Sub-mini Bluesmaster

[evirob]

Heavily inspired by the sub miniature Express that was posted years ago by Dana of Hall Amplification, I've long wanted to give the Overdrive Special the same treatment. I'm sure I'm not the first to do so. I've definitely seen sub-mini ODS preamp pedals, but here are my efforts.

The circuit is a Bluesmaster HRM, and despite being literally scaled down, the amp is full featured with regards to fx loop, FET input, channel switching etc. and despite the uber tight layout, it runs virtually silent when idle.

The only major deviation from the original circuit is that I cathode biased the power tubes, mostly to save space. For the power supply I used back-to-back toroidal transformers to give me 156v B+ for the sub-mini tubes, which is a setup I borrowed from JJS.at electronics.

I had to improvise with the corner protectors. I wanted the finished amp to look as authentic as possible, so I 3D printed some and painted them silver. It's debateable what kind of job they'd do practically speaking, but they look the part (if you don't look too closely)

ODS_BM1.jpg

ODS_BM2.jpg

ODS_BM3.jpg

ODS_BM4.jpg

[dbharris]

Very impressive and unique build! I'd love to hear how it sounds. How is the clean headroom?

-Dan

[evirob]

Thanks. The clean headroom really surprised me with these tiny tubes. This is the only clip I've recorded so far, and I'm not sure it fully comes across. It's definitely loud enough to annoy the neighbours, even with the master below 1/2 -

https://www.instagram.com/reel/C9IrD7eu ... BiNWFlZA==

I'm running it into a 1x12 with an Eminence Hempdog, which is am EVM12L style speaker with a hemp cone. Great speaker, I thought, but now discontinued.

[dbharris]

Thanks. The clean headroom really surprised me with these tiny tubes. This is the only clip I've recorded so far, and I'm not sure it fully comes across. It's definitely loud enough to annoy the neighbours, even with the master below 1/2 -

https://www.instagram.com/reel/C9IrD7eu ... BiNWFlZA==

I'm running it into a 1x12 with an Eminence Hempdog, which is am EVM12L style speaker with a hemp cone. Great speaker, I thought, but now discontinued.

I thought the amp sounded very nice. Not sure if it is just compression from recording or Instagram, but the cleans have a little hair on them. Congratulations on a really interesting build!

-Dan

[katopan]

That is seriously cool! You can sort of gauge from the parts, but what dimensions are your chassis and/or head shell? Which submini preamp and power valves did you use?

I made a similarly inspired submini version of an 18 Watt Superlite TMB many years ago with 6112 valves in the preamp and 5902 push-pull power stage.

[evirob]

The chassis is a Hammond 1444-18 Hammond, which is 13.5" x 5" x 2" and yes, those are the exact same tubes I used

[evirob]

Oh, and yes I think it does have a bit of hair on the cleans, but phone/Instagram is probably contributed too.