Cmoy pcb too big

[widea]

Hi,

I built the Cmoy (var. Gwado) headphone amp:

but decided it was way too big so built another one :

The first one now contains an OPA2134, the smaller one will have a LM4562.



I finished the 'big' version, sounds wonderful!



Regards,


Cor

 

[Dibya]

Look like nice home brew AMP!

 

[widea]

Thanks Dibya!

 

[widea]

how it turned out...

see Wanderingidea's blog

 

[00940]

Nicely done.

One comment though : that 38r output resistor is much higher than you need. A 4.7r resistor would be more than sufficient. Go to the "tech section" of this review to see why.

 

[widea]

A 4.7r resistor would be more than sufficient.

I will try that, thanks.

 

[widea]

I got rid of R5 completely. Sounds better. If needed I will add an output resistor of 4.7 ohm but for now I am happy with it.

 

[xrk971]

Nice work looks like a fun project! If you ever want more power, try a parallel OP1688 and use two 9v in true dual rail supply. Cap couple output and then you don’t worry about DC outburst in case a battery clip fails.

More here including home etch artwork for PCB.
Cheap as Chips OPA1688 Low-THD Muscle Amp

 

[widea]

If you ever want more power, try a parallel OP1688 and use two 9v in true dual rail supply. Cap couple output and then you don’t worry about DC outburst in case a battery clip fails.

Interesting schematics, so many to choose from and so little time...

 

[xrk971]

Juat realized that above photo was not the dual parallel one, this is:

Another option for a CMOY sized mint tin is the 2-transistor SE Class A "Pocket Class A" or PCA. It sounds terrific - one of the best sounding headphone amps that I have heard.

xrk971 Pocket Class A Headamp GB

 

[widea]

realized that above photo was not the dual parallel one

Yes, I already was searching for the other opamps haha.

The 'Pocket Class A Headamp GB' intrigues me but the BF862 seems a bit 'exotic'.
Suppose nearly the same quality is possible with common through-hole components and the circuit would keep its 'simplicity'. Wouldn't it get the same status as the Cmoy amplifier being build by hundreds or more?
A possible title for a new thread would be: 'the simplest headphone amplifiers using discrete components' or something like that.

 

[xrk971]

There is indeed a through hole version called the DCA. The BF862 is a very nice low noise JFET originally designed for mass production use in things like FM/AM radios. It’s at EOL, so harder to find. I have new simulations for a replacement 2SK209 that’s easier to find. You can also use the “exotic” unobtainium 2SK170 - or recent LSK170. New resistor setpoints have been calculated for all 3 JFETs.

DCA is here:
xrk971 Desktop Class A (DCA) Headphone Amp

Has built in cap Mx PSU with CRCRC.

Wouldn't it get the same status as the Cmoy amplifier being build by hundreds or more?

There are probably over 200 of the PCA amps out in the wild.