Simplistic NJFET RIAA - Page 822 - 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 17th October 2012, 03:35 AM   #8211
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
This phono has built in pre roll-off between stages keep in mind. Its for anti vinyl disc eccentricity, TT VLF rumble and the like.
  Reply With Quote
Old 17th October 2012, 03:38 AM   #8212
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Mild subsonic one.
  Reply With Quote
Old 17th October 2012, 03:44 AM   #8213
andyr is offline andyr  Australia
diyAudio Member
 
Join Date: Nov 2003
Location: Melbourne (Oz, not Florida!)
Quote:
Originally Posted by Rush View Post

You can pick what ever size output cap you have or want and figure the resistor backwards within reason, 1 meg being the highest value resistor.

The roll off frequency should be less than 2 Hz.

Rush
Sure, Rush, I understand:
a) the inverse relation between resistor value and cap value, and
b) the far higher cost of good caps - so it's cheaper to use a 0.1uF cap than a 0.2uF cap!

I was simply wondering if 1Meg was pushing it a bit high!

Quote:
Originally Posted by Rush View Post

I am not the master of JFET knowledge, I leave that up to Salas.
So, Salas ... can you advise?

Q1: Is it a problem to use a 1Meg resistor on the Gate of a JFET?
Q2: Would it be better to use 500K?

Thanks a lot,

Andy
  Reply With Quote
Old 17th October 2012, 03:52 AM   #8214
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Depends on Jfet type and its gate leakage current spec IGXS-VDS. The way we bias them in the simplistic they won't leak more than 100pA, so no problems with up to one meg. I had cranked them up further even and could not see any sudden rise for noise floor in FFT.
  Reply With Quote
Old 17th October 2012, 05:19 AM   #8215
andyr is offline andyr  Australia
diyAudio Member
 
Join Date: Nov 2003
Location: Melbourne (Oz, not Florida!)
Quote:
Originally Posted by Salas View Post
Depends on Jfet type and its gate leakage current spec IGXS-VDS. The way we bias them in the simplistic they won't leak more than 100pA, so no problems with up to one meg. I had cranked them up further even and could not see any sudden rise for noise floor in FFT.
Thanks, Salas,

JFET is Toshiba 2SK170GR with Idss 5-6.5 ma.

Regards,

Andy
  Reply With Quote
Old 17th October 2012, 03:03 PM   #8216
johnm is offline johnm  United Kingdom
diyAudio Member
 
johnm's Avatar
 
Join Date: Sep 2003
Location: Hampshire
Quote:
Originally Posted by kstlfido View Post
Hi John- Please feel free to emulate away!

How does it sound? Great! I only have a Mitsubishi Integra preamp to compare it to. My Salas RIAA build has more dynamics and life. Very happy with it's sound. Of course there are many variables and subjectivity. I'm also using a lab supply to power the shunts as I've been too distracted/busy to build a transformer/CLC power supply.

It doesn't have quite as much gain as the Integra but plenty loud enough. Possibly the latest ideas on this thread will address that. Still good to go. I hope I can get into in a box for Burning Amp in October!

-Kent
Sorry for some reason I missed seeing your reply Kent. Very encouraging to hear about your results. I'm still getting the parts together, but hope to start building next month sometime

Glad it's being enjoyed - does seem to be a universally well-liked and highly praised design. I'm really looking forward to giving it a whirl.

John.
  Reply With Quote
Old 17th October 2012, 06:02 PM   #8217
Siberia is offline Siberia  Lithuania
diyAudio Member
 
Siberia's Avatar
 
Join Date: Feb 2011
Location: Vilnius
Default hmmmmm

Quote:
Originally Posted by Salas View Post
That pic is from the mate's line pre. I put single supply b1 in the ones we are going to check out already, a couple of 1uF simple supreme caps I got, the pot to the 6v6 buffer is 50k, no need I go symmetric supply and dcb1.
Do I understand it right? The line pre is a combination of mezmerize switching control, with some part of b1 and a 6v6 buffer?
  Reply With Quote
Old 17th October 2012, 06:08 PM   #8218
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
No, the second line comment is about the experimental phono. The little line amp will be with some gain, simple symmetric Fet John Curl style cheap to make solution. I had given him a B1 from mid summer now not to be without music, but he has to have some gain, his ARC amp needs that even from a CDP as source.
  Reply With Quote
Old 17th October 2012, 06:34 PM   #8219
RCruz is offline RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
Now with a much better matched k170 at 8mA idss, I get 12v sharp on the output of the cascode.

Using 1k4 to power the buffer (also with 8mA fets) I get 23.7v for Vd on the top fet....

Wondefull... Allready have one board populated... soon to be news about experimental wallis simplistic
__________________
RC
  Reply With Quote
Old 17th October 2012, 06:38 PM   #8220
Siberia is offline Siberia  Lithuania
diyAudio Member
 
Siberia's Avatar
 
Join Date: Feb 2011
Location: Vilnius
Thanks. Sometimes I miss a line switch on DCB1.
  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 02:47 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