This is an absolutely one of a kind, custom made, hand crafted, low output power amp utilizing C3m as driver and the stunning RS288 output tubes.
Topology: Telefunken input transformer/phase inverter. Differential front end with a shared CCS under each pair of C3m. Differential power stage with an individual CCS under each of the RS288 tubes. The individual current sources ensure stable operation even with the very sensitive RS288.
All tubes are operated triode connected.
The driver tubes are DC heated, the power tubes use AC heating.
Power output: The amplifier was optimized for sound quality, especially tonal rightness and PRAT, while no compromises to increase power output were allowed. Therefore the output is limited to around 2 Watts, comparable to a type 45 or RE604 SET amp.
A welcome side-effect is that the tubes are run quite conservatively and should last for a long time.
Size: 22 1/4 x 17 x 7 1/2 inches (56.5 x 43 x 19cm) including the spiked feet.
Weight: apprx. 80lbs (37kg)
Chassis: Constructed like a high end speaker, the base is made of wood and 1 2/3 inches (4.2cm) thick at the base, resulting in an extraordinarily strong and resonance free support for the whole amplifier. The top plate cover is veneered with bird eye maple. Unfortunately the heat of the tubes has caused some thin cracks around the sockets which appeared during testing and were filled by the builder, but remain visible (Hence the 8 out of 10 cosmetics rating). The sides are veneered with a beautiful reddish-brown tropical burlwood.
The surfaces were finished to a smooth, high gloss with numerous coats of real shellac. Unlike the traditional piano finish, the wood grain was not filled, but allowed to retain some of it's original texture. Overall, the amplifier is simply gorgeous.
Power supply: Critical attention was given to the power supply which, aside from the super-sturdy chassis, contributes heavily to the weight of the amp. The PS contains 3 power transformers ( 2 for the heaters and 1 HT). The driver stages and power stages are fed from separate windings of the oversized power transformer. Rectification is via a hybrid bridge with EZ80 (6V4), one for the C3m's and 2 in parallel for the RS288's. The rectifier is followed by a shared cLC filter which branches into two LC sections (one per channel). In total, there are 8 caps and six chokes in the powersupply, resulting in a very quiet and stable B+.
Parts: All parts were individually selected by ear. The result is a mix of vintage parts like input and output transformers, PIO coupling caps and modern elements like foil in oil power supply caps or current sources.
Power supply wiring is generally done with heavy gauge copper wire while the signal section uses thin silver wire. The signal ground bus wire is made of thick, high purity silver.
The transformers are wired for 115V primary, but could be changed to 230V with some resoldering.
Layout and construction: Starting with the large, well vented chassis that gives ample room to keep critical parts separate and running cool, utmost attention was given to the layout and wiring of components. AC carrying power supply components are kept in the back compartment of the chassis which is separated from the signal compartment by a metal shield. Wires are routed in a 3 dimensional layout ensuring short leads and minimal interference.
Ground is wired in a combination star/bus layout with separate busses for AC power supply parts, DC power supply parts and signal stages.
All bare wire and most components on the inside were hand-painted with a shellac based violin varnish.
Disclaimer: The amplifier is a custom project, only this one was ever made. Therefore it did not get UL, CE etc. certified. While I am confident that the amp is built safely, I can take no responsibility for any damage and/or injury that results from the use of it, nor can I offer a warranty of any kind. Please don't buy if you do not accept those conditions.
Btw, the top cap connection on the RS288 is not B+, but the tube's grid. No dangerous voltage is present at this connection under normal operating conditions. Obviously though, the top connection should not be touched while the amp running.
I am new to Audiogon, but you can check my feedback under the same name on ebay. If you have any questions, please just send me a mail and I will get back to you as soon as possible. High resolution photos are also available upon request.
Shipping: Due to its high weight, the amplifier has to be freight shipped. I will double box it and pack it in a way to make sure it gets to its destination safely.
What you get: Included is the amplifier with a complete set of matched, testing as new, tubes.
Conclusion: I will try to resist the temptation to describe the sound in the usual terms, but the amp seems to combine the best attributes of low powered SET amps with the advantages of differential amplifiers. Of course, the limited power output requires highly efficient speakers (it was voiced mostly with Coral Beta 8 and 10 speakers, as well as a custom horn speaker with vintage DNH bass in Carlson enclosure, JBL 2360A/2440 and Coral 104), but if your speakers are happy with a low powered SET, this amp will shine.
In typical differential fashion, the amplifier is dead quiet, even on 100+ dB efficient speakers.
Relaxed, yet clean and dynamic, with tone as good as anything I have heard from a SET, and frequency extension (specially the bass) comparable to the very best push-pull amps, it will sound like no other amplifier you heard before, and you can be sure there won't ever be another one like it.