More BM

[Masco]

What'd you think I was talking about?

The latest Fryer Brian May AC-30: http://fryerguitars.wordpress.com/ac30b ... d-rebuild/

Only 200mA fuse for EL84 cathodes, must be running way cooler. Is that 300nF of coupling cap in and out of PPIMV?

[Colossal]

Brian May of course!! what else could BM mean?

Thanks for posting this. Those stripped down BMACs are cool.

[Masco]

I guess since there's a split cathode (Rk/Ck per side), it's 200mA fuse each side. Still on the hot side. The screens have a common WW resistor and individual 330R's, so that's tamed a bit more.

[JoeCon]

Guys

I was checking out the controls on the BM amp. I see Volume and Master then one in between labeled Smooth/Drive. What's this?
Looking at the Dave Petersen one there's two inputs: Booster and Normal and then a Level for the booster input and a Volume for the normal input but no Smooth or Drive....

Thanks.

[Colossal]

Yeah that does look like 300nF on the master. Fryer's last iteration of the BMAC had 220R/3W on the screens so a slight increase on this version. Still running toasty.

[Zippy]

Guys

I was checking out the controls on the BM amp. I see Volume and Master then one in between labeled Smooth/Drive. What's this?

Type of laxative? Metamucil vs Ex-Lax.

[JoeCon]

Zippy

Exactly what I was thinking!! LOL....

[Zippy]

Hmmm, must be a bunch of ol' guys here.

Hey, where's Miles?

[Colossal]

Dammit, can't we have one topic that stays focused and not on poop or laxatives! Nahhh.

The PPIMV looks like it could be the older Type 2 version with coupling caps on both sides of the pot.

[JoeCon]

Dave

But what do think the Smooth/Drive is, just another vol control?? Is there a schematic for this particular amp? I've got the Dave Petersen posted before and no smooth drive on there....

[Colossal]

Dave

But what do think the Smooth/Drive is, just another vol control?? Is there a schematic for this particular amp? I've got the Dave Petersen posted before and no smooth drive on there....

Whatever it is (really hard to tell but it is affecting V1b), it is atypical of the first Fryer BMAC. The BMAC only has the one gain stage wired at 220k plate, 1k5/22uF cathode and from there, straight into the PI, no tone stack. BM boosts the front end with his Fryer treble boost. I am guessing Smooth/Drive is varying the gain from the added stage voiced as a treble boost preceding V1b. Like the Petersen version.

[Masco]

Don't think I've seen the Peterson version. Link?
Hard to make out in the photo, but the smooth drive appears to be a rheostat. Something going on after first stage volume and before second stage input grid. The 1/2W 47k looks grounded before going into pin 2, can't be right.??

[Colossal]

Don't think I've seen the Peterson version. Link?
Hard to make out in the photo, but the smooth drive appears to be a rheostat. Something going on after first stage volume and before second stage input grid. The 1/2W 47k looks grounded before going into pin 2, can't be right.??

Yeah, Smooth/Drive is wired as a variable resistor so maybe a variable grid leak?

Petersen document attached.

[Richie]

should just have a built in Rangemaster too

[Colossal]

should just have a built in Rangemaster too

Yes, that would be good.

Brian's Fryer RM is mounted right on his guitar strap, so it is driving his instrument cable as well as the front end of the amp. I am pretty sure I read something (probably on Greg Fryer's site) that said he had tried it both ways and having it driving the cable was preferred.