Indeed shortest path in mind, absolutely right Gilles 
It matters most for the smallest caps, so the 0.1uF C0G in our case, which really deserves to be as close as possible / have the priority re placement vs the 10uF caps. But no drama in you case... and easy to change should you want it one day.
Well, I mainly wanted to be inventive and to get the OPAs done in a modular way, without any contact risk at the bottom and with the ability to test them on another board beforehand. The only test I could carry out re mods - I couldn't really insert these modules and let the unit go without knowing...
Have a nice WE!
Claude
It matters most for the smallest caps, so the 0.1uF C0G in our case, which really deserves to be as close as possible / have the priority re placement vs the 10uF caps. But no drama in you case... and easy to change should you want it one day.
Well, I mainly wanted to be inventive and to get the OPAs done in a modular way, without any contact risk at the bottom and with the ability to test them on another board beforehand. The only test I could carry out re mods - I couldn't really insert these modules and let the unit go without knowing...
Have a nice WE!
Claude
Hi,
You may want to read the thread, this has been already done and described, even with pix...
Short version
If you think about it, you can't just short it: you need to take it completely out.
And then just put 2 wires (1 for each channel, to connect the corresponding pins again - mass is already continuous). See pix, can be done at the bottom or at the top.
The only way we found to take the damn' pot board out was to dremel it. Desoldering it with a professional continuously sucking desoldering machine, 2 soldering irons, 2 other pumps and 2 quite advanced guys didn't work in our cases (2 amps)... some legs are like glued, perhaps to hold the board in place while soldering it?
Anyway, once you take the vol pot out you get quite a sonic benefit as this is clearly a bottleneck. But you need then a device to enable you to adjust the input level to what becomes a pure power amp.
I hope this helps you, TNT
Claude
You may want to read the thread, this has been already done and described, even with pix...
Short version
If you think about it, you can't just short it: you need to take it completely out.
And then just put 2 wires (1 for each channel, to connect the corresponding pins again - mass is already continuous). See pix, can be done at the bottom or at the top.
The only way we found to take the damn' pot board out was to dremel it. Desoldering it with a professional continuously sucking desoldering machine, 2 soldering irons, 2 other pumps and 2 quite advanced guys didn't work in our cases (2 amps)... some legs are like glued, perhaps to hold the board in place while soldering it?
Anyway, once you take the vol pot out you get quite a sonic benefit as this is clearly a bottleneck. But you need then a device to enable you to adjust the input level to what becomes a pure power amp.
I hope this helps you, TNT
Claude
Dremel the small pot board as we did was the best way we found not to damage anything else. Unsoldering had been impossible for us. Detroying the pot itself, maybe, we did not try. But of course someone else could have a better idea to get rid of the pot ! Feel free to share if you find a better way
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TBH, I don't see a way to destroy the pot that could be more efficient than our simple dremel work. Space is an issue...
I don't remember how the board looks like, but if the relevant tracks all run at the top side (=access) of the board, there could be a way to do 4 track cuts to cut off the 2 channel INPUTS and OUTPUTS without removing the small board.
You to tell us...
Claude
I don't remember how the board looks like, but if the relevant tracks all run at the top side (=access) of the board, there could be a way to do 4 track cuts to cut off the 2 channel INPUTS and OUTPUTS without removing the small board.
You to tell us...
Claude
So, I want to thank all the contributors to this thread. You gave me the confidence to try changing out parts on this amp. I previously had ZERO electronics knowledge, I do however have extensive knowledge of audio and have owned a good amount of quality components over the last 30 years. I have been rolling op-amps on it but nothing that required soldering or replacing capacitors. Im just starting to implement the recommended changes but I wanted to start by changing out the main power caps to see if/how much difference that would make.
I was unable to attain the Nichicon UBY's as theyre out of stock everywhere here but I did get a good alternative until I can get those. I was able to find what looked to be (based on specs) what were after for these amps (low ESR, high ripple, and a short enough cap to fit in this case).
Nichicon UHV1V222MHD - 2200uf
I honestly wasnt really expecting to notice a difference but its actually a fairly noticeable one. I would say a +2 based on the scale used in this thread. Highs are more open and transparent and the lows are more controlled. The overall sound is just cleaner. I would say this took a couple steps closer to sounding like an "Audiophile" amp.
Im also going to do the listed bypasses to see where that gets me but I would recommend at the very least people change out their op-amps and power caps.
I was unable to attain the Nichicon UBY's as theyre out of stock everywhere here but I did get a good alternative until I can get those. I was able to find what looked to be (based on specs) what were after for these amps (low ESR, high ripple, and a short enough cap to fit in this case).
Nichicon UHV1V222MHD - 2200uf
I honestly wasnt really expecting to notice a difference but its actually a fairly noticeable one. I would say a +2 based on the scale used in this thread. Highs are more open and transparent and the lows are more controlled. The overall sound is just cleaner. I would say this took a couple steps closer to sounding like an "Audiophile" amp.
