New PassDIY Headphone Amp (now available)

[meldano]

My build plays better than all compared commercial headphone amps up to 1500€.

I use 120mA bias and opa627.
My headphone is a akg k812.


Daniel

 

[drpro]

Does anyone have boards and a BOM?

 

[Algar_emi]

Here my own BOM...

 

[drpro]

Thank you very much, now a board.

My kingdom for a board!!

 

[Algar_emi]

You don't want a horse instead 😉 I'll have an updated BOM in a few minutes...
SB

 

[Algar_emi]

BOM Update, after I assembled my PCB...

 

[zyker]

Just made my own today, since the original is not in store yet 😉
More or less as 6L6 original design, and I followed the published original schematic.

I'm looking forward to see the populated board 🙂

 

[Algar_emi]

Prototype is working fine, pictures to follow soon...
How can I increase the bias to 120ma as Meldano did? I have actually 56ma of bias.

Thanks

 

[meldano]

R16,22,29,32 to 4,99R

 

[generg]

Good morning, meldano!

🙂

 

[meldano]

Good morning my friend 😉

 

[drpro]

So there really are no PCB for this headphone amp out there yet?

 

[Jean]

Doesn't look like it, not yet ?

 

[Algar_emi]

Ok, final measurements, with 112ma bias 😉

Vout max, no load 9V, 32R load 6.46Vac (17Vp-p), Vin max 1.13V
Gain: 15.7dB
BW: 6Hz to 247Khz (ref 1Khz, -3dB BW)
THD (into 32R load, 2Vout): 0.01% (1Khz), 0.008% (10Khz)
THD (into 32R load, Vout max 6.46V): 0.004%
Noise: 0.2mVac, input to gnd, no load

All in all these are excellent specs, reflecting a very well engineered circuit.

Now time to complete the chassis 😉

 

[Algar_emi]

Chassis completed. Working fine. First listening, very direct sound, fast, but analytic, It is not a forgiving amp so far.
Now time for some burning 😉 Tried it with AKG702 & Sennheiser HD600.

You can see a little heatsink was added just in case, but the standard heatsinks seem to be fine for 112ma bias...

Noble volume pot, Mogami internal wires, Vishay CFM55 resistors in the signal path, Solen MKP 1uF coupling cap, Panasonic FC electrolytic. Nothing fancy really...

BTW I'm using not K2013/J313 but FKP3P20/FKP4N20 Mosfet

SB

 

[Algar_emi]

Front and back views. As I said nothing fancy, but a nice, functional case, with blue power-on switch.

 

[blackdod]

Nice!

 

[WalterW]

Super nice! I thought I saw someone doubting if you were able to build it.... now I know it was a joke 😀

 

[fabriciom]

Any of the experts compare this to say the SPL Phonitor. I know its a different animal but just talking about sound quality.

-Thanks.

 

[meldano]

I compared my Muses-Pass-HPA with a SPL Auditor.
The Auditor is a good Amp with clean sound. In my opinion, the Pass HPA is the one with more heart, drive and music.