Type 4 Master Volume

Express, Liverpool, Rocket, Dirty Little Monster, etc.

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shane
Posts: 129
Joined: Fri Jan 14, 2005 2:18 pm
Location: birmingham UK

Re: Type 4 Master Volume

Post by shane »

The lowering headroom effect in the PI is likely where the idea of putting a pot between the PI cathode and it's bias resistor as a master volume comes from.
I've actually tried it on an amp and it works quite well.
I used a 50K rev log pot and it was pretty good with fairly little noise on operation.
It obviously reduces output power too, but on the whole is a reasonable alternative to masters or more active power controls.

In the amp I put it in it was intended as a sort of poor man's power scaling so it was also combined with the type 4 MV previously mentioned.

Cheers
Shane
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M Fowler
Posts: 14017
Joined: Wed Jan 16, 2008 2:19 am
Location: Walcott ND

Re: Type 4 Master Volume

Post by M Fowler »

shane wrote: Mon Oct 30, 2017 7:07 pm The lowering headroom effect in the PI is likely where the idea of putting a pot between the PI cathode and it's bias resistor as a master volume comes from.
I've actually tried it on an amp and it works quite well.
I used a 50K rev log pot and it was pretty good with fairly little noise on operation.
It obviously reduces output power too, but on the whole is a reasonable alternative to masters or more active power controls.

In the amp I put it in it was intended as a sort of poor man's power scaling so it was also combined with the type 4 MV previously mentioned.

Cheers
Shane
The watt control in the PI works well in my cathode bias TW Rocket preamp into octal power amp configeration. No so well on a TW Express in my experience.
shane
Posts: 129
Joined: Fri Jan 14, 2005 2:18 pm
Location: birmingham UK

Re: Type 4 Master Volume

Post by shane »

Yes, the amp I used it in had the basic rocket topology.
Don't know how it would be in an express, but I'm more than happy to take your word on it Mark :D
lpd
Posts: 204
Joined: Fri Nov 14, 2008 1:45 am

Re: Type 4 Master Volume

Post by lpd »

romberg wrote: Mon Oct 23, 2017 8:17 pm
joe6v6 wrote: Mon Oct 23, 2017 3:17 pm
It does beg the question though; could you not have both? ; type 2 and type 4 as they both do different things.
Interesting , I just may try something like this one day. With some control over different areas there may be some possibilities there.
Absolutely you can have both. And I really like having a master before the PI and after. The pre phase inverter master can control the amount of preamp overdrive you get. It also controls how hard you will overdrive the phase inverter. And then the post master sets the overall volume and has some control over power tube overdrive. The combination allows for a lot of flexibility.

I've implemented the pre/post PI master setup in my marshall and hiwatt builds. And I'm going to do the same in the ODS build I'm about to start. It might even be interesting to try it out in an express. I would place the pre master in an express after the third gain stage and before the phase inverter. Because of the gain structure in an express (It is ALL about power amp crunch), I would not expect one would be able to get good preamp gain tones out of this setup. However, I would expect that lower pre master settings would allow for the amp to clean up quite a bit more. It would not be difficult to wire up a simple 1m volume pot right before the phase inverter and try it out. I might try this the next tme I have an expess opened up.

Mike
This master works wonders on my Marshall clone and enables you to dial in a variety of tones, and shape the attack of the amp!!!
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