Measuring IDSS (of META42 JFETs)
post-163984
Thread Starter
Post #1 of 6

Jupiter

100+ Head-Fier
Joined
May 8, 2002
Messages
412
Reaction score
0
Joined
May 8, 2002
Posts
412
Likes
0
I'm having some trouble measuring the IDSS of the JFETs for my META42 following tangent's instructions at http://www.tangentsoft.net/audio/meta42/tweaks.html
I don't understand the part about "apply a voltage through a milliammeter". Could I use my digital multimeter for this? And how should this breadboard be set up?
 
     Share This Post       
post-164011
Post #2 of 6

tangent

Top Mall-Fi poster. The T in META42.
Formerly with Tangentsoft Parts Store
Joined
Sep 27, 2001
Messages
5,969
Reaction score
55
Joined
Sep 27, 2001
Posts
5,969
Likes
55
I just rewrote that section of the site for clarity. Let me know if it's clear enough now; thanks.
 
     Share This Post       
post-164036
Post #3 of 6

Jupiter

100+ Head-Fier
Joined
May 8, 2002
Messages
412
Reaction score
0
Joined
May 8, 2002
Posts
412
Likes
0
Your new section is much clearer and should be detailed enough for newbies such as myself. I tried it and I got values in the correct range. Thanks tangent!
 
     Share This Post       
post-164070
Post #4 of 6

zbuddah

500+ Head-Fier
Joined
Mar 21, 2002
Messages
502
Reaction score
10
Joined
Mar 21, 2002
Posts
502
Likes
10
It is Definitely clearer, so I should be looking for one with a low IDSS value and pairing that one up with a slightly higher IDSS values, I should go back and test mine
. The larger the IDSS difference between Q1/Q2 the less current it will draw right?
By the way that extra resistor on R8 or R9 really makes the amp dead silent at full volume with no source. Darn I wish I had a mini-mini cable, then I could listen to some music rather than dead silence. Gonna go buy one in the morning.
 
     Share This Post       
post-164073
Post #5 of 6

tangent

Top Mall-Fi poster. The T in META42.
Formerly with Tangentsoft Parts Store
Joined
Sep 27, 2001
Messages
5,969
Reaction score
55
Joined
Sep 27, 2001
Posts
5,969
Likes
55
I don't know about Q2 being "slightly" higher -- it just needs to be higher. It probably shouldn't be too close to Q1's Idss value. I'd put 1 mA or more of difference between them, given a choice.

On R8/R9, I haven't needed it myself to get silence at full volume. But then, I favor high-Z phones.
 
     Share This Post       
post-164178
Post #6 of 6

zbuddah

500+ Head-Fier
Joined
Mar 21, 2002
Messages
502
Reaction score
10
Joined
Mar 21, 2002
Posts
502
Likes
10
Quote:

Originally posted by tangent
On R8/R9, I haven't needed it myself to get silence at full volume. But then, I favor high-Z phones.


Heh yeah I can't really hear the hiss with my HD-600's but you know... I tried the amp with my crappy low ohm (16ohm?) ear buds first just in case it were to blow up on me
. Heard some hiss with the crappy earbuds and I just decided to put it in. Dead silence afterwards with the crappy earbuds.

Gonna go out to get me mini-mini cable now!
 
     Share This Post       

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top