JoeMeek OneQ again...

[HellfireStudios]

I've been trying to compile all the upgrades I want to get done in my studio to save on the inevitable shipping costs. The OneQ was upgraded earlier this year to a version with a Cinemag transformer and Burr Brown opamps throughout (for twice the price). This circuit is a channel strip with mic pre, optical comp, EQ, de-esser, exciter, selectable input transformer, and no available schematic. All in all, a total of twenty three JRC072D (TL072 copy? I couldn't find a datasheet...) DIP opamps, one THAT1510, and one JRC13700D.
I've already discovered which Cinamag transformer is used with this preamp, so my concerns lie with which Burr Brown opamps are used to replace the originals. I've heard the OPA2134 is an alternative to the TL072 but the power consumption is around 3 times more (2.8mA compared to 8mA). I love this chip in guitar pedals and headphone amps. Would I need to beef up my power supply to compensate? How do I tell what my power supply can produce safely (all four of the regulators are rated at 1 Amp)? Is another BB opamp more compatible?
I will probably keep the THAT Corp. opamp in place, but what about the JRC13700D? I believe the NJM version called it a Transductance Amplifier. No clue what it means. Should I leave this one alone, as well? If a change is inevitable, which BB could replace the JRC13700D? Thanks for any help you can give.

-James-

 

[Rochey]

You may not need to swap out every single tl072.

If any of them are being used in a low gain configuration, or even as a buffer with little current drive requirements, you may not have a big advantage in changing.

6mA difference x 22 = 132mA increase.

I'd be surprised if your psu will crap out over an extra 130mA...

/r

 

[HellfireStudios]

I did the math on all the opamps in the circuit (assuming JRC072D's are spec'd the same as TL072's), and found that they pull 73mA all together. If I were to upgrade all the opamps to OPA2134's, like the OneQ2 may have done, it would pull 192.6mA. If my MC 7815/7915/7805's are rated at 1A they would be able to handle the 73mA with no problems. Since 1A = 1000mA, 193mA shouldn't be a problem either, correct? Sorry to sound so dumb, but I don't want to replace any power supplies or blown opamps. That can get rather pricey...

-James-

 

[HellfireStudios]

Ok. I think I've settled on my solution. I intend to replace the JRC072D opamps with Burr Brown OPA2134's (all 23). I'm going to leave the original transformer in place becuase I like its flavor, and don't want to rewire for the Cinemag (which I hear is wired in permanently). I'm also leaving the JRC13700D and the THAT Corp. 1510 chips in place. Does anyone see a problem with my plan? Any potential pitfalls I should be warned of? Thanks.

-James-