I have some history with the GamuT D200 power amplifier; the original version was my reference amplifier for many years and powered at least two generations of Bowers & Wilkins 802 Diamond speakers. I liked it a lot, but somewhere along the upgrade path to MkIII status, it began gathering dust and I let it go. Hearing the latest D200i brought back what I loved about this Danish beast.
GamuT makes two power amplifiers, of which this is the stereo option. The M250i is an even more powerful monoblock, but the as the name suggests, the D200i’s delivers a healthy 200W in its own right. GamuT amplifiers use a single high-current MOSFET output transistor per channel, where most other solid state amplifiers use multiple output devices and if these differ in their electrical characteristics, distortion creeps in. Manufacturers therefore tolerance their output devices as tightly as possible; Naim takes this to its logical extreme with its Statement amps, where each set of output transistors are made from adjacent pieces of silicon from the same die – but that is clearly a pricey approach.
The reason that solid state amps have multiple output devices is because this gives more power and more power needs more heat dissipation. So how does GamuT get away with using only one device? I asked engineer Benno Baun Meldgaard this question and he explained that they use industrial transistors that were developed for motor control and welding, and are even able to handle 400 amp peaks. This type of transistor is not available in the usual complimentary positive and negative pairs (PNP and NPN), but just NPN or ‘negative’ and GamuT had to do a lot of work to stabilise two of these devices for each channel, effectively turning them into a pair. To Benno’s knowledge, Constellation Audio is the only other company that does this and then with multiple pairs rather than one.
The latest D200i now has a single emitter resistor network, which consists of three paralleled 0.12ohm resistors, creating a combined resistance of 0.04ohms. That is about 5-10x lower than most amps. The transistors themselves are of higher quality and the power supply has been reconfigured with better parts and a quieter transformer than before. Rectification is now balanced and has twice the capacity, in the process halving resistance and lowering noise. Finally, the internal cabling has been changed to GamuT’s Wormhole speaker cable, an unusually thin type for a high power amp maker.
GamuT only makes one preamplifier: the D3i. This is described as a dual-mono design and has both balanced and single ended inputs and outputs on its substantial yet not overly weighty carcass. One pair of the RCA phono inputs is marked RIAA with a matching legend on the backlit front panel. However, as things stand it does not connect to a GamuT phono stage, which is still in development but should be available by the end of the year. At present, this input functions as a balanced input on RCA sockets; it works with an XLR to RCA cable, wired positive to centre pin and negative to the collar, plus a flying earth lead screwed under the ground connector. This configuration can also be used with any balanced line level input. The HTH/home theatre input can be used in bypass mode for combined stereo and multichannel systems.