Simplistic NJFET RIAA - Page 125 - 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 4th March 2009, 01:38 AM   #1241
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
You just stack 2 IRFP in the CCS, the one above is shielding the miller of the one below. Have a look in one cascode anode load for a tube preamp that I did, to get the idea. It extends the performance up high a lot.
Attached Images
File Type: gif ccs412b4.gif (5.3 KB, 399 views)
  Reply With Quote
Old 4th March 2009, 01:42 AM   #1242
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Quote:
Originally posted by ikoflexer
L=100mH, C=4700u psrr of the above.
I don't know about the peak and roller coaster curve. Although great in dB region. I like soft trends. My guess is that a wee bit of capacitor imperfection, some layout reality, and a few cm of wire, will never let any reg do better than 100-115dB real life magic.
  Reply With Quote
Old 4th March 2009, 01:46 AM   #1243
iko is offline iko  Canada
diyAudio Moderator
 
iko's Avatar
 
Join Date: May 2008
Location: Toronto
franken output impedance.
Attached Images
File Type: jpg frankenregoutimp1.jpg (23.6 KB, 365 views)
  Reply With Quote
Old 4th March 2009, 01:49 AM   #1244
iko is offline iko  Canada
diyAudio Moderator
 
iko's Avatar
 
Join Date: May 2008
Location: Toronto
Quote:
Originally posted by salas


I don't know about the peak and roller coaster curve. Although great in dB region. I like soft trends. My guess is that a wee bit of capacitor imperfection, some layout reality, and a few cm of wire, will never let any reg do better than 100-115dB real life magic.
The peak and roller coaster curve has appeared on absolutely all the regulators I have simulated so far, the Jung, yours, all, when the LC filter is inserted in the input. I agree with you that those number don't mean a thing in reality, with all of its imperfections. Ah well, at least it looks good on paper
  Reply With Quote
Old 4th March 2009, 01:51 AM   #1245
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Better avoid then. It smells interactions. To the contrary, a cascode CCS surely helps on self noise, extending the good region of CCS performance a lot in frequency. But it is more of a hassle to implement. Good for low parts count are DN depletion Mosfets from Supertex.
  Reply With Quote
Old 4th March 2009, 03:06 AM   #1246
iko is offline iko  Canada
diyAudio Moderator
 
iko's Avatar
 
Join Date: May 2008
Location: Toronto
The cascode doesn't seem to help at all. I might try just go ahead with this version to see what it can do in reality.

By the way, thinking back to your almost perfect scope trace... you got some major filtering before the regulator right? That might explain it, since the regulator does not need to work so hard; I only used an LC filter of about 8000uF and 150uH. In any case, I will report any good news here if I get the time do it.
  Reply With Quote
Old 4th March 2009, 03:11 AM   #1247
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
I only have 33R to 10.000uF. The Cascode maybe does not show in the sim. See Jung's FFTs for CCS comparisons. But what you are about to try has so much potential that the cascode is just a nice potential add on.
  Reply With Quote
Old 4th March 2009, 10:08 AM   #1248
RCruz is offline RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
Hi Salas

Just did the GND mods as per your sugestion and the result is a better stereo image, better stereo integration and much better bass (detail - extension).

There are two issues that I need to deal with:

1 - The hum I am hearing is lower but always present... I can hear it when not playing a disc and the pot is half way up. It seems to me it is related with the regulation because it sounds like a motor running (a little faster than 50Hz).

2 - Everytime I cut the power to the Riaa (to do some mods) and power it up again, I need to wait for 5 - 10 minutes until it stabilizes. During this warm up period, I hear spitting and thunder coming from the speakers. I measured the DC offset in the output and it oscilates between 200mV and -40mV until it reaches 9mV and stays put.... Is this normal ?

Ricardo
__________________
RC
  Reply With Quote
Old 4th March 2009, 10:55 AM   #1249
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
1. Did you have it before in the other box? Your shunt is a new build? Try one way shielded to output rca gnd too instead of just wire.

2. No it is not normal to hear noises.
  Reply With Quote
Old 4th March 2009, 12:52 PM   #1250
RCruz is offline RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
Before I replaced all the rsistors in the Riaa, I did not have any of those power up noises.

The shunt is the same as before.

By the way the DMM reads in the output after power on, I believe there is some oscilation in the circuit until it stabilizes completely... The spitting thundering is the same I heard before when I did some mods in the DCP (new psu for the opamps) and latter I found there where some dry joints in the GND connections (now cured).

I believe I need to sit down and search for GND dry joints in the Riaa also.

BTW... The sound is unbelievably good right now.... Of course I miss the bass grip and detail of the CDP, but the high freq is so much better as well as the stereo image and presentation !

This can only be improved by changing the tonearm... I am using a SME 3009 II Improved (fixed headshell with 6.5g effective mass) and it is not the best choice for the MC ACE M Benz.

I would like your oppinion on the Roksam Nima unipivot.

Regards

Ricardo
__________________
RC
  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 02:50 PM.


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