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Suggestions needed on cmoy amp for MS1

Feb 5, 2005 at 6:27 AM Thread Starter Post #1 of 10
brian183

brian183

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I'm a proud and very satisfied customer of a pair of alessandro MS1 cans. After owning them for awhile I've decided it's time to build myself a small amp for them just for fun really. Right now my main source is an EMU 0404 and great as it is it requires and an amp. Currently I'm using either my AM150 mixer or my sansui 7000 receiver for my headphone amp and both of them do a pretty good job but I think a Cmoy would be much better for my situation. Since this little amp is kind of a popular one on this board I figured I'd ask my questions here. So anyway...

1. What opamp would you suggest for MS1 cans?
2. What gain would you suggest for MS1 (11 seems a bit much for a 32ohm can)?
3. Would one 9V battery(split in half for + - Power) suffice or would two in series (split in half for + - Power) be better?
4. What is the battery life in general for these cmoy amps?
5. What good rechargeable 9V's would you recommend?

Ok I think that's it for now. Thanx guys/gals
 
Feb 5, 2005 at 6:56 AM Post #2 of 10
Quote:

Originally Posted by brian183
1. What opamp would you suggest for MS1 cans?


Either OPA2227PA or OPA2132PA. Either one would blend nicely with the MS-1s. AD8620 or AD823AN might be a bit harsh.

Quote:

Originally Posted by brian183
2. What gain would you suggest for MS1 (11 seems a bit much for a 32ohm can)?


I'd suggest a gain of 3. Gains of 2 or even unity gain would also work well with those efficient cans.

Quote:

Originally Posted by brian183
3. Would one 9V battery(split in half for + - Power) suffice or would two in series (split in half for + - Power) be better?


If you've got the room, 18V will sound better than 9V. You can also run two 9V batteries in parallel to extend battery life, but voltage will remain only 9V. Alternatively you can also place a DC input jack on the amp for use with a regulated linear power supply (such as an Elpac) for when you're not portable with the amp.

Quote:

Originally Posted by brian183
4. What is the battery life in general for these cmoy amps?


Not sure exactly. My CMoy is still on its Plainview's first charge, but then again I rarely use it so I can't give an accurate figure...

Quote:

Originally Posted by brian183
5. What good rechargeable 9V's would you recommend?


Plainview rechargeable 9V formfactor NiMH batteries are really nice.
 
Feb 5, 2005 at 9:23 PM Post #3 of 10
Quote:

Originally Posted by aeriyn
Either OPA2227PA or OPA2132PA. Either one would blend nicely with the MS-1s. AD8620 or AD823AN might be a bit harsh.


I have also read this same sentiment all over the boards. I'd go with Aeriyn here.

As far as the 18v versus the 9v, I have read in places that the quality gain isn't terribly significant. Is this not the case? I'd like to hear some debate on this.
 
Feb 5, 2005 at 9:35 PM Post #4 of 10
Quote:

Originally Posted by Hase
As far as the 18v versus the 9v, I have read in places that the quality gain isn't terribly significant. Is this not the case? I'd like to hear some debate on this.


The quality gain is noticeable on cans that require lots of voltage. Grados probably could get by just fine on one 9V battery or two wired in parallel to extend battery life.

If you're powering Senns or 250ohm Beyers or something, you might need more voltage than just 9V, depending on the opamp used.
 
Feb 6, 2005 at 5:01 AM Post #7 of 10
I'd go with opamp and gain as suggested (I use 5.5 gain, but 3 etc. would be fine). One thing I would look into is the A47 instead of the CMoy. I personally think it sounds better, and only requires another dual opamp, socket and a pair of 47 ohm resistors in addition to the CMoy. It can be built easily on slightly modified version of Tangent's CMoy plans, and provides more current than a single opamp will, which is what Grados or any low impedence headphone is looking for.
 
Feb 6, 2005 at 6:14 AM Post #8 of 10
Quote:

Originally Posted by Pars
I'd go with opamp and gain as suggested (I use 5.5 gain, but 3 etc. would be fine). One thing I would look into is the A47 instead of the CMoy. I personally think it sounds better, and only requires another dual opamp, socket and a pair of 47 ohm resistors in addition to the CMoy. It can be built easily on slightly modified version of Tangent's CMoy plans, and provides more current than a single opamp will, which is what Grados or any low impedence headphone is looking for.


is there any guides for this A47 ?
 
Feb 6, 2005 at 10:56 AM Post #9 of 10
Quote:

Originally Posted by Anthrax
is there any guides for this A47 ?


google turned this up:

http://www.feistworks.com/ben/a47/default.asp


As for opamps/gain. I've got ms-1s and I'm running a gain of 11 with opa637's and a tpa6120. Rarely does the volume knob see more than about 40-50%, but the sound produced is fantastic. (note the 637 needs about a gain of 8-9 to be stable - spec sheets say 5, I wouldn't try it that low)

That said the opa627 and 637 are hungry suckers so will drain your battery faster than the other BB/TI chips mentioned, they're also more expensive, and single chip opamps (you'll need two on a browndog adapter to use them in something like this). The other side to this is they sound better with the ms-1s and grados as a whole than the other amps, according to the many many posts I've read.
 
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