Used and special one-off 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, used amplifiers that I’ve refurbished/rebuilt 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).

I have one B-stock Carbon amps in stock now with a 10% discount.  This one is a silver unit has a small scratch (more of a rub mark really) on the front panel but is otherwise perfect and a brand new unit.  The picture above I had to get at the right angle just to show that so it is very minor indeed.

Price:  4140$ plus shipping

Here is my take on the BHSE, single chassis amp measuring just about 33cm deep with the volume knob. There were two of these amps under construction for a while of which this is the latter unit. This a full blown BHSE running at 20mA per tube and with the +/-400V power supply built into the chassis. It’s a tight fit but it all works nicely though the transformer can hum a tiny bit as it is suspended from the top panel. There is no hum present in the headphone output though.

The amp will shipped with a matched quad of JJ EL34’s and all the adjustment for the tubes is made through the top panel of the amp. I don’t endorse tube rolling at all but it’s a good idea with any BHSE amp to monitor how the tubes are doing from time to time. The amp can be set to either 117V or 230V via an internal switch. There is just one of these amps and I won’t build any more for a while at least.

Price: 5100$ plus shipping

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.

From a performance point of view, this in some ways a worse version of the 727 and not really an upgrade.  The tube input adds new issues and you can’t change the tubes at all since they have to be hand picked to meet very strict parameters for the amp to work at all.  The output and gain stages are similar to the 727 but a bit worse as Stax runs out of the older parts needed to make them good.  It’s one saving grace compared to the 727 is the global feedback which the 727 lacks and gives that amp the overly warm tone.  This one is leaner and a bit bright even.

Price: 4000$ plus shipping

I was asked to a fully encased version of the KGSSHV as I did a few of these a couple of years ago.  The heatsinks can be a bit sharp so with children around, it can be an issue.  I said why not and made a small batch of these, same power supply as the regular KGSSHV but a new amplifier board with on board heatsinks.  Same specs as the regular KGSSHV too and these amps are the first to sport the new custom made Stax sockets I had made.  As with most of my other amps they have an internal switch to select between 117V and 230V but as always. will be configured correctly before shipping it out.

The KGSSHV is my take on the maximum performance for a price.  When the Stax T8000 is just a badly done tube input version of the 727 (with some real degrade in terms of tech) the KGSSHV has more voltage swing, more current, fully regulated power supply and better performance for half the price.

Price: 2200$ plus shipping

Here is one I thought I’d never sell but then again, I never use it. So this is a Stax SRA-7S which as the first popular Stax amplifier and designed for the SR-1. This was back in 1967 so before even the SR-3 or SR-X mk1 was released. It’s an all tube design and quite small for the amount of circuitry that is in it. So I got this amp from Japan and it has been completely rebuilt. The only original parts in this as the chassis, output sockets, tube sockets, amplifier PCB and the original tubes as they all measured good. The rest is all new and improved. There is a thread on head-case.org where I documented the lengthy rebuild process but basically when I got the amp it was 100V only and the power supply was basic to say the least. There was also no place to put the improved power supply so the first thing I did was to scrap the phono input as it took up so much space and was terrible to begin with. The transformer was scrapped and a new unit from Hammond was installed with the +300/+600V power supply from the Octave. The amplifier board was completely rebuilt with far better parts and moved further away from the transformer.

I really went to town here though as everything else was changed and upgraded. The front panel markings were peeling off when I got the amp so I cloned them and had my laser shop etch them onto the same plate once I had cleaned off all the old labels. The back panel RCA sockets had not aged well so I replaced them with new gold plated Neutrik sockets and redid all of the input wiring. There was a new input switch fitted plus a new volume control and balance pot, both Alps RK27. The power and mono/stereo switches were also both replaced with new units from Japan plus one output was converted to Pro bias output to make it more modern.

This amp has one unique feature which Stax stopped adding in the 70’s… it has a tone control. Basically this is a switch which has 4 settings and it increases the amount of series resistance there is inline with the output of the amp. Now the stock configuration was odd as it treated just one half of the push pull output so when I rebuilt it, it’s done right with matched sections for each output phase. Finally the amp was fitted with new feet, a proper power cable with strain relief and the top cover was powder coated. Last but not least…the knobs used on these are still being made in Japan so I custom ordered new ones as the old ones were unsightly.

The prices for these amps are crazy in Japan now even with tatty samples hitting 1000$ or more. I paid way too much for this one and the rebuilt was…insane so that explains the high price. I also kinda don’t want to sell it but that’s how it is… 😉

Price: 1700$ plus shipping

While working on the latest batch of SRD-7 units I made this one special unit with transformers pulled from SRD-7 Mk2 transformer boxes, a teflon output socket and improved internal wiring.  I also wanted to try to change out the appearance a bit  to make this unit different to all the others I’ve built.

Price: 760$ plus shipping

This is a preamp I used for testing and I got off ebay a while back.  The basic circuit was sound and used good transistors but there is always room for upgrade so I replaced all the capacitors with Black Gates, Panasonic FC and Phillips caps, redid the input wiring with pure silver wire and silver plated copper and replaced the volume control with a DACT unit.  The end result was an excellent little preamp but I just upgraded so I don’t need it any more.

The unit is set to 230V now but I should be able to change it to 115V easily.

Price:  290$ plus shipping

Here is a modified and refurbished SRM-Xh I’ve had for a while.  I fixed the bias supply, replaced all the capacitors and replaced the volume control with the excellent TKD 2CP-601.  It’s a lovely amp but I don’t need anything like this now.  It will come with one of my power supplies for these amps with either a Euro or US power plug.

Price:  230$ plus shipping

Audio-GD R2R15.  100% stock and I just bought one to look at the circuitry inside.  It’s impressive that they can build this for 400$ or so, discrete R2R dac and a pretty good amp for dynamics.   It can even be used as a single source preamp.  I just have way, way too many dacs at this point and I need to thin the heard.  It looks like new and I even replaced the stupid screws they used on the top panel with much nicer counter sunk ones.

Price: 230$ plus shipping

Last updated 04.12.18

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