As I don't have a profound knowledge about phono preamp circuitry (yet, may or may not change), that compact design is indeed appealing.
Would love to see performance characteristics and comparisons to the OPA1656 design you're working on !
Hi 1093i3511
I'm also very curious to compare these two versions.
At the moment I'm waiting to receive the prototypes of the MarcelvdG version. That will be the first one I can try.
I still have some difficulty with the availability of two smd components for the version with OPA2192, but I should solve it soon.
The last component I'm missing is the transformer.
And unlike what I said previously, I think I'll will buy the Talema 2x15V 10VA version.
Powering only the Preamp stage, I suppose less than 10% of the 333 mA it can deliver will be needed.
With the advantage of a lower cost and smaller size, compared to a 15-25VA.
I know, I did it all by myself...🙂
I'm also very curious to compare these two versions.
At the moment I'm waiting to receive the prototypes of the MarcelvdG version. That will be the first one I can try.
I still have some difficulty with the availability of two smd components for the version with OPA2192, but I should solve it soon.
The last component I'm missing is the transformer.
And unlike what I said previously, I think I'll will buy the Talema 2x15V 10VA version.
Powering only the Preamp stage, I suppose less than 10% of the 333 mA it can deliver will be needed.
With the advantage of a lower cost and smaller size, compared to a 15-25VA.
I know, I did it all by myself...🙂
Was also thinking about using an opa2192 in a preamp, any special quirks for these new tangled CMOS chips?
Hi Tashi1,
Sorry, but I don't understand what you mean with:"any special quirks for these new tangled CMOS chips".
About the RIAA Pre with OPA2192, it is a design that was suggested by Nick Sukhov and it is an op-amp that I have never tested.
I should start printing this PCB in the next few days, so for now I can't make any comments.
About the RIAA Pre designed by MarcelvdG with High Pass Filter I have already received the pcbs, but I am waiting for the transformers for the power stage. Within the next week I should be able to put everything together and perform the first "raw", tests.
I will update the post as soon as I see that it works.
(my PCB, not the MarcelvdG Design...)
Sorry, but I don't understand what you mean with:"any special quirks for these new tangled CMOS chips".
About the RIAA Pre with OPA2192, it is a design that was suggested by Nick Sukhov and it is an op-amp that I have never tested.
I should start printing this PCB in the next few days, so for now I can't make any comments.
About the RIAA Pre designed by MarcelvdG with High Pass Filter I have already received the pcbs, but I am waiting for the transformers for the power stage. Within the next week I should be able to put everything together and perform the first "raw", tests.
I will update the post as soon as I see that it works.
(my PCB, not the MarcelvdG Design...)
OPAx192 is nice but not really a universal audio opamp: https://www.diyaudio.com/community/...really-not-a-good-choice.428152/#post-8023192
Gotcha, be interested to hear how it goes.
I was just referring to the fact that using CMOS opamps for audio seems to be a fairly recent thing (I could be wrong), and the OPAx192 is chopper stabilised which means it uses some strange tricks to achieve its remarkable offset at such a cheap price.
Low offset isn't a requirement for audio (which is AC coupled), and chopper-stabilization creates spectral artifacts which might be audible. If you were monitoring a thermocouple however it would be great choice.
CMOS opamps have only come down in 1/f noise in the last few decades, and still lag behind JFET and bipolar in this respect. They usually have good bandwidth and output drive capability.
CMOS opamps have only come down in 1/f noise in the last few decades, and still lag behind JFET and bipolar in this respect. They usually have good bandwidth and output drive capability.
No, it is factory-trimmed for low offset, similar to the expensive laser resistor trimming just very much cheaper. The process is called e-Trim: https://www.ti.com/lit/ab/sbot037d/sbot037d.pdf
The non- e-Trimmed version of the OPA192 (still with low offset) is the OPA197 at basically half the price.
Chopper-stabilized introduces no 1/f-noise which is the other main asset besides low offset.
While the OPA192/197 is exceptional at "true DC" it has tons of 1/f noise and thus is very drifty near DC. The JFET-based opamps like 1642 and 827/828 are much better, and the latter have low offset, too and all have good modern specs overall (what you mentioned already).
You’re absolutely right, apologies for the confusion, I was thinking of the OPA189
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OPA192/197 are not a chopper and have no more 1/f noise than typical JFET-input OPA627\1655
Yes, see my post above.
I was referring to 828 or 1642, not CMOS 1655 or grandfather's 627.
OPA828: 60nV/rtHz @ 0.1Hz
OPA192: 300nV/rtHz @ 0.1Hz
OPA828: 0.34uVpp
OPA192: 1.3uVpp
OPA1642 is even better with 50nV/rtHz @ 0.1Hz and ~0.3uVpp:
Nick, can you explain what is a "transadmittance cascade at the output" and show some examples please,