Thursday, January 30, 2014

This Week on Things Done at Midnight...

I recently had a hankering for a pair of Superlux HD 681s, which are some of the best cans you can buy at the bag-of-rocks price-point (or, so the internet tells me).

But before getting into such shenanigans, I thought it'd be a good idea to have a decent amp to go along with them. I found among other designs, Pete Millet's "Starving Student" hybrid headphone amp, which, as its name implies, is meant for people like me. huehuehue.

Note: The potentiometer package is a placeholder as the real pot which will have wires that run to the front panel. 

Of course, the original Pete Millet design seems to have been so widely popular that the original tubes (19J6) are virtually gone from the marketplace, which helped spawn another version using the 12AU7 (The design I'm copying, which is available here).

I haven't been able to find any measurements for the 12AU7 variety, but the 19J6 variant has an impressively flat response, and the neverending head-fi thread about this object make this venture very promising.

Opting to do this on the classier side of things, I acquired a lacie hard drive case from James as the main casing.

The plan is to cut the thing to fit the depth of the PCB and then mount the board inside with some standoffs. Unfortunately, the case doesn't come with a slot for the PCB to slide in.  

The front and back panels are going to be lasercut - a decision based on my desire to avoid having to precisely drill out the corresponding holes for the power and volume knobs. It would also allow for the power indicator LEDs to nicely illuminate the interior of the amp. 

I realize that the hole for the rear power socket  is on the wrong side according to the countersunk holes. However, this won't matter since the countersinking will be done by hand after the basic shapes are cut out.

I've decided to add aluminum accents around the tubes to hid the edges of the tube socket holes.

I sourced most of my components from digikey to save on shipping, using mouser for the odd tandem potentiometer and a few knobs. The tube sockets are from ebay.

The total component cost came in at around $50 (~$70 if you count the enclosure and shipping),although you could very easily take off ~$10 by not buying fancy aluminum knobs and a two-pole rotary switch.

To be continued...

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