beatnik

Gates M5381A Studioette program amps racking up
« on: September 28, 2018, 02:17:02 PM »
Hi everybody

I got hold of a pair of preamp boards from a Gates "Studioette" broadcast console.

These preamps feature 3x EF86 and 1x12AU7 tubes and were used as program amps in the console.

I would like to rack up the modules as stand alone mic preamps.

I have located a suitable power transformer, that should be enough for powering two channels.

https://www.tube-town.net/ttstore/Transformer/Power-Transformer/Toroidal/Toroidal-56VA::4908.html

I need to design some sort of power supply for powering the modules, I was wondering how much filtering should be used, each preamps already have filter capacitors on each preamp stage. Might be enough just using a single reservoir capacitor or better cascading a few rc filter stages ?

I have attached a schematic for this circuit


beatnik

Re: Gates M5381A Studioette program amps racking up
« Reply #1 on: September 28, 2018, 02:20:28 PM »
So far I have replaced all capacitors and started checking out the resistors as well.

L´Andratté

Re: Gates M5381A Studioette program amps racking up
« Reply #2 on: September 28, 2018, 05:23:08 PM »
Hey those transformers look tasty. I didn´t know that tubes on pcbs was already done in the old days!

I cannot give you a definite answer to your question, but to a certain degree the more the better since it is about filtering power supply ripple and noise.

Why not check the loaded supply line with an oscilloscope for visual evidence of those?  And then add filtering as needed...

This can also be used to drop the +voltage btw

And I´m reading this atm ;)
http://www.valvewizard.co.uk/smoothing.html
Strictly amateur since 1973...

beatnik

Re: Gates M5381A Studioette program amps racking up
« Reply #3 on: October 19, 2018, 02:07:49 PM »
I am gathering parts for racking up these preamps.

I was thinking to use an Hammond aluminium chassis, and was hoping to rack the two modules together with power supply.

The space is a bit tight and I am a bit worried of potential hum issues, especially on the channel nearest to the power transformer.

What do you think of this layout ?

« Last Edit: October 19, 2018, 02:26:32 PM by beatnik »


 

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