6G3 master volume

[suncrest]

I just finished a 6G3 clone....it sounds BillyGibbons-ish like i had hoped, but sadly i will rarely get to enjoy it wide open. 
The only difference from stock version is that I added a 20K pot to make the bias adjustable, with overall range from -20 to -40 VDC. 
I want to add a master vol, and in the interest of simplicity am thinking of robrobs trainwreck type 3.
I'm not smart enough to tell if this type MV will have dangerous effect on power tube bias.
My gut instinct says it will work, as I'm not removing the grid leaks, just wiring in the MV as per the attached.
Part of the appeal of this version MV is ease of install/removal.

Any comments/advice appreciated.

[sluckey]

Very easy to try. Most people don't like it.

[tubenit]

ARCHIVES has a considerable amount of information on master volume choices.  This may be useful to you?


Master Volume (el34world.com)


With respect, Tubenit

[pdf64]

A Type 3 works a lot better with a 10k resistor in series with each of the coupling caps.
As a typical 12AX7 LTP waveform turns to yuk when the loading between the anodes drops too low, eg much below 10k. The outputs actually flip from balanced to being common mode signals. And that occurs before the signal levels has dropped far, when I tinkered around with this, I couldn’t even achieve -20dB. So a straight Type 3 is a poor choice for domestic friendly overdrive SPLs.
But add the 10ks and it’s a different story. 

[Bieworm]

I added a larmar mastervolume on my 6G3. Works super good! Would do it again in a heartbeat

[suncrest]

Thanks for the replies 

Most people don't like it.
I see why....

works a lot better with a 10k resistor in series with each of the coupling caps.
It was better, but still kind of meatless until it's wide open...

ARCHIVES has a considerable amount of information.
I added a larmar mastervolume.

Will read thru the archive stuff, and probably try the larmar next.
Thanks again....

[tschwarz]

...
It was better, but still kind of meatless until it's wide open...
...

I get the exact same effect on an insanely loud DC30 with a type 3 PPIMV built-in. With every bit less volume the sound gets more sterile. Maybe try an attenuator in front of the speaker(s)? I use both an older THD HotPlate I got with the amp as well as a newer Rivera RockCrusher. Huge, huge  difference. Night and day. And the HotPlate is a purely resistive load, so something simple built from power resistors might do. Ive seen schematics floating around here...

Power section distortion is a big part of many amp design's sound, IMHO. The 6G3 definitely belongs to this category, again IMHO...

[Bieworm]

...
It was better, but still kind of meatless until it's wide open...
...

I get the exact same effect on an insanely loud DC30 with a type 3 PPIMV built-in. With every bit less volume the sound gets more sterile. Maybe try an attenuator in front of the speaker(s)? I use both an older THD HotPlate I got with the amp as well as a newer Rivera RockCrusher. Huge, huge  difference. Night and day. And the HotPlate is a purely resistive load, so something simple built from power resistors might do. Ive seen schematics floating around here...

Power section distortion is a big part of many amp design's sound, IMHO. The 6G3 definitely belongs to this category, again IMHO...

I have to disagree on that perception with deluxes. The LarMar in my 6G3 works thát good, that I removed the half power switch of my imperial clone and put a LarMar in there too.
The half power switch I had was found on robrob's deluxe pages. That was resistive load stuff.I found that one too sterile and fizzy...

[tschwarz]

Not trying to start yet another PPIMV skirmish here.

Maybe it's a property of the output tubes. 4xEL84s, cathode biased and no NFB  vs.  2x6V6s, fixed bias with NFB?
I'm currently prototyping a Trainwreck Rocket(ish) amp with a smaller 2xEL82 power section and tried both LarMar (tandem pot) and Type3 (x-over). Same result. I'm running it with the Rivera and building in the type 3 as a mere compromise when there's no attenuator available...

[suncrest]

Waiting on 250k dual pot, will try one of the many larmar variants i saw while archiving.
I'm sorta skeered of attenuators, never tried one........

[mresistor]

"Good" attenuators are expensive, however if you have one you can usually use it with any amp you have.

[suncrest]

Not trying to start yet another PPIMV skirmish here.

:laugh:Never thought so, thanks for sharing your experience(s)...

"Good" attenuators are expensive, however if you have one you can usually use it with any amp you have.

Two things: *Not asking you to do my research, but what is "good"?
                   I bounce between a markhuss JCM800 clone, a 5E3 copy, and now the 6G3.
                 
                 *And can I build a good one that's "safe" or whatever?

[tschwarz]

...
Two things: *Not asking you to do my research, but what is "good"?
                   I bounce between a markhuss JCM800 clone, a 5E3 copy, and now the 6G3.
...                 

My 2 cents: I've used 4 different attenuators from the "reasonable" end of the price spectrum:
- Harley Benton PA-100: https://www.thomann.de/gb/harley_benton_pa_100_power_attenuator.htm. Really cheap, don't like the sound much (loses crispness, sounds muffled)
- Bugera PS1 Power Soak: https://www.thomann.de/gb/bugera_power_soak_ps1.htm. Still pretty affordable, much better than the PA-100. Resistive, this is what I'd expect to get (at least) when building one myself
- THD Hot Plate: No URL because they're no longer made. You could find one on ebay, maybe - but at a premium price. The last one i saw had a $ 400.- price tag. That's insanely expensive. Has two switches to compensate for losses at both ends of the spectrum. I've used this for many years and really like the sound
- RIVERA RockCrusher: https://www.thomann.de/gb/rivera_rockcrusher.htm. This is the best one out of the four. Reactive load - "simulates" the interaction of a speaker with the amp's power section. Also has frequency compensation built-in. Can be hooked up to 8 and 16 Ohm speaker outs at up to 120W.

In any case, you should make sure your speaker's impedance can be used with whatever power soak you chose. My DC30 has its speakers wired at 4 Ohms so I need to switch the amp to 16 Ohms and use an external Blackstar 2x12 cab...

I'm in no way affiliated with thomann...

[Edit]: I'd add that one day I'll fix that muffled sound problem on the cheapo HB  PA-100 by bypassing the series resistor with a capacitor. Just like a "bright" cap in a gain stage - same problem, same solution (at 50W !). Resistive attenuation is no rocket science...

[mresistor]

Suncrest - personally I like Weber Mass attenuators.  There is plenty of info out on how to build a cheap resistive attenuator.

[acheld]

The M2 attenuator from the Marshall forum works very well.  It includes an inductive load in addition to resistive. 

https://www.marshallforum.com/threads/simple-attenuators-design-and-testing.98285/

[SILVERGUN]

Here's an easy one to try. This is snipped directly off of a confirmed schematic for a Clapton Tremolux.
If it's good enough for EC it's good enough for any of us common folk.