Integrated Amplifiers

Synthesis Action A100 Titan DAC
Included within the A100 Titan is a dual-mono WM8740 DAC-based digital stage employing a tried-and-tested linear-phase filter offering a full 92dB stopband rejection. As the USB interface is limited to 48kHz/16-bit only, our tests were performed via the coax S/PDIF input and via the line/preamp output. The engineers at Synthesis have avoided the schoolboy error of providing a preamp output without also independently muting the power amp section. Bravo! We still encounter DAC-equipped integrated amps where the 'preamp' is unable to offer a useful output – especially when fed a 0dBFs digital input – without simultaneously slamming the integrated power amp into clipping (even when disconnected from speakers). Here, the preamp's RCA outs offer a maximum 2.23V from a 96ohm/1kHz source impedance, increasing to a rather high 6.2kohm/20Hz. The frequency response shows a commensurate bass roll-off, falling to –2.4dB/20Hz while reaching up to +0.2dB/20kHz, –2.6dB/45kHz and –16.3dB/90kHz with 48kHz, 96kHz and 192kHz media, respectively.

Noise is higher than with most solid-state DAC/preamp solutions, and the A-wtd S/N slightly lower at ~92dB. This feeds into a linearity trend where –90dBFs signals, for example, arrive some 3dB higher than anticipated (resolution is ~15-bits). 'Digital jitter', in this instance, is clouded by PSU intermodulation [see Graph 2, below] and amounts to ~26,000psec. (Digital jitter or analogue IMD? The subjective impact is the same or similar.) Harmonic distortion is slightly lower at 20kHz (0.05%) vs. 1kHz (0.13%) [blue vs. black infills, Graph 1, below] and falls to a minimum of 0.005% over the top 20dB of its range. The stereo separation holds to within 71-93dB (20Hz-20kHz). PM

Synthesis Action A100 Titan Amp
With two pairs of KT66 'kinkless tetrodes' per side, the A100 Titan version of the Synthesis Action series is a powerful tube amp that consumes 289W at idle – much of this released as heat – and over 400W at maximum output. For this you receive a power output of 2x65W/8ohm and 2x82W/4ohm which is still a little short of the brand's 100W/6ohm specification, even with the 'one channel' caveat offered in its user manual. While many tube amps have a soft clipping behaviour that allows greater power at 2, 3, 5%, etc, distortion, the A100 Titan has a definite 'clip' point and so there's little more continuous power to be squeezed out. However, there's some headroom in the ultralinear tube configuration, amounting to a dynamic output of 75W, 105W, 122W and 101W into 8ohm, 4ohm, 2ohm and 1ohm [all re. 1kHz/10msec/<1% THD, see Graph 1, below].

Within the A100's power bandwidth, distortion increases gently with output from 0.015%/1W to 0.045%/10W and 0.25%/60W (all at 1kHz/8ohm), and at low frequency to 0.25%/20Hz through transformer core saturation and high frequencies to 0.2%/20kHz with diminishing feedback [all re. 1W/ohm – see Graph 2, below]. Maximum gain is a high +41.5dB, requiring just 23mV input for 1W output and possibly squeezing the achievable S/N which amounts to an A-wtd 80.5dB (re. 0dBW). The response shows a gentle HF roll-off to –2.1dB/20kHz down to –13dB/100kHz but it's the +5dB 'bump' at 5Hz that cautions its marriage with vinyl-playing systems, or at least those without a 'rumble/warp' filter option on the phono preamp. There will be some further, speaker-dependent, modification of system response courtesy of the ~1ohm source impedance. PM