I build that with a OPA1637.
Note that the value of the OPA1632 in the schematic are strange because the low R values will act a voltage divisor, then probably that's why the gain of the diff buffer is 2.
Simulation show that the overall noise is quite same with 1k for every R (gain=1), with an overall gain quite same also because it does not act as a voltag divisor at the input.
Knowing output impedance of the source can clarify that (usually near 200 to 400 ohm).
Note that the value of the OPA1632 in the schematic are strange because the low R values will act a voltage divisor, then probably that's why the gain of the diff buffer is 2.
Simulation show that the overall noise is quite same with 1k for every R (gain=1), with an overall gain quite same also because it does not act as a voltag divisor at the input.
Knowing output impedance of the source can clarify that (usually near 200 to 400 ohm).
Hi ctfrommn, if you wouldn't mind, could you specify what style/type/genre of music? I've been following your contributions here, and it would go a long way in helping understand your Op Amp choices. However, this could easily be too personal of a question; if so, please disregard. Thanks.
Interesting....
Looks like the TI proposed Opamp feedback capacitor (Cop 330pF) was removed and a 100MHz filter added (R10-13 100 ohm, U8-U11 100pF) to the input of the TPA3255 to filter out the switching frequency.
Attachments
Size of pins on DIL Adapters !!!
The pins on the Op-Amp adapters - if you use the good quality round turned pins - are about .5mm. This is comparable with the legs on a DIL Chip (2.5mm by .5mm).
The cheaper adapters use .6mm round pin or some are even larger. The OPA627AU chips on adapters that I purchased from a China Seller are using .6mm pins and are a really tight fit in the sockets of Aiyima. Good chance to damage the sockets !!
.6mm pins are a really tight fit in the turned pin sockets in most amplifiers and most likely will damage them - forcing them to open more than they should !
Try and ensure that you only use adapter with good quality turned pins - most likely gold plated and .5mm in diameter. Absolutely do not use the Adapters with the cheap square pins as these will destroy the sockets !!!
Just switched opamp to OPA1656 on brown dog adapter from the original 5532. Nice improvement for me. The 5532 was great and clear but had a in your face sound. THe OPA1656 is more enjoyable, laid back a little bit without loosing the detail. The harshness that I would get from the 5532 is gone! Magic without over emphasizing anything. Me be most happy!
Claude thank you ever so much. Still remaining is to solder the cap on top of the opamp and switch to the Meanwell power supply. Can't hardly believe it can get better than it already is?
Claude thank you ever so much. Still remaining is to solder the cap on top of the opamp and switch to the Meanwell power supply. Can't hardly believe it can get better than it already is?
And it will 
Excellent news, glad you are happy. IME the OPA1656 gives you much more details than any 5532 and also a much better bass. 5532 can indeed sound bass heavy and compensate for small speakers, but it is a muddier / less differentiate bass, whereas OP1656 has IMHO both impact and clearness on the bass lines.
Now, the good news is that the 3 bypass caps we added in situ to the OPA1656 made nearly as much difference to the sound than the step from 5532 to OPA1656. And that would probably be the same for any OPA as it is more a Aiyima OPA PS issue than OPA related, well noting some OPA are less transparent resolving hence being less sensitive to it.
So you can still expect some gains re bass and treble in particular, also depth of soundstage and pace consistency... all more relaxing and more resolving, 2 things that usualy not come together and that are very enjoyable to my ears.
Last but not least, the I am looking forward to reading your findings with the Meanwell vs whatever you are using now (what is it?), something we didn't bother doing as we went straight big Meanwell for 2 amps and added later 2 SMPS filter.
Have fun and well done
Claude
Excellent news, glad you are happy. IME the OPA1656 gives you much more details than any 5532 and also a much better bass. 5532 can indeed sound bass heavy and compensate for small speakers, but it is a muddier / less differentiate bass, whereas OP1656 has IMHO both impact and clearness on the bass lines.
Now, the good news is that the 3 bypass caps we added in situ to the OPA1656 made nearly as much difference to the sound than the step from 5532 to OPA1656. And that would probably be the same for any OPA as it is more a Aiyima OPA PS issue than OPA related, well noting some OPA are less transparent resolving hence being less sensitive to it.
So you can still expect some gains re bass and treble in particular, also depth of soundstage and pace consistency... all more relaxing and more resolving, 2 things that usualy not come together and that are very enjoyable to my ears.
