Willsenton R8: Final Thoughts Willsenton R8 Tube Amp
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- Опубліковано 7 лип 2024
- This is the final wrap up video for this series. I go over some corrections and clarification of some details based on questions I have received. Then I walk through prioritizing the mods and then a final evaluation of this popular push pull Vacuum tube amplifier.
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.
The BOM and final schematics are here:
www.skunkiedesigns.com/r8-mods
A great book for DIY amp building info!
Morgan Jones: Building Valve Amplifiers.
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You can buy this amplifier here
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If you would like to join my Patreon to help support the channel:
www.patreon.com/user?u=87080658
Or donate on my website:
www.skunkiedesigns.com/donate - Навчання та стиль
Thank you Skunkie for this excellent series!
Thanks Stephe, I have really learned a lot about my amp from watching your videos. You do a fantastic job!
Thank you for a great series Stephe. It really helped lots of people
I'm so glad!
Thank you for sharing all of your work, are really looking forward to doing these mods.
Much appreciated!
Really like all the changes you did. and the fact that you explained so clearly why they were needed. I think the choke is a very good upgrade too.
Your series are just so well done and enlightening! Thank you!
Glad you like them!
A million thanks for all your hard work, enthusiasm, expertise & being truly grounded & honest! I now know, I made the RIGHT first decision to get into tube amps & taking this plunge into this amazing budget tube amp with proper tweaks & upgrades. You & many other audiophile technicians & specialists add more value to the music we all listen to. You command my respect & all your loyal followers! Love your channel!
I appreciate your work.
You have great educational skills,
a nice way of speaking and listening to. Thanks!
Great series and review Stephe. Loved it.
Thanks so much!
LOVE IT!!! Thank you for such a great project!! So motivations. GREAT STUFF ❤❤❤
I really enjoy your expertise and candor. From one audio lover to another:) One of these days I'll retire and jump with both feet in, not just listen, but do. If it gets to hard I'll rent a travel van and hand deliver it for your tlc. Thank you Skunkie!
I would wear a Skunkie tube tee shirt. Just saying...
Thanks so much for this R8 mod series , ive sent you a donation for all your hard work 👍
Much appreciated!
Well done! You've clearly analysed this amp and your advice is very valuable. I now need to find an expert who can work on my amp as I am totally incapable of doing this! Many people will be grateful to you.
I loved this series. I trust your work so it is meaningful and much appreciated. I also think this is a good amp. Especially since I can't spend double or more on something that might be better. Great Great job as always. Thank you
Glad you enjoy it! And I've honestly been tempted to buy one for myself.
@@SkunkieDesignsElectronics if you have thought of buying one then I call that a hell of an endorsement.
I am impressed by your competence. One day I will build one of your recommended DIY Kits. Kind regards from Germany 🙂
I really appreciate a more technical look at these amps which other UA-camrs love. A more honest and sober look at them.I'm still saving up for the Wilsenton R800i. Am definitely looking forward to you finishing that.
Honestly, from the design flaws I have seen with other Wilsenton amps, I would not buy one of those assuming it was done right.
the R8 coverage was very enjoyable to watch Skunkie, thanks for all of it!! i really hope you get a R300 and gut it, have one and its pretty nice for money, although would be curious about the channel seperation wiring though, feel like something is a tiny bit off... but could be just in my head lol
cheers!
Thank you again for the excellent information you have provided in this series. I just completed all the upgrades in the series with the exception of volume control shielding. It is now back up and playing music too my enjoyment. Two things I ran into, one is after doing the dual rail power mod the amp had a noisy volume control but once I did the star grounding that noise disappeared. The other are the voltages on the schematic are about five percent lower in my amp. For instance the schematic has the power transformer ac output at 345v mine in 320v and the heaters 6.3v mine is 6.1v hence everything upstream is off about five percent. It seems to working great so I have no worries! 🙂
Yeah that's no issue, likely the power transformer was made for a higher voltage than you are using? Hard to say but enjoy!
If you ever do this upgrade for someone else you should do this video series again but with a part kit you sell and the newer knowledge you gained. Because I do remember in the video you redid a thing or two in the next video in the series. For example, you can have a bag of parts for step 1 video. A bag of parts for step 2 video etc.. then you can also have a lot more content on your channel to monitize with more ads. Just a thought
Hmm interesting. Cause yeah, I normally do these "live" and talk through what I am doing and what I am thinking. It's not as much of an instructional video but more educational if that makes sense?
