Simplistic NJFET RIAA - Page 483 - 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 11th September 2010, 05:10 PM   #4821
diyAudio Member
 
Join Date: Apr 2003
Location: Southern Tier NY
Andrew. 211mA-60mA = 151mA or 140mA if you allow for control current. I was looking for an easy way to measure it vs. calculating it.

Salas, Let me make sure my understanding is correct. No assumptions here. Q1(irf9610) is the CCS fet. Q4(irfp9140) sets the voltage. If so, what is interesting is that as I ramp up the Vin, the current will stay <70mA until it hits the regulation voltage. At that point it jumps to 215mA. If I understand the circuit, Q1 is full on and Q4 is off till it has enough voltage headroom to regulate.
__________________
Living Life Doing the Waltz in 4/4 meter.
  Reply With Quote
Old 11th September 2010, 05:15 PM   #4822
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
The voltage is set by the Vref which is the translation of current through a resistor by a Jfet CCS. The main CCS references to Vout in this, hence it won't open properly until you get the expected voltage conditions. If it will turn on instantly without a variac it should pull instantly too.
  Reply With Quote
Old 11th September 2010, 05:20 PM   #4823
diyAudio Member
 
Join Date: Apr 2003
Location: Southern Tier NY
I put .1uF mkp on Vin. Big change but not a solution. Frequency jumped to 14mHz and is a cleaner sawtooth. See before and after in attached.

I have to pull board off of heat sink to implement change on gate resistor. (will do however if proper next step)
I also measured Vref across LED as 1.92V
Attached Images
File Type: jpg DSC02605.JPG (148.2 KB, 140 views)
File Type: jpg DSC02606.JPG (144.9 KB, 136 views)
__________________
Living Life Doing the Waltz in 4/4 meter.

Last edited by SGregory; 11th September 2010 at 05:23 PM.
  Reply With Quote
Old 11th September 2010, 05:24 PM   #4824
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Reinforces my suspicions that the resonance resides in the CCS. Make that 0.1uF a 47uF local decoupler, so we see where it goes, maybe some nH from layout resonates with something. Lets see about the gate stopper and possibly the base stopper values around the Mosfet and its control element next. Is the input voltage pre filtered BTW?
  Reply With Quote
Old 11th September 2010, 05:28 PM   #4825
diyAudio Member
 
Join Date: Apr 2003
Location: Southern Tier NY
The power supply is the power supply used on V1. SInce it is seperate now, it was an easy thing to bring it back to my bench and use it. Rcore 2x18V through a CLC filter.

I will install the parallel gate stopper resistor now. Be back in a few.
__________________
Living Life Doing the Waltz in 4/4 meter.
  Reply With Quote
Old 11th September 2010, 05:31 PM   #4826
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
So there is a long shielded cable carrying Vin to the board. Make that Vin local decoupler in that 33uF you just tried elsewhere, so we see what changes.
  Reply With Quote
Old 11th September 2010, 05:42 PM   #4827
diyAudio Member
 
Join Date: Apr 2003
Location: Southern Tier NY
With parallel 120R to make 60R for R3 no change. Vin decoupler still has same effect.

BTW please take Vpp and Vrms from scope and multiply by 10x. Had the probe in 10x configuration. At 1x I am seeing 80mVrms. 13MHz
__________________
Living Life Doing the Waltz in 4/4 meter.

Last edited by SGregory; 11th September 2010 at 05:46 PM.
  Reply With Quote
Old 11th September 2010, 05:44 PM   #4828
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
The lytic decoupler does not change the shape?
  Reply With Quote
Old 11th September 2010, 05:53 PM   #4829
diyAudio Member
 
Join Date: Apr 2003
Location: Southern Tier NY
The lytic decouple at the output did reduce what appeared to be higher order harmonics, but did not have the impact the the mkp did on Vin. I will re-install the lytic Vout decoupler and report back.
__________________
Living Life Doing the Waltz in 4/4 meter.
  Reply With Quote
Old 11th September 2010, 06:00 PM   #4830
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
80mV is too much, its oscillation. Lets see, can we move the compensation from the error amp nearer to the CFP? 9140 has 140pF Crss when 9240 has 81pF. We can be having a resonance there that can be read across the reg. I have done that once when I had to use a more capacitive shunt Mosfet because I was out of 9240.
Attached Images
File Type: gif Comp.gif (2.4 KB, 117 views)
  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 10:00 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