more complementary pairs than IRFP240/IRFP9240

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marconi118

Member
Joined 2008
#1
it seems that the IRFP240/IRFP9240 is not the best complementary pair

some state that IRFP240 match better with IRFP9140

or

244/9240
340/9240

the same for irf630/irf9630 a better match is irf630/irf9530

having to buy new parts what pairs match the best?
 
#5
Nelson Pass said:
It's not difficult to get matches if they come from the same tubes.

Also, matching to .1v is generally pretty adequate. At PL we use .01V
only because it's easy to do.

np
Click to expand...

Do you match pairs for each particular amplifier using that circuit's Vds?

I have looked a the eBay seller Punkydawgs. He uses 9V to characterize his matches. The F4 circuit that I am building uses the K170/J74 JFETs at about 14.4V Vds.

If a pair is matched at 9V Vds, that is no guarantee that they are a match at a higher Vds, correct?
 
#7
woofertester said:
Do you match pairs for each particular amplifier using that circuit's Vds?

I have looked a the eBay seller Punkydawgs. He uses 9V to characterize his matches. The F4 circuit that I am building uses the K170/J74 JFETs at about 14.4V Vds.

If a pair is matched at 9V Vds, that is no guarantee that they are a match at a higher Vds, correct?
Click to expand...
The operating temperature inside the closed case will also make a difference. The jfets are very sensitive to the temperature. So, if you want to have a "closely" matched pairs (or quads) under your amp's operating condition, a temperature control jig is also needed.

FWIW, in the F5X project, NicMac acquires hundreds (if not thousands) Toshiba jfets and matched them in NNNNPPPP under Patrick's (EUVL, the F5X designer) matching instructions. There were not too many yields, and each set cost a fortune but still good price for what they are!!! However, they are not perfect match (still good match) in a different operating condition (can be affected by many factors in the DIY world 🙂). No prematch set will satisfy each diyer's creativity.

One thing for sure, a matched pair at 9V is going to be many times better than a random pair. Given these jfets (Toshiba and Linear) are close to impossible to buy in bulk to match ourselves, we probably will have to accept the general 9V matching practice to get the project going and be happy.
 
#14
pchw said:
The operating temperature inside the closed case will also make a difference. The jfets are very sensitive to the temperature. So, if you want to have a "closely" matched pairs (or quads) under your amp's operating condition, a temperature control jig is also needed.

FWIW, in the F5X project, NicMac acquires hundreds (if not thousands) Toshiba jfets and matched them in NNNNPPPP under Patrick's (EUVL, the F5X designer) matching instructions. There were not too many yields, and each set cost a fortune but still good price for what they are!!! However, they are not perfect match (still good match) in a different operating condition (can be affected by many factors in the DIY world 🙂). No prematch set will satisfy each diyer's creativity.

One thing for sure, a matched pair at 9V is going to be many times better than a random pair. Given these jfets (Toshiba and Linear) are close to impossible to buy in bulk to match ourselves, we probably will have to accept the general 9V matching practice to get the project going and be happy.
Click to expand...
This helps. Thanks. Where is the definitive write-up for matching the K170/J74 pairs? I have downloaded the write up on PassDiy but it was not totally clear to me.
 
#18
My original questions were rather simple,

is the 9140 more complementary to the 240 than the 9240 ?
is the 244 or 340 more complementary to the 9240 than the 240?
is the irf630 more complementary to the irf9530 than the irf530?

asking because I have to buy new mosfets for PASS amps (F4 F5 etc)
 
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