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Alto Alpha Mic Tube

Stereo Tube Preamp By Paul White
Published August 2003

This metal half-rack mic preamp, powered from an included adaptor, offers variable tube drive and has combi jack/XLR sockets on the front panel with switchable phantom power. Outputs are on both rear-panel jacks and XLRs (the jack is unbalanced), and the jack input has a 1MΩ impedance, making it suitable for passive instruments as well as line signals. Other than Gain and Drive controls, each channel has phase reverse and 20dB pad, plus an eight-segment meter.

Because the voltage available from an external adaptor can only be multiplied over a limited range, I guess that the 12AX7 dual triode stage at the heart of this preamp is run at a lower voltage than it was designed for. So I wasn't expecting anything sounding too special, but it actually worked pretty well. The sound didn't have the smoothness and transparency of a real high-end preamp, but it was rather sweeter than the mic preamps in one of my budget analogue mixers — less hard sounding, but at the same time solid and reasonably detailed. When a cardioid mic is used close up to exploit the proximity effect, the warmth and character come over nicely. I've heard quieter preamps, but this one is no noisier than a competent budget mixer preamp.

The Alpha Mic Tube is well suited to close-miked vocals using capacitor microphones, where its noise performance is more than adequate, while its added 'character' should work well for those singers who need to smooth out their vocal sound or thicken it slightly. You need to work with the Drive control below the 12 o'clock position for vocal use, otherwise the distortion gets intrusive, but the extra range is handy when you're warming up synth or guitar parts, and it has a distinct character that I found quite flattering. Even if you already have a decent mixer, this unit might be worth considering for its extra character.


  • Inexpensive.
  • Flattering tonal character.
  • Variable valve drive.


  • No significant cons at the price.


Given its budget UK price, the Alpha Mic Tube turns in a very creditable performance and can produce very high-quality results with close-miked sources.


£136.30 including VAT.

Proel +44 (0)20 8761 9911.

Published August 2003