6AL5 Tube Sidechain Input

[mrkrawn]

Hi everybody

Is there a nice guy who can tell me where to connect a mono input jack to the 6al5 sidechain pin.
I look the datasheet and seems to be pin 5&7 but i need someone to confirm this.
I didn't find any thread or topic about this tube and i would like to add it to my Vk1 compressor

Best

 

[radardoug]

We need more information. What are you trying to do? Tie two units together? That is the rectifier diode for the sidechain signal.

 

[mrkrawn]

thanks you radardoug

I'm trying to add the sidechain function to my vari-mu vk1 compressor to trigger the compression from an external signal.

This compressor has the sidechain function, but the designer has omitted to show us where to connect the mono unbalanced signal(external key) to the compressor.
I don't know if i have to inject the external key directly to the 6al5 pin or before the attack pot.
i 've attached the shematic if you want to look ,that would be very nice.
More info here:
http://www.tubefreak.com/

Thanks you to help me
Best

 

[mrkrawn]

and somes  files i find for the 6al5 tube

 

[mrkrawn]

 

[mrkrawn]

any idea??

 

[emrr]

The threshold pot, with it disconnected from the output stage. 

 

[mrkrawn]

Thanks you for helping me.

Could you explain a little more please, i would like a clear answer if it's possible.

It would be a shame to burn this wonderful craft.
Best

 

[mrkrawn]

I do not just believe that among all those geniuses and talented builder nobody knows that.
will be nice.

 

[mrkrawn]

So if i understand, i need to break the  internal sidechain signal before the input of threshold
and insert my external key at the input threshold.
also a swith for turn off external key and activate internal sidechain.


Best

 

[mik]

in this design is to difficult to add an external side chai signal, because  signal there is high impedance high voltage, very high voltage, so to control gain reduction action you  need an exernal high voltage high inpedance signal too, quinte  unobtainable ,  without another active stage to drive threshold network before the 6A5L input.

M.

 

[emrr]

It does not have to be high impedance, nor is it high voltage.  It would be better if balanced, but will work unbalanced too.  The biggest problem is it's a feedback compressor, and to side chain is to remove that feedback from the behavior, it may be very erratic. 

 

[mik]

yes emrr is absolutely right, didn't note the local negative feedback around 12AT7

 

[mrkrawn]

Thank you my friends for your help.
It makes me really happy to read clear written responses by guys like you.
if you are talking about the R102 and R103, these are negative feedback resistors of the 12AT7 stage. These are used to prevent distortion and tame the output.
I didn't solder there resistors in my version for more gain.
I did not think it would take a balanced signal.
delighted to discover this good news.
I carefully watch the shematic.
the sidechain come from pin 2 & 5 and out by 5 & 1 for one channel
if I want the wired balanced sidechain should I take hot and cold at the output 5 & 1 before treshold.
Best

 

[Suburban Ninja]

very intresting post.I build mine too and i want it too.
it's seems to be a great update