Simplistic NJFET RIAA - Page 929 - 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 12th February 2013, 11:32 AM   #9281
RCruz is offline RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
Quote:
Originally Posted by Jallhalla View Post
Hi,

What are the voltage and current demands for the folded simplistic?
I need two bibīs to be one of the cool guys, right? And they are both positive?


Thanks!
You can start with just one BiB set for 35V ... I suggest a minimum 300mA current.
__________________
RC
  Reply With Quote
Old 12th February 2013, 11:37 AM   #9282
RCruz is offline RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
Hi Salas

A learning tech question for you.

Imagine I would like to lower input noise and use 4 x k170 there.

This would double Id current so I would need to increase Vdd to around 60V in order to have enough curren over R4 right ?

This is only a suposition, but using the same R13 (1500r) I would also increase gain to around 47dB right ?
__________________
RC
  Reply With Quote
Old 12th February 2013, 01:31 PM   #9283
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
Quote:
Originally Posted by buzzforb View Post
Oooops I didn't see thanks.
  Reply With Quote
Old 12th February 2013, 02:21 PM   #9284
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Quote:
Originally Posted by Jallhalla View Post
Hi,

What are the voltage and current demands for the folded simplistic?
I need two bibīs to be one of the cool guys, right? And they are both positive?


Thanks!
The demands are monopole +35V @ 30-35mA per channel. We usually set the SSLV regulator much higher for it to work its MOSFETS better. Usually at 150-300mA CCS per channel depending on how much sinking you are prepared to use.
  Reply With Quote
Old 12th February 2013, 02:25 PM   #9285
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Quote:
Originally Posted by RCruz View Post
Hi Salas

A learning tech question for you.

Imagine I would like to lower input noise and use 4 x k170 there.

This would double Id current so I would need to increase Vdd to around 60V in order to have enough curren over R4 right ?

This is only a suposition, but using the same R13 (1500r) I would also increase gain to around 47dB right ?
To increase the current you don't need to increase the voltage also. Its a matter of redesigning for proper current biases around the input stage. Buzz uses 2XK170BL @ ~60dB gain with 0.5mV cartridge and he is reporting OK for noise though. Are you going for LMC? There is the 2X369BL 63dB example there already that Merlin has in mind.
  Reply With Quote
Old 12th February 2013, 02:29 PM   #9286
massimo is offline massimo  Italy
diyAudio Member
 
Join Date: Dec 2002
Location: Milan, Italy
Quote:
Originally Posted by Salas View Post
There is the 2X369BL 63dB example there already that Merlin has in mind.
Not only
  Reply With Quote
Old 12th February 2013, 03:07 PM   #9287
RCruz is offline RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
Quote:
Originally Posted by Salas View Post
To increase the current you don't need to increase the voltage also. Its a matter of redesigning for proper current biases around the input stage. Buzz uses 2XK170BL @ ~60dB gain with 0.5mV cartridge and he is reporting OK for noise though. Are you going for LMC? There is the 2X369BL 63dB example there already that Merlin has in mind.
No, I am just trying to understand the 1st stage biasing.

I found your post here: Simplistic NJFET RIAA

Just do not know how you determined the 12r for k170 Rs
__________________
RC
  Reply With Quote
Old 12th February 2013, 03:44 PM   #9288
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
4 Rs in parallel amount to 1/4 the value, its just we use one each for better current sharing, auto matching by local feedback in other words. So we get a total current in a single virtual "super transconductance'" JFET device with lower noise, more gain, more gate capacitance. Then the CCS resistor (1K in that example) steals that current from the PSU node just shy of what we need left for the PNP cascoding BJT to run through its resistive load folded to ground (2K2) for centering it voltage wise so we get a symmetrically clipping sinewave at max input drive.
  Reply With Quote
Old 12th February 2013, 06:49 PM   #9289
RCruz is offline RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
So if you used only one common Rs for the four k170, it would have to be 3r to generate the same Vgs right ?

Now I did not think of the 1k resistor as a CCS.... that explains a lot. That resistor must be correctly dimensioned to let go only the right amount of current so if it runs on the fets and also on the folded load resistor.

If we decrease the CCS resistor, more current will flow and as the current through the fets is fixed by Rs, there is more current through the folded load resistor and so more Vdrop there. That is how the trimmer works

Thank you again for your cristal clear explanation.
__________________
RC
  Reply With Quote
Old 12th February 2013, 06:57 PM   #9290
RCruz is offline RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
Now in the double K369 schematic you used the same 2r2 as in the single K369 schematic (Not 4r4).... The difference in this case is in the CCS resistor that is smaller (1k2 instead of 2k2)

So your choice of Rs does not follow a strict trend... It must come from your simulation and experience.
__________________
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 09:13 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright Đ1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2