Im also going to do the listed bypasses to see where that gets me but I would recommend at the very least people change out their op-amps and power caps.
Hi there
Well done!
Yes, replacing the PS caps can give some benefits. On the other hand, cheaper, easier and probably as efficient is to bypass these the way we did it. Further cap tuning (at our SMPS filter output) didn't really improve things.
You can still try the 2x2.2uF + 0.1uF bypass on your new PS caps though, it may give some further benefits (I guess so, but probably a tad less than starting from the OEM caps). In fact, once properly dimensioned and bypassed, PS "caps assembly" are likely to sound close regardless the starting point / initial big 'lytics.
Regarding opamps, sorry, I know no comparable device and no close one in "big size". Some seem to like AD843, OPA627 etc.: you to try.
I would though really recommend to go for OPA1656 and its PS bypasses, regardless the extra cost... it would probably cost 10 times more to get comparable sonic benefits elsewhere on a hifi system as that is a real bottle neck on this unit.
Enjoy
Claude
Well done!
Yes, replacing the PS caps can give some benefits. On the other hand, cheaper, easier and probably as efficient is to bypass these the way we did it. Further cap tuning (at our SMPS filter output) didn't really improve things.
You can still try the 2x2.2uF + 0.1uF bypass on your new PS caps though, it may give some further benefits (I guess so, but probably a tad less than starting from the OEM caps). In fact, once properly dimensioned and bypassed, PS "caps assembly" are likely to sound close regardless the starting point / initial big 'lytics.
Regarding opamps, sorry, I know no comparable device and no close one in "big size". Some seem to like AD843, OPA627 etc.: you to try.
I would though really recommend to go for OPA1656 and its PS bypasses, regardless the extra cost... it would probably cost 10 times more to get comparable sonic benefits elsewhere on a hifi system as that is a real bottle neck on this unit.
Enjoy
Claude
Can you order at digikey? I believe I got my adapters from them and they sell one type in a pack of 4 that are reasonably priced.
Im definitely doing all the bypass caps as well, but wanted to do the main caps first. I actually am not as big a fan of the OPA1656's that everyone else seems to be. Theyre a bit too "colored" for my taste. My personal, current favorites are the vastly cheaper, simpler, LM4562's. Ive tried roughly a dozen and mostly like all of them but these stand at the top for me. The other one I really like and is equally great, again for me, is the even cheaper RC4560IP. That chip just does so much right for my setup. I havent really cared for any of the OP/OPA chips Ive tried as all of them see to be very "V" shaped to varying degrees. I prefer a more neutral sound personally.
Regarding the Nichicon caps I referenced above. This new found "clarity" did come at a cost of less bass. I think dropping to 2200uf caps probably affected that as my understanding is that lower capacitance caps cause higher resistance at low frequencies. Im getting some 4500uf United Chemi-con caps to try out. These have a very low ESR (22mOhm @ 100kHz) so I have high hopes for their quality, plus I want to test the affect of going up in capacitance as well.
Ill keep posting updates and findings as I have them but this is definitely a fun, new hobby to mess with. I wish someone would have told me how big this potential rabbit hole was before I started though.....lol....Im heading deep down it now.
My end goal with all of this is to get enough knowledge to build my own amp, potentially from scratch. Id also like to find/make a pwoper power supply for this. The Meanwell 200-36 looks very nice but I need something with a case. Still low on my priority list but Im certain a real power supply would help a lot vs the 32v 5a Aiyima one Im using.
Side note.....I would have NEVER guessed, even in all the years Ive been an audio lover, that such small changes can so drastically change the perceived sound an amp puts out. Its actually stunning to me.
Regarding the Nichicon caps I referenced above. This new found "clarity" did come at a cost of less bass. I think dropping to 2200uf caps probably affected that as my understanding is that lower capacitance caps cause higher resistance at low frequencies. Im getting some 4500uf United Chemi-con caps to try out. These have a very low ESR (22mOhm @ 100kHz) so I have high hopes for their quality, plus I want to test the affect of going up in capacitance as well.
Ill keep posting updates and findings as I have them but this is definitely a fun, new hobby to mess with. I wish someone would have told me how big this potential rabbit hole was before I started though.....lol....Im heading deep down it now.
My end goal with all of this is to get enough knowledge to build my own amp, potentially from scratch. Id also like to find/make a pwoper power supply for this. The Meanwell 200-36 looks very nice but I need something with a case. Still low on my priority list but Im certain a real power supply would help a lot vs the 32v 5a Aiyima one Im using.
Side note.....I would have NEVER guessed, even in all the years Ive been an audio lover, that such small changes can so drastically change the perceived sound an amp puts out. Its actually stunning to me.
