Today, a whole new topic in DIY electronics – audio. Audiophiles (or just anyone looking to get good sound quality) can spend hundreds or thousands of dollar on systems whose parts may only cost a tiny fraction of the retail cost. So the DIY community has stepped up to the plate, with many extremely knowledgeable engineers and hobbyists collaborating on original circuit designs that rival or better many commercial “audiophile” products.
Recently, I had the great fortune to get in on a group buy of sorts, for a modified version of the Starving Student Millet Hybrid amplifier. The SSMH started life as a simple but ingenious hybrid (tube and solid state) design by Pete Millett, in which he used the heating element of the tubes to put a load on the MOSFETs of the amplifier, cutting complexity and cost. Originally, it was a very basic amplifier with a budget-minded soul, built into whatever enclosure was handy with point to point (P2P) wiring. You can see the original build at his site here, and the forum thread following it’s history here.
DIY forum user Dsavitsk then improved on the design with some slight modifications to the circuit. He also developed an equally ingenious way to mount the amp in an enclosure – a PCB would be developed and attached to the sliding top of a standard Hammond enclosure, allowing the tubes to be mounted to the “underside” of the PCB and stick out through the case. This would eliminate the P2P wiring that caused many problems in DIY builds of the amp – problems with grounding and bad connections had plagued countless hobbyists.
Collaborating with Tom Blanchard of Beezar Audio, the two developed PCBs and set the project in motion. Tom took on the arduous task of organizing the procurement of the increasingly rare 19J6 vacuum tubes, the custom-machined Hammond cases, and all the other various parts needed to develop kits of the SMMH.
I was lucky enough to get in on this undertaking and purchase a kit, and after a couple months (during which the cases were machined), I recently took delivery of the kit and quickly put it together.
The ease of construction of this amp is a great testament to the amount of work that Tom, Dsavitsk, and originally Pete put into this design. I had the amp completed from start to finish in less than 5 hours, with no serious problems. With me and DIY projects, that’s unheard of. Tom made it extremely smooth with his excellent instructions. I flipped the power switch, watched the glow of the tube heaters and LEDs come to life, and plugged in my headphones and source. I wouldn’t call myself an Audiophile, but the sound of this amplifier far outranks anything I’ve listened to, and blows my own basic DIY amps out of the water. Plus, it looks amazing on my desk. Glass tubes? How quaint!
For those looking for a great audio project with that old-school tube feel, there are still PCBs and tubes available, with a chance that more custom cases will become available. [EDIT] As of February 2010, the supply of 19J6 tubes has been nearly exhausted and no more PCBs or kits based on this tube will be produced unless a stash is found in the corner of a warehouse somewhere. The possibility of doing this build point-to-point still exists if you want to buy the tubes in small quantities at high prices, and there are modifications that can be made to use this design with more common tubes – see the SSMH website or the Head-Fi thread for details.
Even if this amp seems like too much of an undertaking, I highly recommend dabbling in DIY audio – a great place to start is the classic CMoy headphone amp in a mint tin. Tangent has some of the most complete instructions here.
Un-Disclaimer: I’m in no way involved with Beezar audio or anyone else mentioned in the post; this was just an awesome project that came together through the power of the DIY community.