prowla Posted March 11, 2023 Share Posted March 11, 2023 What's this connector on the back of an old Trace Elliot GP11 preamp? Quote Link to comment Share on other sites More sharing options...
bartelby Posted March 11, 2023 Share Posted March 11, 2023 Connection to a power amp stage, I'd guess. 1 Quote Link to comment Share on other sites More sharing options...
prowla Posted March 11, 2023 Author Share Posted March 11, 2023 🙂 Was kindof hoping for something a bit more precise than that! (For sure it's power, BTW, but may also include signal.) Quote Link to comment Share on other sites More sharing options...
Mottlefeeder Posted March 11, 2023 Share Posted March 11, 2023 Are you aiming to mate with it or check out whether it is passing the right signals? David 1 Quote Link to comment Share on other sites More sharing options...
Merton Posted March 11, 2023 Share Posted March 11, 2023 21 minutes ago, Mottlefeeder said: Are you aiming to mate with it or check out whether it is passing the right signals? David Not sure human/amplifier mating is to be encouraged 😄 1 Quote Link to comment Share on other sites More sharing options...
BassmanPaul Posted March 11, 2023 Share Posted March 11, 2023 2 hours ago, Merton said: Not sure human/amplifier mating is to be encouraged 😄 Oh BABY!! LOL Quote Link to comment Share on other sites More sharing options...
Mottlefeeder Posted March 11, 2023 Share Posted March 11, 2023 Too easy 1 Quote Link to comment Share on other sites More sharing options...
BassmanPaul Posted March 11, 2023 Share Posted March 11, 2023 I agree that it's for connecting a Trace power amp board. I tried to read the schematic I found on the web and could see the wiring for the socket but the site was flaky so the diagram didn't stay long enough on my screen to be certain. I'm betting that this unit came from a deceased head as it has no connectivity on the back panel. Quote Link to comment Share on other sites More sharing options...
bartelby Posted March 11, 2023 Share Posted March 11, 2023 (edited) 7 hours ago, prowla said: 🙂 Was kindof hoping for something a bit more precise than that! (For sure it's power, BTW, but may also include signal.) signal and power Preamp board, connector circled. That would connect to the power amp board here: Edited March 11, 2023 by bartelby 2 Quote Link to comment Share on other sites More sharing options...
BassmanPaul Posted March 11, 2023 Share Posted March 11, 2023 Thank you @bartelby for going to the trouble of supplying the schematic. @prowla if you are wishing to use this pre-amp standalone you'll have to provide a power supply and audio cabling to feed a suitable power amp. Good luck with that! Quote Link to comment Share on other sites More sharing options...
Mottlefeeder Posted March 11, 2023 Share Posted March 11, 2023 OK, back to my original question - do you have the amp that this was connected too, in which case you have the mating connector (with or without working electronics connected to it) or are you hoping to source a connector that will fit? David Quote Link to comment Share on other sites More sharing options...
prowla Posted March 11, 2023 Author Share Posted March 11, 2023 Thanks for the input, folks. No, I don’t have the power stage; iI am looking at this as a stand-alone preamp. Getting a suitable power supply might be a bit of an ask. Quote Link to comment Share on other sites More sharing options...
BassmanPaul Posted March 11, 2023 Share Posted March 11, 2023 Connector pin assignment Pin 1 - Ground Pin 2 - Full Positive rail Pin 3 - Audio Signal Pin 4 - Full Negative rail Pin 5 - Not used Pin 6 - Not used Quote Link to comment Share on other sites More sharing options...
BassmanPaul Posted March 11, 2023 Share Posted March 11, 2023 It looks as though the pre-amp is powered between the positive rail via a regulator and ground. that's a little odd in my mind. The negative rail just seems to drive a couple of lamps. Hmmm! Quote Link to comment Share on other sites More sharing options...
