Simple tube compressor circuit from 1954

[tubologic]

I just found this circuit in the Oct.1954 issue of RADIO-ELECTRONICS magazine and thought it might be interesting to some DIYer's and experimenters. It's a simple vari-** type tube compressor using only 4 cheap common radio tubes and a voltage regulator.
Performance is quite good for such a simple circuit, the main limitation factor is that being a single-stage circuit it has not much gain. There's provision for input tubes balancing and treshold level adjustments (the 25K pot across the OD3 regulator). The dual recovery time constant can be  easily modified by altering the values of R1/C1 and R2/C2.  A 12AT7 side chain driver amp is used to give a faster attack time. Recommended transformers were UTC A-12 for the input and A-27 for output but other xfmr's may fit.
Simple,cheap, easy to build, common parts and decent performance: can we ask for more ? Maybe a good basis for your next "poor man's" tube compressor ? Full description and construction details can be found in the above magazine.   

[millzners]

That's pretty interesting.  Whats the OD3 component?  Optical Device?  Overload Deffuser?  Octoplex Decoupler? Opposum Droppings?

Oh wait you said voltage regulator...  Good, I was hoping to save those droppings for something else I was building.

Some of those tubes don't ring a bell with me, never heard of a 6AL5...  Maybe that's good, they're probably cheap b/c the audiophiles and guitar gods aren't into them.

...Turns out that's a twin diode electron tube you can find for around $4 USD...  sweet.

[emrr]

use SEARCH!   Another member built a pair of these several years ago, there's a big thread about it already. 

[millzners]

If it makes you feel better I just did a search for 15 minutes and couldn't find the thread... 

[tubologic]

use SEARCH!   Another member built a pair of these several years ago, there's a big thread about it already.

I DID but can't find any references to this exact circuit. There are many hundreds posts related to tube compressors, I didn't read them all and maybe I missed it. Sorry about that. It would have been more useful and constructive for all of us if you
provided a link to the thread you mention instead of harsh comments.
If my post is really redundant I'll delete it.

[emrr]

It's not harsh, it's informative.  I have no idea where it is, but it's here.  Full analysis therein.  Just because I remember it does not mean I have to lead the search party.   I think it was cannikin. 

[tubologic]

It's not harsh, it's informative.  I have no idea where it is, but it's here.  Full analysis therein.  Just because I remember it does not mean I have to lead the search party.   I think it was cannikin.

Being informative is just that: giving the complete information, which you failed to do.
Nor you or I, or the previous poster above were able to find the "big" thread you refer to and we all used the search function.
This doesn't mean it doesn't exist somewhere,but if nobody can't find it my post is not redundant.
Next time, please USE THE SEARCH function.

[emrr]

Like I said, I never looked for it. I just know it's there, and I let you know.  You're welcome. I didn't use the word 'redundant, and being informative has not ever meant spoon feeding you.  I can get harsh now if you need me to.

[gyraf]

Please, good people - let's not turn this into a problem.


A search for OD3 finds stuff like "The 1954 limiter": http://www.groupdiy.com/index.php?topic=27226.0

Jakob E.

[DaveP]

Tubologic,

First of all thanks very much for posting the schematic, the original has disappeared and all my efforts to find it have come to nothing.  I tried PM'ing Cannikin to no avail.  Well done.

Secondly, please don't judge EMRR on that post, he is a mainstay of this forum and his contribution has been invaluable.  It is very frustrating to the older members that people don't use the search facility as much as they should, and they can end up answering the same questions over and over again, so they can be to the point sometimes, they have thousands of posts under their belts.

If you had put the title of your post into the search box, the old thread would have come up, but you were probably not to know that.

best
DaveP

[emrr]

You can't really tell how often I post from my phone, while between tasks elsewhere, nowhere near my computer.  While riding in a van, etc.  Impossible to do all that much from a phone, really.