Adding a buffer to my Zen V3 - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

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 5th October 2005, 07:53 PM   #1
diyAudio Member
 
Shoog's Avatar
 
Join Date: Aug 2002
Location: Eire
Default Adding a buffer to my Zen V3

Hi there,
I dragged out my old ZenV3 a few days ago. I haven't had a chance to listen to it recently and I want to compare it to my Valve Parafeed amp.
The Zen was my first project and is a bit delicate so I don't want to do much to it, but I feel it needs its low input impedance issues to be addressed before it can go head to head. I really don't want to alter it as much as converting it to the Zen V4, so I have devised a simple gainstage which I can add to the front end to bring up its impedance and gain.
Anyone care to comment on whether it will work.

Thanks Shoog
Attached Images
File Type: jpg zen buffer.jpg (18.9 KB, 447 views)
  Reply With Quote
Old 5th October 2005, 08:20 PM   #2
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
I would put maybe 100 ohms on the Source to ground of the
transistor, and make the 100K input resistor a pot so that you
can adjust the DC output value.
  Reply With Quote
Old 6th October 2005, 07:21 AM   #3
diyAudio Member
 
Shoog's Avatar
 
Join Date: Aug 2002
Location: Eire
Thanks for that Nelson. I will certainly add the 100R resistor, and will think about the 100K pot.

Will report back on the final result.

Shoog
  Reply With Quote
Old 6th October 2005, 05:35 PM   #4
diyAudio Member
 
Shoog's Avatar
 
Join Date: Aug 2002
Location: Eire
Everything seems to work just fine. Getting probably a 3db gain and no major distortion. Only tried it with a test speaker so far.
Managed to short out my capacitance multiplier so now have quite a bit of hum - will work on a "neat" rebuild tonight. Should be in business by tomorrow.

Shoog
  Reply With Quote
Old 7th October 2005, 10:15 PM   #5
diyAudio Member
 
Shoog's Avatar
 
Join Date: Aug 2002
Location: Eire
Hi all,
Just a status report. Got everything working. After repairing the capacitance multiplier I still had a hum, which I didn't remember from before. Tracked it down to the buffer. Added another stage of filtering 22R followed by 1000uf. That did it - nice and quiet.
Listening now on my main system. Sounds nice. Very soft sound. Unfortunately clarity and punch is less than my parafeed amp, so it will probably go back into storage again. I didn't do an especially good job on my Zen so there is no saying that someone else hasn't got a Zen which could better my other amp.

Thanks all

Shoog
  Reply With Quote
Old 11th October 2005, 05:21 PM   #6
diyAudio Member
 
Shoog's Avatar
 
Join Date: Aug 2002
Location: Eire
Hi there,
Made a small adjustment to the buffer. Changed the 500R for a 1K resistor. Improved the top end a huge amount.
Closer examination shows that the circuit I used was the V2. Still not as good as my parafeed amp or buffered gainclone, but good enough to have had playing in the main system for the last four days. very enveloping sound which is great on jazz and folk, but when thing get complex with techno or hard rock, things seem to get muddled.
An interesting experiment overall.

Shoog
  Reply With Quote
Old 11th October 2005, 05:39 PM   #7
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Would not you better use N-MOSFET source follower as a buffer?
  Reply With Quote
Old 11th October 2005, 05:47 PM   #8
diyAudio Member
 
Shoog's Avatar
 
Join Date: Aug 2002
Location: Eire
Buffer is really the wrong description for what I did. I had the irf610's to hand and I wanted a little gain (to make it fit with my unity gain preamp) as well as impedance increase, so this circuit suits my purposes perfectly. It works well and I am happy.
It certainly may not be the best solution for everyone. I would expect most people would be building ZenV4 by now, which should perform better.

Shoog
  Reply With Quote
Old 11th October 2005, 06:27 PM   #9
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
In case you use source resistor, as per NP's recommendation, it might be OK. The gain would be roughly

G = drain resistor / source resistor

Omitting source resistor would lead to high distortion.
  Reply With Quote
Old 11th October 2005, 06:45 PM   #10
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
Quote:
Originally posted by PMA
Would not you better use N-MOSFET source follower as a buffer?
A P channel enjoys some cancellation with the N channel, if
that's what you're looking for.
  Reply With Quote

Reply


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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Diamond Buffer - Super Buffer peranders Solid State 34 16th May 2010 01:46 PM
adding aux's bodaddy Instruments and Amps 10 22nd May 2008 05:40 PM
Adding gain to this buffer.... theAnonymous1 Chip Amps 12 3rd August 2007 05:17 PM
Opamp + buffer, how to bypass buffer at HF for unity gain? Christer Solid State 10 29th October 2003 06:50 AM


New To Site? Need Help?

All times are GMT. The time now is 03:38 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2