Reisong owe you some serious credit. The fact you pulled this one back from the brink is really something.🙂

I watched all the A12 mod videos and finally finished my amp. I upgraded to Sovtek 5AR4, JJ EL34L and Genalex Gold Lion 12AX7 (regular) tubes. I also used 620K p-t-p feedback. I am running this amp to 1986 Klipsch La Scala speakers with the AL crossover. This is my first tube amp and first mod attempt. I don’t have measuring equipment, just my ears. Before mods, I thought the amp sounded very raspy and grainy. High frequency sounds were harsh and fatiguing. After mods I can definitely hear much cleaner and clearer vocals and more pronounced and pleasing dynamic range with improved bass. I would like to thank Skunkie Designs for all the time and effort you put into fixing this amp and creating the videos. I will definitely enjoy this amp regularly now.

Mod complete worh Pro-ject speaker box bookshelves. Used 560k feedback resistor. Much improved. Even more volume which I definately needed . thank you for everything!

Stephe ROCKS! Ignore anyone who says different. I have had a Reisong A10 (not A12) for several years gathering dust. It just didn't sound very good to me, even after tube rolling in some NOS tubes. I followed her videos here, and the results were frankly amazing! SO much smoother, much better bass and overall enjoyment. I am actually playing with the Schade resistor value a bit. It's a bit bright for my speakers, but I can't say enough about this upgrade. For very little cost, this is now a nice little tube amp that I will use regularly. THANKS, Stephe!

Thanks Skunkie for the amazing mod and in depth videos - this amp is so much better without the distortion and cleaner at higher volumes! For anyone interested, I settled with 620k Schade feedback resistors. Nice rounder sound than stock, with a touch more warmth. Using Monitor Audio Silver 100 bookshelf speakers

Well, I did the mods to the letter as described in this video and it's predecessor. Mine started out as an A10 which I rewired to an A12 firstly so I didn't have to use converters. As well as Skunkie's changes I also changed the smoothing caps to better quality (Rubycon and Panasonic) and changed the feedback caps to Miflex. Powered it up and straight away there is a considerable improvement in the sound quality of this amp. Much more body and real power and clarity. The feedback resistor I'm using is 820k and that sounds just fine through my Snell Jii's. The PT does get much warmer after a couple of hours playing but not too hot to touch. I'm a newbie to DIY audio so if I can do it then I would expect most people could if they follow carefully Skunkie's instructions. Thank you for your time and your detailed videos.

Great job on part 2 and love your excitement on how well it sounds after your simple tweaks. 😀

love the gas pedal/brake analogy

Truly appreciate this series of video on making the A10 / A12 a better sounding amp. Thanks a lot Stephe. And in regards to the feedback resistor, I played around quite a bit, from the lowest 470k, 520k, 570k, 600k, 620k, 660k all the way to 820k. To me with my speaker set up (a pair of Klipsch RB-51 II bookshelf), 660k seems to sound best. Anything below 570k does add quite a bit of bass, but on some songs I listen to everyday, it starts sounding too warm and lose a bit of airiness, detail and holographic effect. And anything above 700k sounds too bright to me. Also for those of you with the A10, I didn't convert the driver tube to 12AX7, I simply cut half of triode as what Stephe did, ground one side of it completely and also ground pin 9, and it works just fine. I m not sure if the 12AX7 will sound better than the 6N2, to me seems like they have very similar characteristics, and the 6N2 although the choices are quite limited, they are considerably cheaper than most 12AX7. So for now I just stick with the 6N2 until they burn out.

Just finished the mods on my A12. Holy cow it’s so much better now! I was really disappointed with the amp when it first arrived, I ordered it seeing some glowing reviews. Your mods have totally made this amp a pleasure to listen to now! Thanks for everything you do!!!!

Skunkie, did mods on A12 , noticed huge improvement in Bass at lower volumes I use. I use Reference 3A Dulcet speakers with Berlarim tweeters, equals bright sound, I played with 820K , 300K, 470K and finally settled on 600K to balance the tone to my liking. I feel this feedback resister option is the key to voicing your amp to your speakers. This is the best lesson on amp modding I have ever found, most appreciated. Brian and Kathy Orr (Niagara Falls, Ontario)

I ordered the parts today, I’m ready to give it a try. Thanks so much for the detailed videos.

