# Homebrew JTM1



## epis (Feb 25, 2012)

Hi guys, I wanted to share with you my last build.
At last Ottawa guitar show, guy from Tundra music presented Marshall offset JTM 1W amp, witch sounded surprisingly good.
After finding how much it cost, I've decided to start collecting info and build one.
The guys from Ampgarage saved me a lot of work, schematic diagram and layout posted there was a great help.

http://ampgarage.com/forum/viewtopic.php?t=24671

If you're interested in it and how it sounds, go here :

https://soundcloud.com/jeremyslemenda/jtm1-5-2

Sound clip isn't mine, but my amp sounds almost same , he's better player 
"This is with the .1W setting, which doesn't sound quite as good as the full power setting. The first part is with the gain on 4, then 7, then 10. At the end I backed off the guitar volume to demonstrate how it cleans up. Tone controls at noon, with bass backed off a little "

I built it with full tone stack and with Lpad as an attenuator at output.
Despite the power - 1W, amp is very loud at max loudness, but attenuator works very well.
There is some clean headroom up to 11 o'clock, after that just crunch and really cool smooth distorted sound when dimmed.
It is nice small amp for apartment use.
A few details about the build, I used the parts I had in my parts bin, PT from old radio, I rolled my own OT ( I didn't want to pay more then $50 for a small Hammond transformer), chassis is reworked recycled workshop over-the-bench light fixture, for cabinet I used 1/2"plywood and covered with leftovers of vinyl from previously built champ amp.
Here are some images :

http://s1210.photobucket.com/user/epis1/library/JTM1?sort=3&page=1

Happy Canada Day  , Damir


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## keto (May 23, 2006)

Nice work, love the repurposed chassis and the headbox came out very well!


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## greco (Jul 15, 2007)

Congrats !!...Great looking amp (both inside and out) and matching cab. 

Very impressive that you made your own OT.

Cheers

Dave


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## epis (Feb 25, 2012)

Thanks Greco, that cab is actually Champ in oversized cab for 12" speaker, I took the picture because it looked cool together.
My next project will be a 1x12 slant cab for the amp. Cheers, Damir


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## mhammer (Nov 30, 2007)

Can't see the pictures from work (or hear the soundclip), but I look forward to seeing/hearing when I get home....and when I come over to your place.

What gauge of magnet wire does a person use for a homemade output transformer of this type?


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## epis (Feb 25, 2012)

I hope to see you soon Mark :smile-new:. I took apart SE output transformer from that same radio. Primary was wound with thin wire I compared to some wire I have for winding pickups.
Very close match, it looked same to me, was AWG 41.
Secondary had 120 turns for 8Ohm impedance. Simple math gave me 3000 + 3000 turns of wire for 20K primary impedance.
I used my primitive pickup winder (cordless drill) and wound it: 1/2P + S +1/2P Simple, but worked well.


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## mhammer (Nov 30, 2007)

Well, then. I'll have to bring you the roll of #36 I have so you can make heavier-duty OTs. :smile-new:


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