Noob Building a α20 Headphone Amp

Hi All,
Please be kind, this is my first DIY build. Planning on a a20 with sigma 25 power supply.

Raspberry Pi > DAC > a20 with Sigma 25 > headphones (Sennheiser HD650, Sony MDR7506, Grado SR80, ACS Custom IEM, Denon D2000)

So far have ordered:
(1) Potentiometer
(1) Volume Knob
(2) a20
(2) Sigma 25
(2) Toroidal Transformer
(1) Headphone Connector
(1) IEC with on/off and fuse
(2) RCA Connectors

Thinking I will figure out the Raspberry Pi > Dac once I have the headphone amp built. Welcome suggestions !

A big thank you to Hikari1 for his guidance.

Thanks, Mark
 

Bibio

Member
2009-03-08 3:36 am
i use a RPi/dac/headphone amp combo and it sounds pretty good to my ears. i use moode with the RPi/DAC combo.

the pi, is very picky of power and ground loops so take care with that.

at the moment i have the RPi with iqaudio dac+ and i power this off a LM7805 and 12v wallwart which is not the best solution. the only problem i have is a ground loop. the RPI is silent and the headphone amp is silent but plug them both together and it creates a ground loop so you might want to think of the RPi and the amp as one unit taking power from a single multi volt supply.
 
i use a RPi/dac/headphone amp combo and it sounds pretty good to my ears. i use moode with the RPi/DAC combo.

the pi, is very picky of power and ground loops so take care with that.

at the moment i have the RPi with iqaudio dac+ and i power this off a LM7805 and 12v wallwart which is not the best solution. the only problem i have is a ground loop. the RPI is silent and the headphone amp is silent but plug them both together and it creates a ground loop so you might want to think of the RPi and the amp as one unit taking power from a single multi volt supply.

Dear Bibio,
Thank you for the suggestions about ground loop.
All the best,
-Mark
 
sigma 25s finished

Hi All,
Working slowly, finished the two sigma 25s last night, both reading 4.95 volts. Now starting on the alpha 20 boards.

Still have not decided about a DAC to go with the alpha 20

Thank you for the encouragement !

[IMGDEAD]https://goo.gl/photos/FmTZTmkAChBUvxwe9[/IMGDEAD]
 
Last edited:

Dimdim

Member
2008-09-02 7:46 am
Athens
I use a couple of α20s to drive my Fostex T50RP MKIIIs and I'm very pleased with the result.

Be sure to set the gain of the α20s appropriately..

But 5VDC sounds way too low. The α20s are specc'ed for +/-12VDC operation. I'm running mine on +/-18VDC with Salas BiB power supplies. The Fostexs like a lot of power.