Name these volume knobs, please (Bassman Micro)

King Fan

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That's super helpful, my friend. Thank you!!! BTW, I think I watched this one before, but your helpful description above (and a bit more time with the layout and schematic) make it even clearer. That's a nice range of sound options, and nicely demonstrated. Do I recall that's basically Rob's Bassman Micro with a 12AX7 in V1? I don't mean in every detail (nice switches!) but overall?

Anyway, nothing like sound and moving pictures to answer a question. Thanks again.
 

dan40

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Some manufacturers will label the final MV as "global" though I prefer the term "level" myself. I have found in these smaller amps that having the MV after the phase inverter is really helpful. It's very easy to over overdrive the smaller power tube when turning up your pre-PI master volume so having both types of MV really helps to dial in your best sound. The pre PI MV will allow you to overdrive the gain stages before it while not hitting your PI and PA with too much signal. The post PI MV allows you to dial in a bit of PI distortion and control the final signal level that hits your power tube.
 

joulupukki

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That's super helpful, my friend. Thank you!!! BTW, I think I watched this one before, but your helpful description above (and a bit more time with the layout and schematic) make it even clearer. That's a nice range of sound options, and nicely demonstrated. Do I recall that's basically Rob's Bassman Micro with a 12AX7 in V1? I don't mean in every detail (nice switches!) but overall?

Anyway, nothing like sound and moving pictures to answer a question. Thanks again.
Thanks! It’s always fun to make these vids. This one is new that I recorded earlier today but similar. This time mostly with MV turned all the way up because that’s how I think the NFB and presence knob is most discernible. That’s the way I run it most of the time too and just fiddle with the preamp volumes. To me, the first volume potentiometer seems to act more like a gain knob than a “Bright” Volume. If I re-made my front plate, I’d have it say Gain, Volume … and then on the farther left next to the Presence, Master Volume.

Yes, I’m using a 12AX7 in V1 and a 12BH7 as the power tube. I can’t tell any diff in sound/etc with the 12BH7 vs. 12AU7 so I left the *BH7 in. I didn’t really give the 12AT7 much chance in V1 (I think that’s the tube for a bassman) because I had previously tried it in the princeton reverb and didn’t really want to make this amp any quieter. It’s got plenty of knobs otherwise to address that.

I’m not sure if I would put in an NFB switch again for this particular build. It’s barely discernible and in the JTM45 position I had to change the resistor value to something like 2.2K. Otherwise, it was like switching between three different barely-different sounds.
 

trev333

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As long as you know what they are... call them anything,,;)

more bananas!...

BWM Kong controls.jpg
 

StoneH

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Q: Name 3 men and what they did for science.

A: Washington, Jefferson, and Lincoln . . . Nothing.

Carry on.
 

wangdaning

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Keep in mind the PI Master should actually be hooked up at the junction of the grid leak and grid stop resistors, not the grid stop and coupling cap junction. The layout is different than the schematic. I would go with volume, gain, and master. I left out the pre amp master on mine, so I have volume and master. I might remove the master though and just have volume.
 

Skyhook

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As everyone here knows by now, I'm working up plans to build an EF80 Bassman Micro as designed by our amazing friend @robrob. As many of you know, it has a 'preamp MV' and a (Type 3) post-PI MV.

View attachment 1000823

But how would you label their knobs? Plain ol' "Pre MV" and "MV"? Not very informative. I want short labels that'll fit on a crowded faceplate. Is there a single word that captures the essence of the preamp MV? Would you give the plain ol' volume knob a different name? Could the Type 3 have a better label than 'Master'?

Part of my problem, I admit, is this will be my first MV amp, but worse than that, I'm not smart about how they'll affect the sound. I get how the Type 3 works, but my whole concept of preamp v. power amp distortion is vague.
Can't help you there, but when I read the thread title my initial reaction was: Jocelyn, Brady, Nell ... and little Pookie. :lol:
 

King Fan

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Keep in mind the PI Master should actually be hooked up at the junction of the grid leak and grid stop resistors, not the grid stop and coupling cap junction. The layout is different than the schematic. I would go with volume, gain, and master. I left out the pre amp master on mine, so I have volume and master. I might remove the master though and just have volume.

Thanks. Yeah, I compared the various layouts and schematics on that Bassman Micro page. It must be crazy hard keeping them all consistent. But didn’t @robrob say in some thread this year that either of those Post MV wirings would work?

Interesting you left off the Pre MV. In that nice demo by @joulupukki , it sounds like it has a big effect, or maybe it lets the first volume pot have a big, different effect. And almost like the Master is more just a squelch or attenuate thing. Have you considered replacing the Post with the Pre?
 

FenderLover

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While having a level control at each stage sounds like the ultimate for tweakability, I've gone the other way with just one volume, post-PI. The Gain, or Volume, is on your guitar. All manner of clean to dirty is a function of the player and gain-staging set in the amp. At any volume. It's a very engaging approach that I'd encourage the free-lance builder to give a try.

I'll add a comment that Gain and Volume controls do different things. If it is a Gain control, take the time to measure a 'useable' bottom limit and install a resistor so that it does not go down to zero. Volume controls go down to zero. Just a peeve of mine. Let's get it right.;-)
 

TelZilla

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If it was just for my use, I'd just do "Pre" and "Post".

If you're selling them, maybe something clearer. Pre Gain and Post Gain? Gain 1 and Gain 2? Dirt I and Dirt II?
 

bebopbrain

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I guess the idea is to throw away just enough gain with the MV to get a driver stage to clip just before or after the PI clips. Should be interesting. I might add a few VU meters to aid in dialing everything in.

My vote:

- pre post
V MV MV
 




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