Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Pass Labs This forum is dedicated to Pass Labs discussion.

Pass HPA-1, what do we know?
Pass HPA-1, what do we know?
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 30th November 2016, 08:55 PM   #1
Hikari1 is offline Hikari1  United States
diyAudio Member
 
Join Date: Jun 2012
Location: Seattle
Default Pass HPA-1, what do we know?

Pass' new HPA-1 is certainly getting good press.

Pass Labs HPA-1 headphone amplifier | Stereophile.com

Do we know anything about the design? Push-Pull or single-ended? Based on any currently known topology (Aleph, etc.)?

Just trying to figure out what Pass considers the best approach for headphone amplification.
  Reply With Quote
Old 30th November 2016, 09:32 PM   #2
xrk971 is offline xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
Pass HPA-1, what do we know?
A picture is worth a thousand words...

Click the image to open in full size.

Zooming in on the left channel, I see 12 active devices in a very symmetric layout. It looks like 10 actives prior to the two big output MOSFETs with large 3w source resistors. I see one DC offset trimpot, 1 bias trimpot. There is a TO92 programmable voltage source (TLM431?) providing bias current adjustment, it's not in the audio path. The opamp is in between the two channels and I don't think it is in the audio path either.

Click the image to open in full size.

I suspect it might be a push-pull output stage with something resembling one of Juma's creations.
Attached Images
File Type: png Pass-HA-crop.png (966.7 KB, 1157 views)

Last edited by xrk971; 30th November 2016 at 09:35 PM.
  Reply With Quote
Old 1st December 2016, 02:37 AM   #3
Hikari1 is offline Hikari1  United States
diyAudio Member
 
Join Date: Jun 2012
Location: Seattle
The op amp is likely a servo. Some of the to-92 active devices may be regulators or voltage references. Probably push pull I would imagine. Still would like to know more...

The big film caps are curious if they are not rail decoupling.
  Reply With Quote
Old 1st December 2016, 05:34 AM   #4
seanny is offline seanny  United States
diyAudio Member
 
Join Date: Oct 2008
Location: Orange County, California
On the CES video someone said the only IC on the board is for servos.
  Reply With Quote
Old 1st December 2016, 05:41 AM   #5
seanny is offline seanny  United States
diyAudio Member
 
Join Date: Oct 2008
Location: Orange County, California
5 pairs = 4 beasts and a cascode?
  Reply With Quote
Old 1st December 2016, 11:12 AM   #6
mrWagner is offline mrWagner  Hungary
diyAudio Member
 
Join Date: Oct 2006
I like 6moons better as they show lot more of the devices inside.
  Reply With Quote
Old 1st December 2016, 12:57 PM   #7
Kovax is offline Kovax  Croatia
diyAudio Member
 
Join Date: Aug 2002
Location: Zagreb , CROATIA
Current feedback design by the looks of it.
Something like one of our great minds here has already offered on the topc of another Pass designs, just this one is sized for headphones. Here is the link.

Pass XA25?
__________________
If it can't be fixed ... use a bigger hammer
  Reply With Quote
Old 1st December 2016, 01:09 PM   #8
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
> Do we know anything about the design?

More than you need to reverse engineer it, even down to component level.
Read the 6moon review in detail, not only the pictures.

> Push-Pull or single-ended?

Single-ended (as opposed to balanced) push-pull.

> Based on any currently known topology (Aleph, etc.)?

No.

> 5 pairs = 4 beasts and a cascode?

6moon :
"...... I tried different devices including bipolars and in the final analysis we chose Toshiba Jfets for the input stage,
Fairchild Mosfets for the outputs and bipolars in the current mirrors
so we ended up using all three device types.....
the voltage gain occurs in the Jfet/mirror stage and the Mosfets provide the current drive....."


Patrick
__________________
xen-audio.com

Last edited by EUVL; 1st December 2016 at 01:11 PM.
  Reply With Quote
Old 2nd December 2016, 12:27 AM   #9
proid is offline proid
diyAudio Member
 
Join Date: Sep 2011
Quote:
Originally Posted by EUVL View Post
> Do we know anything about the design?

More than you need to reverse engineer it, even down to component level.
Read the 6moon review in detail, not only the pictures.

> Push-Pull or single-ended?

Single-ended (as opposed to balanced) push-pull.

> Based on any currently known topology (Aleph, etc.)?

No.

> 5 pairs = 4 beasts and a cascode?

6moon :
"...... I tried different devices including bipolars and in the final analysis we chose Toshiba Jfets for the input stage,
Fairchild Mosfets for the outputs and bipolars in the current mirrors
so we ended up using all three device types.....
the voltage gain occurs in the Jfet/mirror stage and the Mosfets provide the current drive....."


Patrick
Sound like this one: http://gilmore.chem.northwestern.edu/lc.pdf
  Reply With Quote
Old 2nd December 2016, 09:33 AM   #10
juma is offline juma  Germany
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Berlin
Something like this roughly fits the bill and sounds nice ....
Attached Images
File Type: gif mb.gif (6.5 KB, 784 views)
__________________
Please don't use private messages for question related to audio projects. It defeats the purpose of the forum.
  Reply With Quote

Reply


Pass HPA-1, what do we know?Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
My first Desktop HPA The Coolest Headphone Systems 19 26th November 2015 05:04 PM
HPA-nxV300 & HPA-nxV300se what's the difference? pcsl999 Holton Precision Audio 14 3rd September 2013 10:24 PM
HPA-nxV101 Signature sonnya Holton Precision Audio 10 28th July 2012 08:10 AM
MI-HPA banginon Music 0 10th February 2011 04:40 AM
HPA-nxV201 Released Soon! The Saint Holton Precision Audio 5 23rd September 2009 05:33 AM


New To Site? Need Help?

All times are GMT. The time now is 03:41 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki