FS: Super CMOY, desktop headphone ampifier, Great for testing op amps! [EU]

Hi!

I have made a headphone amplifier and I wish to sell that and then make somebody happy with their purchase. 

This amplifier has a SMD CMOY core with changeable op amp. Gain is set to 5. The op amp used affects the sound most because it drives the headphones directly. The active ground is driven by op amp too (not so big impact on sound) and buffered by OPA633 (heatsinked). Power supply on this amplifier is based on L7812 regulator (adjustable). I have only 230V wall wart, which puts out unregulated 32V. You need ac adapter that has positive tip, 2.1 x 5.5 mm, and puts out 32-36V (unregulated 24V works best), for 110V use. Inputs are RCA with plastic 2.2 uF caps. Power led is orange and headphone jack is 6.3 mm. Volume potentiometer is Panasonic.

I have been listening to this amplifier and it compares very well with my PPA v2 high end amplifier. The SMD build keeps noise level down and makes amplifier more stable and less prone to interference. It is as silent as my PPA v2 when I listen the background noise without music. Basic CMOY core means that Grados or other low impedance headphones are harder to drive. Active ground helps a lot and I can install a more powerful op amp if you have low impedance headphones. Superior op amps add a little to the cost. If I say it compares very well with PPA v2 then this amplifier has truly a hifi sound quality. If you love changing op amps and listening to the differences then this amplifier is what you want. The op amp drives the headphones all alone. 

Transparency is excellent with a good op amp and because there is active ground channel the bass is well presented too.

I can ship this to US, Canada, Europe, Australia and some other countries. It is located in Finland, Europe. 

The price for this unique item (with generic op amp) is 40 USD + shipping cost. Better op amps add some € to price. I have lot of them, just ask. Payment can be made with Paypal or bank transfer in EU. 

OP amps tested in this amplifier (ground channel TLE2082/OPA1642):

AD8397 works very well, DC offset under 20 mV,  very nice sound. With this op amp the amplifier is 49$ + shipping

OPA2107 works also well, DC offset 5 mv and 1 mV. Little bass shy but very nice sound anyway. 55$ + shipping

AD8599 has low DC offset, 7 mV and 4 mV. Quite quiet. Is one of my favorite op amps. Sweet, accurate and musical sound. 50$ + shipping

OPA2111: DC offset 1 mV. Little louder hiss. Quite balanced highs and lows, bass is very present. Perfect soundstage. 45$ + shipping

AD8620 (left and right) + OPA1642 (ground): DC offset as low as 0.5 mV. I have always liked OPA1642 is best on the ground. It makes the sound so perfect, like polished imperfections away. AD8620 is praised everywhere and it is default op amp in high end amplifiers like PPA v2 or M3. I like it too, it is just right soundstage, excellent highs and lows,  and it drives headphones very well because it has high current output circuitry. 59$ + shipping

PS. If buyer has 110V transformers at home, please look what specs they have and what size is their plug. Or buy a new one, Output 24V unregulated, 2.1mmx5.5mm tip positive, 300 mA, I can try to look for such wall wart if there is interest in the US for this amp.

I started testing different op amps with this amplifier and adjusted the price. 

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