B1 Buffer Preamp - Page 360 - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

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 8th October 2012, 05:09 AM   #3591
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
P.S. If you can't find very good matches because just six, use the lesser IDSS one in a channel pair as the one with g,s pins going together in same node.
  Reply With Quote
Old 8th October 2012, 05:14 AM   #3592
tessier is offline tessier  Canada
diyAudio Member
 
Join Date: May 2008
Hi

How much close we need to match jfet to put two in parallel in the B1 circuit ?

Thanx

Paul

Last edited by tessier; 8th October 2012 at 05:44 AM.
  Reply With Quote
Old 8th October 2012, 05:49 AM   #3593
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Don't do it, its not a proper B1.

P.S. IDSS is only indicative of Vgs(off), Yfs, those are not exact in each die for even same ID. And then you got two different housings trying to follow in each position each other thermally and double the Ciss making it slower, leads and traces... no cigar, no real B1, you lose much more than in a GR B1.
  Reply With Quote
Old 8th October 2012, 06:13 AM   #3594
tessier is offline tessier  Canada
diyAudio Member
 
Join Date: May 2008
Hi

Ok, no paralleling.

But anybody know how much more thd wen using 2SK170 with only 5 ma IDSS in the B1 ?

Thanx

Paul
  Reply With Quote
Old 8th October 2012, 06:17 AM   #3595
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Depends on signal level a lot too. Someone has got to make or simulate GR and BL B1 then FFT from min to max level so to speak in numbers.
  Reply With Quote
Old 8th October 2012, 06:29 AM   #3596
tessier is offline tessier  Canada
diyAudio Member
 
Join Date: May 2008
Hi

I use Ltspice but the 2SK170 model do have a IDSS of 10ma

.model J2sk170 NJF(Beta=59.86m Rs=4.151 Rd=4.151 Betatce=-.5 Lambda=1.923m Vto=-.5024 Vtotc=-2.5m Cgd=20p M=.3805 Pb=.4746 Fc=.5 Cgs=25.48p Isr=84.77p Nr=2 Is=8.477p N=1 Xti=3 Alpha=10u Vk=100 Kf=111.3E-18 Af=1)

How can we change this model IDSS to 5 ma ?

Thanx

Paul
  Reply With Quote
Old 8th October 2012, 06:37 AM   #3597
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Lower Beta to 30m then Vto, until you will see 5mA for a k170 g,s shorted to gnd off a 9VDC source.
  Reply With Quote
Old 8th October 2012, 06:53 AM   #3598
tessier is offline tessier  Canada
diyAudio Member
 
Join Date: May 2008
Hi

Here is the new model for the 2SK170-GR, it have a IDSS of 5.04 ma. with a
9 volt dc source.

.model J2sk170gr NJF(Beta=30m Rs=4.151 Rd=4.151 Betatce=-.5 Lambda=1.923m Vto=-.4274 Vtotc=-2.5m Cgd=20p M=.3805 Pb=.4746 Fc=.5 Cgs=25.48p Isr=84.77p Nr=2 Is=8.477p N=1 Xti=3 Alpha=10u Vk=100 Kf=111.3E-18 Af=1)

Thanx

Paul

Last edited by tessier; 8th October 2012 at 06:55 AM.
  Reply With Quote
Old 8th October 2012, 06:51 PM   #3599
tessier is offline tessier  Canada
diyAudio Member
 
Join Date: May 2008
Hi

I've done Ltspice simulation of the B1 using those two model to compare.

The BL type of 2sk170:

.MODEL 2sk170 NJF (VTO=-5.211e-001 BETA=3.683e-002 LAMBDA=4.829e-003 IS=1.000e-009, RD=0.000e+000 RS=0.000e+000 CGS=5.647e-011 CGD=2.562e-011 PB=4.860e+000 FC=0.5)


The BR type of 2sk170:

.MODEL 2sk170b NJF (VTO=-4.911e-001 BETA=1.983e-002 LAMBDA=4.829e-003 IS=1.000e-009, RD=0.000e+000 RS=0.000e+000 CGS=5.647e-011 CGD=2.562e-011 PB=4.860e+000 FC=0.5)

I simulated with a 1 volt 1 khz signal at the B1 circuit input.

Adding a low pass filter capacitor at the input did cut a lot the thd of the BR type of 2sk170.

Thanx

Paul
Attached Images
File Type: gif B1-b-final.gif (15.8 KB, 349 views)
File Type: gif B1-b-final-with input filter.gif (18.7 KB, 346 views)

Last edited by tessier; 8th October 2012 at 06:57 PM.
  Reply With Quote
Old 8th October 2012, 07:07 PM   #3600
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
With 24V supply its probably able to go near that as Vpp out max. What does with 2VRMS which is a typical digital source? Some go 3VRMS, what ever. Can you post the .asc so I get to see the details?
  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


Similar Threads
Thread Thread Starter Forum Replies Last Post
buffer/preamp? TheDriver41 Chip Amps 2 3rd October 2004 08:40 AM


New To Site? Need Help?

All times are GMT. The time now is 04:29 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