Melcor AML-27 Preamp questions

Hello,

I just bought two Melcor AML-27 preamps off of ebay, listed as line amps but they seem to have input trannies. Anyone familiar with these preamps? I did not get a pinout or schematic with the cards but they look almost identical to the 312 cards but with a different pin config and a 1731 doa.

I am looking for the pinout if anyone has them or for some help in identifying the pinout. If anyone is interested I can post pics.

As well, thanks to everyone here for such an amazing resource. I finished my first project yesterday, ssl comp with chefs amazing boards, powered it up and recieved immediate satisfaction. Pics comming as soon as I finish a chassis for it. two 1176's half filled, g9 half filled :grin:

I am a newbie and a diy addict.

:guinness:

Cheers, Jason

I could use the info too. Anyone?

Hi guys,

I scored five of these just as the first of these started showing up on ebay about a month ago. I also got the rack for them with the connectors and connections intact! And best of all, I got them all for free!!!!!! :green:

I traced the pinout, but I'll have to find it amongst all my other crap. Give me a day and I'll post what I found. :thumb:

Jeff

So here's what I found.

Oh, also I emailed the guys at Glenford Sales, the guys selling the cards on ebay. Paul Cohen over there was kind enough to email me a schematic that they drew up that confirmed what I found. If anyone wants a copy let me know.

First what I traced on the board, then what the connections are at the connector.

What I traced:

Pin 1=output xfrmr Green
Pin 2=output xfrmr Orange
Pin 3=output xfrmr Yellow
Pin 4=com
Pin 5=input xfrmr Yellow
Pin 6=input xfrmr Orange
Pin 7=input xfrmr Red
Pin 8=input xfrmr Blue
Pin 9=com
Pin 10=opamp input negative
Pin 11=n/c
Pin 12=opamp output
Pin 13=Vneg
Pin 14=com
Pin 15=Vpos

the connector:

Pin 1=output neg
Pin 2=output pos
Pin 3=output center tap
Pin 4=tied to Pin 10 through a 70R resistor
Pin 5=input neg, tied to Pin 8 through a 610R resistor
Pin 6=tied to Pin 7
Pin 7=tied to Pin 6
Pin 8=input pos, tied to Pin 5 through a 610R resistor
Pin 9=n/c
Pin 10=tied to Pin 4 through a 70R resistor
Pin 11=n/c
Pin 12=n/c
Pin 13= -15V
Pin 14=com
Pin 15= +15V

My thoughts:

the 70R resistor between Pins 4 and 10 sets the gain of the amp

the input xfrmr has 2 (maybe 150R, or 300R) primaries. Pins 6 and 7 tied together and connecting input to Pins 5 and 8 gives you a 600R, or maybe 1200R input impedance. 610R resistor between Pins 5 and 8 ensures 600R termination.

Thoughts??

Jeff

Thanks Jeff. I'd like to know what the resistor strapping is for. I've seen Melcor pre/eq's with the same input transformer. This Melcor shite is hard to find.

Yeah, unfortunately Melcor docs seem to be pretty rare.

So you've seen Melcor mic pre's with the same input xfrmr? When I got mine, I was told that they were line amps, and the ones on Ebay were described as line amps. If you've seen the same input xfrmr on mic pre's, that would seem to indicate that they are either actually mic pre's or multi purpose amps capable of enough gain for a mic.

Jeff

They made a two band EQ with a mic line switch and gain presets. Not unlike the Langevin AM-4 console. I've even seen the accompanying compressor, with THREE 1731 inside.

did the 2 band eq with mic/line switch use the same input xfrmr?

Jeff

are these also know as channel strips from "the green monster"?

i have two of these.. and i have rev engineered most of a schematic (minus the 2 band passive eq)

can you post a pic?

IIRC it was the same. Same casing anyway.

Man you guys are great! Thanks Jeff :thumb:

I am going to free up some time to experiment with the info given.. im hoping these end up being mic pre's. If not, here comes a 1731 summing mixer :grin:

:guinness: :sam: :sam: :guinness:

No problem :!:

I'm sure these are capable of enough gain for some mics or loud source material at least. I want to find out how much gain they are actually capable of.

Please let us know what you find, as I'm sure you will get to these before I do.

:thumb:

Jeff

the eq channel strips have beyers.

I would kill to check out melcor limiters, one of my all time favorite records was done with LOTS of melcor compression.

dave

It wasn't an a channel strip per se. It was a small module, smaller than a 500 series API. I believe it was a variation of a model called the AE-20. Pat More-turd has schematics. I may know someone that could have some info...

Gimmie a couple days.

one of my all time favorite records was done with LOTS of melcor compression.

Click to expand...

what record was that?

I have some info on the AM-27. It has a description, pin outs and a chart for setting gain from between 25 and 65dB. No schematic though. I'll post it when I get it scanned.

[quote author="Jeff Goodman"]
what record was that?[/quote]

uncle meat.

dave

Gold,

That would be excellent, and very much appreciated. :thumb:

Soundguy,

Uncle Meat, huh? I'll have to check it out.

I also have two of them from e-bay. I have re-capped and slightly altered the circuit, and will rack mount them with gain select resistors and a pad. They sound great, and generate loads of third harmonic. The 1731 does not behave exactly like a standard op-amp, but I have managed 70dB of system gain with the AML27 card... Stock, they have 50dB gain with the primaries paralleled.

zmix,

can you post what you have done?

Jeff