Audiophonics PRE-TC10 preamp with tone controls - review and measurements

[AnalogSteph]

Yes, OPA2828 (dual version of 828) should definitely work well in this preamp, with a socket adapter

It has low noise, high GBW, high slew rate and is unity gain stable. A good candidate for those who want to play, definitely.

Bit of a pricey sucker though (which, mind you, is not unexpected for a low-noise JFET input opamp).

I would give OPA1652 and OPA1656 (and maybe OPA1688) a closer look as well. Their MOSFET input with very low common-mode modulation of input capacitance should be a good match to the highish-impedance circuit. Even the bipolar OPA1662 would have a more suitable en/in balance than the stock LME49720. Does anyone make a hot-rod NJM4580/8080, NJM2068/8068 or LM833 (and is NJM5532 any good for input impedance distortion)? Stuffing some of those in there would be interesting for sure.

 

[pma]

It seems that the preamp circuit could be something like this:

This is the revised and corrected "reverse engineering" version ()

Both bypass ("direct") and controls paths are shown. It can be seen that:

1) direct, bypass path is non-inverting. Maximum measured output voltage is 9.1Vrms.
2) tone controls path is inverting and has reduced gain when set "flat", with maximum measured output voltage of about 5Vrms when pots set to "flat" frequency response.
3) the direct x control paths are selected by a relay switch.

 

[maty]

OPA828 / OPA2828 vs OPA627

OPA828 / OPA2828 vs OPA627

By now it has been a while since OPA828 (and OPA2828) were released. Any detailed comparison done (in the context of audio) to the opamp, OPA627, that they are supposed to replace? Thanks!

www.diyaudio.com

 

[pma]

Interesting thread, @maty ! Thanks!

 

[maty]

OPA828 / OPA2828 vs OPA627

Rings my alarm bell too much :)

www.diyaudio.com