Kevin Aylward wrote:
Scott Dorsey wrote:
input transistors. That's, dare I say, just plain daft, and don't work.

Its like nails scratching nails down a blackboard to us analogue
designers. There are so many reasons not to try this. Indeed, in my
current designs, there arnt any, its all current sources.

(Note that by input I was referring
to the negative-going input on the differential pair that is used for
feedback, but of course if you offset one side of the differential
pair, you offset both of them)

You also offset the output, which don't do very nice things to the
speaker.

No. There is a capacitor in the way. That's the point. You want that
offset on the capacitor.


To further clarify, if you offset the + input, the negative input will
follow. If you offset the - input, you have to force the + input to
follow. By itself, it will stay just where you set it.

To do what you suggest requires having the + input as usual, that is
connected to Ov in order to ensure that the output is also zero.

No, the + input is also floating above ground. There is a DC blocking
cap between the input jack and the + input. If you raise the voltage
of one input, you raise the voltage of the other.

The
bypass capacitor is then offset with a voltage and fed via a resister.
The junction of the resister and cap would then be bypassed solidly to
the 0v reference point to minimise distortion and hum loops. Since we
now have two caps, it would be simpler to just wire them in series back
to back without the bias circuit at all.

There is _already_ a bias circuit. We aren't _adding_ anything here.

hint: http://www.anasoft.co.uk/EE/index.html

Sorry, I tried to look at the "very low distortion amp" circuits, but
the resolution was very poor and they were pretty much unreadable,

Strange, it aint that good, but its certainly readable on my system.

My problem is that I couldn't read the numbers on the parts, either on
the screen or printing it out. So I can't say things like "what is the
base on Q1" set to, because I can't tell if that is Q1 or Q7.

so
I can't judge anything either way.

Well, if you download SuperSpice, I can send you the proper schematic so
that you can simulate it.

I'll pass, although we have Spice on the HP-UX boxes here.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."