Atma-Sphere - UltraViolet preamp


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UltraViolet preamp

Basic Preamplifier


Features :

The UltraViolet preamplifier is based on a circuit that we have used for many years, but never marketed before. About 40 years ago, Ralph Karsten began developing his own circuit for use for friends on a budget but with high end audio aspirations. Over a period of decades, the circuit has seen a lot of refinement. It is a simple circuit (and obviously a complete departure from our other products), based on a very capable and refined 6SN7-based line section with a simple phono section based on 12AT7s. We have seen this preamp best preamps costing up to five times more; when we say 'refined', we mean it!

We never really considered marketing the circuit though, as it is so different from the rest of our product line. But friends and associates convinced us that we had something special, especially for its price so here it is.

The preamp is available in three forms: a basic line stage, a full function preamp with high output MM capability, or with the addition of of a set of Jensen stepup transformers, it works with any low output moving coil cartridge as well.
  • Simple zero feedback line section
  • Cardas RCA connectors used thoughout
  • optional dual output connections
  • Shunt-style balance control
  • heavy-duty construction aluminum chassis
  • Precision components used throughout
  • Low-noise "star" grounding topology
  • Three-year general coverage warranty with one year warranty on tubes

Specifications :

Line stage frequency response

2 Hz-200 KHz, +0 dB, -2dB

Line stage gain

15 dB

Line stage input impedance

100 Kohm Ω single-ended

Line stage output


Output impedance

400 Ohms from 2Hz to 100KHz

Phono stage input impedance

47 K Ω,

Phono stage input overload

500 mV

Phono stage gain

55 dB

Phono bandwidth

5 Hz-90 KHz within ½ dB

RIAA accuracy

Within .1 dB

RIAA Phono sensitivity

( for 0.5 V @ 1 KHz ) 0.2 mV

Tube complement

2 x 12AT7 phono
2 x 6SN7GT line section


15 3/8" wide x 7.5" deep x 5." high


7 lbs