Just finished doing your mods to my A10 now A12 and I had to send you a comment. It really does sound much better. Went with your BOM and I'm using RP400M speakers with a Polk Sub for now. Can't wait to try it with my Cornwall (original) speakers which are in storage. Thank you so much for doing the work and sharing.

Just finished your mods on my a12! Yes bass is way better. Much clearer richer sound! Right now I'm running a speaker with about 86db efficiency. Can't wait to try this on my cornwall iv when they arrive! Thankyou so much for your videos!

Thanks Steph, Although I am an Idiot concern electronics I have done the changes and I must say, now it really sounds good, not as crappy as before. Only I found it was a little bit difficult to follow the video as far as the resistors values goes but you know I am really a dummy in this fIeld. So again many thanks .

Very well explained and fascinating video. Thanks.

great job, you stuck with it and won

Well Done Stephi Sweetie 💖🙏 Awesome Mods 🎶🎵🎧

modification done, and absolutely loving the sound of the amp now. Thanks so much for your videos!!!!

Thank you thank you thank you love your style

Well done! Bet the owner will be happy.

How true......! Like a brand new amplifier. In each and every respect. Did the job last night. Not only loads of more useable power, but dynamics , detail and punch in a truly other league than stock. Tried both with and without 820k Schade feedback loop. Guess I preferred without, but that is to soon to tell anyway, and will take quite some experimenting and listening to settle. One thing that may be of interest to other guys who plan to do this mod is, the resistors brand and type one choose. Since I had used european dealer hifi-collective England a lot already, I figured I order the components from them instead of Mouser. HiFi-collective are not into general electronics, but niched more towards mid- to upper class audio spec components. The 2W resistors I bought, TKD 2W Metal Film Resistor, indeed seem to be of very high quality, but diameter of resistor itself is about twice that of the Mouser ones you use, and the leads are also much thicker and stiffer, making the adapting and mounting job much more demanding, and also it gets alot more crowded around tube sockets etc. Anyway, Steph, thanks a lot for your good work, and helping me understand what a decent EL34 SE amp should be like. More than anything, I would love to hear your strategy and reasoning for each of the changes you made, and which of them you judged the major bottle necks if any obvious. Now I will only have to get rid of the 50 cycle hum I have, but not due to this mod, but my recently installed remote volume ALPS pot, with total rerouting of the yellow hotwire from RCA in the back etc. It worked nicely until yesterday, so I must just by coincidense have put the wires to close to transformer or similar. Experimentation will most likely solve that tonight after work. Best regards, Magnus

That's a big help. Thanks.

Thank you to explain between SS diodes and Tube Rectifier, I will keep SS diodes as it instead of swapping tube rect.

I completed the Skunkie Electronic Design modification today, definitely worth the effort. It is a big improvement in every way over the original layout. I have also added Miflex coupling capacitors and upgraded the C302 to a Nichicon 330uf 450v also.

Well, yesterday, after many deliberations with myself, I finally proceeded with the mods. Using a 620 k for the local negative feedback, with a pair of 807’s on a pair of Audiovectors sounds exactly for my tastes. With a pair of EL34’s Winged C Svetlana sounds a bit darker for my tastes

IT's the WE local FB trick , seen on many WE old amplifiers ..............and yes , it works fine , one can listen and adjust the value , ( also with the driver tubes chosen this may vary )..............one can even get rid of overal NFB and stil have extreme low distortion on low signals ( less than 0.01 % with 100 mW output..............( condition is met with the very best OPT !!! ) Nice to study some of these old WE schematics and the results.....

Feed back resistor personal update! Ended up with 315k. Sounds great with my klipsch cornwall iv. Any more and it was just too much treble. But now it sounds perfect for my setup! No noticeable distortion

Love it. Thanx…

Great job with those mods. I’m glad it sounds good too and has nice low end. I’m with you regarding the rectifier tube in this case. I’d swap it out for some diodes and make it solid state rectified. As you said, it’d cool down the PT, and it’d also most likely give you cleaner tighter low end too. My main amps are a pair of Quicksilver mid mono monoblocks which are PP using two KT88’s and a 12ax7 input tube and a 6922 driver with solid state rectification per amp. They’re also completely hand wired. I voided the warranty of em within a week by upgrading a few parts. So, like you were saying, if you’re gonna modify something don’t plan on sending it back for repairs. The beauty of it, is that amps like the A12 and my Quicksilvers are easy to work on, and you can own em forever with little to no issues. Another excellent vid! Thanks!

