rearturo said:
I used TRS (on the patch bay) to XLR balanced cables (i have XLR connections on my GssL) .. what do you mean by non floating please? .. never heard of that when it comes to balanced connections ...
Wiring of insert jack is depending on mixer (FI Behringer, Allen&Heath,... TRS insert jack is tip=send, ring=return, or just the other way round FI Soundcraft,... TRS insert jack is ring=send, tip=return). With the other split insertwire end going to male and female XLR plugs, this makes a difference, hence my 'detailed' request.
The GSSL input exclusively operates the differential between XLR-pins2/3, so with an unbalanced signal feed you connect the TRS 'send' wire to XLR-in-pin2 and TRS shield to XLR-in-pin3. All XLR-pin1 connect to GSSL case in the shortest possible way and 0V reference voltage is connected to your case ground in one single spot.
The GSSL output is non floating balanced out. XLR-out-pin3 is the inverted signal from XLR-out-pin2, each referencing the GSSLs 0V reference voltage. If you link XLR-out-pin3 with XLR-out-pin1 (would be correct for a transformer floating output), you nearly short out this inverting opamp stage (and the chip will induce a whispering "this guy wants to fry me, don't buy his records" to every track you record for the next two weeks. ;D). For the GSSL output connecting to an unbalanced receiver (your mixers insert return jack), XLR-out-pin2 connects to the TRS 'return' wire and XLR-out-pin1 connects to wire shield. Leave XLR-out-pin3 unconnected. With given parts values and a connection for unbalanced out, you will lose 6dB, to come by by either increasing the makeup-gain pot setting for this amount, or decreasing the 27K resistors that connect to audio-VCAs-pin1 to 15K resistors (same value as feedback resistors in the VCA following current-to-voltage converter stage).
Operating the GSSL with impedance balanced output would only require two additional jumper wires and cutting two pcb traces, giving the advantage of same output level, no matter of connecting balanced or unbalanced, and not risking to short out the last opamp. A cross-coupled output stage with balanced line driver chips (THAT1646,...) on an addon pcb or piece of perfboard would be another alternative.
Connections were fine, I had them double checked with someone else as well so I guess no problem there...
maybe (hence my request for detail, IE TRS-tip goes to XLR-pin???...)
but is it wrong to have bridge soldering if the pcb soldering pads were connected cause I'm not 100% sure about this?
Most often wouldn't matter only
IF these pcb pads in question would be connected in short distance by a pcb trace. Have a look at the GSSLs pcb self etch file for confirmation, if pads in question should be connecting to neighbouring pads or kept separate.
Your 'IC on the left from the input XLR was getting hot very quickly' implies a condition exceeding parts limits, maybe caused by a short (your bridging soldering pads?) or wrong parts value(s) or orientation. This chip should not even get warm.
Yes, I need to do some research on how to measure these rail voltages cause unfortunately I'm not an electrical engineering and have no experience here...
Set your multimeter for measuring DC voltages in a range higher than expected, maybe 20VDC, just in case your multimeter is not auto-sensing. Plug your black wire probe into your meters [COM] terminal. Plug your red wire probe into your meters [V,Ohm,...] terminal. With GSSL powered on, you get a sign sensitive VDC readout with your black probe wire tip pointing to 0V reference voltage (the center pin of the aux.12VDC connector might come handy, or any spot at the big filled pcb traces) and red probe wire tip pointing at a spot you want to measure in respect to this 0V reference voltage, FI NE5534-pin7 or NE5532-pin8 for +15VDC, NE5534-pin4 or NE5532-pin4 for -15VDC, TL072-pin8 for +12VDC, TL072-pin4 for -12VDC, ...
