i have a technics su g91 int. amp that i want to use as a pre amp and run a crown xls1000 as the amp. there are no pre outs. however there is an rca jack labeled "mono center out" anyone have a clue what this is? google search turned up nothing. could this be a pre out? if not, is it possible to crack 'er open n solder in my own pre out jack? thanks
My guess would be a mono mixed output. To make a pre out, you basically just solder some wires onto the poweramps signal inputs and run these to a rca jack on the back.
You may also want to include a switch so you can switch between using the internal amp or the external amp.
You may also want to include a switch so you can switch between using the internal amp or the external amp.
i thought if u run from the pre out on the integrated to the external power amp it will bypass the amp section of the integrated automatically? if i solder rca jacks into the signal inputs wouldnt it just make another input instead of a pre out?
You could do like on some commercial amps, desolder the preamp outputs from the poweramp inputs, run these to a rca jack and run the poweramp inputs to another rca jack, the you bridge the jacks to use the internal amp, or hook the pre out to an external amp.
Or use Y-splitters to use the internal amp and an external amp at the same time.
Or use Y-splitters to use the internal amp and an external amp at the same time.
is this something that an amature can do without destroying things? how do i locate these? i cant track down the schematics anywhere
Try ElektroTanya | Service manuals and repair tips for electronics experts for a schematic on this one. I've done this to the G91 I have here on my desk (adding preamp outputs)
perfect. i downloaded the schematic from the link you gave me but..like i said, im an amature lol. is there any way you could walk me thru exactly what i have to do to solder in these pre outs? (place on the schematic that shows me where to tap in, pictures, part numbers, where to drill holes in the back to mount the jacks, etc) Id appreciate it!
With almost no threads on the forum, you can assume few members have even seen this particular model, let alone take pictures and draft instructions of how to modify it.
If you want blow-by-blow directions, you will at least have to provide the high-res pics so that we can identify likely parts of the boards where the connections are made. Specifically, you need to find the input connections to the power amplifiers. From these, it may be possible to simply fit a 10k resistor from each connection point and run shielded leads from this resistor and associated ground connection to RCA sockets that you fit to the rear panel in a convenient position - away from power leads, transformer and anything electrically nasty. You could also simply sacrifice the connections to any second set of tape-out sockets and reconnect for this duty,
It's all very simple if you know what you are looking for and how, generally, to go about it. You may need tools like a suitable size drill, soldering equipment, the insulated chassis mount RCA sockets, some cheap shielded signal wire and a couple of 1/4 watt resistors that will have to come from an electronic parts store. Otherwise you can still get lost in there real quick - schematic and layouts or not. Are you sure you want to got through with this?
Consider that used and new preamps that may be better than this series amplifiers are available cheaply online everywhere.
If you want blow-by-blow directions, you will at least have to provide the high-res pics so that we can identify likely parts of the boards where the connections are made. Specifically, you need to find the input connections to the power amplifiers. From these, it may be possible to simply fit a 10k resistor from each connection point and run shielded leads from this resistor and associated ground connection to RCA sockets that you fit to the rear panel in a convenient position - away from power leads, transformer and anything electrically nasty. You could also simply sacrifice the connections to any second set of tape-out sockets and reconnect for this duty,
It's all very simple if you know what you are looking for and how, generally, to go about it. You may need tools like a suitable size drill, soldering equipment, the insulated chassis mount RCA sockets, some cheap shielded signal wire and a couple of 1/4 watt resistors that will have to come from an electronic parts store. Otherwise you can still get lost in there real quick - schematic and layouts or not. Are you sure you want to got through with this?
Consider that used and new preamps that may be better than this series amplifiers are available cheaply online everywhere.
