Swamper amp project

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guitardude57
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Re: Swamper amp project

Post by guitardude57 »

Pretty cool amp Mark!

Cathode biasing makes things a little more forgiving, and keeps the volume somewhat more manageable, (especially if you don't have a master volume) on those big bottles.

My first (Testing - Proto chassis) Express circuit uses Cathode Bias on 6L6gc/5881 type, and love it. Helps keep the paint on the walls and the Border Collies from howling!
Mike


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M Fowler
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Re: Swamper amp project

Post by M Fowler »

Thanks I changed the screens from 470R to 1k/5w tonight.

I think I will change the amp to adjustable fixed bias being I have a bias tap on this PT. I would like to hear the difference. Also maybe change it to switched SS recto/tube recto.

It does have a master volume so I can tune it down for stage volume.

Had previously played around with different plate load resistors on V1a&b as well as different bias cap/resistors values. Even tried three different types of caps there as well. Right now I backed the gain down to more reasonable level.

Its really looking ratty with all the unsoldering and changes.

I find it best with JJ/6L6 rather than EL34.

Mark
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M Fowler
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Re: Swamper amp project

Post by M Fowler »

Lastest version of the Swamper amp.

Suppose to be sunny tomorrow maybe I can find a better backdrop and take better pictures. :lol:
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RJ Guitars
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Re: Swamper amp project

Post by RJ Guitars »

Nice work Mark! I think it is only fitting that something called a "Swamper" amp has a snake skin covering.

Sunny in Minnesota in January may be good light for photos shoots but I heard the wind chill there today was -36F... forget those "cryo" cured tubes... we should just send a few of the regular ones to you and you could put them out on the back porch for a day or two.
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JazzGuitarGimp
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Re: Swamper amp project

Post by JazzGuitarGimp »

That's a good looking' amp, Mark! Are the first two controls volume? How are they arranged?

edit: Oops, sorry, I didn't see you had posted a schematic on page 1.
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M Fowler
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Re: Swamper amp project

Post by M Fowler »

Thanks guys, it was either snake or alligator for the swamp look.

Now you know why I don't have tube problems rj, my secret cryo tubes.

Some values have changed on the schematic and this one is fixed bias.
Colossal has offered to make an updated schematic so I will get on that.

Mark
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Structo
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Re: Swamper amp project

Post by Structo »

Looks great Mark.

Sounds like you have refined the design and it is performing well.
Tom

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M Fowler
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Re: Swamper amp project

Post by M Fowler »

Thanks Tom there is always room for improvement but this circuit has been local guitar players approved :)
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M Fowler
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Re: Swamper amp project

Post by M Fowler »

This is using a Mojotone BF Bassman chassis so I had to get the faceplate to work with the existing pot holes so this is what I came up with working with mojo's faceplate guy. I think he did a great job with the plate.

The cabinet is mojotone and currently speaker is WGS G12 C/S-75w American bite. :)

Mark
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randalp3000
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Re: Swamper amp project

Post by randalp3000 »

Looks great Mark, of course. Have you ever tried it without the Cathode follower and tone stack?
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M Fowler
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Re: Swamper amp project

Post by M Fowler »

No I wasn't looking to experiment on this circuit I've have many other amps I can play around with.
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M Fowler
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Re: Swamper amp project

Post by M Fowler »

My early Swamper amp http://ampgarage.com/forum/download/fil ... &mode=view has changed hands a few times but keeps on Rocking Fargo ND area these young guys are keeping Rock alive thankfully. New tubes (Cathode bias). A year ago I put in a new mid pot 250k, added presence and resonance on the back panel. Cheaply built amp but sounds great. Channing guy on strat with rag hanging off head stock/singer in a band called the Knotties.

https://www.youtube.com/watch?v=2XWju7qBJZc

https://www.youtube.com/watch?v=AsaV6FNt_og
telentubes
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Re: Swamper amp project

Post by telentubes »

Nice sounding amp
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M Fowler
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Re: Swamper amp project

Post by M Fowler »

Thanks, it's hard to get good sounding video but in person the amp has tone qualities I like.

He thinks it's too bright which I could reduce the mid pot the previous owner had me add for more mid range and that Strat doesn't help with it's lip stick pups. :D
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