Good call on needing to rewire the A10 drivers to a 12AX7’s. I had forgot that. At least I can get rid of the adapters.. Also, I don’t mind a more forward presentation as my ears are damaged by 30+ year’s of working in marine engine rooms. From screaming 2 stroke EMD’s to rumbling MAN’s. Probably why I like horn speakers 😁

When installing a electrolytic cap always point the top so if it decides to pop the insides of the cap won't take out more parts.

I have a A10 and need a little more input gain with the stock 6n2 tubes. Do the stock pre driver tubes need a little more drive to get them up? What values to change to?

brilliant as always - hope people understand what your doing here - ive seen some pretty ugly FB comments regarding all of this !! - i mentioned to you before about the boyuurange el34 kit - available through douk store - its the one with the gold trim front panel - its a good kit but i wonder if you could get hold of one and do a series on it with your added advise -- all the best - lovin the videos

Love the channel!! Can you you supply the list of components needed for the mods? I want to try doing the mods myself. But just wanted to make sure I get the right resistors value and caps value. Thanks again for the great job!!!

Loved watching these. Thanks. As a noob, can these mods be applied no matter what the domestic voltage is? Just wondering if the changes are the same for 240V mains.

Update: I (you) finally did it. After messing around with values and stuff which got me nowhere, I got my 5AR4 rectifier tube (I was using a 5V4), plugged it in and WOOOWW. Everything sounds great now and instruments are finally in place. You really did it! But, of course, now I want a little bit more... If you wanted to improve the soundstage (deepness/3-dimensionality of the sound), what would you try? Replacing the orange coupling cap? Bypassing the electros with some 0.1uf film caps? All ears on your recommendations. Thanks a lot!!

Hi Steph, great video. I replaced the Chinese rectifier a while back with a NOS 5V4G. Can I keep that rectifier and do the mod or should I replace it with a 5AR4?

What do you consider as an audio grade cap? I always thought that fb is to be returned to the cathode of the driver tube/valve.

Can I power up with the 250r resistor and 470uf only added? I am.waiting on other parts. Thank you for all this i am so amazed at your vids. So inspiring.

Question: Do you ever blow on the solider to cool it off or do you let it cool naturally?? Is one better then the other???

Hi Steph, I’m going to do your mod this weekend. While I have the unit open, I was thinking about upgrading the C302 from the 150uf 450v to a 330uf 450v. I have a nice Nichicon in hand, do you think that would work without any problems?

Great vids and mods, thanks a lot! I'm completely new on this. Could you tell me if this can be done even if I've already put it in triode mode? And one more thing, sorry for that. If I wanted to replace the potentiometer for an ALPS one, could you tell me the specs for it so I can find it? Thanks again!

Skunkie could the reisong badge fall off in time, is it glued on or taped? And do you sell similar sized Skunkie design badges for the builds that you design if we build them. Do you have a merch shop. Would love you to send your version off to some "Audiophiles". :) How about some decent caps and tubes next. Wonder how that will work. Please dont leave it here. In uk its so expensive and hard to get decent iron etc, modding is a serious option. Interesting about the bass response love el34 but rarely use them due to lack of punch and bass v my music taste. Please keep doing what you are doing.

Phenomenal series. May just give this a shot! Does the volume control need upgrading and/or does it bypass in full volume mode? Thanks so much for the videos. 👍 PS - if you sold mod packages to go along with your videos, I’d be first in line.

Got my A12, out of the box it sounded pretty good after I cranked up the output of my Schiit Mani to 48db of gain. Measured about 1.4W just before clipping but the top of the wave was fatter than the bottom. Noticed some component value differences from the original schematics you posted. B1 filter cap was now 220uF instead of 150uF, and the ultra linear tap resistor was 10 Ohms instead of 100 Ohms. Wonder if it was the same on your unit or if they changed the components. Anyway, mods on the works now, looking forward to giving it a listen when complete. Thanks!

