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Tube VCA revision question

Tube VCA revision question

2007-06-19 by The Alison Project

Regarding the 330K resistors, do you see any problems using a DPDT toggle

1. connecting 330K to negative rail and pin 4 of tube to pin 2

2. connecting 330K to pin 1 of tube and pin 4 of tube to pin 1

thanks
Chris

[Non-text portions of this message have been removed]

Re: Tube VCA revision question

2007-06-19 by sasami@hotkey.net.au

I see no real problem. You may get a thump on the output when switching, but
that's all.

Ken
Show quoted textHide quoted text
>Regarding the 330K resistors, do you see any problems using a DPDT toggle
>
>1. connecting 330K to negative rail and pin 4 of tube to pin 2
>
>2. connecting 330K to pin 1 of tube and pin 4 of tube to pin 1
>
>thanks
>Chris
>
>[Non-text portions of this message have been removed]
>
>
>
>The CGS Modular Synth home page: http://www.cgs.synth.net/
>
>Yahoo! Groups Links
>
>
>
>
_______________________________________________________________________
Ken Stone sasami@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Re: Tube VCA revision question

2007-06-23 by thealisonproject

I finished my Dual Tube VCA today, this thing is great. I added the
DPDT switch like mentioned in this topic and there is no pop at the
output when switched, works perfectly... Adding feedback is where I
really like this thing, pure crunch...
Show quoted textHide quoted text
--- In cgs_synth@yahoogroups.com, sasami@... wrote:
>
> I see no real problem. You may get a thump on the output when
switching, but
> that's all.
>
> Ken
>
> >Regarding the 330K resistors, do you see any problems using a DPDT
toggle
> >
> >1. connecting 330K to negative rail and pin 4 of tube to pin 2
> >
> >2. connecting 330K to pin 1 of tube and pin 4 of tube to pin 1
> >
> >thanks
> >Chris
> >
> >[Non-text portions of this message have been removed]
> >
> >
> >
> >The CGS Modular Synth home page: http://www.cgs.synth.net/
> >
> >Yahoo! Groups Links
> >
> >
> >
> >
> _______________________________________________________________________
> Ken Stone sasami@...
> Modular Synth PCBs for sale <http://www.cgs.synth.net/>
> Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>
>

Re: Tube VCA revision question

2007-08-08 by squidb0i

Sounds interesting and I do have that board in the cue.. what does
this mod do exactly?

~!J!
Show quoted textHide quoted text
--- In cgs_synth@yahoogroups.com, "thealisonproject" <alison@...> wrote:
>
> I finished my Dual Tube VCA today, this thing is great. I added the
> DPDT switch like mentioned in this topic and there is no pop at the
> output when switched, works perfectly... Adding feedback is where I
> really like this thing, pure crunch...

Re: Tube VCA revision question

2007-08-09 by The Alison Project

From Ken's site, see schematic on page

On the first (yellow) run of PCBs, the grid bias resistor (330k) goes to the negative rail. In this position, it causes some distortion of the signal. This can be a good thing. I prefer the resistor in this position when using the unit as a timbral gate. This is shown in BLUE on the schematic. An alternative is to bias the grid to around 1.2V with respect to the negative rail - in other words, to the other end of the heater/cathode. This is shown in RED on the schematic. Doing so will reduce the distortion at low input levels. Do not put in both red and blue options at the same time or you will short out the heater. It may be appropriate to connect pin 4 of the tube to pin 1 of the tube instead of pin 2 as well, if making this modification.

----- Original Message -----
Show quoted textHide quoted text
From: squidb0i
To: cgs_synth@yahoogroups.com
Sent: Wednesday, August 01, 2007 8:16 PM
Subject: [cgs_synth] Re: Tube VCA revision question


Sounds interesting and I do have that board in the cue.. what does
this mod do exactly?

~!J!

--- In cgs_synth@yahoogroups.com, "thealisonproject" <alison@...> wrote:
>
> I finished my Dual Tube VCA today, this thing is great. I added the
> DPDT switch like mentioned in this topic and there is no pop at the
> output when switched, works perfectly... Adding feedback is where I
> really like this thing, pure crunch...





[Non-text portions of this message have been removed]

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