Anyone played with the OPA1688 which comes in SOIC8 package which may be simpler to implement than OPA1622 ?
Thanks for the link on the linear power supply. I will consider it for my next DIY project. I am also waiting for Nelson Pass to release his new design for a single-ended Sony VFET Class A amp. I built the previously released Sony VFET amp, and it is impressive to say the least.
In the meantime, I am enjoying my Aiyima A04 TPA3251 2.0 in my living room system driving my KEF LS50 monitors. The Burr-Brown OPA627AU op amps I currently use were purchased from e*** seller alice1101983 for $3.68/ea. (3.38 Euros/ea). They are either fakes or they are used for the seller to offer them so cheaply, but I took a chance and they sound like the real OPA627AU op amps to my ears:
- Detailed
- Lush midrange
- Strong, articulate bass
- Large, deep soundstage
I purchased more of these OPA627AU op amps on DIP8 adapters from the same seller, and installed them in an Aiyima A04 amp I lightly modified for my friend in California who replaced his dying C-J MV75-A1 tube amp. He is very satisfied with this amp and he is using a low cost, brick-type 30V/5A switching power supply from e*** seller best_tech.
When I get my order from Mouser, I'll post photos of installing the Coilcraft MA-5173 inductors. Working with the Aiyima amp's chassis and PCB is pretty easy. I would really encourage people to use their favorite hookup wire to connect the PCB outputs to the speaker binding posts. Replacing that cheap wire and touching up solder joints for the signal path thru-hole components on the PCB makes an audible improvement.
Intrigued by the comments I read here, I decided to have a very quick ‘closer look’ at the AIYIMA TPA3251 amp. I don’t have the schematic and it is very difficult just based on pictures to deduce what has been really engineered, but randomly below a few potential ideas in hope they might open a discussion to those who seem to enjoy this unit.
Just as a pure side note, as for myself I am somewhat mitigated with FDAs and Class D amps, although never having listened to ones in the 5 figure bracket. On one hand I recommended 2y ago an AD18 to a friend of mine, had a look at it inside and tested it and it really was great fun for the money. On the other hand they aren’t IMHO (yet ?) giant killers. At the end, listening to a few chinese units, I came to the conclusion they are worth 4 to 10 times their price, which is already great news. But the thing is you can find excellent A/B amps at reduced prices, so that carefully spent 400E give you usualy already better results (equivalent sonics and better reliability or ability to drive complex loads etc.) and TBH I personaly don’t want lower HIFI than that. Of course regarding space and heat management they are VG… but I found them also not as good as A/B amps with LS presenting difficult impedance variations, nor VG at 2D imaging and natural flow. But again, some sonics traits are interesting (bass control) and encouraging. Anayway, it would be interesting to read how far one can go before chips with feedback loops including the LS load will be made available. ALL IMHO !
With all that in mind, I can’t help thinking about tweaking them, keeping in mind one shouldn’t probably spend more than 70E on tweaks as diminishing returns and probably hit a natural sonic limit is also hit whatever you do, so rather looking here at stupid mistakes or bottlenecks in the Aiyima. ALL IMHO, I don’t even own these devices…
The obvious:
- Replace the 2 entry Op amps with OPA1656
- Fit a decent PS and possibly add capacity at the SMPS output before entering the unit… or go linear PS but not sure worth the cost vs previous SMPS+caps
- As already posted, trying 4 better output coils seems a good idea (usual suspects)
The less obvious:
- I believe I see 10uF caps at the power chip analog input, electrolytics, as per TI datasheet. I suspect TI might have been quite conservative here. Entry impedance of the chip seems to be 24k so one could probably do with 1.3uF DC (cutt off -3dB at 5Hz… or probably even go for a lower capacity if not using full range LS) decoupling caps and that opens the door to PPP or MKP caps. Space is tight, one would probably have to fiddle a bit to put small and affordable ones in place of the existing electrolytics… or go the risk to slightly open a loop and fit them on the empty side of the main board where there seem to be plenty space… DC 940s might be too big (?), but Panasonics, Vishays or Wima polyprops could already be an improvement
- I can’t see if that amp has a remote volume control. If yes, ignore what is below, the volume knob being digital command only probably. On the other hand, it seems to me that the volume is really managed by a tiny entry pot on the additional small board. If so, then it is probably advisable to replace it by a better one, those small no names are notoriously robbing quite a lot of the music signal (see my B1 Korg report on potis). The Tocos Cosmos would be great, but would it fit at all (sideways? Some pix show even a higher hole on the front plate ?). The Tocos is excellent and non expensive, one has to consider cost of course
- I don’t know if the 1000uF PS proximity caps for the chip are adequate (sounds low ?) re impedance and energy for deep bass, I am unsure if it is worthwhile increasing or changing their value in situ -but I would add some on a remote outboard. One might wonder if decoupling from below the board these 1000uF with say 1uF and/or less could be a plus (without introducing oscillations.)
