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Building the Perfect Cmoy for Grado SR 225s

post #1 of 18
Thread Starter 
What's your opinion on the perfect Grado SR 225 Cmoy !?

1. Parts Required? Cost? Where to get them?
2. How to?
3. The Way it changes the sound (I'd prefer information to make a ROCKIN amp for my Grado 225s, but this forum ain't just for me! It's for the public!)

Thanks!
post #2 of 18
Grado's love lots of current, so your CMoy will need an opamp that can supply it. You may also want to consider 18 volts (2 x 9v batteries).
Another option would be to build an A47 amp which uses a second opamp as a buffer to increase current output. It is also a simple and relatively cheap build like a CMoy and I believe it was designed specifically for Grado's.

Apheared's 47 Amplifier
How To Build the Grado A47 Headphone Amp
post #3 of 18
A Cmoy is probably not gonna have enough current out for Grado's, how about adding some output buffers (ideally three BUF634 per channel)?
post #4 of 18
Quote:
Originally Posted by NiceCans View Post
Grado's love lots of current, so your CMoy will need an opamp that can supply it. You may also want to consider 18 volts (2 x 9v batteries).
Another option would be to build an A47 amp which uses a second opamp as a buffer to increase current output. It is also a simple and relatively cheap build like a CMoy and I believe it was designed specifically for Grado's.

Apheared's 47 Amplifier
How To Build the Grado A47 Headphone Amp
off topic

"benfeist" on the second link, is he the brother of Feist?
post #5 of 18
Definitely consider the Mini^3. The AD8397 opamp will provide lots of current for your Grados. I loved it with Grados!
post #6 of 18
x2 on the Mini³, I have the 325i's and I think that the Mini does a great job. It does a good enough job that I am going to make a desktop version (like Grado Ra1) to sit on a desk by my computer.
post #7 of 18
clone a grado RA1



post #8 of 18
a regualr cmoy might sound better
im going to find out soon
post #9 of 18
I would suggest you go with an RA-1 Clone.

I have built numerous portable amps (cmoy, 47, buf634's, etc) for my SR-125's and the RA-1 sounds the best for me.

I have also built numerous RA-1 clones and the one that sounds the best for me is the original one. Use a NJR4556 op amp with a split battery power supply. Solen 5.1uF input caps and .1uf caps near the power supply pins. If you want to use just one battery I found that a tle2426 with a couple 470uF caps works pretty good too. Use the same resistor values too (100K, 464K, 122K).

the ONLY part that I found made it sound better was the volume pot. I'm using an ALPS 50K.

Parts are cheap. I ordered the solen caps from parts express and the rest from mouser. I think I built it for less than 20 USD. And it sounds good to me.
post #10 of 18
i think the biggest reason why the RA1 sounds the best is due to the power supply used. Although it's prone to instability but the centre tapped ground provides a much lower impedance ground. It's comparatively a "better" ground. I believe even ppl himself prefer the sound of it. (If i'm not wrong, i've read about it in his very old portable amp in some old thread ago).
post #11 of 18
The fact that there is basically no capacitance in the PSU does make it fairly unique, but I do prefer a lot of amps vs the RA-1 with my SR225. No doubt RA-1 is nice for Grados: 100mA output off the JR4556 with the smoothness (forced rolloff via Solen 4.7uF input caps) is adding some some necessary punch and warmth to the Grados, but I like other amps more.
post #12 of 18
RA-1 was tuned for tone to suit Grados. There's no other reason to explain why was it made this way. You may take it or just turn to high current output 8397's with no smoothing caps.
post #13 of 18
Quote:
Originally Posted by ECM View Post
I would suggest you go with an RA-1 Clone.

I have built numerous portable amps (cmoy, 47, buf634's, etc) for my SR-125's and the RA-1 sounds the best for me.

I have also built numerous RA-1 clones and the one that sounds the best for me is the original one. Use a NJR4556 op amp with a split battery power supply. Solen 5.1uF input caps and .1uf caps near the power supply pins. If you want to use just one battery I found that a tle2426 with a couple 470uF caps works pretty good too. Use the same resistor values too (100K, 464K, 122K).

the ONLY part that I found made it sound better was the volume pot. I'm using an ALPS 50K.

Parts are cheap. I ordered the solen caps from parts express and the rest from mouser. I think I built it for less than 20 USD. And it sounds good to me.
You wouldn't happen to have the schematic for that would you? I would be interested in building one too.
post #14 of 18
Quote:
Originally Posted by headphonejunkie View Post
You wouldn't happen to have the schematic for that would you? I would be interested in building one too.
I believe you can find it right here
post #15 of 18
headphonejunkie, the schematic can be found on the link NiceCans posted, which is page one of this very thread.

It's a fairly straight forward build. The schematic is basically a cmoy with huge 5.1uF Solen input caps and .1uF power supply bypass caps.

I'll mention it again that it's been my experience that even the resistor values play a role in the sound of the amp. Don't have an explanation, but the closer you get to the original, the better.

FallenAngel, I have a Benchmark DAC1 (usb version) running off a balanced isolation transformer that sounds fantastic with my 125's, but sometimes I prefer my RA-1 clone. I totally agree with you that the combination of opamp and input caps is what makes this amp sound good with Grado's. This is why I feel it's the "Perfect Cmoy for Grado SR 225s."
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