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thank you CTfrommn. I placed an order for the opamps you mentioned. Easy drop in replacements to give it a go. Hope I don't blow my new amp? I love it very much stock, but it has (to my ears) a nasty ringing sound at high frequency, like Styx lead vocal guy, along with just a smidge of simblance? It only has an hour of run time on it though
Op amps... taste and colours, glad you find the ones that suit you most. I wouldn't call myself the OPA1656 anything but neutral and musical - providing it has admittely a good PS, but that's just me and not the debate anyway. First time in 2 decades I diverge from AD, so must say something though, GLOL
Whatever you do, consider that this Aiyima amp isn't perfect, so depending on your system resolution and taste you may want or prefer OPAs that kind of "correct" the overall sound so your entire system experience is even more enjoyable. At least, that's the way I considered it, so no absolute terms or amp here.
Whatever you do and OPA you go for, please consider that in our experience the OPA PS of this Aiyima can be bettered and if not modded detracts the sound of the OPA quite a bit. In short, whatever your favourite OPA, please consider at least trying decoupling the OPA PS rails with 0.1uF C0G and possibly with your favourite mix of 'lytics and or X7R( and or PPP if you find the space LOL) to add at least 10uF at the pins directly, 20uF being possibly more suitable IME on various units. More not necessarly needed.
Regarding the PS caps, Class D differs quite a bit from traditional Class A or AB amps in terms of PS requirements. I am not sure adding capacity, as one would wish to do for traditional amps, is key. Low ESR and ripple ability far more though, and can indeeed sometime come with bigger caps. We need quick caps to follow HF current calls... Bypassing helps, as better caps to start with, capacity increase without the right specs not so sure. Same capacity with much lower ESR and higher ripple quality caps, on the other hand should be great. Bypasses aswell, which also reduce ESR, although in some frequency bands...
If experimenting - my understanding being that you like to play and learn- it might be advisable therefore not to mix capacity increase with lower ESR in one go, to perhaps taste the tendencies separately? But whatever, it will be nice to read you!
Last but not least, building your own amp: GREAT! There is new promising chip amp project here in Class A/B since Xmas, it might also hint to a different sonic signature from your Class D... and plenty really high end amps in the Pass section or by Fab. Or perhaps one day you create a Class D kit if sticking to that technology, or a FDA, who knows
The Meanwell 200-36 looks very nice but I need something with a case.
=> Why not building your own case around of it, or adapting one?
And leave some provision/space for a SMPS filter. Mark is working on a new SMPS filter for 6A needs, should be another winner and better than the one I very quickly designed. I am looking forward to Mark's work and if it would haven been already around while I was still on that Class D project I would have gone for it.
Enjoy tweaking very much and keep us posted
Claude
Whatever you do, consider that this Aiyima amp isn't perfect, so depending on your system resolution and taste you may want or prefer OPAs that kind of "correct" the overall sound so your entire system experience is even more enjoyable. At least, that's the way I considered it, so no absolute terms or amp here.
Whatever you do and OPA you go for, please consider that in our experience the OPA PS of this Aiyima can be bettered and if not modded detracts the sound of the OPA quite a bit. In short, whatever your favourite OPA, please consider at least trying decoupling the OPA PS rails with 0.1uF C0G and possibly with your favourite mix of 'lytics and or X7R( and or PPP if you find the space LOL) to add at least 10uF at the pins directly, 20uF being possibly more suitable IME on various units. More not necessarly needed.
Regarding the PS caps, Class D differs quite a bit from traditional Class A or AB amps in terms of PS requirements. I am not sure adding capacity, as one would wish to do for traditional amps, is key. Low ESR and ripple ability far more though, and can indeeed sometime come with bigger caps. We need quick caps to follow HF current calls... Bypassing helps, as better caps to start with, capacity increase without the right specs not so sure. Same capacity with much lower ESR and higher ripple quality caps, on the other hand should be great. Bypasses aswell, which also reduce ESR, although in some frequency bands...
If experimenting - my understanding being that you like to play and learn- it might be advisable therefore not to mix capacity increase with lower ESR in one go, to perhaps taste the tendencies separately? But whatever, it will be nice to read you!
Last but not least, building your own amp: GREAT! There is new promising chip amp project here in Class A/B since Xmas, it might also hint to a different sonic signature from your Class D... and plenty really high end amps in the Pass section or by Fab. Or perhaps one day you create a Class D kit if sticking to that technology, or a FDA, who knows
The Meanwell 200-36 looks very nice but I need something with a case.
=> Why not building your own case around of it, or adapting one?
And leave some provision/space for a SMPS filter. Mark is working on a new SMPS filter for 6A needs, should be another winner and better than the one I very quickly designed. I am looking forward to Mark's work and if it would haven been already around while I was still on that Class D project I would have gone for it.
Enjoy tweaking very much and keep us posted
Claude