I have used opa627 in various circuits and found they are very good in its sonic advantages but was considering moving to AD812
one the slew rate is very good and for I/V application it should do the job much better than opa627.
Even the settling times are also very good for AD812.
one the slew rate is very good and for I/V application it should do the job much better than opa627.
Even the settling times are also very good for AD812.
It's the wrong Opamp for your application. The DC bias current and offset voltage is bad.
Power supply rejection and open loop gain is only medium. The speed is unnecessary and causes only trouble.
Use a standard 5532 or LM4562.
Udo
Power supply rejection and open loop gain is only medium. The speed is unnecessary and causes only trouble.
Use a standard 5532 or LM4562.
Udo
Maybe best is to go for a I/V unity gain conversion then a voltage gain aop after for some reasons. Not sure both of AD812 or OPA627 are unity gain stable (or not easy decoupling).
rwo cents, not a specialist myself)
rwo cents, not a specialist myself)
there are faster fet input today - but Vnoise isn't stellar (1/f corner - be very suspicious of 100 kHz noise spec parts) - can help S/N a little by increasing output Vswing, using bigger Rf
for bjt Analog has new "highly linear" input that they are doing a poor job of advertising
ADA4898 is one
for bjt Analog has new "highly linear" input that they are doing a poor job of advertising
ADA4898 is one
I have recently used the ADA4898-2 in an 8 channel ES9018 build and it performs wonderfully there (mainly from reading jcx's recommendation towards that series in the 'other' thread). I'm using the AD8610 for the differential converter as I happened to have 8 of those lying around. It sounds great and measure well too.
I'm getting 0.0003-4% THD on my first PCB after the CS3318 volume control and TPA6120 output buffer. I don't really see any reason for trying to improve upon this as it's at the limit of my measurement capabilities and close to what the hardware can manage anyway.
The 4898 certainly isn't limiting anything and on top of that it has a very high output current driving capability. This makes it very easy to integrate into a wide array of following output circuitry.
Edit - I will say though that the only thing against the 4898 is it's highish quiescent current. If you are using the dual package and running it from high voltage rails you will need to solder the exposed pad to the reverse side of the board. This is a pain as the exposed pad is supposed to be soldered to the -ve voltage rail. I did this via a small isolated pad beneath the chip on the ground plane. I am only running them on 9 volt rails and they get hot enough for my liking, if I were to need to run them from 12 or 15v then I'd need to increase the surface area of the cooling pad, or swap to the single op amp per package.
I'm getting 0.0003-4% THD on my first PCB after the CS3318 volume control and TPA6120 output buffer. I don't really see any reason for trying to improve upon this as it's at the limit of my measurement capabilities and close to what the hardware can manage anyway.
The 4898 certainly isn't limiting anything and on top of that it has a very high output current driving capability. This makes it very easy to integrate into a wide array of following output circuitry.
Edit - I will say though that the only thing against the 4898 is it's highish quiescent current. If you are using the dual package and running it from high voltage rails you will need to solder the exposed pad to the reverse side of the board. This is a pain as the exposed pad is supposed to be soldered to the -ve voltage rail. I did this via a small isolated pad beneath the chip on the ground plane. I am only running them on 9 volt rails and they get hot enough for my liking, if I were to need to run them from 12 or 15v then I'd need to increase the surface area of the cooling pad, or swap to the single op amp per package.
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What 'other' thread?
5th element, what 'other' thread regarding the ADA4898 are you referring to?
5th element, what 'other' thread regarding the ADA4898 are you referring to?
http://www.diyaudio.com/forums/digital-line-level/34324-best-opamp-i-v-conversion-dac.html
jcx mentions the highly linear series a couple of time more towards the end of the thread iirc. I figured why not give them a go 🙂
jcx mentions the highly linear series a couple of time more towards the end of the thread iirc. I figured why not give them a go 🙂
Thanks, element. Would you say, that the ADA4898 chip has given you the most satisfying sounding DAC I/V circuit utilizing a monolithic op-amp?
Hi, Thanks for recommending trying the ada4898. I have a pcm1796 dac with dip sockets. I tried various op amps. all seemed much of a muchness. soldered some ada4898-2 onto adapters with heat pad, and then soldered through hole in heat pad , from below, to ensure thermal contact with op amp. At 15 volts these got insanely hot. Tough little things still work though! I reduced rails to 12v and fashioned heat sinks to fit under adapter, contacting heat pad, from 75mm strips of 1.5mm x 5mm thick copper strip. Even this gets plenty hot. The sound compared to the opa 275 or lm4562 in the i/v stage is transformed (left lm4562 in differential output stage). I had no expectations. Skepticism born from op amp rolling in various buffer circuits and other i/v converters, but the difference is so marked as to have me re listening to my entire music collection. Simply much better.
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