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Old 19th March 2015, 04:45 AM   #1
6L6 is offline 6L6  United States
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Default New PassDIY Headphone Amp (Coming Soon)

Just to create some interesting discussion, here is a preview of the new PassDIY headphone amp. Wayne's been working on this, and everything so far has been very, very promising.

A few answers first --

As of this post in March '15, it's not yet available. Hopefully it will be for sale in the diyAudio store before summer.

These photos are of the first, non-conforming PCB. The final version will look very similar, the changes for the revision are all very minor, mostly silkscreen stuff.

Of course, it's Class-A. The output stage is really neat.

It has no 'Klunk.'

It will be able to drive any headphone to deafening levels. Gain can also be turned down for super-sensitive headphones.

The whole circuit is on the one PCB. Input jacks, output jacks, and AC are all chassis mount. Of course, you could chassis mount the pot as well. Or use a fancy stepped attenuator. This is DIY, after all.

Click the image to open in full size.

A photo of a partially-stuffed PCB and some other parts.

The mosfets will mount to their own heatsinks on the edge. This will make it easy to utilize whatever chassis you like. In fact, the floor of a metal chassis will be enough heatsink and you could just mount the devices to that.

Click the image to open in full size.

Click the image to open in full size.
This is a nice touch - the PSU is able to be configured for fixed OR variable regulators. This is the proper hook-up for the 7815/7915 pair. But if you would like to use LM317/LM337, or another 3-legged critter with the same pinout, feel free, the pads are there for the extra resistors and cap if needed.

Click the image to open in full size.

(Obviously, this is a partially-stuffed PCB) The heart of the output circuit, the 4N35 optocoupler being used as the bias control. (This is a Nelson invention, I believe...) Bias is rock steady, and easily adjustable by simply changing the source resistors.

Oh, did I mention that you don't need matched output mosfet? And that you can use Toshiba, Fairchild, IRF, or whatever you happen to have that's similar? Cool.

Click the image to open in full size.
Being tested. The two 560 ohm resistors are the test load. (No, there is no headphone jack installed on this chassis, yet....)

Click the image to open in full size.
Install whatever headphone jack you have/want on the chassis. Some people will want a big one, some a small, some will want the power switch on the front, others will want it on the back. Make a fantastically gorgeous chassis from wood, unicorn horn and platinum, or just use the cheap&cheerful Hammond that the PCB happens to fit. It's DIY!

The name is still up in the air, things that have been discussed are "Perl D" (a workup of "PERsonal Listening Device" and Wayne's Grandmother named Pearl, of whom his previous DIY projects are named. )

I've come up with "Whammy". (Wayne's Headphone Amp Must Make Yourself) But that's kinda silly. (Although I do like it... )

Any good name suggestions will be considered.

Last edited by 6L6; 19th March 2015 at 04:48 AM.
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Old 19th March 2015, 04:46 AM   #2
6L6 is offline 6L6  United States
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Placeholder post for more photos or the schematic in the near future.
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Old 19th March 2015, 04:54 AM   #3
ammel68 is offline ammel68  United States
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Thank you for posting all this!

I've been curious about the Pass DIY headphone amplifier.

What is the the purpose of the DIP-8 op-amp? Is it the first gain stage after the volume pot?
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Old 19th March 2015, 07:02 AM   #4
EUVL is offline EUVL  Europe
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+/-15V and 2SK2013/2SJ313 output per channel. That gives a good idea of maximum power.

I wonder if Nelson would let us pimp into the actual Pass Labs headphone amp ....
This is the real thing.

CES 2015: Pass Labs Upcoming Headphone Amplifier | InnerFidelity


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Old 19th March 2015, 07:16 AM   #5
Zen Mod is offline Zen Mod  Serbia
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just to stir things up , I have few questions :

-can we use 12V6 Accus ?
-will it drive F4 ?
-is it better than BA3 FE ?
-will it drive F4 ?
-can I use 32R phones ?
-can I use Stax statics ?
-will it drive F4?

no doubt , I'll be back with more ......

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Old 19th March 2015, 07:18 AM   #6
EUVL is offline EUVL  Europe
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Good questions .........


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Old 19th March 2015, 09:44 AM   #7
The Dastardly Dad of Three
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slurpp yummy

Hmm.. wonder whats that op-amp socket doing in there ?

Like the name you suggested Jim ....

Last edited by kasey197; 19th March 2015 at 09:48 AM.
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Old 19th March 2015, 09:54 AM   #8
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I keep throwing money at my screen but nothings happening

Watching this one eagerly.
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Old 19th March 2015, 10:06 AM   #9
Zen Mod is offline Zen Mod  Serbia
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most probably servo IC ?

everything else around is just to be able to drive F4



HUGS , for name ?
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Old 19th March 2015, 11:55 AM   #10
6L6 is offline 6L6  United States
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Quote:
Originally Posted by Zen Mod View Post
-can we use 12V6 Accus ?
-will it drive F4 ?
-is it better than BA3 FE ?
-will it drive F4 ?
-can I use 32R phones ?
-can I use Stax statics ?
-will it drive F4?
In order:

12V6 Accus?? Not sure what that is...

Of course. Heck - the suggested gain opamp is the OPA 2604, which can run on +/-24V. Get a slightly bigger transformer, use 7824/7924 regulators or 317/337, and swing even more volts.

No idea yet, I'm waiting for a couple of parts. The BA-3 gainstage is beautiful, as you know, but this will drive headphones, as the output stage is source-follower.

Yes.

Of course. Or 600ohm headphones. Or low-efficiency planar headphones. Or super-efficient IEM.

If you have the Stax step-up transformer, of course.

Yes.

Quote:
Originally Posted by kasey197 View Post
Hmm.. wonder whats that op-amp socket doing in there ?
The socket is to try different opamps. I've got a few on the bench I want to try.

Last edited by 6L6; 19th March 2015 at 12:02 PM.
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