Hello Zen!
As always... a hard worker!
This summer I was thinking to mount trim pots in my Aleph Js so I can lower a little bit the bias of the Aleph CCS, because with 30C room temp the amps were getting quite hot and to null the output offset.
Now that I see the new front end of the Babelfish J I am very curious to try it in my Aleph Js.
Since in my Js I have some j74bl with 10ma idss I would like to use these, can I reach with them the 10ma setting that you reccommend? At what helps increasing current in the ltp?
At what current do you run the mmbf ccs? I Ask because I also have at hand some k117gr that I want to use also.
Thanks !
As always... a hard worker!
This summer I was thinking to mount trim pots in my Aleph Js so I can lower a little bit the bias of the Aleph CCS, because with 30C room temp the amps were getting quite hot and to null the output offset.
Now that I see the new front end of the Babelfish J I am very curious to try it in my Aleph Js.
Since in my Js I have some j74bl with 10ma idss I would like to use these, can I reach with them the 10ma setting that you reccommend? At what helps increasing current in the ltp?
At what current do you run the mmbf ccs? I Ask because I also have at hand some k117gr that I want to use also.
Thanks !
whatever JFets you have for input LTP , only important is that they're having Idss above targeted 5mA (per LTP half)
so , 10mA are good ones , being in most practical BL grade (6-12mA) and 10mA CCS will take care of their Iq
LED string thingy is fed with anything between 3-5mA ; it can be resistor or MMBF JFet , but I like 3mm greenies combined with JFet CCS sponginess
regarding JFet LTP current - keep them at 5mA per side - that way you're having most practical values of xconductance , drain resistor value , small source degeneration (few ohms) ...... resulting in most practical OLG/CLG/NFB ratio
if you're in mood for more ballsy mosfet's gate drive , either put 2+2 JFets in LTP (doubling current to 20mA and halving drain resistor) or put emiter follower (20-25mA Iq) in between
that would give ~6db THD decrease
edit - regarding summer and heatsinks - don't be skimpy - just make Babysitter for amp
so , 10mA are good ones , being in most practical BL grade (6-12mA) and 10mA CCS will take care of their Iq
LED string thingy is fed with anything between 3-5mA ; it can be resistor or MMBF JFet , but I like 3mm greenies combined with JFet CCS sponginess
regarding JFet LTP current - keep them at 5mA per side - that way you're having most practical values of xconductance , drain resistor value , small source degeneration (few ohms) ...... resulting in most practical OLG/CLG/NFB ratio
if you're in mood for more ballsy mosfet's gate drive , either put 2+2 JFets in LTP (doubling current to 20mA and halving drain resistor) or put emiter follower (20-25mA Iq) in between
that would give ~6db THD decrease
edit - regarding summer and heatsinks - don't be skimpy
- just make Babysitter for amp
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It`s a nice ideea and I thought about it some time ago but what are the chances that used with monoblocks it could finish with different temps for each amp ?
When you say ~6db THD decrease you are talking about entire amp or ltp?
If I paralell input devices how much would input impedance decrease?
What would be the input impedance of the V2 with a single pair of j74 ?
When you say ~6db THD decrease you are talking about entire amp or ltp?
If I paralell input devices how much would input impedance decrease?
What would be the input impedance of the V2 with a single pair of j74 ?
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just piggyback additional JFets , double current though LTP , halve drain resistor
input impedance will stay the same , being dominated with values of input/CLG defining resistors
though , it's best that each LTP JFet is having own gate stopper resitor
~6db THD decrease for entire amp , at least when using (emiter follower) buffer in between LTP and mosfet gate(s)
input impedance will stay the same , being dominated with values of input/CLG defining resistors
though , it's best that each LTP JFet is having own gate stopper resitor
~6db THD decrease for entire amp , at least when using (emiter follower) buffer in between LTP and mosfet gate(s)
I am very tempted to try the iterations of the first stage you done but I still want to connect the collector of Q6 to -V as the original schematic.
I have to find a way to stuff all on a very small proto board that I will fit on top of PD board without doing a big ratsnest.
Thanks Zen for the patience!
I have to find a way to stuff all on a very small proto board that I will fit on top of PD board without doing a big ratsnest.
Thanks Zen for the patience!
collector of Q6 ; it's fluffy fun residue from past , slightly ewffective in a good way only when JFets aren't cascoded (see it as anti-cascoding move 
)
it stays as is mostly from fun , and in case someone won't use cascoding bjts , to spice things a little bit
so - detail pretty much irrelevant for your intention , just ignore it and connect Q6c to -V
btw- that thingie with small daughterboard and Aleph J-fication is already done several times
but , I can't remember by whom and in which threads exactly
)it stays as is mostly from fun , and in case someone won't use cascoding bjts , to spice things a little bit
so - detail pretty much irrelevant for your intention , just ignore it and connect Q6c to -V
btw- that thingie with small daughterboard and Aleph J-fication is already done several times
but , I can't remember by whom and in which threads exactly
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I know
besides working in my little service , I'm breathing old school speakers and wakoo amps , Papamps being bigger part of those in last decade
so - I did listen ; comparable to Papa's FW original , certainly not being worse
this particular one made to be scalable , covering almost entire range of (previous, non-J) Aleph stable , bringing J-fication to that
besides that , easily set ........ though demanding some use of brain**
**but , I simply couldn't avoid that