@@SkunkieDesignsElectronics yeah I get it. But this will be a way to monitize the series even more with parts kits and video ads. Example, video 1-2 could be the "Must do mods" and have a parts list for each video. videos 3-4 could be optional with parts kits as well. Then you can sell each parts bag for each video since some people may not want to do the optional upgrade. That way you can easily ship out parts kits too because you can have them premade up. I would personally lay the kit out, take a picture of it, then when using the part in the kit, circle it in red from the picture and then show you installing it.
If you did this I am a very likely customer.
I would buy your parts kits in a heartbeat, along with written assistance so I don't have to be watching all your great videos while I'm working on the amp. Thanks, again for a really great series. I appreciate all your hard work!!
Hi Skunkie, I made the first upgrade to my R8, the bias boards.I put the Mundorfs and Audio notes.As you said it is an audible change in sound.It is more clarity and precision.I am happy.I will do step by step the other modifications.
It is an interesting fact with my Willsenton R8.I bought it last year in May from China hi-fi... and guess what? It has no headphone output! It is like they anticipated your opinion that in a tube amplifier like this the output headphone is not necessary !
I am sure the next R8's will be changed according to your ideas.
Thank you again
Really love this vid series, have parts on order to do all of it to my R8. As for the sand/gravel in the transformers...as I understand it, it is very common to use sand/gravel as filler in the potting epoxy, its not about "making them weigh more". Clearly, there should not be any loose stuff, if that is indeed what is shown in the photo. I've looked closely at mine, no loose sand/gravel, but it does exist mixed in with the epoxy. Presumably the higher end stuff might not do this, but I'll never know, I'm way too cheap. Anyway, thanks Stephe, appreciate your hard work.
Stephe you helped a lot. I got one a year ago and I see that they have upgraded to your recommendations in many cases. For example the 100k bias protection resistors have been added, and the main PSU caps are 500 VDC rated.
There is also a 30 second delay after switch-on before HT is applied to the tubes.
In one of your videos concerning mods to the dual triode voltage stabiliser you omitted the small value capacitor from plate to ground. This cap probably prevents possible HF parasitic oscillation : the impedance of the big electrolytic caps at HF can be quite high. This goes against theory of course, but in practice the construction of electrolytics means that HF is not well decoupled. This from an old RF engineer.
Thanks a lot for your very useful videos.
It was my pic you posted 😂 yeah, that was a disspointment seeing that.. the Yaqin MC100B i had fee years ago (about same price as R8)
Had way bigger OPTs and real dual mono and felt even more money was spent on chassie/ buildquality.
Thanks for this series and all other work you do. Have a great year. I will continue watching your videos no matter what you post. Thanks!
Did you replace the output transformers? I'm looking to but would like to know which part you bought and from where. A link to the output transformers online would be awesome.
I didn't but I too am curious if any other OT fit this amp.
No i didnt but contacted Lundahl in Sweden and very helpful guys… they want some 200 euros (each) for upgrading them.. not sure if i wanna spend more money on this amp atm.. if i do i let you guys know.
I'm gonna do it. I ordered the BOM (except the coupling caps) from Mouser ($116, including tax and shipping). The Mundorf caps are coming from Madisound Speaker Components ($100, including S&H). I'm confident in my hobbyist skills to do it but am feeling a little squeamish about opening a fairly new amp that sounds great. But I know it's for the best in the long run.
Great mods skunkie. The grounding, and PSU caps are a must and worrying to me that they need doing. Worrying too about gravel. If i had one I would definately be doing your mods. Interesting about the mundorf choice, I like them too, also like the odams range of caps, very nice too but a bit more £ though. Good tip about oversizing resistors, I will do this, now too only ever spent £££ on mills wirewound for cathode resistors in my Tubelab SSE, some one recomended I do it at the time. Great that you show people how to improve things for low cost, particularly in this financial climate. My first mod was to a China amp. Then built 3 diy 834 phonos, then a tubelab sse and now I am building point to point amps. Grounding I am starting to understand just now, star grounding confused me for ages, and now I realise how simple it is.
It really is simple.
Thanks Skunkie. Yeah I'll never understand that grounding design.
Yep, very weird.
I very much enjoyed the R8 mod series of videos. Please,please,please, the same on the Willsenton R300 wound be much appreciated. I think it might have a potentially high ceiling with the right mods. I’m hoping part of it’s heft isn’t from sand & rocks under those pretty dark blue transformer covers. From what you found on the R8 , I’m thinking that there’s work that needs done on this amp as well. Thanks.
