Simplistic NJFET RIAA - Page 1282 - 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 5th June 2014, 12:17 PM   #12811
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
What is the lowest DC rail your assortment allows via VR2x with R3x at 9.1k?
  Reply With Quote
Old 5th June 2014, 05:21 PM   #12812
Marra is offline Marra  United Kingdom
diyAudio Member
 
Join Date: Nov 2009
Location: Near Lincoln
I will check in the morning but the voltages I listed were with VR2 at the end click.
  Reply With Quote
Old 5th June 2014, 05:40 PM   #12813
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
If you got the rail range for proper TP readings now then you need change nothing. MM arrangement won't drift as much as the MC anyway, so you aren't after much trimming.
  Reply With Quote
Old 6th June 2014, 09:28 AM   #12814
Marra is offline Marra  United Kingdom
diyAudio Member
 
Join Date: Nov 2009
Location: Near Lincoln
Quote:
Originally Posted by Salas View Post
What is the lowest DC rail your assortment allows via VR2x with R3x at 9.1k?
Lowest that I can go is 34.8v on one channel and 35.1v on the other.TP1/2 readings are 3.25v and 3.124v.
  Reply With Quote
Old 6th June 2014, 10:34 AM   #12815
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Obviously the IDSS of your Q3x Vref biasing JFETs falls somewhere between usual R3x value matches for providing balanced enough target trimming range.
Engage VR1 from this point on and try for 3.6V TP1/2. If it again won't reach you may use 8.2K for R3x pursuing extra DC Rail bottom range but you are not in unacceptable readings area already.
  Reply With Quote
Old 6th June 2014, 12:08 PM   #12816
Marra is offline Marra  United Kingdom
diyAudio Member
 
Join Date: Nov 2009
Location: Near Lincoln
I forgot to mention that altering VR1 makes very little differance to the TP1/2 reading.At least not enough to hit 3.6V.Will have a listen to it as I don't think I have any 8k2 resistors.
  Reply With Quote
Old 6th June 2014, 03:45 PM   #12817
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
In MC VR1 would make more difference, in MM can be used for better matching mainly. By lifting one leg of R12 you can much extend its influence.

You made the 40dB with 91R R2 version I presume. That one uses the least bias current. For what cart model, and is it drifting comfortably little on TP1/2 readings after warm up?
  Reply With Quote
Old 6th June 2014, 06:32 PM   #12818
Marra is offline Marra  United Kingdom
diyAudio Member
 
Join Date: Nov 2009
Location: Near Lincoln
Yes the MM with 91R R2 for use with a Decca Microscanner Gold.TP1/2 fluctuate very little unlike the 63db version I built previously.
  Reply With Quote
Old 7th June 2014, 12:48 PM   #12819
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Quote:
Originally Posted by Marra View Post
Yes the MM with 91R R2 for use with a Decca Microscanner Gold.TP1/2 fluctuate very little unlike the 63db version I built previously.
Quintessentially British cart maker. Everything in it designed different than the norm.
  Reply With Quote
Old 7th June 2014, 01:02 PM   #12820
Marra is offline Marra  United Kingdom
diyAudio Member
 
Join Date: Nov 2009
Location: Near Lincoln
So true.
  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 04:12 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