[macky112]

If you look at the D.C. Levels at those caps then add the max voltage swing.

For input probably not more than +/-2v plus 1.5vdc so a 5v could theoretically work. For output D.C. is about 7v. Max output swing is about +/-5v so 12v would be minimum for output. But for lower distortion you don't want to have a cap too close to limit. I use 35v Elna Silmic and film cap is 50v rated.

Thank you for the explanation!

If I want to roll caps in my other devices, would measuring the positive leg of a cap relative to ground give me a good idea of what voltage rating I need?

 

[xrk971]

Yes - plus add possible AC component.

 

[xrk971]

Here is a new single ended to balanced output phase splitter under development with Hugh Dean of Aspen Amplifiers. This circuit follows the Pocket Class A ethos of simplicity for a purity of sound - it uses just two transistors and runs pure Class A single ended mode of operation (just like the amp) with very low distortion. Can drive two 27k ohms loads to 10v peak to peak. It has perfect analog phase splitting. Oscope screen shows actual music and you can see the positive and negative phase outputs. So combining this with a single Pocket Class A amp yields a single balanced channel out. I will build up another one and then modify my OB-1's for balanced drive then have a test listen.

Combining two of these and two of the Pocket Class A amps but modified for higher bias desktop use might be a nice addition to the current lineup.

The phase splitter is unity gain and requires 45v Vcc in order to produce the full 10v p-p output swing. It can run at lower voltage if we only need a few volts to feed into the power amp stage. But for lowest distortion, a 45v rail will give 0.0027%THD to drive 1.4v (0dBu) into the amp stages.

 

[gwompki]

Hello all. I'm way late to the party. This looks like a killer build!

I read most of this thread and a good chunk of the thread over on DIY Audio. Is there still a place to buy just the PCBs? I see the populated PCBs on @xrk971 Etsy shop but was wondering if you could buy just the board still? The group buy posting on DIYA doesn't seem to have been updated in a while. Thanks and apologies if this has been covered elsewhere.

 

[xrk971]

Let me put the PCBs up on Etsy.

.... ok done.

 

[gwompki]

Let me put the PCBs up on Etsy.

.... ok done.

Thanks! Just curious, if you buy the kit are the FETs matched or is it just luck of the draw? I'm trying to decide how lazy I feel

 

[xrk971]

Kit includes matched FETs. You just need to provide the tin and cut the holes.

I can provide a blank tin with precut holes for $10 if you are real lazy.

 

[gwompki]

Excellent. Now I just need to decide if my laziness or budget will win out!

 

[gwompki]

Just ordered a kit to build one bone stock and a pcb for experimentation later. Can't wait!

Will try them with my HD-6XX and TH-X00 as well as various budget earbuds.

 

[xrk971]

Thanks for the order. What impedance are your earbuds?

 

[gwompki]

Thanks for the order. What impedance are your earbuds?

Earbuds are anything from 16 ohm to 300 ohm.

HD6XX (Sennheiser HD650) is 300 ohm. This is the most picky set I have. Looking forward to this pairing.

Fostex TH-X00 are 25 ohm bio dyna drivers.

 

[gwompki]

Just got my kit today. Incredibly fast responses and shipment from @xrk971. Awesome guy to deal with!

This is my first time with SMD components. Let's just say this not going to be my best looking build LOL. If it were all through hole I could probably have all of the on board components soldered in under 45 minutes. I'm about an hour in and have 6 resistors on the board . The solder paste and hot plate method are looking really good for my 2nd build.

One question for @xrk971...if I use standard Duracell 9V batteries will that be Ok with the 25V 2200uF caps? I know you specify the rechargeable which have 8.4V max if I recall correctly.

 

[xrk971]

SMD is slow at first due to learning curve. You will soon find that it is way faster than through hole as no leads to bend or clip and only one side of board to work on. Apply solder to one bare pad. Place part and hold in place with pressure from tweezer. Touch iron to pad with solder puddle to remelt. Then add solder to other pad. That's it. Removing is trickier but alternately heat ends while lifting with tweezer.

9v alkalines are fine. Even with 16v 2200uF caps. It's only 9v for a few minutes. Your 25v rated caps are well above 18v so no issues there.

Good luck.

 

[gwompki]

It's alive! Very impressed so far with the HD6XX. I only got about 20 minutes to listen after I finished building, but so far so good. More detailed impressions to follow... hopefully this weekend.

Don't laugh too hard at my soldering work on this one. Next one will be better

 

[xrk971]

Nice!