THE MUSICAL MACHINE
THE LITTLE AMP WITH THE HEART OF AN ARTIST

In Bolivian Rosewood

In Sapele

The Machine is an ongoing (for eleven years) experiment in reducing the number of components, stages, parts, in a purist music reproduction system to the absolute minimum; in making a Lean, Mean, Musical Machine - thus its name.  The amp circuit is absolutely as simple as technical rigor allows; a singly-driven differential 5965 is the gain / splitter / driver for a pair of triode 6V6 outputs. Source switching and volume control is onboard; no preamp is neccessary.  The whole rationale here is to have as few devices, components, pieces of wire and solder joints in the signal path as possible.

The developmental path of this amp actually was sort of spooky.  It played like a born musician on first fire-up, and ten years down the road, all I've done to it is reduce the load on the output tubes (10K rather than 7K), draw a little more current in the front end tubes, and upgrade some parts. I would never have guessed, as speculative as this circuit was, that it would require so little development.

If there is a constraint in the application of this amp, it is the lowish power and moderate output impedence, as with any small zero-feedback circuit.  There are high quality speakers in the market that are not only quite cold, sensitivity-wise, but very unkind loads, dipping down to near 1Ω at certain frequencies, and up to 50Ω at others.  On the other hand, I have a client who plays his into a pair of BBC LS3/5a's, and is ecstatic.  I would expect that there are some volume limitations to this situation, however.

Since each piece is made on order for the individual, input/output configurations and parts choices are to your preference, as well as such niceties as boutique connectors and a dedicated power amp (no switching or volume control) configuration.  I do have a base model of which I try to keep an example either on hand or chassis-constructed.  This will have a single output, and two inputs selected by a center-off toggle.   Switches are SwitchCraft silver contact, volume control is a TKD 2500 series , tube sockets are ceramic/gold.  Power rectification is by a 5AR4 dual vacuum diode , power supply capacitors are Panasonic TSHA and Nichicon Muse.  Signal capacitors are Mundorf Silver Supreme or Jensen copper PIO, signal resistors are Riken and Kiwame.  Signal wire is high purity copper or silver in teflon. The chassis rim is cabinet quality exotic hardwood, currently I have Jarrah (a dark red hardwood, see the picture of Mœbius), a little Bolivian Rosewood, and Sapele, which looks a lot like Mahogany, but is tighter, much harder and denser.  Chassis plates are ⅛” aircraft aluminum, all fasteners are stainless steel.  Construction is by a thirty-year guitarmaker.

The base configuration now includes an upgraded volume control, improvements in the transformer ratings, and vacuum (5AR4) rectification, as well as some improvements to the grounding topology that reduce noise+hum down to microvolt levels.  Price is $3600.

If you would like to build your own, the project is up on the Projects side of the site.  For those contemplating purchase, it will give you a good idea of exactly what's in the box; I keep no secrets about these things.  Perhaps the main element of my product is the implementation skill and workmanship I am able to bring to the predicament, the developmental and parts buying savvy are yours to take if you wish.

If you're interested in this very nice little amp, either as a client or a builder, drop me a post; my mailto is at the bottom of the page.  Let's talk story about it.

Poinz

BACK TO PRODUCTS           BACK HOME

Last Updated February 22, 2006
© and Page Development: Eric Kingsbury
Email me at:
Best viewed in Internet Explorer at 1024 x 768