Mpp - Page 837 - 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 17th February 2013, 12:55 PM   #8361
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
An extra small concern may be the high burden voltage in some DMMs (the voltage drop in their "shunt" current measuring resistor) for their mA range. You can test that by measuring the red mA range terminal with a DMMs red probe when set for Ohm. Don't be surprised if finding 10 Ohm+. Combine all that and you may need VDD+ to really measure at 10V across the JFET in current mode test. One of the reasons the FETS bias somewhat harder than expected when put in PCB. Can be a problem or not depending on the circuitry concept and the JFET type curve. Some don't change much their IDSS over 2V, other types may do. It can be enough of a concern if measuring IDSS at low VDD for near 2*Pinch off VDS use for instance.
  Reply With Quote
Old 17th February 2013, 01:28 PM   #8362
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
Before i used a curve tracer i measured with 18V and a 1kOhm resistor.
  Reply With Quote
Old 17th February 2013, 01:56 PM   #8363
diyAudio Member
 
Bksabath's Avatar
 
Join Date: Dec 2007
Tanks Joachim and Salas
18V and 1 K sound fine besides Paradise runs at 18 V so even better
PS
I have a Little test rig for HFE tanks to Hesener for help on that one
The circuit I have posted came out of Salas Simplistic tread
I am drowing a PCB to include those 2 test circuits + Led Voltage tester and VBE tester
Again Led voltage is out of Simplistic and VBE test is one I have posted a while ago (apolologies due as can't recall source for that)
VBE test is included as I got space on 160 X100 euro card.

I hope this may be useful for Music loving population which may not have test gear avvaliable.

I got a first PCB in the bath at the moment and as soon as tested I will take this forward
  Reply With Quote
Old 17th February 2013, 01:59 PM   #8364
diyAudio Member
 
Bksabath's Avatar
 
Join Date: Dec 2007
Quote:
Originally Posted by Joachim Gerhard View Post
Before i used a curve tracer i measured with 18V and a 1kOhm resistor.
Is New Atlas PRO now capable of differentiate therminals on J FETS ?

Old one could not ....
  Reply With Quote
Old 17th February 2013, 02:12 PM   #8365
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
Nope. You can measure it.
Make a simple preamp. Say a common source single ended BOZ with a gain of ten.
Measure frequency response one way and the other way around. One conection may be more extended in the treble.
That is the correct one. That is beacuse capacitance in one direction is a bit lower but not much. I even found J-Fets that where totally symmetric.
  Reply With Quote
Old 17th February 2013, 02:22 PM   #8366
diyAudio Member
 
Bksabath's Avatar
 
Join Date: Dec 2007
Tank you Joachim

And apolologies for temporary Hi Jack of this tread
Here is Pre view of test all rig
Can pick 4 different voltages on the LM 317 regulators
Dill switches and IC sockets for now
Finished one will have rotary switch for selecting test feature and meter connections.
Attached Images
File Type: jpg Tst rig.JPG (320.4 KB, 188 views)
  Reply With Quote
Old 17th February 2013, 02:36 PM   #8367
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
No regrets, that is useful.
  Reply With Quote
Old 17th February 2013, 04:25 PM   #8368
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
There are some news on the Paradise front.
I talked to Hesenr today. He made some simulation what the big elcaps do at the input.
We already talked about that they have to setle down a bit to "form" so that the leackage current goes down. That has a direct effect on the output offset that gets a bit down with time. Ones they have settled and the real values and types are known he found a slight resonance peak at ca.80kHz that can be damped with a snubber. He is working on the values and we will inform you when that has proven to work.
It has to be seen if that improves the sound. We also talked about a new group buy of PCBs. There are some new and late commers and the issue is also discussed on the German Analog Forum. I also have an idea for a balanced Paradise that uses two PCBs per side for a total of four. A bit over the top but again there is some interest to explore that option.
  Reply With Quote
Old 17th February 2013, 08:04 PM   #8369
RCruz is offline RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
Quote:
Originally Posted by Bksabath View Post
Almost got spontaneous brain burn out caused by math symbols and 2 remaining brain cells being almost 50 proof.
Nothing to worry about.

In fact gm = 2 x (Idss / Vp) x ( 1 - Vgs / Vp)

But as ( 1 - Vgs / Vp)2 = Id / Idss

gm = 2 x (Idss / Vp) x sqrt(Id / Idss)

So at Vgs =0 you have gm0 = 2 x Idss / Vp

It is all the same.
__________________
RC
  Reply With Quote
Old 17th February 2013, 08:22 PM   #8370
RCruz is offline RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
Quote:
Originally Posted by Joachim Gerhard View Post
We already talked about that they have to setle down a bit to "form" so that the leackage current goes down. That has a direct effect on the output offset that gets a bit down with time. Ones they have settled and the real values and types are known he found a slight resonance peak at ca.80kHz that can be damped with a snubber. He is working on the values and we will inform you when that has proven to work.
I will wait for that option before I continue populating my new boards
__________________
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 08:40 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