Geloso connections (with pictures)

[Mo-Kay]

CLICK HERE FOR THE PICTURES


Hey everybody,

I've had a 1970's mic-pre GELOSO G 3276-A for some time now, but haven't used it yet because I HAVE NEVER SEEN THE TYPE OF SOCKETS that are on this thing! LOL

The front of the manual pictures this pre-amp together with the G 3270-A valve amp and says "AMPLIFICATORE COMBINABILE"

THE G 3276-A has 4 mic inputs, a single aux input, and a single phono input.
It has two outputs, that appear to be intended for connection with the G 3270-A.




The microphone sockets look like XLR sockets, but MALE, and the 3 tips are hollow. I have tried to connect a female XLR connector to these sockets, but it didn't fit.

The output connectors are circles, with cutouts like a swirl around them, with a hole in the middle, that looks like it could fit a jack-plug. Yet again, I've tried, but yet again, no succes.



I really want to use this unit, but in order to do that I really need to know what these connectors are!


Does anyone have any idea? Maybe some Italian users? Since I've heard some connectors, like XLR can vary per country.

Thanks a lot

Mo-Kay

CLICK HERE FOR THE PICTURES

[decadex]

You could try replacing the current outs with your common xlr i/o....

[jpmorris]

The 'outputs' are actually valve bases.

See: http://www.hificollective.co.uk/valves/valve_bases.html

Look at the octal VBASE025..

[The Ghost of FM]

I really want to use this unit, but in order to do that I really need to know what these connectors are!

This thing looks very much similar to the series of basic PA mixers from Shure that were simple mono mic mixers.

As to the mystery connectors, they are indeed tube socket connectors that have been bastardized to work as output connectors and possibly as power connections as well? It's hard to tell as your photo doesn't show any labeling for those sockets?

In any event, this unit doesn't seem worth the trouble as it is not a pre-amp. It is a mono mic mixer, probably designed to be used for simple PA applications like speeches at convention halls and such.

Cheers!

[Mo-Kay]

they are indeed tube socket connectors that have been bastardized to work as output connectors

Yes, that's what I believe too...


Still, since everybody in this section of the forum is such a diehard crack...

I'd say somebody please help me hook this thing up!!!

Mo-Kay

[Herm]

Since its Italian made I would say that the mic inputs are just of their design
As for the outputs it used to be pretty common in the 40,s or 50,s to use that type of connector for outputs to speakers in old cabinet radios. Also didnt hammond organ use connectors like this on their amps and on leslies?

[Track Rat]

Originally Posted by Herm

Also didnt hammond organ use connectors like this on their amps and on leslies?

Close. My 147 has a 6 pin connector (not tube type). There were some 9 pin type as well.

[Mo-Kay]

So what would be my options? Can I get cables etc to hook this thing up? And where?

[The Ghost of FM]

Originally Posted by Mo-Kay

So what would be my options? Can I get cables etc to hook this thing up? And where?

You'd need the schematic diagram for your unit to know which pins represent some sort of normal, line output to work from. Good bloody luck finding that!

You might try opening up the unit to see if you can spot any clues as to ground and experiment from there with a cable that has a standard connector at one end, to go into your amp and the other end should be fitted with miniature alligator clips so you can experiment, one at a time on the remaining wires to find the one that carries the summed output from the mixer's summing buss.

Be sure not to be standing in a bucket of water when you do this!

Cheers!

[Mo-Kay]

The schematics are actually in the manual...

but still, being able to hook it up and leave it like it is, would be a lot easier since I'm not all that technical..not in this way anyway

[The Ghost of FM]

Originally Posted by Mo-Kay

The schematics are actually in the manual...

Then you're in luck!

But, if you can't read a schematic, you're not out of the woods yet.

Can you scan the section of the diagram that pertains to the pin outs of those jacks and upload them here so we can take a peak? If not, we can be of little more assistance to you.

Cheers!

[Mo-Kay]

I'll try to get something up tomorrow...thanks

[Mo-Kay]

I'll try to get something up tomorrow...thanks

[arjoll]

As everyone has already said, those outputs are octal valve sockets. Ferrograph used them for their "aux" connector on the early models (like one I'm restoring) - in that case they carried heater and HT voltages as well in order to run outboard equipment.

I'm not sure where you get these (or if you still can). You might need to modify the unit to incorporate TRS or XLR outputs (probably would be an idea to isolate TRS jacks from the case).