DGBass Posted March 11, 2023 Share Posted March 11, 2023 (edited) 38 minutes ago, BassmanPaul said: Connector pin assignment The pin assigment can vary on TE pre-amp sections. Seeing the front panel might be helpul to identify your version. The schematic applies to MKV GP11's. MK II GP 11's also had extra wiring for the ECI function ( earth continuity indicator ).The MKV GP11's were used on a multitude of different amps but mostly AH150 heads and AH250 heads. Both had different feed voltages from the power section tranformers. Basically they use a half wave rail voltage from the main power supply, a big step down resistor on the pre-amp main board, a voltage regulator and zener diode run the pre-amp on roughly 30-35V dc. On my AH250 the feed voltage to the GP11 MK V via the 6 pin connector is 65V dc. On my AH150 GP11 MKII it is actually higher at 71V but thats because it has a rare 50V transformer and not the usual 40V one. The step down resistors are the critical part as they drop enough voltage so as not the smoke the pre-amp🥵 Some of these pre-amp sections aren't really interchageable between different models even though they have the same 6 pin multi plug socket. Might or might not work and you might or might not get smoke! I've just rebuilt one recently ( a MKV GP11) that had been through the wars. The multi plug was missing, long gone on a dodgy amp service years ago and the cables were hard soldered onto the pins. See pic, the red and black are the power supply, the blue is tip/signal out and the signal out screen is on pin 6. A 2 core screen cable out to a power amp and a pos and neg from a supply voltage ( anything around 60v dc would likely do) and would most likely get your pre-amp working assuming its in good order. Edited March 11, 2023 by DGBass 3 Quote Link to comment Share on other sites More sharing options...
BassmanPaul Posted March 11, 2023 Share Posted March 11, 2023 I'll bow to your superior knowledge. Many thanks for helping out. Quote Link to comment Share on other sites More sharing options...
Mottlefeeder Posted March 12, 2023 Share Posted March 12, 2023 A simple power supply is not a major problem - it has a fuse, transformer, bridge rectifier and two smoothing capacitors. Your cheapest option to avoid paying out for an amplifier-rated transformer would be to buy two smaller 18-0-18 transformers and wire the outputs to give 36-0-36. That's still £40+ just to see if it works... Connecting to the board would be neater with the right plug, although you could just bypass the plug as in the photo - you could hard-wire it, or use an XLR for power and jack for signal. I'm wondering if the plug is a Molex - they were common at the time, but some were limited to 12v max. They are still used on PC power supplies to disc drives. David 1 Quote Link to comment Share on other sites More sharing options...
bartelby Posted March 12, 2023 Share Posted March 12, 2023 Here's the full schematic for the Preamp. Quote Link to comment Share on other sites More sharing options...
prowla Posted March 12, 2023 Author Share Posted March 12, 2023 So, it may be a Molex connector, like in a PC, or something similar which is rated at a higher voltage. and the pins are: Ground (power and signal) +ve rail, which may be 30V, 36V, or perhaps 71V, current unsure. Signal. -ve rail, as per +ve. n/a n/a I'm pretty sure it's originally from a head or combo, but the power supply/amp stage has presumably shuffled off this mortal coil and so the question is whether it can be converted to a standalone preamp and whether it is worth the effort. The background is I've been looking at buying it, probably for £50, but I think I'm going to pass, as it'll just be another project for me (I seem to collect projects!). If anybody's interested, it's on FB Marketplace: https://www.facebook.com/marketplace/item/564451868674188/ Quote Link to comment Share on other sites More sharing options...
DGBass Posted March 12, 2023 Share Posted March 12, 2023 It's an earlier MKII GP11 in the FB ad so above schematics wouldn't apply. These also have the ECI wiring which is a heap of trouble if you can't test its working before buying it. It will likely have come from an early AH150 or AH250. The ad picture looks like a rather poor condition and well used unit with missing knob caps and a non standard input jack. So its had work before and i would guess would need a fair bit of work to bring it up to standard. You could easily spend another £50 getting it working and at the end of the day you would struggle to ever recoup that. £25 spares/repairs is probably more realistic unless the seller has the old blown power amp unit he could throw in. The power amps are generally bullet proof and very easy to fix if they do stop working. The pre-amps are a bit more complicated. The trouble with starting a project like this these days is that folks are stripping down old trace amps because they realise they can make a lot more money selling parts than a whole unit for spares or repair. Parts are sold as no return/untested so if you do by a dud part theres little comeback. Whole working TE amps of this era in good nick and reasonably original condition are becoming very scarce nowadays and that will probably encourage the parts strippers to break up anthing they can get their hands on. Saying that, its a good enthusiast project and with a bit of work, a suitable power supply and a nice slim 2U rack case it would make a great wee project and a brilliant pre-amp once working. These old GP11 pre-amps have a great silky smooth tone. I can vouch for that as I have one in perfect working order and very good original condition 😁 1 1 Quote Link to comment Share on other sites More sharing options...
BassmanPaul Posted March 12, 2023 Share Posted March 12, 2023 On 11/03/2023 at 12:40, Mottlefeeder said: Too easy But not cheap! Quote Link to comment Share on other sites More sharing options...
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