jFET input ,full symmetrical class A circuit - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 25th July 2002, 03:16 PM   #11
diyAudio Member
 
promitheus's Avatar
 
Join Date: Jan 2001
Location: Germany
Yeah why not?
If Kevin is a member here and can share some extra info on this design it would be a great help .
I donīt know what name Kevin uses in this forum at all but any idea would be great.
  Reply With Quote
Old 25th July 2002, 05:31 PM   #12
paulb is offline paulb  Canada
diyAudio Member
 
Join Date: Jun 2001
Location: Calgary
I believe the name he uses is "kevin gilmore". Unless that's somebody else.
  Reply With Quote
Old 25th July 2002, 05:54 PM   #13
Banned
 
Join Date: Feb 2002
Location: As far from the NOSsers as possible
It is based on having done this many times, over many years.

You can put a capacitor across the load resistor. A JFET of BJT follower after it would be a good idea. (Actually.....you will need a few more parts to bias the whole thing up......and as they liked to say in college...."the solution is left to the reader as homework....".)

Borbley's version has too much stuff, and he mucks it up with feedback, as I recall.

I have some ideas on making a differential output circuit using only one DAC. At >$33 each for a '1704, using a total of 4 seems too expensive. However, it is still in the idea stage, as I have more pressing problems.

Like no job.....and thanks to crooks like Bernie Ebbers.....no retirement fund anymore....., so it may be some time yet before I get back to it.

Jocko
  Reply With Quote
Old 25th July 2002, 08:09 PM   #14
diyAudio Member
 
morsel's Avatar
 
Join Date: Apr 2002
Location: Mountain View, California USA
Kevin Gilmore's amp is outstanding just the way it is. Reducing the number of output BJTs will increase the output impedance and is not a good idea. The DC servo is an excellent, noninvasive method of protecting the output from DC at the input. Since it integrates the output signal to produce a bias voltage to correct DC offset, there is no reason to use a discrete circuit in place of the opamp.
  Reply With Quote
Old 26th July 2002, 10:35 AM   #15
diyAudio Member
 
promitheus's Avatar
 
Join Date: Jan 2001
Location: Germany
Hello ,

Jocko Homo I was looking at Nelson Passī design which uses two 610 MosFETs only. Do you know this design from his DAC in the passlabs site ?
the link is here:
http://www.passlabs.com/pdf/d1-srv-man.pdf
  Reply With Quote
Old 27th July 2002, 05:33 PM   #16
Banned
 
Join Date: Feb 2002
Location: As far from the NOSsers as possible
That works fine, and a good place to start. My idea is more convoluted.

Jocko
  Reply With Quote
Old 27th July 2002, 07:59 PM   #17
diyAudio Member
 
promitheus's Avatar
 
Join Date: Jan 2001
Location: Germany
I thought this circuit wouldnīt work for me because I thought it was balanced and a one circuit.

After you saying about a capacitor across the load at the outptut of the DAC I rechecked Nelsonīs DAC and saw that it was 2 independant circuits, one for every phase.

I think the filter is in the input, I am still not sure how it works and how the volume works. It also has caps in the output which I dont know if they are supposed to be there. If the Circuit has DC at the output than I will need to use those.

I like it because it is simple.
  Reply With Quote
Old 27th July 2002, 09:21 PM   #18
diyAudio Member
 
promitheus's Avatar
 
Join Date: Jan 2001
Location: Germany
I am really sorry I made a mistake here.
You canīt see it at first but the two parts are connected through the volume control.
Strange volume control.
I wouldnīt know how to make something like this for unbalanced signal.
The input IS a common gate mosfets configuration, but I think the filter is at 20 KHz only for CD use.
  Reply With Quote
Old 27th July 2002, 11:13 PM   #19
rickpt is offline rickpt  Portugal
diyAudio Member
 
rickpt's Avatar
 
Join Date: Jan 2002
Location: portugal
Thumbs up I/V stage

I think what you want is something like this one...

I found it on the tweaker's asylum...

Here is the link: http://www.audioasylum.com/audio/twe...ges/57022.html
I hate mosfet's but some guys like them, you can change them if you want...

Regards

Rick
  Reply With Quote
Old 27th July 2002, 11:16 PM   #20
rickpt is offline rickpt  Portugal
diyAudio Member
 
rickpt's Avatar
 
Join Date: Jan 2002
Location: portugal
Cool pic

sorry
Attached Images
File Type: jpg dac_iv.jpg (41.6 KB, 918 views)
  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
Jfet input for Aleph 60? Dansk Pass Labs 14 22nd January 2011 01:34 PM
discrete jfet input opamp rubydac Solid State 5 12th March 2008 04:59 PM
JFET input SuSy Chipamp Russ White Pass Labs 4 7th May 2007 08:12 AM
JFET in-circuit matching Leolabs Solid State 5 9th April 2006 01:44 PM
Symmetrical input stage hjelm Solid State 19 22nd April 2004 12:37 PM


New To Site? Need Help?

All times are GMT. The time now is 08:54 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright Đ1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2