- Wonder if there are other electrolytics in the signal path at the entry, I can see quiet a few 10uF ones… of so, worth digging as per above. Or are these PS caps in which case worth decoupling them ?
All this shouldn’t be too expensive nor difficult to test while being retroactive in case it doesn’t work as expected. It could quite enhence what seems to be already a fine unit while keeping things reasonably in line re budget and potential results.
There might be other paths or this could also be BS or rehearsal of what has been already posted - I am just thinking loud and again I don’t even own the unit nor did anything else than having a quick look this morning at the pix posted by Daniboun, so pardon my intrusion !
Good luck either way
Claude
PS : wonder how say an AKITIKA would fare against this amp, has anyone compared ?
Just as a pure side note, as for myself I am somewhat mitigated with FDAs and Class D amps, although never having listened to ones in the 5 figure bracket. On one hand I recommended 2y ago an AD18 to a friend of mine, had a look at it inside and tested it and it really was great fun for the money. On the other hand they aren’t IMHO (yet ?) giant killers. At the end, listening to a few chinese units, I came to the conclusion they are worth 4 to 10 times their price, which is already great news. But the thing is you can find excellent A/B amps at reduced prices, so that carefully spent 400E give you usualy already better results (equivalent sonics and better reliability or ability to drive complex loads etc.) and TBH I personaly don’t want lower HIFI than that. Of course regarding space and heat management they are VG… but I found them also not as good as A/B amps with LS presenting difficult impedance variations, nor VG at 2D imaging and natural flow. But again, some sonics traits are interesting (bass control) and encouraging. Anayway, it would be interesting to read how far one can go before chips with feedback loops including the LS load will be made available. ALL IMHO !
With all that in mind, I can’t help thinking about tweaking them, keeping in mind one shouldn’t probably spend more than 70E on tweaks as diminishing returns and probably hit a natural sonic limit is also hit whatever you do, so rather looking here at stupid mistakes or bottlenecks in the Aiyima. ALL IMHO, I don’t even own these devices…
The obvious:
- Replace the 2 entry Op amps with OPA1656
- Fit a decent PS and possibly add capacity at the SMPS output before entering the unit… or go linear PS but not sure worth the cost vs previous SMPS+caps
- As already posted, trying 4 better output coils seems a good idea (usual suspects)
The less obvious:
- I believe I see 10uF caps at the power chip analog input, electrolytics, as per TI datasheet. I suspect TI might have been quite conservative here. Entry impedance of the chip seems to be 24k so one could probably do with 1.3uF DC (cutt off -3dB at 5Hz… or probably even go for a lower capacity if not using full range LS) decoupling caps and that opens the door to PPP or MKP caps. Space is tight, one would probably have to fiddle a bit to put small and affordable ones in place of the existing electrolytics… or go the risk to slightly open a loop and fit them on the empty side of the main board where there seem to be plenty space… DC 940s might be too big (?), but Panasonics, Vishays or Wima polyprops could already be an improvement
- I can’t see if that amp has a remote volume control. If yes, ignore what is below, the volume knob being digital command only probably. On the other hand, it seems to me that the volume is really managed by a tiny entry pot on the additional small board. If so, then it is probably advisable to replace it by a better one, those small no names are notoriously robbing quite a lot of the music signal (see my B1 Korg report on potis). The Tocos Cosmos would be great, but would it fit at all (sideways? Some pix show even a higher hole on the front plate ?). The Tocos is excellent and non expensive, one has to consider cost of course
- I don’t know if the 1000uF PS proximity caps for the chip are adequate (sounds low ?) re impedance and energy for deep bass, I am unsure if it is worthwhile increasing or changing their value in situ -but I would add some on a remote outboard. One might wonder if decoupling from below the board these 1000uF with say 1uF and/or less could be a plus (without introducing oscillations.)
- Wonder if there are other electrolytics in the signal path at the entry, I can see quiet a few 10uF ones… of so, worth digging as per above. Or are these PS caps in which case worth decoupling them ?
All this shouldn’t be too expensive nor difficult to test while being retroactive in case it doesn’t work as expected. It could quite enhence what seems to be already a fine unit while keeping things reasonably in line re budget and potential results.
There might be other paths or this could also be BS or rehearsal of what has been already posted - I am just thinking loud and again I don’t even own the unit nor did anything else than having a quick look this morning at the pix posted by Daniboun, so pardon my intrusion !
Good luck either way
Claude
PS : wonder how say an AKITIKA would fare against this amp, has anyone compared ?
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I read your detailed and interesting comment ... I unfortunately do not have your mastery of English ... I understood in outline what you express.
It would make me happy that a user like you get your hands on this amplifier.
I imagine that many people may think that I am very rave about my impressions of this small amplifier. But frankly, for the price it is something crazy!
You should buy it just for the pleasure of reading your pragmatic opinion and know if you will get goosebumps after listening.😉
Have fun amigos
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I do not want to read the previous 137 pages, but did you ever tried the Texas Instrument EVM or the 3e card in order to compare with this unit?
