New PassDIY Headphone Amp (now available)

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#161
2 picoDumbs said:
I haven't read all 15 pages just yet, but I'm begging you to do away with opamps. This is DIY.
Even a baby AlephJ with 2sk2013 output wouldn't be hard to build and appeal to many.
Or headphone version of firstwatt SIT Amp
Click to expand...

There are many discrete op-amp plug-in modules out there. Or like you said, build an Aleph Mini or Zen Headphone and skip this build since they already exist in cyberspace.
 
#162
I'm more busy these last days that I was expecting, so here's a few photos of the PCB. I have started construction, but not to a point where I have anything useful to share. Hang in there.

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#167
This project does not use K170/J74 Jfets.

The output devices, although listed in the schematic as Mosfet K2013/J313, are able to be replaced with any similar mosfet, or even bipolar transistors with just a few simple changes.

I'm currently waiting on a chassis for this project, and then all the info will be released.
 
#171
6L6 said:
With the PCB that will be made it would be awfully hard to adapt a discrete front-end.

You could, of course, use a discrete opamp, like the Burson.
Click to expand...

I'm not sure what you're saying. What is the difference? Opamp/front end that's just a word.
Is there anything stopping someone from making a Erno Borbely jfet front end mounted on a pcb with pins to fit into an opamp socket.
 
#174
> the Erno Borbely jfet front end sounds like essentially what the burson is ....

The current generation Burson has BJT input stage with almost 0.3mA input bias current.
Input offset current can be as high as 120µA. So definitely not FET input.

Their earlier generation did look something like this :
ºÍ§Ó*µ响

We built the Pass DIY Opamp in 2008 and like the results a lot.
http://www.diyaudio.com/forums/pass-labs/120445-pass-discrete-opamp-dip-8-package.html

But you will have a hard time getting it DC stable without a servo.
The problem is that when running in pure Class A, the FETs do heat up.
But the N-JFETs and P-MOSFETs have different tempco.
So they will not track each other in bias even if you have perfect thermal coupling.

There are many discrete circuits from Borbely that has a all-FET frontend followed by a follower.
But I guess that is not what this project is about.


Patrick
 
#176
#178
EUVL said:
> the Erno Borbely jfet front end sounds like essentially what the burson is ....

The current generation Burson has BJT input stage with almost 0.3mA input bias current.
Input offset current can be as high as 120µA. So definitely not FET input.

Their earlier generation did look something like this :
ºÍ§Ó*µ响

We built the Pass DIY Opamp in 2008 and like the results a lot.
http://www.diyaudio.com/forums/pass-labs/120445-pass-discrete-opamp-dip-8-package.html

But you will have a hard time getting it DC stable without a servo.
The problem is that when running in pure Class A, the FETs do heat up.
But the N-JFETs and P-MOSFETs have different tempco.
So they will not track each other in bias even if you have perfect thermal coupling.

There are many discrete circuits from Borbely that has a all-FET frontend followed by a follower.
But I guess that is not what this project is about.


Patrick
Click to expand...


I think I was thinking of the earlier version when I said that. Thanks for correcting me 🙂. That said, BJTs sound like they will be quite at home with this amp also.

I love what you did with the Pass OPAMP. I was intending on using this circuit as Wayne intended, and I might still do that initially, but after seeing what you achieved it is tempting to try something similar.
 
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