Thanks again for your reviews and time involved with this,. This amp does sound nice on my KLIPSCH . Like I said in an earlier post if there's a problem sometime I would like you to go through it, no hurry either. ....
I seriously would think about at least adding those four 100K bias board resistors.
Do you accept R8’s for the upgrades you have suggested. If I purchased one, I would have it shipped to you directly. Your body of knowledge is eleventh level. You never even hesitate in thought while conveying technical knowledge combined with the back story’s relating to other products. It’s frankly astonishing.
Hold tight, their newer ones may have most of my upgrades! They shipped me a new version, I plan to do a video on it soon.
Have you reviewed the new version? What upgrades are done or missing?@@SkunkieDesignsElectronics
Hi. Love the series. Im just confused about the GNFB part. Where are the 24k 2w resistors and 330pf mica caps? Pls explain. Thanks in advance. Pls!
❤💪💪
Thanks for all your work. If I take the plunge, what output transformers should I source for the swap? Can you tell me what specs would be recommended? Thanks.
Probably some Hashimoto would make sense.
Thanks for this series on the R8. I wonder if they initially designed this amps power supply just for EL34 tubes then someone had the bright idea of making it work with KT88 tubes and they did the minimal redesign to accommodate those tubes?
Most likely
If this is the case could it be said that the stock resistor values found are suited to el34 tubes and that the upgrades you made are to better accommodate the "hotter" kt88s? I own an R8 and have replaced the stock kt88s with NOS SED "Winged C" el34s and the stock 6sl7 tubes with NOS milspec Sylvanias ($280 total spent). There is no question that this has made a significant improvement in SQ. I wonder if the reason for this is twofold, 1 being the superior tubes and 2 being more headroom or better suited values in the circuitry parts. BTW my amp is dead quiet, no hum to be heard on any input selected. Many R8 owners or prospective buyers may be turned off by your tests and while I do not doubt your expertise I still think the R8 represents great value and great sound for those who aren't blessed with unlimited funds.
Cheers and thanks for your significant efforts!
Hello,
thank you so much for sharing all the steps in improving this amp. And this is done very clearly. For an amateur like me, I feel capable of doing it.
I plan to buy this amp soon.
That said, I live in Europe and I wanted to know if your modifications are also made for 220/230 Volt?
And if not is there another amp that you would recommend in the same budget please?
the only difference would be the way the primary side of the power transformer is wired, the windings would be in series instead of parallel. everything else is identical.
Was looking in your channel if you ever reviewed, worked on, or listened to the Willsenton R800i 300B
No, several people have offered to send me broken ones to fix/review. The crazy high voltage scared me in a China made amp. I honestly draw the line at 550-600VDC
Does adding a tube amp to my receiver from my pre outs add the the current wattage of my receiver or does it just go to whatever I have in my pre output. Thank you for time and videos
No, it's just using the "front end" of your receiver as a pre-amp. The output wattage is whatever the tube amp has.
dear Skunkye, do you think it is appropriate to put a 470k 2watt resistor on the 330mf capacitors to be discharged when the amplifier is turned off?
There already is a voltage drain on these caps via the voltage divider for the heaters.
Hello Skunkie, got to ask what engine is on your shelf behind you? Happy I found your channel. Keep rocking out your vids
I was wondering who would be the first to notice. Yamaha KT100a open class kart racing engine from decades ago when we used to kart race .
@@SkunkieDesignsElectronics A friend of mine used to race at Barnesville and was a protege' of Lynn Haddock.
Hi, I really enjoy your work. Do you plan on doing a series on the Wellsenton 300R? You can work on mine!
Hit me up via my website, I might be up for it in a couple of months.
Thank you, can you help to add the part numbers of the components on the pdf sheet?
No I can't. The problem is these parts come in and out of stock under slightly different part numbers, so then I get endless emails about "Will this one letter different part number with the same specs work?" Or "Can I use this brand of capacitor or resistor instead". Yes, this means you have to do a little bit of this work yourself.
Does the voltage and tolerance on the GNFB Mica Caps matter ? Did you buy yours from Mouser ? Thanks
I don't think they even make these in low enough voltage to be an issue, and value % isn't critical here.
Where and how to do the GNFB mods pls. Sorry im new to this.
Hi Stephe, great videos, but you already know that. I will start doing the mods on my R8 and just wondering if you posted a list of all the parts you used in the R8 project. Thank you!
www.skunkiedesigns.com/r8-mods
In the future this is something I could use some support from a viewer doing, as it's not something I am good at and I end up spending 5+ hours creating these BOMs (and they still end up with errors!)
