Tweed Bassman build thread
 

Been a couple of years since I've posted one of these, but now it's time to do it again.

My Mojotone Tweed Bassman kit was delivered today while I'm here at work. This is one of those bucket list amps for me. Been wanting to build this one for a couple of years now, especially after building its English twin brother, the Marshall JTM45, for a friend a while back.

I've been doing a lot of reference book studying, learning, and have learned a ton about tube circuits since my first amp. I've also learned a handful of little tips and tricks from some pros I'll point out as well as I go. I've also bought a lot of upgrades to my tool and test gear collection that make this a lot easier and more fun.

I'll start unboxing and inspecting parts tomorrow and Monday, and do a full inventory to make sure I have everything I should. Pics will start coming then.

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Excellent! I built a Marshall Plexi Lite 18 watt a few years ago and am considering jumping in on a 5E3 deluxe sometime down the road. I'm keen to follow your Bassman - one of the finest circuits ever designed

I will be following. I just found a 70's oscilliscope this week for checking tube amps and may do a build in the future. The Bassman would be on my bucket list. -- Darwin

Awesome... will be watching!

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Checked inventory this morning, and I seem to actually have all the parts! That hasn't always been the case with these kits, but looks like they tightened up their process for pulling parts for orders since I last bought one. Kudos!

I'll likely load the speakers in, and maybe wire them today or tomorrow. I'm pretty busy the next week or so, then I'll start in earnest. I was figuring on having to get them to send some missing parts, honestly.

To be continued....

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Looking forward to the progress on this one, Clint. Good luck!

Installed some parts in the chassis tonight, and the speakers into the cab. Nothing to complicated, but I'll probably spend too long tweaking parts later until everything looks nice and straight to me.

Work week starts tomorrow, so this will get picked back up later this week or early next week. I'm ordering a small trim pot in a day or two so I can change the bias to adjustable instead of the stock design.

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I'll get a pic of the speakers in the cab when I start installing the chassis and wiring in the speakers.

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Bright, shiny and clean!

Sweet!

I'm in on this thread...

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Drilled the chassis mounting holes in the cab, then mounted the transformers and choke. These are seriously hefty chunks of iron, but remember what this amp was originally designed for: bass guitar. You need a lot of iron to keep the low frequencies from saturating at high power and getting muddy.

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Easy way to keep flying leads from wiggling around when soldering.

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Board is mostly populated. I tested each component as it went in, to verify the right value and to make sure it was a good part. Saves a lot of grief later if something is wrong.

Those caps are Jupiters, and are built to the same spec as the old Astrons that were used in the vintage amps. They're also marked for the outside foil end, which saves me a few minutes. One thing I've learned is that the orientation of caps affects the noise floor of the amp. Connect them the right way, and outside noise gets sent to ground instead of being amplified.

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Looking good!

Awesome! Interesting about sending noise to ground.

If anyone is interested in the science side of it, here you go.

http://www.aikenamps.com/index.php/w...-on-capacitors

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Heater wiring done. Per Merlin Blencowe's recommendations, each heater pin's wiring stays tightly twisted up to the socket, then jumps straight across to the opposite pin on the preamp tubes. This minimizes the chance of the AC heater wiring radiating hum that is picked up in the sensitive signal wiring. Runs between sockets are pushed up into the chassis corners to maximize distance and shielding for those runs. Done right, this all combines to reduce as much heater hum as practical. Takes a couple of hours, and can it really build tension in your neck and shoulders from the tight quarters in a chassis.

Break time!

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