[fureshi]

I'm working on my first CMoy amp and have most of the parts ready. I basically followed Tangent's list (thanks for putting that together!) and ordered it all from Digikey. The only problem now is that they are back ordered on the OPA2132PA until 9/28. I've tried Mouser but they don't seem to have the right part. Does anyone know of anywhere else to order this part from? Thanks!

 

[JMT]

Don't know about other sources for the 2132, but you could use the OPA2134 and save a couple of bucks.

http://www.digikey.com/scripts/us/dk...660&Row=221281

 

[stereth]

I agree - get the 2134. According to Tangent's reviews, pretty much the only difference between the 2132 and 2134 is stability at low voltages -- voltages you probably won't be dealing with.

Mouser doesn't have many audio opamps. I tried the NE5532 from them and couldn't get it to work, back in my first diy here.

 

[Jupiter]

fureshi,

You could also get the OPA2132P from Digi-Key, $9.14 each.

 

[tangent]

I wouldn't recommend the 2132P -- waste of money for this amp. It would be better to go with a OPA2227 or OPA2604 instead.

The deal with the 2134PA isn't stability at low voltage. Instead, it sounds like clipping. This may only apply to a CMoy type amp. If it's buffered or has a stable ground, that criticism may not apply. Anyway, if you're willing to give it enough voltage for your headphones, it sounds the same as the 2132 to me.

 

[fureshi]

Wow, lots of great information. Thanks for all of the replies! Is there a difference in the way the 2227 or the 2604 sound?

 

[tangent]

Yes, but all three share the same basic characteristic sound. Which one you'll prefer is largely a matter of personal taste.

 

[fureshi]

Quote:

Originally posted by tangent Yes, but all three share the same basic characteristic sound. Which one you'll prefer is largely a matter of personal taste.

I've just re-read your article about alternate op-amps. I'll most likely be trying the OPA2227P and the AD823.

 

[BPRJam]

I really like the OPA2604 with 2x9v. It sounds like the 2132, but somehow more airy, I don't know how to describe it. IMO it beats the pants off of the 2132 with 2x9V.

I like the OPA2227 too, but it is significantly different from the 2132 and 2604. It still has the burr-brown laid back style, but in a brighter, more detailed way. In fact, I find more similarities between the AD8620 and the 2227 than I do between the 2227 and 2132, but maybe that's just me. Plus, I've tried them in a Mint, so that might make a difference, too.

Tangent:
IIRC at one point you mentioned that you found the OPA2227 to be prone to instability in a CMOY, but not in a Mint. Do I recall correctly, or did I just dream that?

If I didn't dream it, would you still recommend that fureshi put one in his CMOY?

BPRJam

 

[tangent]

You're recalling my OPA2228 test. It's the uncompensated version of the OPA2227, so it's about 4x as fast and requires a gain of at least 5 and a better layout. No doubt I had problems because my layout was suboptimal. I definitely wouldn't recommend it for someone's first project. The 227 is tame, so I don't mind recommending it.

 

[Voodoochile]

I listened to a lot of OPAs in my CMOY, and found the 2227 to be the best fit for me. Decent battery life, too.

 

[averydonovan]

Quote:

Originally posted by BPRJam I like the OPA2227 too, but it is significantly different from the 2132 and 2604. It still has the burr-brown laid back style, but in a brighter, more detailed way. In fact, I find more similarities between the AD8620 and the 2227 than I do between the 2227 and 2132, but maybe that's just me. Plus, I've tried them in a Mint, so that might make a difference, too.

I just tried out the OPA2227, OPA2228, OPA2132, and AD823 in my amp today. I had tested them all many months ago and stuck with the AD823, but I decided to try them again. I definately agree with the OPA2227/2228 being a bit different from the OPA2132. The word I would use to describe them is analytical, with the OPA2228 being more analytical than the OPA2227. The OPA2132 came off as too dark, and too laid back. The AD823 is more detailed, but not really analytical, and has better treble extension. My amp also has BUF634 buffers, but in a global feedback loop rather than multi-loop like the MINT.

I'll chime in with the OPA2227 for a CMOY amp, fureshi. The AD823 that you're considering is good, but puts out very little current and needs to be buffered to sound best. The OPA2227 sounds good, is easy to work with, and as Voodoochile mentioned it gets good battery life. I had two of them going in an A47-type amp and got at least 20 hours out of each battery (single 9V supply).

 

[Voodoochile]

Quote:

The AD823 that you're considering is good, but puts out very little current and needs to be buffered to sound best.

This is also very true. I don't like that OPA at all in a cmoy.

 

[grahamndodder]

I have made my opa2132 CMoy with one 9v, which is unecessarily limiting, since it is not to be portable. I have heard from the DIYAudio chip amps board that I should go to at least to (or even three) 9v's for better sound.

Does this make sense? How would the sound improve just by raising the rail voltage if I am already within the chip's parameters?

Assuming I did up the rails to 9v each, would the opa2604 just drop in to the socket, with no other changes?

If I were to try "opamp rolling" (I tube roll with my home loudspeaker amp), what would be a good selection of dual opamps to get for trying different sounds?

GnD

 

[Ghostie]

I vote for the opa2227 also.