Official M2 schematic

[Mark Johnson]

I use a ceramic capacitor with "C0G / NP0" dielectric, for C1 of the M2's RC terminator network (across the Edcor secondary), and I recommend it in the Bill Of Materials for the M2x clone of the M2. See the red box on the attachment below.

It is Mouser part number 81-RDE5C2A681J0K1H3B price is USD 0.41 qty=1.

C0G/NP0 is a Class 1 Ceramic, you can read more in the Wikipedia article about ceramic capacitors


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[Zen Mod]

use biggest SMD you can find, solder some tiny wires as legs

these are good enough , whatever they're called

 

[juanitox]

speaker impedance

i have a choice between a 12" 8ohm and a 16ohm Medium/bass driver , what will be the best for the M2 ?

 

[Zen Mod]

do not worry about M2 , think of every other relevant factor

 

[6L6]

Yes. What ZM said.

 

[juanitox]

i'm not worried at all ZM as i have your mighty name printed on the boards

it's just that i have the choice between a 8R and a 16R version of the same driver. some says that with low damped amp like tube amplifer 16ohm will sounds better?

 

[kilohertz]

Normally I wouldn't even think about using a ceramic cap in an audio circuit but would a ceramic cap be ok for C1 or do I really need to use a silver mica cap?

Why not use a film cap? There are many available from Digikey, Mouser etc. Polypropylene, Polystyrene etc.

Cheers

 

[6L6]

juanitox - What we are trying to say, in a round fashion, is that you need to make decisions about your speakers in regards to the entirety of the speaker system.

The M2 will gladly and authoritatively drive whatever you choose.

 

[juanitox]

The M2 will gladly and authoritatively drive whatever you choose.

thanks for the info 6L6 , and same gain or less with the 16ohm load ?

 

[Zen Mod]

same gain

 

[Chiptech]

when you're in doubt , just stop;
make a coffee (or tea) , chill , and take a long and pleasant safari through pictures of Papamps on 6moon site

This is great advice. Thanks

 

[marconi118]

could the M2 use the same bias system as the F4 with a TL431 (or low current version of 431) ?
this could allow to remove the source resistors and increase the square law

 

[Zen Mod]

good luck with fixed bias at gates of IRFP without source resistors

F4 is having them, for reason(s)

see Babelfish M25 and necessary added complexity, to achieve exactly the same - square law

there are some other ideas for biasing, but it'll take some time

 

[marconi118]

see Babelfish M25 and necessary added complexity

do you refer to hall effect measuring boards to measure drain current without inserting any resistor?

 

[Zen Mod]

yup

difference between F4 and M2 is current per mosfet

in F4 it's smaller, so action of source resistor is big enough to keep mosfet out of thermal runaway, on condition that heatsinking is up to task ( but that's general condition for all amps)

in M2, current per mosfet is greater enough, so you'll need impractically higher value for source resistor to achieve the same, so Papa introduced old t=rick of his ( in newer and more innovative way) to have active biasing mechanismus

beauty of this is that M2 is having almost exactly the same Iq, be it cold or hot

 

[marconi118]

what is the role of Q6 and Q7 voltage regulators?

 

[Zen Mod]

where?

 

[marconi118]

on the M2 schema just before the optocoupler

 

[indra1]

what is the role of Q6 and Q7 voltage regulators?

Hmmm, still want to depend on others. Read Official M2 schematic post #87.

 

[Zen Mod]

optodiode protection

and symmetry-sation of D1-D3 string, which is clamp-protection of OS modulation node, to keep mosfet gates of overvoltage