Turtlerock Forum

Hi all,

Up for sale are a pair of Optro 7500 console channel strips.
Great mic pre's with a 3 band inductor EQ and transformer outs.

These are unracked.

$500

Will post Australia wide.

Will post pictures on the weekend.

SOLD - pending payment.

I also have a few of these for sale if anyone is interested - really great sounding pre's.....

yes

have been chasing some of these for ages and missed out every time. Also Chris I'm in Tas now if you're up for a beer?

Hey Dave - welcome to the land of 2 heads!
I'm up for a beer.
PM me if you want some modules - I was going to build a mini console but have way too much gear - and little precious time - so that dream can now be for someone else (I'll keep one pair instead )
How you settling in ?

Settling in well thanks – still surrounded by packing boxes and not quite used to the cold but Hobart's really growing on me.

Hi Chris, I'm always up for anything Optro.
To the seller, are you sure the eq on these 7500 strips is inductor? My sources tell me it is an I.C. gyrator circuit.
The pre's are discrete though. Correct me if I'm wrong.
Cheers,
Paul Maybury

I'm pretty sure you are correct Paul

Hi Paul,

No i am not sure, this was just what i was told and i just assumed it was true because i didn't know any better. Definitely didn't mean to mislead anyone.

]Mine have IC's in the eq circuit.
Tasmanian Chris' are a bit different but essentially the same.


These are the Optros with inductor eq:
[attachment=0]Optro_Module.jpg[/attachment

So the 7500's are transformer in, gyrator eq. No transformer on the output of the actual channel strip. I assume any output balancing was done elsewhere in the console.
Cheers!
Paul Maybury

That's a good question - when I dismantled my Optro console, there were no other transformers in the console.
Chris H has made a small Optro console out of 7500 strips - what did you use Chris?

When I got my 7500's, they cam with output channel strips together with a bunch of spares and nice VU meters. As the output ones where all mono I had two combined into one to give me two stereo outs and two mono outs. I also made up a 2RU dual mic pre box with two of the modules that is to my knowledge unbalanced out.

Interesting - my console had 16 channels into 6 mono and 2 stereo groups. (Plus 10 compressors + 4 gates)
Now this is starting to make sense - the output trannies are on the group out modules. I do recall seeing these massive transformers on each group module - they must have shared the output trannies? - something Q8 use to do on some consoles too
I originally thought it was not possible to share output transformers - but I'm no techie.

Ive also got 24 spare mic transformers - they look like the trimax ones painted black - anyone know if this is true?

I thought they where Byer untill Alan told me that Graham wound them himself.

You really should make a console out of what you have.....unless you already have too many pre amps. But it's very handy to have ten mic pre's for recording that can also sum to stereo etc.
ps i just sent you a pm

Hi Chris, do you want to let go of a couple of those mic input transformers?!

Yes Paul - they are just sitting around in my list of "WTF am I ever going to do with all these mic transformers" pile of stuff to sell when I get around to it....
PM me

Are the compressors any good?

Ahh - good question.
They use a type of compression called a Gilbert Multiplier, and the co - designer of these has had them for a few years now so that he can draw a schematic out.
I think the old EMT compressors use the Gilbert Multiplier (but I could be wrong)
So I'm waiting for this (now) retired old gent to draw a schematic so I can get them going to test them out - I have a feeling they may be really great - like all of the great Graham Thirkle's designs & co-designs.
Graham notoriously threw out all of his lifetimes schematics at the tip after a row with his wife!
Rob had a go at them and could not make sense of them without schematics
I desperately need them looked at by the only guy left on the planet that knows about their design.
So I wait....................................................................................................................................

I had a full EMT desk once. Really nice! But too big to bring to Australia.
I really liked the limiters on the master section.
EMT's would possibly be another nice summing compressor option.

Very nice - EMT console!
I forgot these Optro's are limiters as well - can switch between comp and limit.
Cant wait to try these beasts one day.

I'm just about to get two of these racked by Rob. Chris, I think these are ex your studio? I got these from Harry. They look very similar, but slightly different.

Yep - they are from my console.
You've got two Neve eaters there in them mic pre's.
Everyone I know who has used them all say they sit in between a vintage neve and a vintage API soundwise (me included)
Did you find a schematic for them Owen?

can i has some

I don't have schematics for them. I'm just going to mail them to Rob as he knows what's up. I'm excited to hear them, they don't look anything special at first, but reading your feedback and gaining enough money to pay Rob reminded me to get them up and running!

Oh, I'll make sure to post some photos once they're back in business.