How to Make the Most Compatible CMOY?
Dec 21, 2007 at 7:34 PM Post #16 of 27

heatmizer

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Build a cmoy 1st then maybe an a-47 later for the grado's. You won't need anything larger than .22 uF for the input cap. I would use 470-1000 uF power caps though and use a tle2426 for the rail splitter instead of the 2 resistors.
 
Dec 23, 2007 at 6:07 AM Post #17 of 27

infinitesymphony

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I think his question about the OPA2227 was about potential bandwidth issues. The OPA2227 has the same gain bandwidth product as the OPA2132, so either should work in a basic Tangent CMoy.

You may run into problems if you ever decide to roll in the AD8620, or other "fast" op-amps like the AD823 or OPA2228. I solved the problem by adding two decoupling capacitors, one between the op-amp's V+ pin to ground, and another between the V- pin to ground. I used these cheap 0.1 uF ceramic capacitors from Radio Shack, and they worked perfectly. The CMoy went from distorted to great-sounding.
smily_headphones1.gif
 
Dec 29, 2007 at 7:40 PM Post #19 of 27

balou

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you're blocking out the voltage supply to your opamp with those caps..
they should go from V+ and V- to GND, NOT on the opamp pins directly
wink.gif


Working with Cranky Op-Amps
this site describes what you need to do to make a cmoy which will work with almost all opamps (also shows the right way to add the decoupling caps)
 
Dec 29, 2007 at 9:33 PM Post #20 of 27

HPIMTRACER

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i just made one of the cmoy amps and i get a noise when the head phones are plugged in sounds as if there being amplified to much.. Can this happen? i didnt install a pot because i didnt see any in any near by stores. Can the pot be the reason the headphones sound like they have to much power.. I was using apple ear buds was testing to let you know. LAst question is what stores sell the pot needed for this amp the Alps RK27 or somthing similar
 
Dec 30, 2007 at 6:58 AM Post #21 of 27

infinitesymphony

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Quote:

Originally Posted by HPIMTRACER /img/forum/go_quote.gif
i just made one of the cmoy amps and i get a noise when the head phones are plugged in sounds as if there being amplified to much.. Can this happen? i didnt install a pot because i didnt see any in any near by stores. Can the pot be the reason the headphones sound like they have to much power.. I was using apple ear buds was testing to let you know.


A Tangent CMoy or something else? What op-amp are you using?

If you don't have a pot and you built it with a gain of 11, chances are you'll be totally overdriving your iBuds.
Quote:

Originally Posted by HPIMTRACER
LAst question is what stores sell the pot needed for this amp the Alps RK27 or somthing similar


You may need to order online. Both Tangent and amb sell the RK097.
 
Dec 30, 2007 at 7:00 AM Post #22 of 27

infinitesymphony

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Quote:

Originally Posted by balou /img/forum/go_quote.gif
you're blocking out the voltage supply to your opamp with those caps..
they should go from V+ and V- to GND, NOT on the opamp pins directly
wink.gif



Are you talking about my CMoy or his schematic? If you're talking about mine, what are the alternatives for that particular board?
 
Dec 31, 2007 at 11:07 PM Post #25 of 27

infinitesymphony

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Quote:

Originally Posted by Petri H /img/forum/go_quote.gif
I'm going to build my first CMOY probably next week and I have sr80, which has 32ohms, so what gain would you recommend for my amp?


It's up to you, but I'd recommend 6 or less for low-Z headphones. I have a 32-ohm pair of Sennheiser HD497s and with a gain of ~5.5, I could only get near the pot's halfway point.

For compatibility (since that's the thread's title), a gain of 5 is recommended. Some op-amps require 5 as a minimum to function properly.

If the op-amp you've chosen is unity-gain stable, you can go all the way down to 1 without problems. Check the datasheet to be sure.
smily_headphones1.gif
 
Jan 1, 2008 at 5:18 PM Post #27 of 27

Earwax

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Quote:

Originally Posted by Sonichedgehog360 /img/forum/go_quote.gif
Should it look like this (in attachment) if I want my CMOY to have compatibility?


You'll need to add the de-coupling caps going from the power supply pins to ground (not in series with the power supply as you have shown) I added caps like that to the bottom of some a cmoy board after it was built. It's a bit tricky to solder that way but then you can follow Tangent's tutorial exactly and make the modifications later.

Definately lower the gain if you plan on getting Grados later.

OPA2227 will drop into the basic cmoy without any changes.
 

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