Phonostages — Boulder 2108

The Boulder 2108 is the reference phono preamplifier of Boulder Amplifiers, the Colorado manufacturer with its own production facility in Louisville. Launched in 2019 as part of the 2100 Series, it is the second generation of Boulder's top phono stage and follows the 2008. Audio circuits and power supply sit in two separate chassis, and fully balanced inputs serve up to three turntables.

Key specs that matter

There are three pairs of balanced inputs, convertible to unbalanced, and two pairs of balanced outputs with an output impedance of 100 ohms. Maximum input impedance is 1000 ohms for MC and 47 kohm for MM. RIAA gain is 70 or 60 dB for MC and 50 or 40 dB for MM. RIAA accuracy stays within 0.10 dB from 20 Hz to 20 kHz, THD is 0.005% at 1 kHz, crosstalk is -100 dB or better and maximum output reaches 28 Vrms. Available equalisation curves are RIAA, FFRR (London/Decca), EMI and Columbia. The audio chassis weighs 16.8 kg and the power supply 21.8 kg, and power consumption is 75 W at most.

Engineering and use context

Gain comes from Boulder's 995S, a modular discrete circuit used only in the 2108, hand-built and calibrated inside a potted, precision-machined housing. Against the 2008, the newer model has improved ground paths and planes, a revised topology and more surface-mount circuitry produced on Boulder's own SMD lines, which cuts parasitic capacitance and lead inductance. The lower noise floor let Boulder add gain for low-output MC cartridges without raising noise. Each input takes a Personality Card that sets MM or MC mode, resistive and capacitive loading and high or low gain, so three different cartridges can be matched one by one. The extra EQ curves allow correct playback of records cut before RIAA became universal in the mid-1950s. A low-cut filter with three settings removes rumble and warp-induced low frequencies, and switchable pass-through connections accept an external demagnetiser for MC cartridges. Power supply and standby circuits live in their own chassis, keeping hum away from the high-gain audio stages. The machined aluminium chassis is non-resonant by design and does not pass mechanical vibration into the gain modules.

Pairing

Balanced outputs and a high maximum level make the 2108 a natural match for Boulder's 2110 preamplifier or any balanced line preamplifier. With three Personality Card inputs it can serve a multi-arm turntable or a mix of MM, MC and mono cartridges.

Alternatives

Boulder's 1108 is the single-chassis phono preamplifier of the 1100 Series with balanced circuitry.