Low output impedance preamp needed. - 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 12th April 2007, 11:14 AM   #1
Dxvideo is offline Dxvideo  Turkey
diyAudio Member
 
Dxvideo's Avatar
 
Join Date: Nov 2003
Location: Turkey
Send a message via Yahoo to Dxvideo
Default Low output impedance preamp needed.

Hi all,

I need a low output impedance (about 1K) preamp stage with no gain. I prefer JFETs to use and if possible with one transistor on each channel.

Does anyone know that kind of preamp schematic?

Thanks a lot in advance.
__________________
Best regards,
Ozgur
  Reply With Quote
Old 12th April 2007, 03:30 PM   #2
Ayne is offline Ayne  Pakistan
diyAudio Member
 
Join Date: Apr 2007
JFET input .
No gain.
Low output impedence..

I think it's all u needed.
Attached Images
File Type: gif buffer.gif (2.3 KB, 263 views)
  Reply With Quote
Old 12th April 2007, 10:18 PM   #3
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
a source follower will give you what your after. Well nearly, the Rs <<1k0 and gain may be <1.0
It will perform better if a CCS loads the tail.
Have a look at the various schematics here and in diyhifi.org
__________________
regards Andrew T.
  Reply With Quote
Old 13th April 2007, 07:18 AM   #4
Dxvideo is offline Dxvideo  Turkey
diyAudio Member
 
Dxvideo's Avatar
 
Join Date: Nov 2003
Location: Turkey
Send a message via Yahoo to Dxvideo
Thank you Ayne.
But I am a bit confused about op-amps. Because I have tried TL072, NE5532, LM833 and LM4562 also.They all for specially audio applications. But I afraid I need a warmer sound. Because my amplifier is a lateral MOSFET Class A-AB one.
I like its sound too much but when I connect it a high output impedance device then I can hear some noise and I want to reduce that noise. This preamp is needed for that. And naturally I dont want to change its sound.
__________________
Best regards,
Ozgur
  Reply With Quote
Old 13th April 2007, 07:21 AM   #5
Dxvideo is offline Dxvideo  Turkey
diyAudio Member
 
Dxvideo's Avatar
 
Join Date: Nov 2003
Location: Turkey
Send a message via Yahoo to Dxvideo
And for Andrew;

Click the image to open in full size.

Do you mean a circuit like that?
__________________
Best regards,
Ozgur
  Reply With Quote
Old 13th April 2007, 07:44 AM   #6
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
No.
that's a dual complementary LTP with cascode and then a complementary follower (or is it a VAS?). =8fets, expensive in real estate and dollars.
You asked for single jFET transistor.
I suggested a follower (on it's own).

I think NUUK's site shows exactly what you are after. His update right at the end after the opamp options.
__________________
regards Andrew T.
  Reply With Quote
Old 13th April 2007, 07:45 AM   #7
juma is offline juma  Serbia
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Zemun
No, Andrew meant a circuit like one of these :
Attached Images
File Type: gif sf1.gif (7.4 KB, 147 views)
  Reply With Quote
Old 13th April 2007, 07:47 AM   #8
juma is offline juma  Serbia
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Zemun
Sorry Andrew, you were quicker !
  Reply With Quote
Old 13th April 2007, 07:49 AM   #9
Dxvideo is offline Dxvideo  Turkey
diyAudio Member
 
Dxvideo's Avatar
 
Join Date: Nov 2003
Location: Turkey
Send a message via Yahoo to Dxvideo
Ok I see. I saw a lot of circuit like that. But somebody says
"that kind single ended circuits very prone to noise"
What do you say about that?
And also what do you say about that circuit;
Click the image to open in full size.
Is that the same kind circuit?
__________________
Best regards,
Ozgur
  Reply With Quote
Old 13th April 2007, 08:12 AM   #10
juma is offline juma  Serbia
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Zemun
Yes it is. The lower JFET acts as a constant current source (the source resistor should be of smaller value - something like 22 Ohms). But you said that you want a circuit with one JFET.
Source follovers are not noisy, but they perform better with good power supply.
  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
3C24 in a SE output stage - output transformer impedance recommendation !!! aldovan Tubes / Valves 15 6th September 2008 10:18 AM
How to calculate Tube Preamp output impedance? john65b Tubes / Valves 20 20th November 2007 02:44 PM
ARTA impedance measurements - help needed!! zobsky Multi-Way 23 3rd August 2007 06:38 PM
Can An Output Transformer Change A Voltage Amp's Output Impedance From 0.1 To 47 Ohms kelticwizard Everything Else 11 25th March 2007 05:17 AM
Matching a preamp to high output impedance source ainami Tubes / Valves 5 29th November 2004 04:02 PM


New To Site? Need Help?

All times are GMT. The time now is 11:08 PM.


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