Swamper amp project

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M Fowler
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Swamper amp project

Post by M Fowler »

OK here is an experimental amp based on hi/low mixed first stage. The pre is from the Swampthing schematic into Bassman PI and power amp cathode bias.

Not sure exactly what to think it doesn't sound bad and doesn't inspire me either. despite my experimental cobbling together it is a quiet as a church mouse.

I will chang up a few thinks including the cathode resistor/cap combo.
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Andy Le Blanc
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Re: Swamper amp project

Post by Andy Le Blanc »

I'd ditch the master volume and tone in that position. Set up the input to
the 6v6 with just a coupling cap and usual grid return. I would double check just
where you have the max plate dissipation set. Its not a safe assumption to
think that the bias point for triode and pentode will be the same.
Double check. If you're after a hi and low, use the first volumes as tone's
and mix, then follow with just a master, you will save parts and not experience
the loss of another tone stack and volume. You can follow each
of the first gain stages with a simple filter, maximize the response for each.
lazymaryamps
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M Fowler
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Re: Swamper amp project

Post by M Fowler »

Andy I already built that SE amp (Swampthing) and this is what I call the (Swamper) a push pull two 6L6 amp but using the preamp section of the SE schematic shown. It couples off the master volume wiper to the PI.

This Swamper 50W amp works well but I am just voicing it and actually tonight got nice tone with old stock 12AT7 and 12AU7s rather than the 12AX7s. Going to mess with different gain and frequency for V1A/B and see what that does. I naturally want to go 12AX7 tubes to get good gain as we don't need no stinking pedals for that.

Just having fun.

Hoffman 50w fender replacement iron and choke.
Andy Le Blanc
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Re: Swamper amp project

Post by Andy Le Blanc »

and I was have so much fun ramblin on about the SE 6v6.....

A pair of 6l6 can be cathode biased thru the heaters of a couple 12ax7 is the
heaters are series.
It turns the heaters into a one wire to ground affair and gives DC to the first
couple of tubes.

The second stage follower could be replaced by various gain configurations
that use both side of the tube.
Try a marshal super lead , a wreck stage, all kinds of things, cascode, totem
srpp, dress it like a hiwatt.
lazymaryamps
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Mr.Curwen
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Re: Swamper amp project

Post by Mr.Curwen »

Nice touch with the knob rainbow!
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M Fowler
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Re: Swamper amp project

Post by M Fowler »

Ah yes the rainbow knobs, I decided to order a crap load of different color knobs both chicken head and the TW style in something other than black.

Designed the faceplate and order that today, had glued up the drawer cab overnight and rounded over the edges today. Maybe one of these weeks this amp will be called done. Went back to the old 12AT7 tubes I had sitting around that would not work for wreck builds but sound good in this amp.

The weekend is ending rats back to work, well at least I am employed and my thoughts go to those that are having hard times.
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M Fowler
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Re: Swamper amp project

Post by M Fowler »

Well here is my poor job of finishing a head cabinet. I promise I will leave the cabinet work to the professionals. Kids don't follow my example :roll:

Drawer kit, bedliner, oxblood grille, and handle. Needs to be wiped down that what the spots are on the bottom. Its a gigging amp not a show piece.
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M Fowler
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Re: Swamper amp project

Post by M Fowler »

I had some old blue mold caps from an old organ amp so put those in this amp .02 replacing the poly caps which sound sterile compared to these old caps in the tone section. I didn't have enough to all the caps. I do have some .047 for other builds.

The v1a section (low) is using film caps .68/1k5 and 100k plate.
The v1b section (high) currently is switched to film .68/2k7 and 100k plate.

I am done mucking around inside now and satisfied with the tone. I can set MV up to noon or 1 o'clock to get clean. For gain with more treble end set (high gain knob) at about 2 o'clock and low gain at noon. Fun farting around with this design. The 6L6 sound best even better than my 5881. This is cathode bias. One last thing I will do is replace the bias resistor from 250R/10w to a 25w and call it good.
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RJ Guitars
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Re: Swamper amp project

Post by RJ Guitars »

Clips?

It looks really interesting and I would be quite curious how it all sounds.

rj
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M Fowler
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Re: Swamper amp project

Post by M Fowler »

Yeah recording is something I really do need to do and you guys are sticklers for what sounds good and what doesn't. :) But since this amp is for me, it sounds good. :wink:

I have a lot of amps and this one doesn't sound like any of the others and that is what I was after. Fender clean bass with two knobs a high/low to mix the gain for some good rocking. The JTM did this but you had to jumper the inputs. With this amp its internal and without the inherent problems jumpering the inputs has.

Mark
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M Fowler
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Re: Swamper amp project

Post by M Fowler »

Saturday I gigged with my Swamper amp and JCM800/2204.

I changed the preamp bias cap/resistor to 1k5/25uf25v V1a and 2k7/25uf25v V1b on the Swamper. Put in a new 47uf/500v filter cap and off to the show. It was fun to dial in low gain 1 at 1pm and high gain 2 at 2pm and master volume at 1pm for nice classic rock tone. Backing off the volume cleans it up. No pedals required which was a pleasure.

Ran the Roland GR33 keyboard sounds through the JCM800 amp as it is darker which is what I needed for Hammond B3 setting. Ran both amps through my 412 stereo which is loaded with Celestion vin 30s English era.
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M Fowler
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Re: Swamper amp project

Post by M Fowler »

It wasn't until I viewed the Z video I received today that I find out Dr Z built an amp similiar to what I have done here its called the Remedy.

It uses a four 6V6 power section and mine is two 6L6 but we both have full tone stack TMB and we both have gain 1 and gain 2 blend/mix it for Marshall type gain. JTM45 kind of thing and nothing new I know that but it was fun to experiment with. I find it to work better internal jumpered rather than on a four input jumpered Marshall.
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M Fowler
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Re: Swamper amp project

Post by M Fowler »

Here is the schematic and I did change the 8uf to 20uf power supply.
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RJ Guitars
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Re: Swamper amp project

Post by RJ Guitars »

Mark,

That is an excellent pro-look schematic... the amp should sound good just because a glance at the schematic is pretty convincing!

Anyway, I need to look at the actual circuit values and see what you've got. Sounds like it has it's own unique flavor.

BTW - that bed Liner cover looks pretty good. You can cover a multitude of sins If you use enough of it and keep the camera angle right, everything looks great. Kinda like the early Eddie Van Halen guitars before the "vintage" look caught on. Now a Halen-Franken strat is more than $3K from Fender - which had little to do with the originals. When you are a famous name in designer amps that thing will go for $50 grand...

I finally found I could make decent clips with my Nikon Coolpix camera by placing it so that it was several feet away from the amp, facing away from the amp. That formula could be unique to my setup but the clips come out sounding a lot like the real sound in the room... which can be good or bad depending on who's got the guitar.

rj
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M Fowler
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Re: Swamper amp project

Post by M Fowler »

rj, the schematic was done by our colossal and great guy and so talented in many ways.

The amp has been gigged many times and sounds good but could be better. I believe the bias resistor is now 300R or 370R (Edit 350R) its been too long ago I forget. I have to open it up and see about taking those 470R screen resistors out and at least go with 1K/5w or maybe 5.1K like Marshall.

The high gain control and low gain control is such a simple arrangement that actually works well. Plus the master makes it all workable for small or large gigs.

What really pissed me off was the oxblood grill cloth wasn't cloth its vinyl of some kind and I hate the stuff but I got about 2 yards of it.

Mark
Last edited by M Fowler on Tue Jun 22, 2010 2:38 am, edited 1 time in total.
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