GainWire Mk3 CFA pre/phone amp with very low distortion

[donovas]

What is the function of r39 in the 1st schematic?

 

[dadod]

It is a part of the compesation with R48 and C2.

 

[HRDSTL]

Any duel executed?

No. I also have the original pcb, but in the end I built on the boards from @platon.rado, I always wanted a dual mono preamp. I already have Gainwire done, both pcb's worked on the first power up. I have yet to assemble the controller, switching on the front panel with the blue led. I am currently hesitating whether to buy a TKD 2CP-2511 potentiometer or a 48 stepeed atteunator ELMA. Input switcher will be from ELMA, I only need 2 inputs (DAC, Phono). I'm still thinking whether to invest in high quality cinch connectors (copper+gold) or just buy ordinary ones (brass+gold)

 

[HRDSTL]

My opinion is that digital potentiometers are not good enough, the GainWire mk3 preamp has much lower distortion, only passive resistors attenuators are good enough, even best dual potentiometers as Alps or other kind have to big differences between tracks.

I also ruled out digital volume control, I was deciding between the TKD potentiometer and the atteunator. In the end I leaned towards the attenuator from Khozmo (48 steps), ...which is on its way.

 

[gentlevoice]

@HRDSTL : Hi ... looks like a high quality potentiometer

Cheers, Jesper

 

[HRDSTL]

I'm just waiting for the internal cabling from Neotech (pure cu for power supply & pure silver for signal wiring) Furutech connectors and the Elma switch.

The Gainwire MK3 will eventually only be used as a preamplifier. The headphone amplifier will be a DCG3 from Salas.

 

[HRDSTL]

Friends small update, modushop 2U case. I still have to draw the front and rear panels, ...send them to production.

I am still considering whether the headphone output will be in the front or in the back.
I bought top quality headphones, but with very low 25ohm impedance. I just hope that gainwire mk3 can handle them...

 

[dadod]

This phoneamp was designed for headphones down to 32 ohm, never tried with 25 ohm, hope it can cope with it. Let me know.

 

[HRDSTL]

Hi all,
Gainwire MK3 plays unbelievable!!! Now I really enjoy the music.

I replaced the output resistor 2R2 with a jumper. The Gainwire MK3 can tighten even 25 Ohm impedance headphones, and it plays really loud!
@dadod Thank You

 

[dadod]

HRDSTL, you dit not finished GW mk3 on the original board as I understood? With original board you do not need two mains transformer to have dual mono.
There are separate shunt regulators per side, so it is dual mono too.
Do you have any problem with the broom with those boards you used?

 

[dadod]

I don't have intention to offer this last mk3 version PCB any more, but here you have the gerbers for it.
Damir

 

[HRDSTL]

HRDSTL, you dit not finished GW mk3 on the original board as I understood? With original board you do not need two mains transformer to have dual mono.
There are separate shunt regulators per side, so it is dual mono too.
Do you have any problem with the broom with those boards you used?

I only have it temporarily wired up, wiring hastily... to test the sound quality of the GainWire MK3. No hum or noise, the amplifier is completely silent. I compared the sound of the Gainwire MK3 to the hearing aid output on my Audiolab 6000A and it's an incredible difference! I've always wanted a dual mono preamp.

Power supply in my case is very simple CRC (2200uF+2R2+2200uF) + 7815/7915 + 2200uF

Today I would like to draw the front and back panel and send to production for milling, engraving. GainWire MK3 definitely deserves attention, ...everyone should build one.

 

[HRDSTL]

Friends, the panels from production arrived today! Hopefully by the end of the week it will be built GainWire MK3 complete!

 

[passive420]

I don't have intention to offer this last mk3 version PCB any more, but here you have the gerbers for it.
Damir

Feel a fool now having paid you 60 euro for one PCB. Damnit...