Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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

Simplistic NJFET RIAA
Simplistic NJFET RIAA
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 17th April 2018, 10:31 AM   #17081
merlin el mago is offline merlin el mago
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
Salas can't see the pics?
  Reply With Quote
Old 17th April 2018, 10:53 AM   #17082
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Simplistic NJFET RIAA
They are from a recent builder in a local forum so they didn't link to everybody maybe. Now I attached them to the previous post. Can you see?
  Reply With Quote
Old 17th April 2018, 12:09 PM   #17083
merlin el mago is offline merlin el mago
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
Yes now I can see, thank you.
  Reply With Quote
Old 17th April 2018, 03:55 PM   #17084
Pars is online now Pars  United States
diyAudio Member
 
Pars's Avatar
 
Join Date: Jan 2004
Location: Chicago
Thanks Nick, good to know for a baseline. I was using some crap phones and would guess that at the volumes I had it turned up to it would be ear-splittingly loud.
Iíll try to take D-Gnd voltage measurements for all JFETs tonight. I donít question the providence of any of them... 2SK369s are from teabag; 2SK170s came from a GB here years ago.
I do know that R13 is dropping 26.x Vdc across it on either channel.
  Reply With Quote
Old 17th April 2018, 11:28 PM   #17085
patriz is offline patriz
diyAudio Member
 
patriz's Avatar
 
Join Date: Apr 2002
Quote:
Originally Posted by Salas View Post
Yes it is but there can be tolerances to impose such a DC difference. Try with VR1 also. The key is to have almost the same signal gain between your two channels. Do you have any means to check that? Like a test record, function generator, oscilloscope, DMM on AC, sound card and FFT software, whatever. (You have to make make 1:100 voltage divider with 1k&10R resistors in a connector and shielded cable for driving clean low mV from lab gen or pc card)
I checked with an old analog scope and the signal looks the same in both channels.
  Reply With Quote
Old 18th April 2018, 12:09 AM   #17086
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Simplistic NJFET RIAA
Good
  Reply With Quote
Old 18th April 2018, 12:22 AM   #17087
Pars is online now Pars  United States
diyAudio Member
 
Pars's Avatar
 
Join Date: Jan 2004
Location: Chicago
Quote:
Originally Posted by Salas View Post
Yours is not a standard build for board and PSU so I can't tell for sure if there are issues right now. Normally its reported quiet even in MC mode without any special measures while just thrown around. Tell me your DC voltage on the drain of each JFET vs GND and if there's no doubt they are originals.

"Playing fine, noise is close to zero without a box."
I took some measurements:

Code:
board           1       2
Q1             8.42   8.41
Q3             4.54   4.32
Q4            11.51  11.28
Q5            11.42  11.24
Q6            23.61  23.36
TP1-TP2        3.25   3.47
Rail          35.51  35.22
I then looked at the outputs with a scope and with a DMM on AC mV. Scope showed a waveform:

board 1: 4.6 div @ 0.1V/div or .46V. Period was 8.3 @ 2mS, or 60Hz. DMM read 90mV
board 2: 4.5 div @ 50mV/div or .23V. Period the same. DMM read 45mV
  Reply With Quote
Old 18th April 2018, 12:26 AM   #17088
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Simplistic NJFET RIAA
Will check those measurements out tomorrow
  Reply With Quote
Old 18th April 2018, 03:26 AM   #17089
Pars is online now Pars  United States
diyAudio Member
 
Pars's Avatar
 
Join Date: Jan 2004
Location: Chicago
Thank you, and thanks for the design and support! This thing certainly looks the business

Just as a further test, I powered this from my bench supply instead, and scope was showing the same thing. My scope is a Tek 465b, probably needs a recap, and my probes suck. They did however show me oscillation at 70Mhz in a Gilmore Dynafet I had previously never gotten working, so it isn't worthless...
  Reply With Quote
Old 18th April 2018, 03:05 PM   #17090
Pars is online now Pars  United States
diyAudio Member
 
Pars's Avatar
 
Join Date: Jan 2004
Location: Chicago
One other thing I didnít mention, but my workbench is 3 feet or so from my house electrical panel. It always has seemed noisy; scope probes go crazy when not connected to a ground, etc. I should try this somewhere away from this area...
  Reply With Quote

Reply


Simplistic NJFET RIAAHide 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

Forum Jump


New To Site? Need Help?

All times are GMT. The time now is 09:22 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki