Official M2 schematic

[Zen Mod]

yup
Generg meant 2SK1530/2SJ201

 

[Russellc]

I guess you mean 2SK1530 / 2SJ201 ?

Yes. Same here. I cut and pasted from his post!

Russellc

 

[Dennis Hui]

Thanks for the comments. I've been thinking about building an M2 with the Toshiba
mosfets as well. That way I can compare it against a standard one with
the Fairchild parts.

I found the M2 more lively than my Aleph 30, though I do not know how much
the Fairchilds contributed to that.

Cheers,
Dennis

 

[Zen Mod]

JFet-ed Aleph 30 becomes Aleph J , which no-one can accuse of being not-lively enough

 

[ElFishi]

I can switch devices btn 2S and FQA in my build - and I can turn it into an F5 : )
I'm about to finish it these days. A first run with the FQAs put a hefty grin in my face.

 

[Zen Mod]

Liveliest presentation with FQA, more rocking.
IRF more well tempered.

Over all most convincing SK1530/SJ218 combo, but only with not current demanding speakers.
Do not know why.....

decrease source resistors to 0R33 , decrease that 100R connected ditto to optocoupler's LED to 0 and that's it

 

[DIYspaceW]

BOM....How much voltage is on C2 and C3 I have 29V supply and 25V caps rating?

 

[Zen Mod]

C1 - hard to buy voltage which could be too low

C2 - 16V perfect

btw. -I'm speaking of C1 and C2 from schematic , post #1

 

[CeeVee]

decrease source resistors to 0R33 , decrease that 100R connected ditto to optocoupler's LED to 0 and that's it

...that is music to my ears since i have enough pairs of 2SK1530/2SJ201 left over from F5X to make the 2 M2 Channels 😀😀

 

[schubert]

decrease source resistors to 0R33 , decrease that 100R connected ditto to optocoupler's LED to 0 and that's it

I'll be using 2sk1530/2sj201 as well - which resistors are these? I'm guessing R13/14 (change to 0R33) and R10/12 (jumper). Is that right?

 

[Zen Mod]

ref. to schm in post #1 - decrease R13,R14

decrease R11 to (almost) zero

Iq will go up somewhat , but you ought to have that much reserve in heatsinks

 

[schubert]

decrease source resistors to 0R33 , decrease that 100R connected ditto to optocoupler's LED to 0 and that's it

So you meant decrease that 221R to (near) zero, then........that makes more sense. I was a little confused.

 

[syklab]

ref. to schm in post #1 - decrease R13,R14

decrease R11 to (almost) zero

Iq will go up somewhat , but you ought to have that much reserve in heatsinks

R11 is 221R, did you mean decrease R10 and R12 from 100R to near 0R ?

 

[Russellc]

My M2 displays some hum with speaker sensitivities >100Db or so.


Room treatments for headphone users

My Altecs are more sensitive than that....silence.

Russellc

 

[Russellc]

Nelson has made the comment that a slight amount of hum might be present because of the input transformers. At least I think I remember reading this in the past. I have LaScala's and mine is quite but it probably depends on your horns sensitivity. You may try shielding the input transformers or maybe checking your grounding scheme.

I awoke this morning with anticipation of reading your review of this M2 Russellc and was disappointed earlier by not seeing anything but I guess you were too busy listening last night to bother posting anything. I understand. This amp has reached the top of my FW builds as well.

In my opinion, within its power band, it is by far the best I have built so far.
Beautiful! Brilliant! On the vinyl system, it is amazing, spellbinding in fact...

Russellc

 

[Zen Mod]

R11 is 221R, did you mean decrease R10 and R12 from 100R to near 0R ?

leave them as is , except if you want zener chips go poof when you have few glasses of red more

😉

 

[ElFishi]

C3 sees the voltage across R13/14 (some 1.3V) plus the two Vgs to bias the outputs to ca 1.3A. With my very high Vgs Fairchilds the total is 10.8V.
C2 sees half of this.

 

[Russellc]

ref. to schm in post #1 - decrease R13,R14

decrease R11 to (almost) zero

Iq will go up somewhat , but you ought to have that much reserve in heatsinks

How close to zero? Is there a range or is it set by source resistor readings, palm test etc...

 

[ElFishi]

How close to zero? Is there a range or is it set by source resistor readings, palm test etc...

yeah, I find it hard to get from the 4N35 datasheet to what the resistor values will do to the bias current. Hay anyone modeled the M2 in Spice yet and is willing to share?

My Spice-fu is not big enough for this.

 

[Zen Mod]

How close to zero? Is there a range or is it set by source resistor readings, palm test etc...

just zero it

according to LTSpice , it'll be around 2A Iq , but I can't confirm that in vivo - amp is too heavy (and in living room) and my back temporary not in best shape

I have FQ outputs in mine (geschenk from Generg) , and yet to install 2SJ/2SK