Last but not least, the I am looking forward to reading your findings with the Meanwell vs whatever you are using now (what is it?), something we didn't bother doing as we went straight big Meanwell for 2 amps and added later 2 SMPS filter.
Have fun and well done
Claude
The 5532s that come with this are crap. When I changed to real 5532APs the improvement was drastic. That said, 5532s are super neutral and not for everyone.
the meanwell is the 24Volt one you recommended back in the thread. The one I am currently using is a 32Volt 3amp little wall wort brick ps. I am just a little over respectfull of mains power play!. As far as the OPA bypass caps goes is I soldered the .1uf and the 10uf x7r to the bottom of the board as I was not up to soldering to the pins of the 5532 that protrude above the mount socket. I will pull the 1656 and solder the remaining 20uf ?elna simlic to the adapter board on top. I would have been totally ok with the amp as it was supplied if not for your excellent write up of modding this cheap amp to get to enjoy more audiophile quality, The thing is that you rate each mod with a rating to sound improvement and cost. Others I have read just put the best caps and resisters that money can buy in to there mods. To me that is like buying a Yugo for $5,000 and putting $1000 each wheels and tires on it. Yes it might look and dive better but its still a Yugo! Thanks again.
GLOL!
Yugo, had forgotten about that one, has indeed been imported to the US!
Thanks for the compliments, kind of you.
I can't comment on the Meanwell vs your current wall wart as I haven't gone for that comparo myself, but on the paper I am quite sure you will get a better PS whatever. Going for 24V is more than enough (and can be adjusted up to nearly 29V should one bother) and will give you low ripple, probably far less than you have now and that is usualy audible. And you will also benefit of more current should the LS need some help.
As for the OPA bypasses, I see you did well and have "all ready to go". I believe you will like the addition of the 10uF lytic. We didn't like the 10uF X7R alone (well, with the .1uF), but it shone together with the 10uF lytic for whatever reason. You could of course go 20uF if you want but we found that the addition of a 10uF lytic to the 10uF X7R was enough (per OPA of course) and further 10 to 20uF didn't make any difference. Probably no negative though...
Keep us posted and take care
Claude
Yugo, had forgotten about that one, has indeed been imported to the US!
Thanks for the compliments, kind of you.
I can't comment on the Meanwell vs your current wall wart as I haven't gone for that comparo myself, but on the paper I am quite sure you will get a better PS whatever. Going for 24V is more than enough (and can be adjusted up to nearly 29V should one bother) and will give you low ripple, probably far less than you have now and that is usualy audible. And you will also benefit of more current should the LS need some help.
As for the OPA bypasses, I see you did well and have "all ready to go". I believe you will like the addition of the 10uF lytic. We didn't like the 10uF X7R alone (well, with the .1uF), but it shone together with the 10uF lytic for whatever reason. You could of course go 20uF if you want but we found that the addition of a 10uF lytic to the 10uF X7R was enough (per OPA of course) and further 10 to 20uF didn't make any difference. Probably no negative though...
Keep us posted and take care
Claude
I just received my new IC adapters (nice Mill Max ones) and the Brown Dog OPA's still dont fit tight in them. Better than the others but Im not confident these are going to make a good enough contact to use. Not sure why anyone would choose to use such small pins for these. I see zero benefit and lots of downsides.
Yeah, these dont make adequate connection to work. Ill be reaching back out to Cimaron to get a refund. This is ridiculous.
Yeah, these dont make adequate connection to work. Ill be reaching back out to Cimaron to get a refund. This is ridiculous.
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the ones I just installed from Cimaron were actually a tight fit! I was a bit leery to press them down with such force. Guess you really did stretch out your sockets?
These are BRAND NEW sockets. High quality ones too that Cimaron recommended. Did yours push all the way in until they sat completely flush? Mine literally drop into the sockets with zero force and fall right out by turning them over. Now, I didnt attempt to "force" them all the way into the bottom of the sockets though. I would imagine the holes are the same size all the way down though.
Update: Youre correct, these need to be pushed pretty hard to fully "seat" in these sockets. They seem to be fine now. Thanks for mentioning the amount of force you needed to use, I would have NEVER tried pushing them in that far otherwise.
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I would try both the Elna and some other brand if you have to order them anyway. The Elna's color the sound a fair bit. Unless you like overly "warm" sound.
Yep, see my update. Thanks for suggesting pushing them all the way in!