Official M2 schematic

[djonesii]

Dear all

I'm gathering the parts for an M2, and as usual, a case is one of the biggest issues.

I was wondering if anyone has thought of putting a more modern Pass design in an adcom GFA 5400 case?



Maybe even some of the parts could be salvaged ....

Dave

 

[Zen Mod]

you'll need forced air arrangement with that size of heatsinks

so , reworking the case .....

 

[JR_W]

On the cascode schematic, what are some good substitutions for the BPT BC550C/BC560C devices?

Google pointed to some NTE159/NTE123AP as subs, I gather these devices aren't real critical in this application.

NTE159

NTE123AP

 

[Zen Mod]

being on same side of Big Splash as Papa , use his ZTX regulars

whatever , on these positions , universal PNP and NPN small transistors are adequate

 

[JR_W]

Got it, I've never built any of these amps, so wasn't sure what to use. This is them, correct?

ZTX550

ZTX560

 

[grimberg]

Two of a kind

What you selected are two of a kind (PNP), like a same-sex couple.
Use ZTX450 and ZTX550.

 

[JR_W]

Duh, never even looked at the sex, just the 550/560.

Must be why I generally let Papa build the things

 

[ElFishi]

Q6 and Q7 are LM385-1.2

D1,D2,D3 are 1N4148

Q5 4N35

yeah , stick it to the wall and enjoy sheer beauty

Zen, quick Q:
in the schematic attached to your post quoted above you say "put 1uF solid cap in paralel to C3".

In the pictures in your blog it seems that the solid cap bypasses C2.

Am I wrong?

 

[Zen Mod]

you're not wrong

I bypassed them both with 1uF

 

[ElFishi]

you're not wrong

I bypassed them both with 1uF

Thx,
what does C3 actually do, apart from having the amp go from Class B over AB to A in startup?

 

[Zen Mod]

well , several things , but say that most important is that keeps mosfets constantly biased over time

in other words , it keeps bias generator decoupled/independent from rails fluctuation (ripple , sag) and signal envelope

 

[ElFishi]

Would there be any harm if I tuned down R10 and R12 to 47 Ohms?

I am pondering to split the circuit to modules so I can switch between an F5 or an M2. I guess keeping the gate resistors close to the gates would be a good idea such that it was better to have a detachable connector between MOSFET plus gate resistor and the rest of the two circuits.
F5 uses 47 Ohm gate resistors and the manual speaks of a trimmed frequency response due to the gate resistors.

 

[Zen Mod]

don't change these resistors

 

[ElFishi]

don't change these resistors

OK. (why?)
Can the F5 instead take 100 Ohm at the gates?

 

[Zen Mod]

what are having R10 and R12 (in M2 ) with gate resistors ?

ref. to sch in #1 post

 

[ElFishi]

what are having R10 and R12 (in M2 ) with gate resistors ?

ref. to sch in #1 post

my bad! I meant to say R8 and R9

 

[Cinco]

Mono Block M2

I thought I'd run this idea by you more experienced builders. Would a pair of these chassis work for M2 mono blocks?
Mini Dissipante 2U 300mm frontale 10mm ARGENTO coperchi e retro in alluminio 3mm
Not really wanting to end up with a huge, hernia-building, stereo chassis. I do really like fully mono power supplies. Heat wise, it works ok, the issue is having to put one output device on each heat sink (P on one side, N on the other). Is it better to have these thermally coupled? Or does it really matter?

Also the power transformer and autoformer end up a little close...hmm

Cinco

 

[stefanobilliani]

Is it possible to increase a little the value of R14 and R13?

 

[Zen Mod]

yes , it is

that will decrease Iq , of course , and increase output impedance , and decrease A class power

 

[WalterW]

I thought I'd run this idea by you more experienced builders. Would a pair of these chassis work for M2 mono blocks?
Mini Dissipante 2U 300mm frontale 10mm ARGENTO coperchi e retro in alluminio 3mm
Not really wanting to end up with a huge, hernia-building, stereo chassis. I do really like fully mono power supplies. Heat wise, it works ok, the issue is having to put one output device on each heat sink (P on one side, N on the other). Is it better to have these thermally coupled? Or does it really matter?

Also the power transformer and autoformer end up a little close...hmm

Cinco

yes, I have been looking at these new 'Mini Dissipante' chassis too , they are really nice for mono blocks.
I don't think the P and N need real thermal coupling. The opto coupler feedback will take care off the offset.