Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Pass Labs This forum is dedicated to Pass Labs discussion.

Tokin SIT DEFiSIT musings
Tokin SIT DEFiSIT musings
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 13th December 2019, 07:14 AM   #1
woofertester is offline woofertester  United States
diyAudio Member
 
Join Date: Jun 2011
Default Tokin SIT DEFiSIT musings

Having characterized the Tokin SIT for Vgs and transconductance at 24V at 1.5A Ids, I went through my stash of P-channel FETs for a possible match for a DEFiSIT follower.

Parts that I tested are 2SJ162, 2SJ618, IRFP9240. They were all very far away from the Vgs of the Tokin SIT. Interestingly, The 2SJ162 LATFET and the Tokin SIT both have a negative tempco so the Ids falls with temp for the DEFiSIT pair.

I was just about to power down the instruments when I remembered the hockey pucks bought for the F4 beast. Connected the P-channel hockey puck to the curve tracer and BAM! The Vgs of this part is within about 100mV of the Tokin SIT at 24V Vds at 1.5A Ids. The P-Channel puck has a higher Vgs than the Tokin SIT so the pair will have less current than planned.

Quickly lashed up the Tokin SIT to the IXYS hocky puck and POW! Nice steady Ids ~ 710mA after a short warm-up. Increasing voltage rails increases Ids. If you must have 1.5A Ids, just increase the rail voltages.

The IXYS hockey puck that I had on hand and used is the IXTN210P10T. This part at -30V at -2A bias is about 10% of DC SOA and less than 10% of rated max power dissipation.

Looking forward to trying this further when my Tokin SITs show up.
  Reply With Quote
Old 13th December 2019, 09:40 AM   #2
Zen Mod is offline Zen Mod  Serbia
Official Court Jester
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Tokin SIT DEFiSIT musings
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM
  Reply With Quote
Old 13th December 2019, 01:57 PM   #3
Soundhappy is offline Soundhappy  France
diyAudio Member
 
Soundhappy's Avatar
 
Join Date: Oct 2012
Location: Montpellier near Mediterranean Sea France
Quote:
Originally Posted by woofertester View Post
..The IXYS hockey puck that I had on hand and used is the IXTN210P10T.
This part at -30V at -2A bias is about 10% of DC SOA and less than 10% of rated max power dissipation.

Looking forward to trying this further when my Tokin SITs show up.
Oh yeah! Can be very interesting amplifier
__________________
class A amplifiers with full range speakers
sings like angels in heaven
  Reply With Quote
Old 13th December 2019, 02:08 PM   #4
woofertester is offline woofertester  United States
diyAudio Member
 
Join Date: Jun 2011
Quote:
Originally Posted by Zen Mod View Post
I have not observed anyone doing exactly this so it looks like a fun thing to try. Fortunate that I had the IXYS pucks on hand.
  Reply With Quote
Old 13th December 2019, 02:17 PM   #5
Zen Mod is offline Zen Mod  Serbia
Official Court Jester
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Tokin SIT DEFiSIT musings
believe me , you don't want to know what I did while thinking what to do , and finally got to SissySIT

in fact , having pair of N and pair of P mos pucks , mein Bruder Generg sent me when I drew first draft of Babelfish M25 , I tried them to combine with THF51 I had at a time

as far as I remember , I got a pair of , met at some 2A2 and rail of 27V , but just one pair ...... and it wasn't a recipe for what I wanted to make in the end

so , approach good for making one specimen of an amp , but tricky for more

that's why Pa made just few "pure" DEFiSIT amps , as proof of concept for later made SIT-3
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM
  Reply With Quote
Old 13th December 2019, 02:53 PM   #6
woofertester is offline woofertester  United States
diyAudio Member
 
Join Date: Jun 2011
Quote:
Originally Posted by Zen Mod View Post
believe me , you don't want to know what I did while thinking what to do , and finally got to SissySIT

in fact , having pair of N and pair of P mos pucks , mein Bruder Generg sent me when I drew first draft of Babelfish M25 , I tried them to combine with THF51 I had at a time

as far as I remember , I got a pair of , met at some 2A2 and rail of 27V , but just one pair ...... and it wasn't a recipe for what I wanted to make in the end

so , approach good for making one specimen of an amp , but tricky for more

that's why Pa made just few "pure" DEFiSIT amps , as proof of concept for later made SIT-3
Thank you. All of that info is news to me and very interesting news, indeed.

