Mpp - Page 505 - 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 1st February 2012, 01:18 PM   #5041
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
One could also not use that resistor at all. The cartridge would then pass the minuscule gate current to the sources and the Fets would then conduct.
  Reply With Quote
Old 1st February 2012, 02:35 PM   #5042
diyAudio Member
 
Jacques Merde's Avatar
 
Join Date: Oct 2009
I could be missing something, but doesn't R12 provide the cartridge load? Would it make sense to retain R12 but place it so that it is connected to the gates and to the node between R112 and R155?
__________________
"For every complex problem, there is a solution that is simple, neat, and wrong." -- H.L. Mencken
  Reply With Quote
Old 1st February 2012, 02:40 PM   #5043
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
Yes, that is what i just wanted to post ! This is then a floating load. Without the resistor the cartridge is its own floating load, terminated by the low impedance of the negative input, weird. Anyway, a floating resistor would make sure that the Fets conduct, even when the cart is not connected.
  Reply With Quote
Old 1st February 2012, 03:16 PM   #5044
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
Here is the corrected schematic. Thanks Jacques.
  Reply With Quote
Old 1st February 2012, 05:00 PM   #5045
diyAudio Member
 
Jacques Merde's Avatar
 
Join Date: Oct 2009
My pleasure

FWIW, I think this is a really cool project. Thank you for doing it.
__________________
"For every complex problem, there is a solution that is simple, neat, and wrong." -- H.L. Mencken
  Reply With Quote
Old 1st February 2012, 05:29 PM   #5046
sampler is offline sampler  Lithuania
diyAudio Member
 
Join Date: Jan 2010
This looks good Joachim, but I'm afraid I already tried this arrangement and if my memory didn't froze over the day from this weather we are having here there was something fundamentally wrong with it. If I remember correctly fets sources were just swinging in phase with a source without any reference to ground, but I may be confusing something here. Let me put it to sim and get back to you. Or even better, I can try it on real proto.
  Reply With Quote
Old 1st February 2012, 06:04 PM   #5047
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
Ok, fine, i think it works as strange as it is. We can reference both input to ground though like in an opamp based differential stage.
  Reply With Quote
Old 1st February 2012, 06:34 PM   #5048
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
Like this : ....
  Reply With Quote
Old 1st February 2012, 06:54 PM   #5049
sampler is offline sampler  Lithuania
diyAudio Member
 
Join Date: Jan 2010
ok, it doesn't work without cascodes in proto (LF oscilation modulated by input signal with gain on fet's sources, same thing as I tried some time ago), but if I'm getting this right now, cascodes IS the key. Time to build some. I'm assuming some low current K170 instead of "High Impedance Current Source" in your schematics would do for experiments ?
  Reply With Quote
Old 1st February 2012, 07:11 PM   #5050
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
Sure, they can be casdoded with J310 and then we are in the several tens of megaohms range. The sources of the Fets have to drive the bases and the current source. The higher the impedance of the current source the more drive goes into the bases. For testing one low current 2SK170 is fine.
  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 03:04 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