CMoy for AKG K601s?
Aug 3, 2010 at 4:33 PM Thread Starter Post #1 of 10

Maxxtro

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Hello!
 
Would be a well-built CMoy with a wall-powered supply and big buffer-capacitors be good enough to drive the 120-Ohms AKG K601s?
 
I know that the are obviously pretty hard to amp due to the fact that the need a lot of current but with some big capacitors...?
 
 
Greetings,
Maxx
 
Aug 3, 2010 at 5:46 PM Post #2 of 10

jcx

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I would choose a higher than average current output op amp - JRC/NJM4556 is a old part, available in DIP package that has higher output current - and is used in Grado's RA-1 amplifier
 
many of the "better", more recent op amps with high output current are only available in surface mount
 
Aug 4, 2010 at 4:19 AM Post #3 of 10

Maxxtro

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Well if that is the truth...  I´ll just listen throug the output of my CD player, which is based on exactly that Chip!
Only thing i see which is a little bit ... not looking too good is the slew rate of just 3V/µs?
 
 
 
Aug 4, 2010 at 11:46 AM Post #4 of 10

jcx

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with the 4556 your desktop CD player output is likely to be as good as a "CMOY" for that headphone - if you have the schematic then checking the signal path DC blocking Cap values would be good - sometimes they are too small and lose the lower octaves
 
to get potentially better performance with DIY would require going with a more complicated project with a high current output buffer
 
Aug 4, 2010 at 11:54 AM Post #5 of 10

Maxxtro

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They are 100µF / 25V Elna Silmic II.
 
Well... could i build a CMoy and put a Diamond Buffer as used for the PPA v2 at its Output?
 
 
 
Edit: Oh and I justed looked on the Grado Website; they are using the 4556, which is specified to a minimum of 150ohm load with their 32ohm headphones? And call it their "reference Amp"?
 
Aug 4, 2010 at 2:59 PM Post #6 of 10

Maxxtro

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Another question about my headphone amp:
 
Before the 4556 on the input there is a high-pass with a -3db attenuation at 2.8Hz, made with a cheap 47µF capacitor and a 1.2k resistor.
After the 4556 there is another filter with a maxiumum of 10Hz made with a high quality Elna 100µF capacitor and a 150R resistor.
 
I´m thinkin about leaving out one of these. Wich one would be better to leave out? I guess it is better if I dont even amplifie DC and so I maybe should leave out the second filter after the amp, right?
 
Aug 4, 2010 at 5:21 PM Post #8 of 10

vgjako

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I would personally choose to build a Pimeta V2 rather than a Cmoy if you are going to add a diamond buffer to the Cmoy. The Pimeta is a better amp then the Cmoy and will serve your headphones better than a Cmoy. You can get the circuit board for the Pimeta V2 from tangent's website: http://tangentsoft.net/shop/
 
Aug 6, 2010 at 7:21 AM Post #9 of 10

MrSlim

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Quote:
Another question about my headphone amp:
 
Before the 4556 on the input there is a high-pass with a -3db attenuation at 2.8Hz, made with a cheap 47µF capacitor and a 1.2k resistor.
After the 4556 there is another filter with a maxiumum of 10Hz made with a high quality Elna 100µF capacitor and a 150R resistor.
 
I´m thinkin about leaving out one of these. Wich one would be better to leave out? I guess it is better if I dont even amplifie DC and so I maybe should leave out the second filter after the amp, right?


I wouldn't leave either of them out.  The one before protects the amp from DC from the upstream device, and the one after protects your headphones in case the amp itself develops some kind of DC offset.  
 

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