Semi-Advanced question; You mentioned some additional tuning by changing the negative feedback resistor from 820k to perhaps 600ish or even 470k. I agree w you (on my speakers also) it still is a bit bright. I was going to try some 620K and possibly 470k/430k. What are your thoughts? Any recommendations or additional mods to mellow out the tone would be greatly appreciated. Your videos and this experience has inspired my DIY itch and I plan on building some stuff from scratch soon. Thank you again for your awesome work!!!!!!

Hi Steph.Brilliant video.I own a Reisong A10 with 6N2J driver tubes.Can i make the same mods to it as you have wth the 12AX7

I am also curious to know why you wired your grid stopper that way? I generally snip it short, solder it to the grid, then on the other side, I connect the input wire and the grid leak resistor. Just how I see it drawn on other schematics.

Love your videos. I did the recommended mods to my A10. Swapped the pins to fit the 12ax7. Double checked all the wirings. Plugged all gold lion matched pair tubes in and turned it on. Once the rectifier tube was hot, it started sparking all over the place and the speakers were crackling. So i turned it off. I am not sure if the GZ34 gold lion tube blew up or if something else was wrong. So I opened up the amp again to make sure everything is wired fine. I am not sure how to measure the B+ voltage without the rectifier tube in. Any help would be appreciated. I am not sure if I just need to buy a new rectifier tube or if I have a dead amp on my hands. Thanks!

Steph, I have a rather odd question. Sort of new to the tube thing, but I'm very good on solid state. I've always found it odd that an audio output transformer is used on tube designs. I understand why, as I have another friend that actually designs these as well, but my question was more about the limitations or loss in lower bass frequencies. I always understood it that transformers react better to higher frequencies, and granted most modern music like todays rap or EDM might venture into the 60hz bass frequencies, but my question is wanting to know if these audio transformers are able to deliver those bass notes or is it sloped?

On an A10, what if we still want the option of running the original driver tubes? 62np?

Hi Steph, I am glad you stuck with the A12 and resurrected it from oblivion. I was afraid you were going to right it off at one point in your analysis of this amp. As an owner I am very appreciative of your assessment and excellent videos on ways its sound can be improved significantly. Before I try to make any mods on mine can you advise where I can get some good advice on procedures to follow to avoid any shocks when beginning this work. Do you have a video or is there one you can recommend? Cheers and thanks. Peter in Australia.

I’m planning on doings these mods to my A10. After theses mods can I use 12Ax7’s instead of the stock 6N2J’s? Thanks for your work on theses mods and I agree with your sound assessment of the un-modded amps.

Hello can you help me please? I have an A10. I have watched your videos many times and followed them with the schematics. I have built many kit amps. I kinda understand what is going on. Your instructions and explanations are very clear. My question is: if I get a tube converter (6N2P to 12AX7 ) can I proceed with the mods for front end tubes? Say hello to Dolly. Cheers from tropical Australia.

Today I finalized the mod and did first sound check. The amp now sounds on next level. Has more dynamics and bass and more clear on the mids and highs You did a great job with limited financial effords. Will you do more upgrades on this litlle amp, e.g. better couppling caps or what ever. Does a solid state rectifier improve the sound as it will reduce the load on the transformer. lokking forward for more

Can this amp drive a pair of 4ohm Martin Logan 30xti bookshelf speakers with 92db?

I have the A10 which I'm going to upgrade to 12AX7’s, the black wires off the power transformer go to pin 4 and 5 (I used from left pin around to the right pin 1-9 going around clockwise), Do I just move pin 5 to pin 9 and connect pin 4 to 5? Or am I missing something there?

Are the Voltages checked with ohny the Rectifyer Tube or with all tubes in place? With only the Rectifyer Tube installed My B+ = 340 V My B2= 340V EL 34 Pin 3+4 = 348 V But: At the Anode Triode Pin 1 or 6 of the 12AX7 have 380V instead of 250V without the tube installed. With all tubes installed: 310v

Hi Skunkie. I just completed all your mods to my 6P1. WOW what a difference! So, ready to move onto my A10. I want to switch to 12AX7 from the 6N2 in it now, without using adapters. On the driver tube sockets, moving the wire on pin 5 to pin 9, and jumping pins 4 and 5 is easy. But on the driver socket on the left (amp upside down, power and volume facing toward me) there is a wire between pin 4 and ground. I watched your video about 20 times and never once saw the left socket LOL. So, not sure, does that wire to ground stay on pin 4 (which will be 4 and 5 after the 12AX7 mod), does it get cut and removed, or does it get moved to a different pin on the socket or different point inside the amp (after modifying it for the 12AX7? Thanks again!

