Special projects and used amplifiers

Time to split up the special’s page into two so one for headphones and another one for electronics.  Here I’ll list what my more unusual amplifier projects plus any other piece I’m selling.  Feel free to contact me at spritzer@mjolnir-audio.com if you are interested in any item here.  I will reply to every mail so if you haven’t received a reply within 24 hours then feel free to send me another email.  Email gets lost all the time or is flagged as spam.  All prices in US dollars (USD).

Ahhh the Stax SRM-T8000. I bought this one as the first used unit to hit the market anywhere as I just had to try the new flagship amp. I got it from Japan but we quickly figured out how change to any voltage so it is now set to 240V. This is serial number 26 so early first batch for people who care about that. It is mint in every way and while Kevin Gilmore and I have both opened it up to see what the circuit contains, it is still perfect. The screws were not in the top as Stax screws always get scratched with use so they were kept secure until the amp ships out.  It comes with everything a new amp would come with except the wait time…  😉

Price: 5900$ plus shipping

This is the original test bed for the Pure Bipolar which was never supposed to be turned into an amp but after my laser guy damaged a set of front and back panels I thought, why not finish it and offer one of these that is slightly cheaper.  On the inside it has all the usual traits of a PureBipolar except it has the newest PCB’s and new input devices that I’m trying out.  These are actually new old stock and no longer made so I’m testing to make a slightly different version.  The amp also has a slightly tweaked power supply and an even bigger transformer.

The reason this one is cheaper is that the right hand side of the front panel has some damage to it.  I tried to take a picture of it but it just wouldn’t show properly but yeah, not acceptable for a normal amp.  The left hand side of the back panel has some minor damage too but it’s not really noticeable.  It seems my laser engraver dropped the panels but he never fessed up so I’m stuck with them.  Over all this is a normal PureBipolar amp that has minor damage.  117V or 230V operation not an issue with an internal switch.

Price: 1900$ plus shipping


Here is the Koss E/90 amplifier that came with my ESP950’s but has been gathering dust for a while now. I opened this to check if Koss had done any tinkering to the circuit and they had updated the PSU part but the amplifier circuit was still built on the 1990 marked PCB. I changed the bias supply to make it 100% compatible to the Stax standard and changed the volume control from the nasty Alpha Taiwan unit to a TKD 2CP-601. Much nicer pot but it is just a single shaft unit so I put on a new volume knob as well. Gotta have some aluminum on that plastic case.

To power the amp I bought this nice PSU which I believe is 117/230 switchable internally and much nicer than the stock Koss unit. The amp also comes with a Koss to Stax socket adapter so it can be used with any pro bias Stax set. It’s a neat little amp that sounds good for its size and it will push a Lambda nicely.  It is in excellent condition and clearly a recent build but with Koss it is impossible to know for sure.

Price: 370$ plus shipping

This King Sound M-10 came bundled with a set of KS-H3’s I bought but I only wanted the headphones. Not that they are good or anything, just the collector in me. 🙂 Anyway, this amp is a bit of a basket case stock so I removed the horrid “plate” resistors and swapped in super nice Kiwame units, redid the bias supply so that it won’t kill any Stax sets you use with this amp and is actually safe to use. Asking tiny surface mount resistors to handle 600V is a bit silly to me. I also added heat sinks to the board to try and cool the output and HV regulator transistors. Now it will run cooler and not drift as much. The sound quality is ok with Stax sets and it will easily drive Lambdas. This one is easily switched between 117V and 230V on the back.   There are some scratches on the silver front panel but over all it is in nice condition.

Price: 460$ plus shipping


Last updated 08.10.17