@@SkunkieDesignsElectronics Thanks for your answer. Including errors on any list is my strong point, so I could help with that. Looks like I will have to figure that out myself, then.
Heeey! You are a mad scientist. Love it.
Have you ever built any of those Elekit amps from Japan? I couldn't find any on your channel, but people say they are pretty good.
Unfortunately not. If someone wanted a built version but didn't trust their skills, I'd be happy to build one for them for the channel.
@@SkunkieDesignsElectronics I can't swing it right now, but maybe someday...
Do you have to disconnect NFB from 8ohm in order to put it on the scope for measurement?
no
Amazing... well done !!! Curious, ever think of providing these mods (e.g. all or nothing) as a service to your audience for a fee ? Also, I wonder if Willsenton is willing to consider these improvements to be incorporated in future builds ?
I'm doing one right now, the biggest issue is shipping these things is $$$$$
@@SkunkieDesignsElectronics perhaps contact Willsenton and see if they would simply think to incorporate these mods, assuming they wouldn't add too much to their price. That would be the key. At under $2000, they have sort of hit the sweet spot many are willing to pay for a tube integrated amp.
@@SkunkieDesignsElectronics I hear you ! Shipping would be at the owner's expense. Seems like a VERY HIGH VALUE service you can provide to your fans... Glad to hear you are able to do it.
Skunkie for the win! Do you have a link to the output transformer that would be a replacement and upgrade? I'm looking to take your advice and make my R8 top notch with replacement output transformers but, I'm unsure which size to buy.
Honestly, I don't and I never measured what was in the amp now, so can't make a recommendation other than I have personally used Hashimoto OT and they are excellent.
@@SkunkieDesignsElectronics do you think you'll end up measuring what's in there when you take delivery of the unit that someone sent you recently?
I wasn't sure if you did the soldering with the tubes still installed or not. Is it safe to leave them in?
I wouldn't. They are easy enough to remove,
My PP doesn't have choke since I heard a lot people said the OPT will cancel out the noise. There is no noise or hum on my speakers. Would it improve anything if I add choke to my PP amp? Thank you
A cleaner power supply is never a bad thing. Given when folks spend on audio gear, spending $30 for a choke seems like money well spent.
Hello, great series, I watched them all. Just bought a Cayin MT-45 mark 3, it looks very much similar to the Wellsenton unit even down to the use of the 6SN7 tubes. Do you think they are manufactured by the same company? Cayin is a much established tube amp manufacturer, I would think Wellsenton is just OEM from them, what do you think?
Yeah I have no idea!
When gnfb mod was made? Missed that part :/
ua-cam.com/video/LD10RvhKNP4/v-deo.html
About the final schematics that can be found on your website.
The voltage at pin 4 of the 6SN7 (long tail phase splitter) is indicated in both schematics as 133 V. This looks like a mistake to me. This voltage should be equal to the voltage at pin 3, so 139.3 V.
If pin 4 would really sit at 133 V, and the cathode voltage being 145 V, the bias of this section of the 6SN7 would be -12 V. But at such a bias, and with 150 V between cathode and plate, a section of a 6SN7 would be in cut-off (meaning: no current is flowing) which would be absurd (and is of course not in line with the voltage drop of 121 V over the 39K plate resistor, indicating a current running through this section of 3.1 mA).
Go measure one like I did. I didn't calculate these, I measured them in the running amp.
@@SkunkieDesignsElectronics
Please do some reading on LTP's (Long Tail Phase Inverters). The voltages at the two grid of a LTP are equal. For dc there is no current flowing through the resistor connecting the two grids so there can't be a voltage drop over it.
And please take a look at the curves in a datasheet for the 6SN7.
My guess is that the resistance of the voltage meter you used caused the measuring mistake. If the resistance of the meter is not extremely high, the current that starts to flow to ground through the 470K resistor connecting the two grids and through the meter will cause a voltage drop over the 470K resistor.
I advise you to measure the voltage between the two pins of the LTP. You then will see that the voltage difference between them is zero.
Bam simple.
Why did you buy another amp? It’s at least 10 by now!
11, now 12, and Skunkie did another mod series on this one.
You bought a new amp so you could fix it?
Yes…..
If the Kitchen remodel isn’t finish first, you’re cut off. Just to be clear.
This isn't my amp. :)
These resistors chipping is IMO ,age...They are OLD. They have warehouses full of them!
Highly likely