Can you tell why you doubled the value of the grid leak resistor from 470 k to 1m?

With mods, is this a better amp then the 6P1

Hi guys, I have a a10 and I did some changes on the output tube. My driver tube im using 2ax7 with the adapter my question if i can do this same as a12 to rewire the drive tube thanks to skunkie video step by step instructions and easy to follow … i need more info im a beginner diy my a10 sound better than before for now thanks

I bought this amp over a year ago. Using it with RP600m's for a Rega P2 turntable. I've watched all of your videos on this amp and plan to do the upgrades. What 12AX7 do you recommend to replace the cheap ones that come with it. I will replace the other tubes that you mentioned. Thank you so much for all your time and knowledge about tube amps.

Are you ever going to make a DIY monoblock tube amp setup? Or do you want to make me some nice monoblocks and I'll pay you? Really cool channel that you have here, I've been enjoying it for the last 3 hours!

Oops, missed one more rookie question. I have a Reisong A10 with 6n2p Voskhods, will they still work for it after the mods or I'll have to get some 12ax7s for it?

I would really like to see a picture of the LEFT side of the amp after the mods. I think I have it, but at 4:30 in the morning, who knows lol.

Hi Stephe.I noticed on your modified schematic that you have the 220uf cap on the driver tube and the 470uf on the EL34 tube.Shouldn't they be the other way round.220uf on the EL34

I have a Reisong A10 can I perform the same modifications as the A12?

Houston, I've got a problem. I have the A10, and on the preamp socket I have two different black cables connected to pins 4 and 5. Your video has one connected to pin 4 and jumped to 5 and then another one to pin 9. Pls help me on rewiring that so it remains the same as yours. They seem to come from the same pins on the other channel's socket. Do I just need to unsolder pin 5 and solder it to pin 9 making sure I connect it to the same pin on the other channel? And putting a jumper from pin 4 to 5? BTW, my A10 also had a cap from pin 7 to ground, which I've removed, is that ok?

Schade is pronounced "Shah-duh". It's a German surname and comes from the guy that wrote an article about plate to plate local feedback back in 1938, O.H. Schade. Great series of videos on the amplifier though.

Hi, how come the mods are only on one side?

For the remaining half of the 12ax7 , if we connect this 12 ax7 to SRPP. For yor oppinion will we got any improvement of the better sound?

Very nice. I'm happy to see your results were so positive. On your driver stage, did you consider using a 220k plate resistor? The load line might appeal to you more with your voltages. I just removed that rectifier and did a bridge with 4*MUR480E rectifying diodes. Slightly more B+ (349) even with the 8.2k and 2x10R on the pcb. I dropped a 680k from plate to plate and removed my global feedback from the 4-ohm tap to the 12ax7 cathode resistor, and I am happy with the results. I did not add the 220uf bypass cap, however.

Does anyone have the (BOM). I think I have all the parts figured out for the modification. I would like to check to make sure before I place the order. I’m new at this and don’t have any spare parts laying around. Any help would be greatly appreciated. I don’t know about you Guys an Gail’s, but I dearly love this channel !!!

Firstly let me just say I love your channel and I don’t doubt for one minute that the A12 was pretty poor in every respect. However, Im just playing devils advocate here because im seeing more and more analytical testing of kit without any consideration as to what it sounds like and how it was voiced by the manufacturer right from the start. Heres the issue I have with the way you undertook the process. You carried out tests on the amp and the results were very poor, you then listened to it and confirmed it sounded terrible. Some might say that because of your findings in testing you were already predisposed to its sounding bad? You then did the mods and listened to it and its very much improved and again some might say that you were already expecting it to be better. Ive seen this with Danny at GR research, he tests everything and rarely listens and suggests that his mods will make a massive improvement in various speakers and berates manufacturers for making speaker that perform badly in testing. The ONLY way to really undertake this sort of testing is for someone who has never heard the A12 to listen to one that hasn’t been modified and one that has in a blind test. Granted the specs might look way better after the mods but that doesn’t necessarily mean that it will sound better in all instances. I have no axe to grind, I just think that there are flaws in the way that this sort of testing is done and then presented.

You can buy the A10 for $400