore. It used to turn them off. Can you look at how Willsenton handles that function. It would be interesting to see what could potentially go wrong with their design. Not much of a headphone guy myself, but sometimes you need to be quiet 🤫

[@SkunkieDesignsElectronics]

I will look at that later :)

[@patrickmccrank8414]

First, I really like this series. Second you give warning not to try this, then show how to do this.?? Third, you have links for tolls but no links for capacitor or resistors. Unless it the same as the tools. And most importantly, what do you charge do perform this service? IOW is this your business? In which case how about a link to your website.

[@SkunkieDesignsElectronics]

I warn people not to do this if they don't understand how to work around high voltages. There are lethal voltages inside. I do plan to put together a list of parts when I am finished and know for sure what the results are. No, this isn't a business, just a hobby I share with people. www.skunkiedesigns.com

[@patrickmccrank8414]

@Skunkie Designs Electronics too bad. These mods, I'm sure will help not just with better audio but also the longevity and safety of the amp. I was ready to send my R8 to you for the upgrade. Oh well, thanks for the entertaining videos.

[@inerlogic]

$1500 amp red-plating and humming with cheap components? Nice....

[@SkunkieDesignsElectronics]

The red plating wasn't the amp's fault, the owners house had a wiring issue that put 150V on the outlet. But yeah, it's a made in China amp trying to be a $4000+ tube amp for $1400.

[@paulconteyoutubesucks2931]

Hey happy new year so happy to see you again 💗