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Hoffman Amps Forum image Author Topic: Hello from the Florida panhandle!  (Read 3640 times)

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Offline jmaygarden

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Hello from the Florida panhandle!
« on: April 16, 2023, 12:03:24 pm »
My name is Judge, and I've been digging into amplifier design for a few months. This forum has been a consistent favorite. So, I thought that I'd stop lurking and join.

I have a BS in electrical engineering, but I've mostly done software work professionally. That's very helpful in an amp-building endeavor, but (a) vacuum tubes were long out of the curriculum 25 years ago and (b) I'm finding experience recognizing patterns in these designs (e.g. LTP vs cathodyne) much more handy that trying to determine anything from first principles. Using your ears and trial-and-error seems to be the name of the game. So, I'm hoping to lean on the experienced builders in this community!

I picked up a Fender Prosonic cheap in the late 90's that served me very well gigging to make rent in college. I started a family and the gigs ended abruptly. Now that I have time to enjoy it again, that Prosonic is too damn heavy! Rick Hayes lived in the area until recently, and I picked up a Vintage 20 from him that is easily carried in one hand and sounds fantastic.

That should have been sufficient, but I came across an amazing deal on a 1964 AA864 Bassman that I couldn't pass up. I love that normal channel with the volume around 6, but that can only happen when the house is empty (and I even stand off to the side to keep from getting blasted). Additionally, I don't really want to bring the museum piece to the bar. So, I've been studying up to build a single-channel approximation.

The normal channel on an AA864 seems to pretty much be the same as an AB763 as far as the preamp and PI. I'd about settled on dropping down to 6V6's and using a Mojotone 6G2 Princeton chassis as it had the right number of holes. I hadn't yet found this thread where another forum member had the similar idea. Then I came across the Hoffman Stout chassis. That's such a great/flexible arrangement, and I plan to order one shortly.

I'm still indecisive on the exact circuit that I plan to use. I've been fascinated by the cathode bias of the similar Stout TMB design as well as the cathode follower before the tone stack of the 6V6 Plexi from the earlier 5F6-A Bassman lineage. So many choices!

Thanks,
Judge

PS - I worked with Randall Aiken about 15 years ago. He was consulting on PCB layout and FPGA programming on some projects that I was running. I wish that I'd had more interest in amps at the time because he has a wealth of knowledge on the subject and is great guy to work with.

Offline EL34

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Hello from the Florida panhandle!
« Reply #1 on: April 16, 2023, 12:03:24 pm »
Welcome to the Hoffman Amps forum

There are many different boards on this forum for different topics.

The Tube Amp Building - Tweaks - Repairs board is where you can post amp questions.

That board is listed here.
https://el34world.com/Forum/index.php?board=13.0

Thanks,
Doug Hoffman

 


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