[SLUSHIE]

I build a CMoy pretty much to the exact specs on How to Build the CMoy Pocket Amplifier.

While it does amplify the signal, by mean of making it louder, I don't notice any difference at all in the sound quality. I was hoping of getting a little more bass, but that is not the case.

I have Beyerdynamic DT770 pro 80s.

 

[mark10001]

What is your source device?

 

[krmathis]

Thanks for letting us know.
The CMoy, or portable amplifiers in general, might not be for everyone...

 

[SLUSHIE]

I've tried it on the FP Audio jack on my PC, my Zune, and a PSP.

 

[NelsonVandal]

Quote:

Originally Posted by mark10001 /img/forum/go_quote.gif What is your source device?

x2

OPA2134 is colored like all opamps. It has a kind of bassy coloration, but you can't excpect to get more bass. The frequency response of any opamp is totally flat in the audio spectra. If you want more bass, you have to add a bass boost circuit like in PPA or LISAIII, look at their schematis. I've also seen CMOYs with bass boost. Do some searching here.

If you're using headphones out, you're lucky if the sound isn't worse. If you're using line out from a CDP, the built in headphone amp is probably as good as the CMOY. In my oppinion there's three unnecessary problems in a CMOY. 1 a degrading input cap (no use for it with a JFET input opamps such as OPA2134), 2 OPA2134 is OK but not high class, 3 the passive ground (a good ground is as important as the amplifying stage).

 

[ishtob]

whats the value on your electrolytic cap are you using to for the power source, i find that using one that is 470uF or more improves the bass somewhat (i made 2 cmoys one with 220 another with 470, the 470 gets warmer sounds near the lower end)

 

[SLUSHIE]

I am using the headphone out on my Zune, because the Zune has no line out. But it is a Zune, so the sound quality is fine.

I am using 220uf caps.


I was just expecting the amp to have a much larger effect, or any effect at all, like the receiver on my stereo.

 

[NelsonVandal]

Quote:

Originally Posted by SLUSHIE /img/forum/go_quote.gif I am using the headphone out on my Zune, because the Zune has no line out. But it is a Zune, so the sound quality is fine. I am using 220uf caps. I was just expecting the amp to have a much larger effect, or any effect at all, like the receiver on my stereo.

I've heard that Zune sounds good from headphones out. I think we can assume that this is a low impedance output with the capability to drive low impedance phones like IEMs. I can't see how an amp like CMOY (or probably any amp) can improve the signal. I think it's one of those myths here that amping automatically improves the sound. I think you'll just add another degrading stage. If the noise level from the output is high (like in many DAPs), adding an amp with it's volume control reduces the noise. This is ofcourse in a way an improvement.

 

[infinitesymphony]

Quote:

Originally Posted by SLUSHIE /img/forum/go_quote.gif While it does amplify the signal, by mean of making it louder, I don't notice any difference at all in the sound quality. ... I am using the headphone out on my Zune, because the Zune has no line out. But it is a Zune, so the sound quality is fine.

The CMoy sounds like your headphone output because... it's plugged into the headphone output!

The goal of a CMoy is to avoid headphone outputs so that you can substitute your own improved headphone stage (i.e. the CMoy). Also, as NelsonVandal pointed out, the parts specified by Tangent are not all of high quality, and the circuit design could be improved.