Below is a closer shot. Basically it's a weird old tube head that Guild made in the 60's that was loved by bassists and guitarists alike. There were a bunch of different versions, but mine is from 1968 and runs on two 8417 power tubes. These are unfortunately no longer in production (as far as I know) and are usually pretty pricey when you do come across them. Alas, the heads themselves can be found for pretty cheap, so I feel like this off-sets the cost of the tubes and in the long run, it's probably still cheaper than a lot of the other vintage tube amps out there. In any case, I recently had mine professionally restored, including a grounded power supply, thorough cleaning, and all filter caps replaced. Before this though, I'm pretty sure it was all original. The first channel is kind of a standard bass guitar voiced channel with defined mids that can be shifted by way of the three position slider switch. The second channel has a very scooped sound, but the character can also be tweaked via its own three position switch. The real magic happens when you patch the two channels together and blend them via the gain/volume controls. The back end is still controlled by the master volume so it's easy to dial in your tone and then adjust the amount of overall volume or power-tube overdrive you want via the master. It's a surprisingly loud and wonderfully versatile amp. Volume wise it puts out almost as much as any 100watt tube head I've played around with, which is plenty for me.
The cab you see in the original picture was handbuilt by my cousin years ago. He was a bit of an engineer and put together some great stuff. I optimized it for my purposes by putting in an Eminence Legend speaker and it gets along beautifully with the Thunderbass.
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Nice! Thanks for taking the time.