Simplistic NJFET RIAA - Page 864 - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

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 November 2012, 10:35 AM   #8631
AndrewT is online now AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Salas,
are you saying use the post8011 sch as a pre-amp and then add a test fixture before it?
Or
Remove Q1 and use this position as the DUT location?
__________________
regards Andrew T.
  Reply With Quote
Old 25th November 2012, 10:42 AM   #8632
RCruz is offline RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
Ok... this seems a nice idea... maybe I could build something like that... maybe it could be used to feed a pc soundcard so we could "see" the noise instead of merely try to determine differences by ear.

I need something to read about folded cascodes... would you point me a good link ?
__________________
RC
  Reply With Quote
Old 25th November 2012, 10:47 AM   #8633
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
I would use 3 female pins base for exchanging Q1 as DUT, a higher source resistor to accommodate wider IDSS, say 10R factoring its noise in. It would take centering at 1/2 the LEDs + Vbe with the trimmer each time, or a steady resistor and variable PSU. By comparing the total amplified output noise each time, the DUT could be relatively characterized.
  Reply With Quote
Old 25th November 2012, 10:50 AM   #8634
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Forget ear, we are talking instrumentation now. For ear you can just exchange Q1 in a full phono on a pins base in a given system and go stick at the tweeter for hiss, is the most practical I can recommend.
  Reply With Quote
Old 25th November 2012, 10:52 AM   #8635
AndrewT is online now AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally Posted by Salas View Post
................... For ear you can just exchange Q1 in a full phono on a pins base in a given system and go stick at the tweeter for hiss, is the most practical I can recommend.
That's the answer I was hoping for.
Best (ear) noise performance in the actual circuit it will be assembled into.
__________________
regards Andrew T.
  Reply With Quote
Old 25th November 2012, 10:52 AM   #8636
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
@RC

Folded cascodes are used mainly in op amps. You can look for some Analog Devices datasheets and they are referred in electronics papers about cascodes in general.
  Reply With Quote
Old 25th November 2012, 02:11 PM   #8637
RCruz is offline RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
Hi Salas

What do you think about the 4391 fets ?
http://www.datasheetcatalog.com/data...3/2N4391.shtml
__________________
RC
  Reply With Quote
Old 25th November 2012, 02:52 PM   #8638
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Those are high IDSS fast choppers that would lead in high source resistance values to control the voltage drops for logical supplies in a circuit like here. Low gfs hence noisier than other options. Good for sampling and fast switching or low drift CCS in an amp's VAS or something.
  Reply With Quote
Old 25th November 2012, 03:12 PM   #8639
RCruz is offline RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
No go

Found those here: Folded Cascode Hijinks with PN4391
__________________
RC

Last edited by RCruz; 25th November 2012 at 03:14 PM.
  Reply With Quote
Old 25th November 2012, 03:23 PM   #8640
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Wrench had a series of great concepts basing on American chopper FETs for MM. That linked one maybe I missed, I will read it again to refresh. Not best applicable for circa 60dB gains and noise levels established here IMHO. Still folding is just another circuitry technique not specific parts related. Can be done with anything and as everything in electronics must be judged to best integration and spec. Roender had it in his amp's input stage with Japanese FETs for instance, and so on and so forth.
  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



New To Site? Need Help?

All times are GMT. The time now is 11:44 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