Pre-Owned Icon Audio MB845 Mono Block Valve Power Amplifier (Pair)
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Features
| XLR Inputs | No |
|---|---|
| Remote Control | No |
| Brand Color | None |
| Warranty The length of time your product is protected by warranty | None |
| Product Type | Other |
Description
These amplifiers are low feedback valve amplifiers that are different in the way they delivers power. Distortion rises progressively and overload occurs gradually with a smooth rounding of the wavetops. Using a 1% distortion limit the big MB845 delivers 85 Watts, or 90 Watts with a 3% limit using the conventional 1kHz test. However, the transformers, which are large but not huge, moved into unhappiness at around 65 Watts from a 40Hz bass tone and managed around 70 Watts maximum (3% thd), so this is the true power output as far as bass heavy Rock is concerned. This result applies to both 8 Ohm and 4 Ohm taps I should add.
At a few Watts the MB845 produced around 0.2% distortion, mainly innocuous second harmonic at frequency extremes of 40Hz and 10kHz, this figure sinking to 0.05% at 1kHz, usefully below Harold Leak’s 0.1% limit! What really matters is what is going on across the frequency band below 10V output (25 Watts into a 4 Ohm loudspeaker) and here the MB845 was producing just a little low order distortion, as our distortion analysis shows, so distortion is not a problem.
Sensitivity was high at 440mV for full output, meaning it will work with many phono stages without an intervening preamp, including Icon Audio’s which have a volume control fitted expressly for this purpose. Noise was low at -102dB and hum virtually negligible at 0.3mV, making the MB845 unusually quiet - useful when sensitive loudspeakers are used.
Frequency response rolls off gently above 15kHz, the -1dB point, measuring -1.5dB at 20kHz. Whilst this is large when compared to conventional solid-state and valve designs which are mostly flat to 20kHz nowadays, it is more than countered by the intrinsic rising response of most modern loudspeakers that are commonly +2dB up at 20kHz. The MB845
will sound just detectably less bright in comparison to other amplifiers all the same.
The Icon Audio MB845 is typical of a well engineered large, low feedback valve amplifier, possessing a stable distortion pattern dominated by innocuous sounding second harmonic at normal listening levels. It should sound smooth, easy on the ear and powerful.