Hiraga The Monster...

[fdegrove]

Hi,

Sorry, I could not resist. There seems to be a lack of humor in the forum these days.

I fully agree there and I recall Grataku even started a thread asking what on earth was going on....I agree with him something has changed...may be it's just me.

Maybe we could convince you to build one.

I think the 20 W " Le Classe A" was better.

Nice try though,

[jam]

Frank,

This will make you happy.

Jam

[fdegrove]

Hi,

Would you believe I could fill half a page telling you about the history of that little tube alone?

And I do mean the history of the one in your picture, not the generic 12AY7A...

So, you're telling me you know your tubes too?

Cheers,

[P.Lacombe]

I don't agree with Mr Pass : substitution of transistors is a very complex problem in the Monster, to day's transistors are not made with the same processes and exhibit different transfer characterisics, internal capacitances, phase lag and so on. As far as I know, internal Ccb variation vs collector voltage, and Rbb' are essential parameters.

Jean Hiraga has invested a considerable amount of time to tune up this amp, not only with measuring equipment, but also with ears and brain. Some particular choices results in a specific distortion cancellation, which can be totally ruined by substituing transistors. (The same occurs in valve amps).

I presume that the correct answer is to entirely redesign the whole amplifier with available transistors... This is (verbatim translation from french !) a monk's work !

Regards, Pierre Lacombe.

[fdegrove]

Hi,

Jean Hiraga has invested a considerable amount of time to tune up this amp, not only with measuring equipment, but also with ears and brain. Some particular choices results in a specific distortion cancellation, which can be totally ruined by substituing transistors.

It was already a big issue when the circuit was published and people wanted to build one.

Maybe there are better alternative transistors nowadays?

Cheers,

[Nelson Pass]

Well, I guess it's just too complicated an issue and
we'll just have to give up.

[mlloyd1]

... and given process improvements over the years in both passive and active components, it is also possible that one could make substitutions and result in an even better sounding amplifier.

Some brave soul with time on his/her hands will have to step forward. Preferably somone who has (or at least has access to) the original for comparative purposes.

I will probably get into tremendous amounts of trouble for saying this (someone has to pick up where jocko and H.H. left off ) - I would venture to guess that one might hear the effects of being limited to 8 watts long before hearing the effects of contributions of the second order (and higher order) characteristics and device parameters you've mentioned.

Now here is, unfortunately, where I have to admit I haven't built the amp, much less listened to it

oh well,
mlloyd1
(who still secretly dreams about building that Pass Class A 20W thingie from 1977 with modern devices!)

Originally posted by P.Lacombe
... substitution of transistors is a very complex problem .... exhibit different transfer characterisics, internal capacitances, phase lag ....

Jean Hiraga has invested a considerable amount of time .... Some particular choices results... can be totally ruined by substituing transistors....
....
Regards, Pierre Lacombe

[jam]

It is not nice to question the Master!

Jam

[fdegrove]

Hi,

In case anyone has scans of the original publications by "L'Audiophile" I'd be happy to assist in translation work.

As Pierre pointed out, this and most other circuits by this team depend heavily on certain parameters for sonic bliss.

Passive components, layout, wires everything was painstakingly thought out.
They were lightyears ahead of the commercial designs of those days and I still go through some of the articles for reference.

Let me know if I can help, I hold most of these publications anyway....I am a bit surprised by this nostalgia though.

Ciao,

[jam]

Frank,

I just picked a tube at random, I bet more appealing than the centerfolds in the Playboys' you have stashed under your bed.

I have built a few tube preamps 12AX7's and 6DJ8's, sounded good but I needed better bass.

Jam