varimu²

bigger pic: http://groupdiy.twin-x.com/albums/userpics/10055/varimu%B2.jpg





the idea of this circuit is having two stages of either mono/stereo varimu compression with seperate time constant controls. only one channel is shown.
the second sidechain amplifier/rectifier is linked for stereo compression, first stage is working mono.


update:
changed the output stage as suggested



bigger pic: http://groupdiy.twin-x.com/albums/userpics/10055/varimu%B2_edit1.jpg

Please don't put 1,280-wide images embedded in posts.

I would think that the matching of the tubes might be very critical especially in the second stage so you don't get thumping and oscillation (control voltage feedthrough), and I agree with kubi - I'd skip the SRPP stage and just build a more traditional balanced drive with the output transformer both acting to cancel any residual CV feedthrough and driving the output. Just my $.02

-Dale

thats 0,04 cents already

you´re absolutely right regarding the output stage-we should change that.
both tubes ef83&ef11 are quite hard to find, so we should find a different solution here.
lets take this as a group project. at least the idea of it.

regards, max

update:see first post

i wonder if the sidechain amps should be fed through the plate of stage two or stage three. maybe mixed.

> sidechain amps should be fed through the plate of stage two or stage three

No difference, except the lower (earlier) you tap, the more gain you need in the sidechain.

You need a LOT of gain somewhere, because the signal at the rectifier has to be MUCH larger than the signal in the VCA grids or the distortion will be large.

thanks prr. what do you think about this idea in general?
its a lot of tubes, i know.
maybe we could adapt that idea to your varimu, using only two 12au7 for each channel.

thanks kubarth,

thanks for your input & no worries, i dont get you wrong, i´m begging for comments!
i´m mainly interested in the idea of combining two vari mu stages with different sonic qualities.

i´ve drawn the schematic with tubes only because i´m more experienced with these than with opamp/transistors. thats why i came up with the idea of adapting the circuit to prr´s vari mu, maybe with two different tubes.