In trying to get a bit more life out of my longstanding Yamaha RX-V357 (B version), I'm looking to extract the surround channels at line-level for which this unit does not have native pre-outs. My thinking is that I can just tap this straight off of the input pins to the STK403-130Y amplifier ICs - where does this logic sit on the scale of reasonable to insanity?
I'm basing this on Yamaha's service schematic, with the block diagram (p53) and main board (p57) showing that this signal should be available over pins 14 & 15 of both IC102 (left channels) and IC103 (right channels). The STK403-130Y datasheet confirms that these seem to be the right pins (for each L/R amp IC - Ch1 is Front, Ch2 is Surround):
RX-V357 Schematic:
https://manualzz.com/doc/o/tpuoa/av-receiver-rx-v357-htr-5830-schematic-diagram
STK403-130Y Datasheet:
https://www.alldatasheet.com/datasheet-pdf/pdf/1314403/SANYO/STK403-130.html
Is there any reason whatsoever that connecting an appropriately shielded cable to these pins won't give me a line-level RCA pre-out for the specified channel?
I'm basing this on Yamaha's service schematic, with the block diagram (p53) and main board (p57) showing that this signal should be available over pins 14 & 15 of both IC102 (left channels) and IC103 (right channels). The STK403-130Y datasheet confirms that these seem to be the right pins (for each L/R amp IC - Ch1 is Front, Ch2 is Surround):
RX-V357 Schematic:
https://manualzz.com/doc/o/tpuoa/av-receiver-rx-v357-htr-5830-schematic-diagram
STK403-130Y Datasheet:
https://www.alldatasheet.com/datasheet-pdf/pdf/1314403/SANYO/STK403-130.html
Is there any reason whatsoever that connecting an appropriately shielded cable to these pins won't give me a line-level RCA pre-out for the specified channel?
Thanks for the advice, though could you please excuse my ignorance and help me understand why this might be advantageous?
Taking IC102 (left channels amp) as an example, I presume that C131 is the coupling capacitor. Would there be an ideal place to tap in along the highlighted circuits? Preferably attaching to a set of existing pins, rather than cutting into the traces!
Never damage a pcb trace unless absolutely necessary. Just tap into the node at a component lead.
It's hard to tell from the pcb foil, since the parts are not labeled on the schematic.
But the actual input, labeled CH1-IN and GND, would be the best place.
It's hard to tell from the pcb foil, since the parts are not labeled on the schematic.
But the actual input, labeled CH1-IN and GND, would be the best place.
Ah, so I should use pin 10 on the STK403-130Y which is directly connected to GND instead of pin 14? That way I can take the signal off at the easily accessible pin 15 and avoid the upstream capacitors.
Thanks for clarifying (and your patience!) - to make sure I'm fully understanding, I should tap into the signal (red circuit) at the R146 lead (or earlier) and avoid pairing it with the green circuit, instead choosing any accessible lead which is directly connected to GND?
After looking at the service manual, it seems that the best place to pick off the audio signal
would be on connector CB101. All the signals and grounds are there. Just make sure there
is no DC voltage on the pins where will you connect the cables. There should not be, but check that.
would be on connector CB101. All the signals and grounds are there. Just make sure there
is no DC voltage on the pins where will you connect the cables. There should not be, but check that.
Excellent, I'll check CB101 first once I get a chance to open it up. It'd seemed like a good candidate when I checked the schematic before, but (as a layman when it comes to audio engineering) wasn't sure if any of the downstream circuitry was necessary - hence working backward from the amp inputs... Really appreciate you taking the time to delve into this!
Those receivers are really complex, so be careful. Make sure there is no DC voltage
on the CB101 terminals first.
on the CB101 terminals first.
Managed to open up the unit today - some things learned, but no success...
The CB101 connector is readily accessible with the top cover off, there are no DC voltages on any of its pins and all of those marked 'E' are directly connected to the chassis earth. Logically, this would suggest that the other pins are the signals as marked (L, R, SL, SR, etc.). However, trying to tap into these with probe wires hooked into the RCA input of another amp did not yield any output.
I tried this on all of the channels available on CB101, with both digital (5.1) and analogue (6ch) sources. Touching probes to the analogue line-level input source worked, indicating that the second amplifier and probe wires were functioning as intended. I'd intended to dig out my USB scope and see if there was any activity at all on the pins, but that device is another saga of disfunction...
Using the same probe method I also tried tapping the signal off of one of the amp chips, also to no avail. Any thoughts?
The CB101 connector is readily accessible with the top cover off, there are no DC voltages on any of its pins and all of those marked 'E' are directly connected to the chassis earth. Logically, this would suggest that the other pins are the signals as marked (L, R, SL, SR, etc.). However, trying to tap into these with probe wires hooked into the RCA input of another amp did not yield any output.
I tried this on all of the channels available on CB101, with both digital (5.1) and analogue (6ch) sources. Touching probes to the analogue line-level input source worked, indicating that the second amplifier and probe wires were functioning as intended. I'd intended to dig out my USB scope and see if there was any activity at all on the pins, but that device is another saga of disfunction...
Using the same probe method I also tried tapping the signal off of one of the amp chips, also to no avail. Any thoughts?