Anybody OP amp rolling?

[SIY]

I didn't do any controls because I did it for myself and don't give a flying fuck at a rolling doughnut what anyone else thinks.

Controls are even more important when you do it for yourself. Voice of sad experience here...

 

[levimax]

Bias currents can be an issue with some bipolar input opamps. Did you try inserting a cap between wiper and opamp input to verify that this was the source of the problem? Of course, you still need a DC path to ground for the input.

The pots are soldered on the board as are the op amps which is why I haven't done anything yet .... good point though to test with cap before de-soldering op amps, thanks.

 

[JayGilb]

Controls are even more important when you do it for yourself. Voice of sad experience here...

I agree. It was the best I could do by myself and I tried to setup controls.

The hacked Digidesign 442 a/b vehicle I built was controlled via c code. It would send a signal from the pc's serial port to a cmos logic circuit mounted inside the 442 that would switch between the two stereo pairs of opamps every x number of seconds using a random number generator and would write a time stamp to the screen whenever the switch was made. The code would then accept keyboard input and map my entry and the corresponding 1/0 value along with the timestamp and was written to a csv file that I could examine afterwards.

I could never get the switchover to be silent all the time, the analog multiplexers in the 442 liked to make random clicks when switching and this was distracting. My results were never consistent enough and after a few weekends of experimentation I moved onto something else.

Edit: The Digidesign 442 is a wonderful design and I bought a stack of them off of Ebay for a few dollars. The layout is really good and they are full of tight tolerance components and are a great source for either parts or a good starting point for experimentation.

Here's the pcb from one of the units I still have:

 

[LTig]

I didn't do any controls because I did it for myself and don't give a flying fuck at a rolling doughnut what anyone else thinks.
Someone on ASR asked a question and I responded, nothing more.

Calm down, please. At ASR one needs to be aware that science rules, and if one thing has been proven by scientific research than this: the human hearing sense is very unreliable in sighted non level matched comparisons (been there, done that). Hence the standard question for proper controls. Without controls your comparison results are just personal opinions which have no value for other people. Sad but true - I wished it wouldn't be the case.

 

[LTig]

The thrust of the question was "Do you have any experiences of op-amp rolling" not "What is your opinion of op-amp rolling."

You are all simply flaming against one another, having no experience of actually doing it. Stop talking out of your hats.

... said the apprentice to the expert

 

[LTig]

I agree. It was the best I could do by myself and I tried to setup controls.

The hacked Digidesign 442 a/b vehicle I built was controlled via c code. It would send a signal from the pc's serial port to a cmos logic circuit mounted inside the 442 that would switch between the two stereo pairs of opamps every x number of seconds using a random number generator and would write a time stamp to the screen whenever the switch was made. The code would then accept keyboard input and map my entry and the corresponding 1/0 value along with the timestamp and was written to a csv file that I could examine afterwards.

I could never get the switchover to be silent all the time, the analog multiplexers in the 442 liked to make random clicks when switching and this was distracting. My results were never consistent enough and after a few weekends of experimentation I moved onto something else.

That's an interesting project. Do you think one could port the code to feed a 4 channel USB interface to get rid of the relay clicks?

 

[Digital Mastering System]

I chip rolled a Carver C-2 preamp, replacing most of the opamps with Opa1656s. I redesigned the tone control section as the stock design was a disaster. The original chips were TLO72s mostly. Overall, the project was successful, but I do have proper equipment and 35 yrs. of EE experience.
(This C-2 project involved more than chip rolling, e.g. the power supply and muting circuits were also redesigned.)
My next project is chip rolling a Rane 1/3 octave stereo equalizer. That thing is loaded with old opamps.
I agree that SOA integrated circuit opamps are better than discrete opamps in general. Even the wonderful 990 discrete opamp isn't that great compared to 4562s or 1656s. Check out Sam Groner's paper "Operational Amplifier Distortion" 2009.

 

[sq225917]

I recently built an rolled an rjm audio Emerald phonostage. The opa1611 on the mc input is a good 6db quieter above 1k than the reccomended opa27.