I agree that the spread of component behaviors will cause the matching of DEF pairs to be time consuming and problematic for mass production.

Given a large enough population of parts, I think that many matched pairs could be found. It would make repair in-situ difficult if not impossible.

None of the problems are of significant importance for DIY.

For me, one of the most important points is that the P-FET is in production and available at Mouser/Digikey/etc
  Reply With Quote
Old 14th December 2019, 07:24 PM   #7
woofertester is offline woofertester  United States
diyAudio Member
 
Join Date: Jun 2011
I have performed some more curve tracing, circuit lash-ups with an adjustable + / - power supply and a lot of reading of the DEF and DEFiSIT threads.

I am satisfied that if the SITs are well matched and the P-FETs are well matched, it should be possible to put together sets of quad devices to make a stereo amp. Both channels should bias up nearly identically.

Each quad will have a unique power supply requirement to achieve a certain bias current using no bias circuitry.

Another option is to use the resistor string trick to bias the devices at a certain current at a certain rail voltage.

For mass production, such as a DIY group buy, the resistor string trick would be the obvious choice.

For the devices that I have in hand, the Vgs voltage difference between the SIT and the P-FET is less than 200mV to create 1.5A of bias at 24V Vds.

I will give the resistor string trick a try for the next step.
  Reply With Quote
Old 14th December 2019, 09:40 PM   #8
claudio52 is offline claudio52  Italy
diyAudio Member
 
claudio52's Avatar
 
Join Date: Nov 2010
Location: Mediterranean Sea, near the Circe enchantress
Tokin SIT DEFiSIT musings
Hi Woofertester, I am following your experiments with great interest.
Perhaps you can do without the resistors string with the Vgs voltage difference between the SIT and the P-FET is less than 200mV.
Antoinel, what do you make of this?
  Reply With Quote
Old 14th December 2019, 10:14 PM   #9
woofertester is offline woofertester  United States
diyAudio Member
 
Join Date: Jun 2011
Quote:
Originally Posted by claudio52 View Post
Hi Woofertester, I am following your experiments with great interest.
Perhaps you can do without the resistors string with the Vgs voltage difference between the SIT and the P-FET is less than 200mV.
Antoinel, what do you make of this?
I connected the circuit with no bias resistors. The drain current is in the neighborhood of 600 - 700mA depending on temperature. You can actually calculate what the current will be from Nelson's formula based on the difference of Vgs divided by the sum of the inverse transconductances.

I can see that a version can be created with a pot between the gates and another pot to set the voltage at the bottom gate. This would allow adjusting drain current and offset.

The P-FET that I am using has a higher Vgs than the Vgs of the SIT at 24V Vds at 1.5A.

The supply voltage rails can be increased until Ids is at the desired level but that would mean finding a proper transformer and every person who wants to build it will have a different power supply solution. Adding the resistor string will allow every person who builds it to use the same power supply and the same Ids.
  Reply With Quote
Old 15th December 2019, 10:33 AM   #10
claudio52 is offline claudio52  Italy
diyAudio Member
 
claudio52's Avatar
 
Join Date: Nov 2010
Location: Mediterranean Sea, near the Circe enchantress
Tokin SIT DEFiSIT musings
The addition of resistor string is a good solution to increase the chances of building a DEF.
Are the two devices mounted on the heatsink?
  Reply With Quote

Reply


Tokin SIT DEFiSIT musingsHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans Zen Mod Pass Labs 874 16th February 2019 04:49 PM
THF-51T old used 5pcs passed the test TOKIN from VGS= 4.3v ... pras1170 Vendor's Bazaar 9 21st December 2018 05:49 AM
FS Tokin THF-51S NOS dBel84 Swap Meet 0 22nd September 2018 09:32 PM
FS. TOKIN SIT 2SK180,2SK180C,TOKIN 2SK 180 D joshvi Swap Meet 46 24th August 2018 05:58 AM
NOS TOKIN 2SK180 V FETish Swap Meet 0 21st January 2018 10:57 AM


New To Site? Need Help?

All times are GMT. The time now is 03:35 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Copyright ©1999-2020 diyAudio
Wiki