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Applying a SUS control in a SE Amp with a Master Volume - Printable Version

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Applying a SUS control in a SE Amp with a Master Volume - makinrose - 05-30-2020

I'm trying to figure out the best way to apply a SUS control to a cathode biased SE amp I'm building.  Overall the topology will be similar to Blackface Champ but it will have Power Scaling and I'd like to add a SUS control.  For the limit control I was planning on adding a Master Volume before the grid stopper of the power tube.  Can the SUS circuit connect where the Master Volume pot usually grounds or is it better to have it work off a grid leak resistor after the master volume control?  Thanks for the help!


RE: Applying a SUS control in a SE Amp with a Master Volume - K O'Connor - 05-30-2020

Hey

Note that the SUS effect is SUBTLE and may be swamped by what Power Scaling can do for you.

As a cathode-biased amp, SUS-2 can be applied around the output stage. It can also be applied to any preamp stage that might clip, however, in the case of the Champ topology only the second stage qualifies and just barely. The two 12AX7 stages can only make a mild overdrive at best, and that will produce way more drive than the 6V6 needs to produce full output. With the MV / Drive Compensation control directly ahead of the 6V6, the situation can be tamed.

Best to remove the feedback loop if present.

Have fun


RE: Applying a SUS control in a SE Amp with a Master Volume - makinrose - 05-30-2020

(05-30-2020, 02:31 PM)K O\Connor Wrote: Hey

Note that the SUS effect is SUBTLE and may be swamped by what Power Scaling can do for you.

As a cathode-biased amp, SUS-2 can be applied around the output stage. It can also be applied to any preamp stage that might clip, however, in the case of the Champ topology only the second stage qualifies and just barely. The two 12AX7 stages can only make a mild overdrive at best, and that will produce way more drive than the 6V6 needs to produce full output. With the MV / Drive Compensation control directly ahead of the 6V6, the situation can be tamed.

Best to remove the feedback loop if present.

Have fun

Thanks for the reply. Good point about the feedback loop.   In the amp I'm doing I'm planning on have a switch to turn on and off negative feedback .  The  mild overdrive with negative feedback has limited use for players but it does extend the clean tones so I think both settings can be useful....

With the SUS I'm hoping it will be most useful with the cleaner tones---with the power scaling turned further up.  Hopefully it will allow the amp to get a firmer feel and more compressed bluesy feel.  [font=Tahoma, Verdana, Arial, sans-serif]I've also[/font][font=Tahoma, Verdana, Arial, sans-serif] been contemplating adding another gain stage---still a clean amp topology but with more character.[/font][font=Tahoma, Verdana, Arial, sans-serif] [/font][font=Tahoma, Verdana, Arial, sans-serif] [/font]


RE: Applying a SUS control in a SE Amp with a Master Volume - K O'Connor - 05-30-2020

Hi makinrose

SUS is NOT a Boss compressor pedal effect and won't do what you are thinking for the clan sound.

Circuits like the Champ cry out for more gain, so adding a tube will open up millions of possibilities for much warmer clean sounds and far better distortion sounds, just as the Champ chapter of TUT3 illustrates in its 36-pages.

Have fun


RE: Applying a SUS control in a SE Amp with a Master Volume - makinrose - 05-30-2020

(05-30-2020, 03:18 PM)K O\Connor Wrote: Hi makinrose

SUS is NOT a Boss compressor pedal effect and won't do what you are thinking for the clan sound.

Circuits like the Champ cry out for more gain, so adding a tube will open up millions of possibilities for much warmer clean sounds and far better distortion sounds, just as the Champ chapter of TUT3 illustrates in its 36-pages.

Have fun
I think I may have overstated what I'm wanting it to do....I've installed it in about dozen amps (with a licence!)  so I'm know how they sound/feel.  It's good to clarify so other folks reading this so they don't misunderstand though.  I'm not trying to get overtly compressed sounds like a compressor pedal but instead try to alter the feel . SUS does that really well.  I find the ability to control how the amp feels  really useful.

I do agree that more tubes opens up possibilities with a Champ. I'm often building for other people and right now the market seems heavily skewed towards clones of vintage amps.  I try to strike a balance between vintage simplicity and adding features that will make the amps more useful and playable.