The inputs look very similar to connectors on an old ribbon mic that my dad had which was designed to run with the Ferrograph. I'm sure that there are similar connectors available from RS, but you might have to study the dimensions of yours and the RS ones to confirm this.

A place to start might be the "EP" series, stock number 460-216 for the 3 pole line socket. These are 28.8mm diameter - if this sounds like the same dimension as yours then you could be in luck. As to wiring, you'd need to work this out from the circuit - I'm guessing it feeds a transformer.

Watch out if you're poking around in there - you've probably got 350v+ DC floating around. Also remember that the Italian gear is probably designed for 220v, so check your mains supply isn't too far out.

Hope this helps - post that schematic and we'll sort it out!

Cya
Andrew

[Mo-Kay]

I'm not entirely sure what you are trying to say about voltage differences.... over here things are 220v too....

anyway...

*drum roll*


I've added the schematics.

They're here

[arjoll]

Originally Posted by Mo-Kay

I'm not entirely sure what you are trying to say about voltage differences.... over here things are 220v too....

I wasn't sure what voltage you were on, just thought I'd point it out. I know that running 220v gear on New Zealand's 230 volt (nominal - up to 240v in some areas) supply has caused problems with some 220v gear, and I thought that Europe had standardised on 230v now.

Some valve stuff had separate 220v and 240v settings (as well as those really oddball settings around 120v ), and in NZ it was always run on 240v.

Originally Posted by Mo-Kay

I've added the schematics. They're here

Just downloading them now! That BMP is huge!

Cya
Andrew

[arjoll]

OK, this isn't valve based at all, just a very very simple transistorised mixer.

Those two octal plugs are identical, and be careful because they have full mains output on them. If you look at the diagram you'll see the unbalanced output is beside the 'key' on the centre of the connector, with earth either side of this.

To be honest I'd agree with Ghost's comment that this probably isn't worth doing a lot with. The BC108 had higher noise than the BC109, and I can't see anything really exciting about this design at all.

Cya
Andrew

[Mo-Kay]

hmmm, okay, that's really too bad

thanks anyway

[The Ghost of FM]

Originally Posted by arjoll

OK, this isn't valve based at all, just a very very simple transistorised mixer.

Those two octal plugs are identical, and be careful because they have full mains output on them. If you look at the diagram you'll see the unbalanced output is beside the 'key' on the centre of the connector, with earth either side of this.

To be honest I'd agree with Ghost's comment that this probably isn't worth doing a lot with. The BC108 had higher noise than the BC109, and I can't see anything really exciting about this design at all.

Cya
Andrew

I'd agree with your summation as well.

Here's a similar current product from Shure that has a normal set of connections that don't contain 110 ~ 240 volts on the output jacks!

http://www.shure.com/mixers/models/200m.asp

Cheers!

[The Ghost of FM]

Originally Posted by Mo-Kay

hmmm, okay, that's really too bad

thanks anyway

Hey! Cheer up a bit. It's not the end of the world ya know.

You thought you had some kind of ultra vintage, European, boutique pre-amp and it turned out to be a basic PA/sound reinforcement utility mixer.

Life goes on.

Cheers!

[Mo-Kay]

Yeah I know, thanks

Still, I know other geloso stuff (valves, normal connections) go around here too, and don't cost all that much

So I'll mos def keep checking


Mo-Kay

[Mo-Kay]

Hey, it's been long, but I'm back on this

I figured, what the heck, I'll just do it.

My question is now: can I just take 4 female XLR connectors for the inputs, and 2 XLR male connectors for the output?

thanks

Mo-Kay

[arjoll]

Originally Posted by Mo-Kay

My question is now: can I just take 4 female XLR connectors for the inputs, and 2 XLR male connectors for the output?

Just downloading the 11MB BMP again (damn slow 1Mbps ADSL) - will get back to you!

[arjoll]

Originally Posted by Mo-Kay

My question is now: can I just take 4 female XLR connectors for the inputs, and 2 XLR male connectors for the output?

In theory yes, but those are unbalanced inputs and outputs, and there is a chance that they might be designed for high impedence. You could just replace with TS jacks.

Re the outputs, they have mains voltage on them - be careful in there. You probably want to trace the mains wiring on them back to the source (probably a tag strip or possibly solder tags on the mains transformer itself) and disconnect them from there.

[Mo-Kay]

allright, thanks!

But TRSs aren't really all that handy for connecting mics, so could I get away with XLRs on the inputs?