Hi Mr. Pass,
Any hints on the technical specs of this particular amp?
Enquiring minds want to know... 🙂
Thanks,
Dennis
there is a thread about DEF amp
so , predecessor to SIT-3 , being called exactly DEFiSIT
you have enough info in SissySIT threads , I gave measurements of my exemplar , and I believe Papa's is pretty much the same
at least I made mine ( rail voltage particulary) by his words and there is no anything else to set , besides output node voltage level
in short - if DEF is on sale , grab it - it's damn rare breed and will stay like that
so , predecessor to SIT-3 , being called exactly DEFiSIT
you have enough info in SissySIT threads , I gave measurements of my exemplar , and I believe Papa's is pretty much the same
at least I made mine ( rail voltage particulary) by his words and there is no anything else to set , besides output node voltage level
in short - if DEF is on sale , grab it - it's damn rare breed and will stay like that
I was curious if Papa put gain in this one. (I saw the basic schematics on
the first page as a follower, but later posts mentioned a transformer for gain.)
Agree with what you said though.
Dennis
the first page as a follower, but later posts mentioned a transformer for gain.)
Agree with what you said though.
Dennis
funny ZM
I forgot that I posted a thread ..... Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans
I forgot that I posted a thread ..... Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans
It is similar to the DefiSIT, but is direct coupled and uses the SemiSouth
depletion mode R085 Jfet coupled with the Harris IRFP9240, and Jensen
transformer driven by Toshiba Jfet input buffer.
I am preparing a set of curves to accompany this offering, and will post
them shortly.
SJEP120R100 is an enhancement mode device; for the DEF you want a
depletion mode one. (such as the SJDP120R085)
depletion mode one. (such as the SJDP120R085)
With a mono amplifier I got a stable offset after 40-50 minutes. I used the best pair chosen between three UJN1208K and twelve IRFP9240.
Nice thing about the DEF is that it is only the difference in Vgs that is
critical. That Vgs would be taken at expected operating current and
voltage for perfection. That Vgs difference will alter the bias current
as divided by the sum of the inverse transconductance of the devices.
For example, if the depletion mode device Vgs is 1A at -4V, and has a
transconductance of 2 and the enhancement mode device is +3.9V with
transconductance of 3. The the increase is bias would be seen as
increase I = .1V/(1/2 + 1/3) = .12 amps
If the depletion mode Vgs is greater than the enhancement mode Vgs,
then your bias is high, which is better than otherwise, as you can insert
a little resistance so as to bring it down.
I got some of my pairs down to .1V or so, and the extra bias doesn't
bother me.
Nice thing about the DEF is that it is only the ...
Thanks for the detailed explanation!
