> Say any of the First Watt amps.
I do not know of any that only use a N-JFET diff pair at 2mA.
So you'll have to ask Wayne.
Patrick
I do not know of any that only use a N-JFET diff pair at 2mA.
So you'll have to ask Wayne.
Patrick
All FW amplifiers I am aware of call for BL grade. I am sure someone will correct me if I am wrong.
Is there a DIY way to evaluate the noise of an individual JFET or a complementary pair?
It would be nice to make a jig that allows swapping of JFETs to perform an A/B comparison.
It would be nice to make a jig that allows swapping of JFETs to perform an A/B comparison.
dissipation can/will be the issue
say instead of one regular in FW amp , using two GR small ones ; that will be 4 in parallel , each case having 50% of dissipation , ref. to original arrangement
I drew my conclusion from the distortion waveforms I get with them used
as complementary followers - mostly 3rd harmonic at .000x% thd.
I don't see that in anything else I've tried. Can you suggest a better
example of P and N?
These are used in Phono stage secondary circuits like you can see in the Pearl 2 DIY phono. This was done with 2SK170's but the 2SK2145 is the current dual I use for stuff like this.
I hooked up several (2145's) and found that gm varied between 14 and 15 for pairs on the same chip.
...and then I tested some more, one 2SK2145 had gm of 11 for one side and 15 on the other.
Here's the JFET tester which Scott illustrated in Linear Audio Volume 3. S1 puts the resistor 604k in series with the gate, or, alternatively connects to the 22M. The 604k resistor gives a 100nV/RtHz noise baseline.
Switch S2 allows the user to switch Id -- suggested ratio of 5:1 so that you can use the JFET equations to calculate gm.
Attachments
And it seems they are gone forever, never to return, meanwhile we can still buy tubes.
Crazy times.