I had a chance to do some more testing today with different op amps.
1.MC1458 - 0.2mV DC offset and it sounds good.
2.KIA 4559 - 4.5mV DC offset and it has a very sharp sound, not good.
3.TL072ce - 2.5mV DC offset and it sounds good.
4.NE5532 - 22mV DC offset and it sounds good.
5. LM833 - 14mV DC offset and it sounds the best of all.
But with the LM833 I had some ringing, I added the 100pf caps and it kills the ringing but something looks a little funny on the rise and fall parts of the wave. This was at 20kHz. Maybe I must make the cap a little smaller..
Advice will be appreciated.
And now my scope seems to start with bad connections on the adjustment knobs, Have to fix that very soon.
1.MC1458 - 0.2mV DC offset and it sounds good.
2.KIA 4559 - 4.5mV DC offset and it has a very sharp sound, not good.
3.TL072ce - 2.5mV DC offset and it sounds good.
4.NE5532 - 22mV DC offset and it sounds good.
5. LM833 - 14mV DC offset and it sounds the best of all.
But with the LM833 I had some ringing, I added the 100pf caps and it kills the ringing but something looks a little funny on the rise and fall parts of the wave. This was at 20kHz. Maybe I must make the cap a little smaller..
Advice will be appreciated.
And now my scope seems to start with bad connections on the adjustment knobs, Have to fix that very soon.
Attachments
I also saw some oscillation on lm833n without the feedback cap, and it was the only op amp doing that across the 8+ tested.
See this post showing gifs of various op amps on 10khz sine at different levels. Interestingly, some do not have an homogenous behavior:
"WHAMMY" Pass DIY headphone amp guide
See this post showing gifs of various op amps on 10khz sine at different levels. Interestingly, some do not have an homogenous behavior:
"WHAMMY" Pass DIY headphone amp guide
osscar, I'm using the 10R source resistors, bias is about 550mV, I'm currently using a smallish transformer for testing. The voltages fall to +-12V under load from 17VDC. I'll build a better psu with a bigger tx the week to finish it off. But it does sound very good as is, maybe I must leave it alone !
Take a look at:
https://www.diyaudio.com/forums/pas...-diy-headphone-amp-guide-314.html#post6427765
I quite accidentally discovered that there is some sort of break-in time with the Burson OpAmps that I did not notice with the Spark Labs or TI op amps I tested in the other 2 Whammys I built. I got away with not using the recommended bypass caps but I found after a couple weeks of daily listening that I started to hear some odd noise that was eliminated as soon as I inserted the bypass.
--Tom
Which value did you end up going with, Tom? I feel like a 0.01uf C0G ceramic may end up working great? Tho, if you have one on hand or are going to place an order, I'd probably go with WIMA film (of which I happen to have extras).
Edit: Doh, you specified in your prior post.
No worries. As the data sheet from Burson says, try different values between .1-.01uF. For me I settled on .1uf. In case you need the part number you can find it here:
I'm done rolling opamps in Whammy. Time to screw the lid on permanently. hah
But seriously, I've been listening to OPA827 the past days, and comparing to OPA627 and OPA1656, which are the other two opamps I really enjoy. All three are fantastic, with OPA1656 the most "composed" probably. But OPA827 is the best sounding opamp to my ears, on my gear (Logitech Squeezebox Touch, Senn. HD560S)
OPA827 sounds a bit more "open" and has a bit more emphasis on lower frequencies compared to OPA1656. OPA627 is very similar, but I keep going back to OPA827, without being able to pinpoint why. I think OPA827 is a bit more fluid up high?
For what it's worth. Differences are quite small, and all three opamps are incredible
But seriously, I've been listening to OPA827 the past days, and comparing to OPA627 and OPA1656, which are the other two opamps I really enjoy. All three are fantastic, with OPA1656 the most "composed" probably. But OPA827 is the best sounding opamp to my ears, on my gear (Logitech Squeezebox Touch, Senn. HD560S)
OPA827 sounds a bit more "open" and has a bit more emphasis on lower frequencies compared to OPA1656. OPA627 is very similar, but I keep going back to OPA827, without being able to pinpoint why. I think OPA827 is a bit more fluid up high?
For what it's worth. Differences are quite small, and all three opamps are incredible