xtp wrote:Did you notice much difference soundwise with all the opamps you tried.
Yes, for clean signals, the noise/distortion levels did vary. However, I found if you put a discrete, fixed gain amp/buffer stage before them, this was reduced quite a bit. I use a simple FET design so that I can set the input impedance too. The J. Tillman one is a good starting point if you're not familiar with them. It's based on a standard design, tweaked for preference.
Mine's a little difference as I have +ve and -ve rails, as well as ground. It uses a Voltage Multiplier to accept a 9V input and give me the supply levels I want. There's also a bypass to use 18-36V input via a voltage regulator.
Rather obviously (IMO), the voltage supply to the opamps, particularly rail-to-rail, is important to overall performance. I spent quite a bit of time sorting out a supply circuit I was happy with, or approaching happy with (TBC). You can get some weird effects if you mess with it though, like sending signals, or LFOs though them.
Tonally, I couldn't really tell much difference. The frequency responce were similar, as was phase. The surrounding components had a much bigger effect on them.
For distorted/clipping signals, I did noticed difference in tone and how well the opamp reacted to high levels. I think this is where it gets subjective as better/worse isn't as quantifiable, as with noise.
Overall, there was a general bang/buck correlation for clean signals, but none really if you wanted to drive the opamp for character. I guess this is in line with the general opinion.
Of the 2 you mentioned, I prefer the OPA2134 for clean signals as it seems less prone to noise/disortion. If I remember correctly, it also accepted distortion well, but I wasn't particularly taken with the clipping tone.
The TL072 is a good workhorse type, which does well for either.
Hope it helps.
I miss MindPrint. My TRIO needs a big brother.