[sdiy] slightly OT: solid state power amp topologies

[aankrom]

Good things to know!. This interstage transformer is pretty big: about 
what you'd see for a 20 watt push-pull tube amp OPT. This organ could 
crank out some major bass from the pedals. If it wasn't so bulky and 
didn'y have so many ciphers and a dead note, I might have kept it, but I 
have my Hammond M111 to restore... So many good parts. And the amp this 
will make should rock. I'm going to try to make an electromechanical 
tremolo so  can use the organ's Reverb and Vibrato rocker switches.

On Mon, 14 Nov 2011 09:50:08 -0500 (EST), Harry Bissell wrote:
> You can't necessarily tell a class B from a class AB by inspection.
> It depends on whether the
> bias causes one transistor to cut off before the other conducts
> (class B) or if there is an area
> where they are both conducting.
>
> Class B is actually pretty rare for audio (imho) as it is tough to
> eliminate or minimize crossover
> distortion, which is level independant and really very noticible (and
> objectionable !)
>
> A Silicon transistor will have a base-emitter voltage drop of around
> 0.7V, germanium will have a drop
> of about 0.2V. That is the best test imho, easier to do out of
> circuit though...
>
> Transformer coupled power amplifier designs are common in PA
> amplifiers as you can match impedances
> very easily. They usually lack some low-end unless the transformers
> are very large and heavy...
>
> H^) harry
>
>
> ----- Original Message -----
> From: aankrom <aankrom at bluemarble.net>
> To: synth-diy at dropmix.xs4all.nl
> Sent: Sat, 12 Nov 2011 15:07:19 -0500 (EST)
> Subject: [sdiy] slightly OT: solid state power amp topologies
>
> I am removing an amplifier from an old Kimball 600 organ. The power
> transistors are unmarked, but in the schematic, they have the same
> (Kimball) part number. Both are PNP with a bipolar supply. Is this a
> class B amp or a class AB amp? If it's a class B would it be possible 
> to
> bias it to class AB? It does have a transformer before the power 
> stage.
> Is there a good test to see if a power transistor is Ge or Si? About 
> how
> much power could you expect from two T03 sized power transistors from
> the mid-70's? The power supply for this thing is a monster - it uses
> four inductors.
>
> I have a speaker cabinet that is perfect for this - it's big so the
> reverb tank will fit easily. It's about 3 feet tall and about 2 feet
> wide.
>
> The organ itself is yielding up two nice manuals, a pedal, a swell
> pedal, lots of wire and nice Ge transistors and Orange Drop caps.
>
> Anthony
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