I tore into the BSG amp last night and thought I'd share some thoughts and pics. I did not get to hear it because I was running late but did get a break out box built and took some static measurements.
Here is the bad Oscar:
And the preamp/ mic Pre/ CROSSOVER!
The amplifier runs on bipolar (duh) 14.8V rails. The Power supply is a PWM switching type unit and is NOT cross-compatible for use in the car; it would be VERY difficult to convert. There is a switch in the Power supply that I believe sets it up for 220V operation. Next to the power switch and HV rectifier, tucked in there is the Fuse, it's a 6.3A puck style commonly seen in European gear, they are not going to be found at rat-shaq so probe carefully, you will need to order spares from an electronics wholesaler like Mouser or Digikey. I plan to grab some in the next order I make, I'll get a part number.
The finals are 2N6488 and 2N6491 made by ST and Moto respectively. There is one each per channel; they are driven by TIP31 and TIP32 devices that are driven by Central CEN-U57 and CEN-U07 transistors. There is a lot of drive here with little gain, the amp should be pretty stout, the finals are 15A/80V devices so they are certainly running in their SOA.
The amp is fused at 6.3A the manual states that it can consume 420 watts, if the amplifier were 70% efficient this would mean that in theory, all channels driven, one could get 49W/Ch out of it, if it is 80% efficient (there IS a PWM supply) then theoretical output all channels driven would be 56 watts.
The manual states that it IS ok to run a 2 ohm load (they say 4 (X) 8 Ohm speakers per channel)
All this is only true if the power supply is up to the task, these are just figures. The HV pulse voltage of the PS is 166V, rectified and filtered right off the AC line. This is then pulsed and stepped down to the rail voltage previously mentioned.
Getting separate inputs...... My unit was sent with 2 audio cables, fortunately, after demolishing a PS/2 keyboard it was found that my specific keyboard did not have all 6 wires in it, just 4 and a shield. I chose to hack up ONE of the cables and save the other.
I used a small bud box and put 6 RCA females into it, I also installed 2 DPDT switches that gang channels 1&2 to 3&4 and 3&4 to 5&6, this way I can use 2, 4, or 6 inputs. I just did a pigtail end for wiring; I was going to not sacrifice a cable and put the jack out of the preamp in it but decided not to.
Here's the unwired box:
Breakout with the switches wired:
Here's the finished product:
Big problems arose when becoming confused while looking at the manual for wiring color codes, the manual is screwed. They state the color coding as follows:
Ch6= Black!!!!! (WTF)
2 blacks? and there is no white or blue!
Here's the correct wiring!!!
Kinda looks like the resistor color codes eh? Whoda thunk it?
The second method of doing this eliminates the BOB and cable, you will need to drill 6 holes in the amp, I would do this under the Speaker outputs, you will not need ground as chassis and signal share common ground. It does not render the stock input useless, it allows for an either/or operation.
IF YOU SUCK AT SOLDERING THIS METHOD IS NOT FOR YOU!
Near the female DIN connector you will see 6 SMT resistors labeled in this order:
With a maximum of 1/16" chisel or screwdriver tip quickly tack 6 wires onto these resistors on the side closest to the input connector. GO FAST with the heat, too much heat will melt the other side and knock the resistor loose, they will re-attach but if you have never worked with SMT stuff it will anger you quickly!
The other ends of these wires will attach to the center conductor of the RCA's you just mounted. The order is as follows:
Now you have 2 different methods of inputting to the amp. Don't use both at the same time as the preamp won't like having signal applied to the outputs!
So there you have it!
Time for a reward!