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CMOYBB and OpAmps

post #1 of 3
Thread Starter 

Probably resurrecting something old and tired and I see lots of posts in the archives here about this but I wanted to take a tiny bit of a different approach.


CMOYBB isn't new but fairly new to me.  Got my first one a couple months ago.  Since then I've built probably 7 or 8 and sold a few and kept a few to play mad scientist with. 


Right now I'm dealing with two different voltage configurations.  I have one CMOYBB with 9v mains and another with 18v mains.


Configs and opamps I have tried so far:


OPA2227 - This is stock with the JDSLabs v2.0.3

MUSES01 with 9v and 18v

OPA627 with Brown Dog Single to Dual Adapter at 9v and 18v

AD8620 at 9v

MUSES02 - doesn't work in the CMOYBB.  Don't know why.  I have multiple, authentic ones and it just doesn't work.


My favorite?  Tough to say.


Perhaps it is the MUSES01 at 18v.  And it could be a toss up with the OPA627 at 18v.


If you factor in EVERYTHING such as cost, ease of construction, obtaining parts, sound, configuration I have to give the nod to the AD8620 though.  They can be bought from Brown Dog pre- manufactured for about the same as buying a chip from Digikey, paying shipping, buying an adapter from Brown Dog and soldering and shipping. 


Where's the fun in that though? I like soldering my owns chips on the adapters.  Anyway an AD8620 can be run easily from a 9v CMOYBB as just a drop in replacement. It's way cheaper than a MUSES01.  Regarding overall cost two 9v rechargeable batteries aren't cheap in Japan (where I live) and then you must buy a larger wall wart (18-24v) if you opt to charge in place.  Since mine is usually strapped to an iPod (4th generation iMod iPod) it's a pain to unstrap and an even bigger pain to remove the two batteries in the tin which barely fit.  Wall wart is a must.


CMOYBB is a great amp,  fun to play with, a fantastic conversation piece and it can be suited to taste by opamp rolling.  As I build these in the future for sale or gifts I'm going to stock them with AD8620's.  Nothing wrong with the stock chip though, although I'm sure they add it to keep the price point lower. 


Right now I'm working my way through an OPA627 which initially sounded great then the next day sounded awful, then after just cranking it up and letting the cans sit sounds much better after a few hours of that.  It opened back up or something.  Really spacious sound, high end is a bit subdued and soundstage a little compressed compared to MUSES or AD8620.  But the mids are spot on.  Vocals are buttery smooth and bass licks dead on.

Edited by Deterministic NL - 6/18/14 at 4:11pm
post #2 of 3

The Muses02 datasheet should give you a clue or tell you what is missing for it to work.


Try OPA827, OPA2209, OPA1612, OPA1642, OPA1652, and AD8597 sometime, they are all really great chips.

The rolling madness has only begun.  :evil:

post #3 of 3

A few things to note: MUSES01 needs minimum +/-9V, so 18V (which splits to +/-9V) is actually only meeting the requirement. I am surprised it doesn't distort with 9V supply, or are you confused 01 with 02? AD8620 is also slightly under powered with 9V, as it needs +/-5V to really start to shine.


You should also pay attention to output impedance and current output as many opamp, including OPA627, isn't meant to drive any load directly. They will never perform as good as they can be in a cmoy setup. Cmoy is great for checking out opamp but it is also a limiting factor as well.

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