DIY Headphone Amplifier ~ Starving Student Millett Hybrid

[lonely boy]

So, over the Christmas holidays I've been busy making a Valve Hybrid Headphone Amplifier - the Starving Student Millett Hybrid or SSMH for short. This is the PCB kit version supplied by Beezar, the same kit that PJPro built his from here.

I've been interested in this little amp for a while, but have no experience with electronics. But after reading PJPro's DIY threads and my own curiosity, I decided to have a go!

Originally I was going to build a point to point version and drop that in a self made wooden box, but decided on the more convenient and slightly more pricey kit route, but still housing it in my own enclosure. I had to mount a few components off the board - the MOSFETs, two resistors, volume pot and headphone jack, also I had to ground the circuitry to a metal plate instead of using the provided Aluminium enclosure, this also doubles as the bottom panel.

I started on Boxing Day evening, but my soldering iron wasn't really up to it (could have been me though

) so sunday I nipped out and picked up a cheap soldering station and Tuesday night had a working amp!

I did made a couple of mistakes and could have done some things better but overall it was fun to do, it's very much worth it, so thanks to PJPro for helping to demystify DIY audio

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[aliEnRIK]

Respect to that. Nice little amp that

 

[Dave_]

Looks good,nice work

 

[lonely boy]

Thanks Guys!

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[PJPro]

That's a great looking case, lonely boy. What do you think of the sound?

 

[lonely boy]

Cheers! I'm quite impressed so far - I tried it with the Porta Pros for a few days, at first it sounded very warm, plenty of bass a bit on the cloudy side. After I had ran it for a while I tried the Sennheiser HD600s - it retains some of it's warm, slightly soft sound, it sounds quite "tubey" so far, but has cleaned up a bit over time - it appears to drive the HD600's pretty well.

I haven't got a proper handle on it yet, but so far it sounds pretty nice!

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[Diamond Joe]

That's a lovely looking bit of work you've done there fella, hope you enjoy it, how many headphone amps have you got now?

 

[lonely boy]

Diamond Joe:That's a lovely looking bit of work you've done there fella, hope you enjoy it, how many headphone amps have you got now?

Thank you very much Diamond Joe - I now have six dedicated headphone amps.

The Sugden Headmaster, Stax SRM-006t, FiiO E5 portable amp and Starving Student are currently in use, I also have an Icon Audio HP8 valve amp stashed away and a Heed CanAmp that I sometimes lend out to people, as well as my 35 year old Tanberg Receiver

So it's a bit crazy - I'll probably upgrade my Stax amp later this year, but that will be it as far as amps are concerned.

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[idc]

Your work looks fantastic lonely boy. How did you get it to look so neat where the valves and the heat sinks connect through the enclosure? Any pictures of the insides?

 

[lonely boy]

Thanks idc! The heatsinks are just sat on top and are screwed on from underneath by small self tapping screws as there is a small hole along the length of the extrusion used for the mounting pins which I removed beforehand.

The holes for the connections to the MOSFETs were done by drilling three 5/32" holes in a line and the I used a very small round file to carefully clean them up just enough to get the heat-shrinked wires through.

The box is made from half inch plywood, as the valve holders are mounted directly on the top of the PC board and are approx 5/8" tall when attached to the surface of the board, that left me with an eighth inch gap - I packed that out with small spacers this allowed room for the soldered joints, the board was then screwed to the underneath of the top of the box.

I also bought a brand new Bosch adjustable wood drill bit and applied a few coats of varnish to seal the surface before drilling to help to prevent ripping the veneer.

I'll post a couple of internal pictures up asap, but it isn't quite as neat as the outside I'm afraid.

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[lonely boy]

Some internal pics -

Because I had to mount the MOSFETs off of the board, I had to put the resistor that connects to it by pin 1 as near to it as possible and in the resistor's place fitted a piece of wire in the space left on the board. To my understanding if you leave to much of a space between these components this can cause the MOSFET to oscillate, causing problems.

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[idc]

Looks plenty neat to me. The overall look has serious wow factor.

 

[PJPro]

You've made a nice job of it!

 

[lonely boy]

Cool - Thanks again chaps!

 

[Anonymous]

We're always looking for fresh talent. Talent !