Can you ID or explain these transistor amplifier cards?

Second item from a batch of parts I bought fron GDIY member fluxivity.  Transistor amplifier cards marked only "Jh004".  I traced out the circuit and it is an odd one to me.  Mix of Si and Ge transistors, and a weird feedback circuit.  See schematic attached.

I powered one up with +24vdc and the best I could get out of it was about 33dB gain from a 50 ohm source into a 100k ohm load.  However the input to the board had to be about -55dB to keep the THD below 1%.  Also, lowering OR raising the power supply voltage lowered the gain.

Does anyone have any idea what these boards may be from or what they are for?

Photo of cards

while not an exact copy,  it bears strong resemblance to the Spectrasonic 101 circuit.

Topology is clearer if Q3 is twisted to better orientation. We have seen this 2nd and 3rd stages before.

I can not make sense of the bias. However it should be clear from Supply Current. If V+ is low, current is silly low (this thing has to draw some power). If V+ is a little too high, the output stages melt.  I am NOT sure my interpretations below are correct.

I'd pull it up, carefully, to 10mA draw, and see if that makes sense.

Pin8 is grounded as well.

Working voltage of the original electrolytics will give a good indication of intended supply range - these looks like they are from a time where voltage ratings were rather costly..

Jakob E.

Thanks everyone! 

They do indeed seem similar to the SS 101, I had not looked at those when searching for similar designs. 

The MCI connection was also a thought because of the "Jh" on the board but they do not match any Ampex 440 schemo I have found.  Fluxivity said the cards came with a bunch of Harrison console parts but did not match anything else.

PRR of course can visualize and simulate circuits without a computer so his input is much appreciated  ;D  I had Q2/Q3 drawn like that in my first draft but then it got crowded and I turned it around in the second.  I will ramp up to a higher voltage and watch the current draw.

Yes Jakob, pin 8 is ground as well.  I indicated that on the edge connector drawing but should label the schematic too.  Didn't mark Q4 either. 

OK, fired up the cards and slowly raised the voltage past the 24v mark.  Got them up to +48vdc and the draw was around 8ma.  Distortion dropped, headroom increased, and 600 ohm loads were acceptable!  Nothing got hot so I ran a few tests and all was very good but the LF was 0.5dB down at 20Hz.  I replaced C1 and C4 with 100uf and that improved.  Here's the results:

600 ohm source and load
32dB gain
-72dB THD+N at +4dBm out
Clipping at +24dBm
Frequency response -0.18dB @ 20Hz, -0.08dB @ 20kHz

Now that's more like it!  Thanks again everyone and especially PRR. 

EDIT: Attached final version of schematic.