Hi Daniboun,
Thanks for your kind words... you do know you were among the 2 posters here that triggered my interest in this unit this morning? 🙂
I hope my post is not missunderstood by anyone: I took the time to have a look at it because reading you guys I believe this unit already deserves interest as it is - it is likely to be that good.. And because of that it may also be interesting to find out "how far it can be brought", tackling reasonably potential improvement paths.
Project anyone? 🙂
It is sad I have no one around me with any need for this kind of amp... who knows, the starting price is low, perhaps one day I may get into it as one tackles puzzles, for the sake of finding out how much vibes it gets out of me 🙂
Thanks again for having brought this unit to our attention and enjoy it very much
Claude
Thanks for your kind words... you do know you were among the 2 posters here that triggered my interest in this unit this morning? 🙂
I hope my post is not missunderstood by anyone: I took the time to have a look at it because reading you guys I believe this unit already deserves interest as it is - it is likely to be that good.. And because of that it may also be interesting to find out "how far it can be brought", tackling reasonably potential improvement paths.
Project anyone? 🙂
It is sad I have no one around me with any need for this kind of amp... who knows, the starting price is low, perhaps one day I may get into it as one tackles puzzles, for the sake of finding out how much vibes it gets out of me 🙂
Thanks again for having brought this unit to our attention and enjoy it very much
Claude
You are so cool Claude )
I am sure that we will make this amp an atomic bomb, a must have!
Hoping that his trasmutation doesn't make it too ugly)
Take care amigo
Oui monsieur ) il a été comparé avec pas mal d'amplis dont un ampli à plus de 3000 euros... ça se passe ici et tu vas être étonné ! Je possède pas mal de carte à base de TPA32XX, c'est la meilleure pour moi...
tu peux cliquer ici ça te donnera une belle idée )
TPA3251d2
I have the TI TPA3255EVM amp and the Aiyima TPA3251 2.0 amp, and I enjoy the TPA3251 amp after making some minor modifications with wiring and installing a set of Burr-Brown OPA627AU op amps in place of the stock TI NE5532 op amps. It’s nice to have a finished compact and energy efficient amp that is capable of driving my KEF LS50 monitors effortlessly. The TI TPA3255EVM is a fine amp and I was able to purchase two of them at 50% discounts. I just enjoy the Aiyima amp more.
Rich, glad you enjoy those inexpensive Aiyima TPA3251 amplifiers...LOL.
Perhaps you should save up and try a REAL Class D amplifier to power your LS50's and NO it will not be an amplifier that uses any of those crappy-sounding TPA325x chips.
Here's a little hint...Hypex.
After rereading your post above, you seem to be more interested in how well an amplifier would "effortlessly drive" your LS50's, which any of the TPA325x chips will do. Since you mentioned nothing about actual sound quality, perhaps "effortless drive" is more important to you than sound quality?
As for me it's ALL about sound quality first and everything else second.
Best of luck with your Aiyima/OPA627 combo.
Perhaps you should save up and try a REAL Class D amplifier to power your LS50's and NO it will not be an amplifier that uses any of those crappy-sounding TPA325x chips.
Here's a little hint...Hypex.
After rereading your post above, you seem to be more interested in how well an amplifier would "effortlessly drive" your LS50's, which any of the TPA325x chips will do. Since you mentioned nothing about actual sound quality, perhaps "effortless drive" is more important to you than sound quality?
As for me it's ALL about sound quality first and everything else second.
Best of luck with your Aiyima/OPA627 combo.
You should take a look here... A member has compared the TPA3251EVM vs a Double Mono UCD400 Hypex and prefered the TPA3251 regarding the Sound quality. If this amp disturbs everyone and leaves everyone perplexed ... it is that after all there is a good reason)
I repeat myself again but it was compared to many other amps in fact ... you have to read in the different threads.
IMG Stageline STA-800D
Read this as well :
TPA3251d2
I also finished my last DIY Amplifier (double mono Fully discret Class D @ 300W) and will compare it to my TPA3251 soon
Class D Amp Photo Gallery
Rest assured, I have no stock market share with TI lol
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Ti and TPA325x offended your grandmother?: D
Everyone here is not interested in your opinion.😉
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That was a good one!
Can anyone help me locate the OPA627 opa which can be swapped with the existing one? Is it possible to buy one in DIP8 form?
Hi amigo,
You can get them in DIP 8 socket below, and they are genuine :
OPA627
BURR BROWN OPA627 AOP Double sur Support (Unite) - Audiophonics
OPA1622 :
OPA1622 AOP Double DIP8 (Unite) - Audiophonics
checkout :
TPA3251d2
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I would avoid this myself.
The product description says: "Product based on reconditioned OPA627"
Rob43
I usually order all my OPA from Audiophonics. This Store is well known for its solid reputation. I have a pair of OPA627 and works fine, no issues; no worries.