Which direction?

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Which direction?

Postby Mars Hall » Thu Oct 17, 2013 2:56 pm

I currently have a JTM45 build loaded with Marstran iron. I installed the RS Spares OT and 20H choke. The power transformer is one that Brian made to fit the reissue chassis. I had gutted a reissue as the platform for this build.

Was thinking of taking this build a new direction and would like some advice. I'm thinking of going with EL34's and either installing a 784-128 or a 784-139. My set up is ideal to make this a black flag style JTM50 amp. With a solid state rectifier conversion, I'm also real close to a 50 watt 1986 style, like one of my main influences Duane Allman used.

What are the main tonal differences between the two OT's?
"You just slide a bottle up and down 'til what you want out of it comes out. You just slide away at it 'til you've got it down." Duane Allman
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Re: Which direction?

Postby neikeel » Fri Oct 18, 2013 5:30 pm

I have used both OTs in JTM50 builds but used GZ34s not SS. The tube rectifier seems to add a bit more hair to the amp as you push it which I really like. At lower volumes you would be pushed to tell the difference.

Why rip it up? Why not keep a nice JTM45 and a JMP50 Model 1986 which is what it sounds like you are wanting to build!

As a real answer to your question in identical amps I found the -139 slightly crisper in the lower mids, you could run the bass a little higher. Brian's -128 is a good representation of an original -128 and as such you may need to run the bass at around 2 or 3 on the dial to avoid it flubbing when you are rocking, although if you want poppy funk you can turn the bass presence and treble up, scoop out the mids and it can sound pretty good.
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Re: Which direction?

Postby Mars Hall » Wed Oct 23, 2013 2:06 am

-Thanks for the tone report. I do have another JTM45 build, which is why i'm looking to do something different. My other build I utilized a 784-103 Metroamp OT and choke. I thought the RS would give me enough of a difference, tone wise, to warrant both being JTM45 builds.
"You just slide a bottle up and down 'til what you want out of it comes out. You just slide away at it 'til you've got it down." Duane Allman
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Re: Which direction?

Postby David B » Sat Oct 26, 2013 12:34 pm

Could sell the JTM45 and as Neil suggests build a 1986...
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