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yes...i do want to go thru with this for reasons most wouldnt understand..im just that type of guy lol. I downloaded the schematics and been studying it. On the pre amp board, theres an input selector (IC 401) which is where all the inputs are going (tape, cd, tuner, etc). Im assuming one side of it is right channel, other side left channel. now all the pins are listed as 0v except for pin 1 and 28 which are listed as 14v...is it safe to assume that this would be the Output which would run to the amplifier section, and if that is indeed the case, would I solder my new rca jacks to these to make the pre outs? sorry if I sound like a total noob
I think you need to google the datasheet for the ic 401 part number and find out what the pins really do! 14V is more than likely the power feed for the IC. If you connect that to your amp input I don't think it will be particularly happy (especially if it doesn't have an input cap!!)
Tony.
Tony.
your main concern is if after all if manage to create a preamp out from the technics the question will be if this preamp out is enough to drive the Crown .
Often inside integrated amplifiers manufacturers use various levels to match the preamp with the amp ... hardly ever this match is equal to 1.5 volts that you need to drive the crown
so by default your approach is wrong ... first you need to measure if the level is enough then you need to see how you are going to implement a preamp out
Often inside integrated amplifiers manufacturers use various levels to match the preamp with the amp ... hardly ever this match is equal to 1.5 volts that you need to drive the crown
so by default your approach is wrong ... first you need to measure if the level is enough then you need to see how you are going to implement a preamp out
Sometimes the preamp in an integrated is simply just a unity gain buffer with the poweramp doing all the gain.
Nope...this is the INPUT to the preamp. You are looking for the OUTPUT. This follows all the controls including the tone bypass, CD direct etc. if fitted. Typically an IC or discrete parts buffer amplifiers follows this section and THEN you have an output, subject to what Sakis and Wintermute have added.
pins 15&16 are the inputs for the 3206, I just used those.
Here's a guy who took pictures of the job on a different model technics (but basically everything still applies)
Technics SA-GX505 Receiver to Preamp Conversion
Here's a guy who took pictures of the job on a different model technics (but basically everything still applies)
Technics SA-GX505 Receiver to Preamp Conversion
i guess i dont really understand how soldering the jacks to those input pins would make a pre out? but i did find them in the schematic...and from what i understand now after studying, the signal goes from the input pins, to an amp buffer, from that to the tone balance, from that to the volume control, from that over to the amp section at the input pins. makes sense in my mind is this correct? also when soldering in the pre outs is it just pins to wires to jacks or do i need resistors? and if so why? lol thanks again guys your learnin me well 🙂
While it would be possible to route the signal from any point between C601/602 to IC601 pins 15/13 directly to an output, I'm not sure whether the electronic volume IC would be all that happy driving unknown external loads.
What you want to do is build a little unity gain buffer on a little piece of protoboard or such, which can then be mounted safely somewhere inside the amp and used to drive the pre-outs.
One 5532 opamp or similar, two small electrolytics for supply buffering (22..100µ, 25 V) and a few connections, that's about it. Signals, ground (maybe pin 14 of IC601) and suitable supplies of +/-14.7 V are available in the amplifier. (You can use separate power and signal ground connections if you want, just don't connect them together.) Any appreciable length of signal connection should be shielded if possible. I'd go with insulated RCA jacks - either that, or ones whose ground connects to the chassis, then the shield of the cables going to them should only be connected at the jack side and not at the buffer board.
How much electronics DIY experience do you have, anyway?
What you want to do is build a little unity gain buffer on a little piece of protoboard or such, which can then be mounted safely somewhere inside the amp and used to drive the pre-outs.
One 5532 opamp or similar, two small electrolytics for supply buffering (22..100µ, 25 V) and a few connections, that's about it. Signals, ground (maybe pin 14 of IC601) and suitable supplies of +/-14.7 V are available in the amplifier. (You can use separate power and signal ground connections if you want, just don't connect them together.) Any appreciable length of signal connection should be shielded if possible. I'd go with insulated RCA jacks - either that, or ones whose ground connects to the chassis, then the shield of the cables going to them should only be connected at the jack side and not at the buffer board.
How much electronics DIY experience do you have, anyway?
there actually is already a buffer amp on the pre amp board...is that what u are talking about? i have zero diy experience but i know how to solder and i know how to locate everything in the schematics
wait a second! why couldnt i just run the signal from the eq into the external amp instead of back into the integrated?
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