Tube Ross Compressor

[phuzle]

I'm interested in trying to modify my newly breadboarded ross comp to include a tube.  After building the valvecaster, I want to figure out how to use all these tubes I have around in my builds, and tube compressors being such a fancy piece of studio gear, I figure it is only logical that we get a solid tube compressor stomp box going!

My only thoughts are using a dual triode (12au7) at 12v to replace the first and second transistor in the ross circuit.  I *think* this should be pretty straightforward, but I don't quite know how to get started.  I assume I need to figure out the gain from the transistors and set up the tube to replicate those levels. 

I may be totally wrong here so feel free to correct me, but it seems that the emitter of the tranny is like the anode of the tube, the base of the tranny is like the grid of the tube, and that leaves me assuming the collector is like the cathode.  Though there are certainly reasons for me to think this is not correct.  Anyways, if anyone has some ideas to get me started, I'd really appreciate it.

[petemoore]

 PLATE: kinda like the collector, the usual place to tap gained output
Grid: The Input [er...most commonly the input
Cathode: Nearest the ground, kinda like an emitter...usually has a small or no resistor to ground, and can be used as a buffer output.
  I have a Blackfinger Tube Compressor I've been trying to sell, it's fine, works perfect, has large footprint and uses it's own adapter, does a good job, just takes extreme settings to get any 'squish'...I found it easier to mod the Dynacomp to make 'hard comp squish-tones' or not. I should keep it for studio works though.

[jacobyjd]

I love my Black Finger

[frequencycentral]

Here's a link to an old thread with a schematic for an even older tube compressor using two 12AX7:

http://www.diystompboxes.com/smfforum/index.php?topic=65518.0



I think I have another scan of that scematic with an explanation, I'll look for it.

[frequencycentral]

Here you go:

[phuzle]

thanks for that frequency, i had seen that before though.  that uses two tubes at high voltage (i believe), which may be awesome, but isn't quite what i'm interested in.  I'm curious about adapting a non-tube pedal to make use of tubes, and at low voltages like the valvecaster.  Perhaps adapting solid state to tubes isn't worth the effort, and tube circuits should just be designed from the ground up... but I am still curious.

[frequencycentral]

Ok, no problem. This thead may also be of interest, and probably closer to what you're looking for: http://www.diystompboxes.com/smfforum/index.php?topic=70261.0

I'm love to work on a low voltage tube compressor too - so I'm in.

[jalien21]

i really want to try to get my hands on this book.

i really need a "psychedelic coloured light unit for audio amplifiers."

any idea about what this book is?

[joelap]

Sorry to resurrect an old thread... but should the 2nd half of that first triode's plate and grid be connected as shown in the markup posted earlier in the thread?  It's operating as a diode, right?

Second question: suppose I am building a bass preamp and want to incorporate this tube compressor circuit.  Would it be possible to do with one tube and a solid-state diode?  Eliminate the first triode which is serving as a Cathode follower and a diode and  place a 1N4007 after the 470k resistor?

Final: assuming that if I wanted to make this switchable, I can use a DPDT to bypass from the Input to the Output connections on the schematic, correct? 

Trying to do this without going to a solid-state device to do any amplification, but also trying to keep my current consumption low by getting it down to one tube... Already in a 1U rack enclosure with 2 other 12AX7's in there...

Thanks,

Joe

[Dragondreams]

i really want to try to get my hands on this book.

i really need a "psychedelic coloured light unit for audio amplifiers."

any idea about what this book is?

Apologies for digging up an old thread...

I found this thread on Friday when I was looking for ideas for a valve compressor. Today, when I was tidying up a bookcase in the attic, by pure coincidence I found the book that the circuit appears in!

It's "Babani Press No.12 - Hi-Fi, Guitar and Discotheque Amplifier Design Handbook" It was first published in 1972, ISBN 0 85934 011 2

The majority of the book looks at building valve amps from 12 to 1100 watt (with schematics). I'm sat here at the moment, leafing through it and drooling.