Power amplifiers

Though Spectral Audio’s team has the access to the most advanced audio technologies they keep following the rule that in any contest between theory or test bench measurements and what the ear actually hears, the ear ultimately decides. I can only add that neither Stradivari nor Guarneri tuned their maestro instruments by oscilloscope screen and still managed to make quite good sounding ones, didn’t they?

100% reference

Function and form

Ease of use

The all new Spectral DMA-250 improves on the DMA-150 with the typical Spectral fashion: it took several years for the new model to appear. The Spectral Audio’s designers are rather downtempo with new developments.

The major improvement of the DMA-250 over the DMA-150 is in its wattage that has increased to 200W per channel into 8 ohms (2x350w into 4 ohms respectively) through modifications in its output section. Should you still need more power you can upgrade to monoaural DMA-360.

Like its predecessor the DMA-250 uses what they call a “focused power” output section, that is built around push-pull driven V-MOSFET devices that are individually fine-tuned via teflon trimmers. The architecture of the amp reflects the need for the shortest possible signal paths so it is arranged in two levels – the powersupply section in the basement and PCBs on the 1st floor. By this arrangement all connections are traced vertically with short or none wiring.

The DMA-250’s gain stage utilizes super high frequency bipolar transistors – the amp is rated up to 150kHz +/-0.1dB – whereas its input stage is based on J-FETs. The real heart of the DMA-250 is represented by 2 massive power transformers, each featuring individually isolated windings and output transistors. The transformers are confined between two thick mounting plates and the resulting 19kg-heavy block structure is then fixed on a rubber floating suspension system similar to the one of a turntable. The whole assembly is then airtight sealed in an aluminum container below the DMA-250’s output section to eliminate EMI and RF radiation and superb noise isolation of the power supply. Audiodrom has always claimed a power supply to be critical for any audio component – here we have a very effective solution.

Also visually the DMA-250 is pretty minimalistic. Unlike the DMA-150 there are two handles integrated into its silver&black fascia, the rest (a pair of single-ended and balanced inputs and unbiwireable speaker terminals) is shared with the DMA-150.

Bass management


Rick Fryer believes (quite correctly) in the integration of the music reproduction system. Normally we all believe in this – it is a written law that an amplifier usually performs the best with a CD player of the same make etc. However, being the family of the stubborn individualists, we always try to combine uncombinable, hoping that perhaps such combinations will outperform any standard. Spectral strictly advises against doing so. That is why they started to optimize all the links of their audio chain and that is also why Music Interface Technologies (MIT) cable company appeared on their list of recommended components. This is where the things start to get complicated.

The MIT cables feature special filters (it is the tiny box that is attached to each MIT’s cable) that facilitate high frequencies roll-off. Remember? The DMA-250 reaches into megahertz realm with its frequency response. With the MIT we actually compensate for unwanted interactions – Spectral’s literature even warns against use of other cables to prevent an amp going into oscillation. This is not to say that you cannot use other wires but it is waste of time, especially with loudspeaker cables.

Clarity & delicacy


When describing the clarity of the DMA-250 I made the note about the critical mass of the Nordost cables in a system. This certainly works in my ´spectralized´ system. My system benefited from adding Nordost power cabling and I also had very good result from using Heimdall or Valhalla between the Linn and the DMA-150/DMA0-250. However, once it came to replace my MIT MA speaker cables with the Nordost I could not bear the excessive brightness of the system – the sound got one-dimensional and bleached like overlit by strong spotlights. Once the MIT MA’s were back the balance and depth returned. I have no reason not to stick to a complete loom of the MIT cables as I have money enough (yes, they are expensive) and they really match my personal preference. Potential buyers of a Spectral amplifier will have to include the MIT’s speaker cables in their budgets, however. No other way out. (Interestingly enough, only after I conceived this review that TAS had published a review (Issue 116, DMA-360) on the subject with very identical observations. I can only reconfirm what they heard).

Tonal accuracy

Temporal resolution

For me, the Spectral sound defines neutrality. This does not necessarily mean that I know what the neutrality is - see my review of Audium Comp-5 to join me in the philosophical quest for this misunderstood phenomenon. In Spectral terms the neutrality means transparency. The DMA-250 (and the DMA-150 too) are the least colored amps in my experience. Like it or not, every single amplifier adds its sonic signature onto music. I am not stupid to pretend that the Spectral does not do so but if it does, it does it so cleverly that I cannot hear it.
During my life with the DMA-150 I have not been able to identify anything that would either harm music or make it more euphonic than it deserved. Is this perhaps the reason why Keith O. Johnson, Reference Recording’s legendary sound engineer, opts for Spectral gear for his untoppable recordings? Is it, vice versa, because Spectral‘s design team uses Reference Recordings‘ master tapes as reality benchmarks? Or is it just because the guys from both camps pay so much attention to listening tests in absolutely controlled environments? Whatever the reason is, the DMA-250 let you hear your what really is on a record/ona a disc, provided that you have a sufficiently transparent and honest source and loudspeakers.

Spatial resolution

Soundstage width
Soundstage depth

Dynamic capabilities of the DMA-250 are enormous. The aforementioned clarity means that silent sounds are really silent and loud sounds explode in huge macrodynamic contrasts. I’m not sure if I could recollect any other amplifier that is so authoritative in this single aspect. Transient information is drawn with a very sharp pencil, however, with a lot of attention to harmonies so the sound never gets mechanized. As far as microdynamic scaling is concerned, the DMA-250 can unmask whole layers of sound that are sometimes missing or incomplete with other power amps. These competencies of the Spectral can be bettered only by 2 machines I have heard so far: Musical Fidelity’s Titan combo and Accuphase’s new A-65.

Price as reviewed:315 000,- Kč

Associated components

  • Sources: CD/SACD/DVD-A Linn Unidisk 1.1, TW-Acustic Raven One with Graham Phantom tonearm and Transfiguration Orpheus cartridge
  • Amplifiers: Bryston 28B-SST2, Spectral DMA-150, phono Gruensch Reference Phonostage MCS
  • Interconnects and speaker cables: MIT MA, MIT MA-X XLR, MIT V2.1 Oracle, Stealth Audio Hyperphono
  • Loudspeakers: Wilson Audio WATT/Puppy 8
  • Power conditioning: Furutech, Oyaide



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