Swamp Thing Amp

[tubeswell]

So you got any soundbytes of it yet?

[Bob-I]

A hint with Visio. Instead of using the freeform line drawing tool, use the straight line and arc tools. You'll end up with neater drawings. Use snap to grid, and zoom in to get things lined up better. Take your time drawing, a good layout will translate to a better amp.

Amp looks good, how's she sound?

[M Fowler]

I no longer have Visio and that was done with my trial version to practice not very good I know.

I'm back to pencil and paper now.

Mark

[M Fowler]

I haven't recorded any of my amps and I sure do need to do that.

But getting my friend over is not easy and I hate handling the recording end of things, he has to do it for me.

I'll do the guitar playing but he can run the recording equipment.

Mark

[Big Daddy]

I looked at that design if it's the same one I have and my feelings are that it is a flawed design.

I only build low wattage SE amps for guitar and I have many variations on that simple design. The one thing I have discovered is that an SE amp needs a driver like a push pull needs a phase inverter.

A driver can control so much of what goes into the power section. I tried cathode driven tone stacks going directly into the power tube and the tone was horrible IMO. For instance having a driver you can add NFB which will help control a higher gain amp. With that design you cannot add NFB.

One of my next builds will be a similar amp but with one channel. Next stage will be the Marshall type with the cathode tonestack and then another driver stage. I think this will be a much better design. Kind of like a champ amp but with a Marshall/tweed bassman stage between the 2 sides of the preamp tube.

One aspect I am not sure about is whether that design is putting out more 2nd or third order harmonics.

If you are not 100% happy with the results try removing one channel and using that side of the tube for the driver to the power tube. A pair of 12AX7's might be too much gain. I am going to try mixing 12AX7's with 12AY7's, 12AU7's and 5751's to get the right gain.

[M Fowler]

I agree the schematic and layout are wrong and I only used that as a reference.

But I am very happy with the way the amp works.

[benoit]

I haven't recorded any of my amps and I sure do need to do that.

But getting my friend over is not easy and I hate handling the recording end of things, he has to do it for me.

I'll do the guitar playing but he can run the recording equipment.

Mark

I'd be willing to help some time, I know a thing or two about recording gear.

[spiralstairs]

Does anyone know a good schematic/layout for this?
I heard some soundclips which really impressed me, and wanted to do this as a cheap/easy build. funny that this thread got bumped right when I was looking for info

Is the amp really flawed and needs overhaul, or just the schematic needs a bit of component playing?

M Fowler, even if you can't provide an updated schem/layout, do you know of anything you did to the schematic/layout that has already been posted?


FYIW, I'm looking for a non-NFB low watter and not something in the marsh/tweed sense. The clips I heard were pretty much what I had in my head

[M Fowler]

I see that it is closely related to the Hi-Octane found on AX84 and works well. Just the layout of the board is funky on the Swampthing and I just went with my own.

Mark

[moonbirdmusic]

Hello - all

Been wanting to build this amp and this thread seems like the only build report out there (that google finds). Anyhoo, there is mention of errors in the schematic and layout flaws. Can one of you who built this be more specific? Would be much appreciated. thx in advance!!

[M Fowler]

I built both the SE version and a PP 6L6 version 50w.

After going over this I don't think I was correct in saying the board layout and schematic were incorrect. When I was making the board I found that one could have added more components on the board then what the original person had done is all. My bad.

I have a schematic Colossal drew up for me the push-pull version I can post tonight. For the SE version just follow what has already been posted. The tranny set for the SE version is still available.

Mark

[M Fowler]

Here is some info on the trannies from mojotone.com under surplus section.

Sundowner/Swamp Thing SE Output Transformer
Part Number: 7024100
Great Champ 8 OHM Output type

Sundowner/Swamp Thing Power Transformer (for SE Application)
Part Number: 7024101

The original was first called the visio broiler then changed to Swamp Thing.

Mark

[M Fowler]

This is the Swamper same thing as the Swamp Thing just PP and 50w.

Increased the 8uf to 20 uf on the preamp power cap.

[moonbirdmusic]

Thanks for taking the time to post this info. Much appreciated!!

[M Fowler]

I will post the original viso-broiler/swampthing amp info tonight so you can see what he had going. I may be able to find the link to the original instead, I believe it is still on line.


EDIT: http://www.cs.cmu.edu/~ehn/ax84/



Mark