help me design a tube power amp "approximation"

[dschwartz]

Hi all, i know this may be discussed many times, but i´ve been thinking about making my own SS amp with a LM3886 chipamp..

I´m triyng to find out how to approximate (not emulate) to power tubes on a AB configutarion, maybe like EL34´s and so far these are the things i have thinked about:

- Signal limiting/transfer curve: i´ve simulated a simple diode cascade clipping giving really soft clipping. and the softness can be regulated by a single pot..
- Output impedance: i can manage to make a simple filter to simulate the 100hz "bump" and the 3-10kHz boost given by the speaker when driven by a high impedance source like tubes.

i think with this both implemented i could get a nice "compressed" and "warm" sound..

what else i should consider? Sag? frequency dependent distortion/compression? gain dependent frequency response? are those important too?

[maarten]

Hello Daniel,
my 2 cents, as nobody took the bait yet:
- Why consider sag if you already have done something to the signal limiting/transfer curve and are expecting a nice compressed and warm sound? At the other hand, you could easily experiment with this: just a 100 - 200 ohms resistor right after rectification, just before the first smoothing cap, might help - if it does not, you can simply bypass it.
- As for frequency dependent distortion or gain frequency response: I would not know of any difference in these between tubes and solid state, other than the "bump" you described and already took care of...

So my opinion is: just go ahead and do it the way you proposed!
Maarten

[sean k]

I get what your saying without getting what your saying but I kinda think the most important thing is good speakers. Paper with paper suspension and ribs around the circumference about halfway between the centre and the suspension... and alnico magnets. Speakers do about 90% of the sound in my book.