6BM8 tubes... what to use them for!

[JoeM]

Does anyone have a schematic of this Eric Barbour circuit?

I've found several references to it but can't find the actual drawing.

Thanks in advance.

Bruce - how's your 6BM8 project coming along?

Chip

I'll see if I can find it and scan a copy of it.

[Alex/Tubewonder]

Does anyone have a schematic of this Eric Barbour circuit?

I've found several references to it but can't find the actual drawing.

Thanks in advance.

Chip

It's standard SE pentode PA right off the datasheet. Nothing beyond the ordinary but makes a very good reverb tank driver. You need up 25Vp-p on the grid to drive it.

[lsmith_33]

6BM8 Plexi?

I kind of want to do a Plexi type of thing with two 6BM8s and some 12AX7s. I am using the "low voltage" tranny from Hammond (250VDC @ 130mA, 261G6). I was going to use 2 12AX7s as the standard Plexi preamp into a LTP made up of the triode sections of the 6BM8s. After reading posts here, that may be too hot, and I'm now of a mind to only use one 12AX7. I want to keep the cathode follower before the tone stack. My two options at this point are:
a) one gain stage going into a CF, tone stack, and LTP with the triode sections of the 6BM8
b) standard Plexi preamp, using one triode of the 6BM8 as a CF, and using the other as a cathodyne PI.
What do you think? Would I get more bang for my buck driving the snot out of the pentodes, or would preamp gain be the better answer? I like gain, but I also like the dynamics of a pushed power amp.

Thanks, Lucas

[TheTinMan]

Lucas - if you do a search for "Little Wing" on the Hoffman forum you'll find a two-12AX7 two-6BM8 amp that sounds great. Basic structure is:

2 triodes in parallel (12AX7)
gain control
gain stage/cathode follwer (12AX7)
tone stack
LTPI (6BM8 triodes)
pentodes

Someday I'm going to gut my Blues Jr. and build this amp with an additional tube for reverb.

Chip

[Tubenit]

Little Wing Reverb

You will need to download the FREE SCH program to open these files but there are several schematics and layouts available for what you're wanting right here:

http://www.el34world.com/Forum/index.php?topic=562.0

With respect, Tubenit

ExpressSCH

http://www.expresspcb.com/ExpressPCB...c_software.htm

[Wrongdog]

I know this thread is on a PP 6BM8 amp but I just got a Maestro M-1 rvt (Gibson GA-1 RVT) in the shop and it is a real interesting SE amp. Great practice and harp amp potential. Blows away tweed champs at first impression. I am not up with you all on the technical design stuff but I am gonna blue print this simple amp and tweak it for home guitar use and playout (miked) harp use!!

[Enzo]

Schematic is posted over in www.ampix.org in my gallery if you don;t already have it.

[Wrongdog]

Thanks Enzo. I had it and the other schematic that uses the 6EU7 and 7199.

http://www.schematicheaven.com/gibsonamps/ga1rvt.pdf

The Maestro I have is the latter one. Now I am wondering if the one you linked me to is even better!!

If you added a tone stack what would be the best? I use the 18 watt marshall one is a lot of my homebrew contraptions. There is little loss with them IMHO and they work okay. With harp I either need a cut switch or full tone control.

[Tubenit]

6BM8 tube amp ??

Hey Bruce,

Did you ever get your 6BM8 amp built?? Just curious. I am still enjoying my Little Wing Reverb alot.

With respect, Tubenit

[Bruce / Mission Amps]

Hey Bruce,

Did you ever get your 6BM8 amp built?? Just curious. I am still enjoying my Little Wing Reverb alot.

With respect, Tubenit

I gutted and built up that little VOXY Pathfinder 10 I showed you the cabinet for but got behind on a few other projects and have not fully fleshed the new project out yet.
It works as promised but the total preamp has too much gain and needs to be tamed down a bit so the stages follow to a happy conclusion at the 6BM8s.
Plus, I picked up a playing gig about 7 or 8 weeks ago and have been spending too much time playing music in my spare time and some weekends ... ha ha.. Sometimes a guy can forget what the heck they got in to this business for in the first place!

[Tubenit]

6BM8 amp

" picked up a playing gig about 7 or 8 weeks ago and have been spending too much time playing music in my spare time and some weekends ... ha ha.. Sometimes a guy can forget what the heck they got in to this business for in the first place!"

Well said! That qualifies as an appropriate distraction! When you get it finished, please post a review.

With respect, Tubenit

[imaradiostar]

uh-oh

So...my Musicmaster Bass amp blew up the other week during practice. It was just the cheap-o tube socket failing but the sound and arcing and smoke scared me for a sec there.

I've been following this thread for a while thinking it would make a good project. The power and output transformers on the little Fender still test fine and I think they'd make perfect donors for this project. The power TF is 500vct and the output measures as 8k:8 ohms.

I thought that a circuit like the one discussed here into a decent quality 12" speaker in the original Fender chassis would be a cool little amp for moderate volume usage.

I had a few thoughts to introduce to the mix. What about a cascoded 12ax7 feeding a LTPI with a post-pi master volume? This way you'd have the grit and harmonics of the cascode stage and you'd have the ability to control how much the PI is distorting and how hard the output section is driven.

Maybe use a 12ax7 cascode for pentode like gain then use one of the 6bm8's as a "distortion tube" with a large value Rc like a Trainwreck into a cathodyne splitter using the other triode. I'd imagine that the single triode phase splitter will create more than enough drive to punish the output tubes.

Thoughts?

jamie

[Tubenit]

6BM8 amp

I think your amp idea might work great and that you should build whatever you want as an idea. It's sounds like an interesting idea. If you build it please let us know how it goes and include a sound bit if possible.

This is the link to DaGeezer's Little Wing amp and sound bit. After hearing it, I didn't think I could come up with anything that would sound better.

http://www.musicwebtown.com/jallenshaw/46763

With respect, Tubenit

[hasserl]

Sure, build what you like. But please don't destroy that MMB! Those are great sounding amps, just need a little rework of the Tone control and a better speaker. I have one I leave at my band's practice room so I don;t have to haul an amp around, and it's one of my favorite sounding amps ever. The only problem with it is it's just barely loud enough with a band, I have to run it mostly flat out. But dang it sounds effin great. Of all th eother amps I have, and I have a bunch of them, what I'd really like is a louder MMB. A 4 x 6V6 or 6AQ5 version ought to do just right, thru a single 15 like P15N. That would be a truly bitchin amp. Anyway, don't screw up your MMBass, if you want to experiment with other circuits just buy a chassis and some trannies and do it.

You'll smoke turds in hell if you tear up that MMBass!

[imaradiostar]

You'll smoke turds in hell if you tear up that MMBass!

why didn't you say that like...four hours ago? I already gutted it. dangit!

I'm not entirely dumb though. I did disassemble it in such a way that it can go back together if I need to.

I've spent a lot of time looking at (and listening to) the "little wing" circuit and intend to build it at some point because it sounds fabulous. For now I think I'm gonna try something a little different just to see what I can come up with. A friend recently commissioned me to build something for him and this might be a good test platform for it.

jamie