Sunday, January 17, 2010

The Audio Research SP3A1

Produced around 1973 to 1974, this vacuum tube preamp definitely raised the bar for the state of audio gear. Many manufacturers had already made the transition to solid state circuitry for their entire model lines. Audio Research (often referred to as ARC) would soon follow with their own solid state audio amplifiers. The basic design of this preamp would continue to evolve for years to come, and carried on in models like the SP6, SP8 and SP10.

Features like a cathode follower buffer stage, a bypassable tone circuit, and a solid state voltage regulator were among the unusual features offered by the SP3. While not new features, few preamps (if any) at the time combined all of them. Add to this a large number of inputs, and a set of AC power outlets on the back that can switch 1200 watts of consumption via a separate power switch. This is great, and even necessary, when using this unit with a solid state power amp. A tube preamp should always be powered on first, and switched off last. Even with modern gear, it's wise to follow this advice.

Of course sound is where the rubber meets the road, and this preamp does not disappoint. Even compared to modern offerings, it can hold it's own. Especially when compared to less sophisticated designs.

This particular example is currently on display at Austin Stereo, in Austin Texas.

1 comment:

faded said...

Just found this blog. I have an SP3A-1 G. I bought it in 1974 and it has been back to Audi Research for service once. It needs to go back again due to old age. It is a wonderful piece of equipment.