Full Differential Amplifier.
One of the best ways to make after-DAC LPF or I/V, balanced output, etc.
Alex.
I'm playing this game as I write this. I believe it is called "op amp rolling", guessing it's named after cigarette rolling where you'd make (roll) your own as opposed to buying ready made cigarettes?
.... anyways I'm listening to a Musical Fidelity M1 dac that has some upgraded capacitors and the final opamp, NE5532, replaced by DIL socket into which I'm trying out different dual op amps. Currently it is OPA1612.
TBH I can't say in hearing any noticeable difference due to any of these changes.
I'm planning to remove the quad opamp and replace it with a socket and do the same.
Op amp rolling has been discussed many times, the only thing I take away from it is that the best sounding op amps aren't necessarily the ones with the best spec.
The game continues...
.... anyways I'm listening to a Musical Fidelity M1 dac that has some upgraded capacitors and the final opamp, NE5532, replaced by DIL socket into which I'm trying out different dual op amps. Currently it is OPA1612.
TBH I can't say in hearing any noticeable difference due to any of these changes.
I'm planning to remove the quad opamp and replace it with a socket and do the same.
Op amp rolling has been discussed many times, the only thing I take away from it is that the best sounding op amps aren't necessarily the ones with the best spec.
The game continues...
Hi,
How is used the op amp in the V-DAC ? Do we talk of transimpedance I/V use, or post filter, or buffer, or, ? Characteristic needed can make one op to sound good here and bad elswhere as said already above.
According the circuitry, all those op amps ratings are useless, but the one of the op (pune intented) cause rolled in his system setup.
And anyway, according the shematic, you can't rank op amps like that cause some values are fixed (Cap and resistto feedback, etc)
There are ic dac that spread current needing more or less strong I/V, some others voltage, some needs differential op amp or shematic at their output.
For instance the AD8066 can be good sometimes or can be too thin sounding according the layout, setup, dac ic, decoupling cap choice, etc !
Also, often whatever the final choice, you may needs a work on lythic caps decoupling or DC blocker's to have the best of the few you choose at the end for the task.
How is used the op amp in the V-DAC ? Do we talk of transimpedance I/V use, or post filter, or buffer, or, ? Characteristic needed can make one op to sound good here and bad elswhere as said already above.
According the circuitry, all those op amps ratings are useless, but the one of the op (pune intented) cause rolled in his system setup.
And anyway, according the shematic, you can't rank op amps like that cause some values are fixed (Cap and resistto feedback, etc)
There are ic dac that spread current needing more or less strong I/V, some others voltage, some needs differential op amp or shematic at their output.
For instance the AD8066 can be good sometimes or can be too thin sounding according the layout, setup, dac ic, decoupling cap choice, etc !
Also, often whatever the final choice, you may needs a work on lythic caps decoupling or DC blocker's to have the best of the few you choose at the end for the task.
Have you tried opa1633 ?
LT1028 advised by Rutgers ?
I try to find a list of op amps with the lowest Z at differential input pin, else as the know usuall suspect CFA or op861... not easy to find, often not in the datasheets according the brand.
I like the AD9631/32 as I/V but it is a little highish there (500 K) alas , however all the rest is sota spec for I/V but that input Z ! (LT1038 is only 20 K, and op861 few ohms at emitter input).
Edit : as I/V 1611 always sounded sterile in my setup. Never tried as buffer though (like AD8597 there as inexpensive little brother of the AD797, ten times less expensive and certainly as good to the ears disto wise).
LT1028 on my next purchasing list to make an I/V just for pcb DAC tests purpose...
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I have some PCBs for single op-amps which I could use for PCM56 and AD1865 DACs I'm trying to put together with my rather limited solid state abilities (I use tubes). Here is a projected circuit just showing the basic components.
Any suggestions for improvements?
Any suggestions for improvements?
if ad1865 has an output voltage with internal op amp, you can use the non inverted input.
But if using pcm56 (current output) and the current output of the AD1865 (better), you must use the inverted input.
Reading the datasheets of such dac ic is instructive.
But if using pcm56 (current output) and the current output of the AD1865 (better), you must use the inverted input.
Reading the datasheets of such dac ic is instructive.
if we forget the values of the Resistors, yes. The I/V R is the 10K in your shematic. And it needs alas some filtering too.
It is not just about calculating the gain alas.
https://sound-au.com/dwopa.htm#s41
It is not just about calculating the gain alas.
https://sound-au.com/dwopa.htm#s41
And this should interrest you then for the special subject of op amp used to convert current to voltage using a "virtual" ground : https://www.by-rutgers.nl/IV-converter.html
The idea is you don't need anymore to use a little value for the R like when used direct then a valve after. Advantage : a way larger flat impedance and bandwidth, which is important here (DAC coutput). The value of the R has less importance noise wise.
The idea is you don't need anymore to use a little value for the R like when used direct then a valve after. Advantage : a way larger flat impedance and bandwidth, which is important here (DAC coutput). The value of the R has less importance noise wise.
Also about rolling the op amps, here a great thread. https://www.diyaudio.com/community/...-checked-to-see-its-stable-havent-you.191389/