Vintage console enthusiast here with a strange transistor project.

[Bob Difazio]

Hey everyone.

Iam a big fan of the old transistor based consoles especially Neve 80 series consoles and the sound of them, I have nerded out on designing my own modules and now I want to take it a little further and use some of my old 1:12 transformers, to make a mic preamp. but with a transistor amp.


Iam looking for transistor based schematics for mic preamp that can use a 1:12 winding input transformer. If it has ever been made. I know a 1:12 ratio winding would be made for tube amps. But I wonder if anyone back in the days 60’S/70’S made any mic pres in consoles for that type of transformer, that was transistor based.
Or also someone nowadays who made it would be of interest.


Let me hear if you heard about such thing or what your thoughts are on the idea.





Kind regards Bob

 

[ruffrecords]

The classic Helios three transistor mic pre used a Beyer Dynamic 1:10 input transformer. Check the tech docs section for details.

Cheers

Ian

 

[TwentyTrees]

The Shure M67 and M68 also used high ratio input transformers - the M68 is closer to 1:12 if memory serves, M67 is even higher. The schematics are available on Shure's website. They're not as clean or quiet as the Helios (only two transistors!), rather I'd call them characterful.

 

[Brian Roth]

The classic Helios three transistor mic pre used a Beyer Dynamic 1:10 input transformer. Check the tech docs section for details.

Cheers

Ian

What was the Lustraphone M10 xfmr in the scheme of things?

I have only seen ONE Helios desk in person in my lifetime. It was the 40 channel red desk owned by Leon Russell and then sold to Lenny Kravitz (who repainted it black).

Bri

 

[ruffrecords]

What was the Lustraphone M10 xfmr in the scheme of things?

You are quite right. The Helios 69 used a lustraphone input transformer. I blame my advanced years

I have only seen ONE Helios desk in person in my lifetime. It was the 40 channel red desk owned by Leon Russell and then sold to Lenny Kravitz (who repainted it black).

Bri

That is one more than I have ever seen! I just missed the one at The Who's Ramport Studio when it was replaced by the Neve I designed

Cheers

Ian

 

[Bob Difazio]

The classic Helios three transistor mic pre used a Beyer Dynamic 1:10 input transformer. Check the tech docs section for details.

Cheers

Ian

Thanks alot for answer ruff, Ok interesting! Do you have schematics for the Helios three preamp?

 

[Ó Draighnáin]

The Helios mic-pre eq used the Lustraphone M10 in earlier modules (the modules that used the 2128 as the mic amp and line amp) but at some point, after or around the incorporation of the 22113 line amp, they changed to little Beyers. The Beyers did not have the -20dB winding like the M10s and used different mic/line switching. I think the eq remained pretty consistent across all iterations.

Member Whoops uploaded pretty much all the documents you need to build a complete Helios console. I think he uploaded at least three different upper and lower bay options (mic-pre eqs and routers).

So as Ian suggested, check the Technical Documents section under Helios.

 

[ruffrecords]

https://groupdiy.com/threads/helios.58393/

Cheers

Ian