Looking for a low cost, high performance, all tube phono preamp?  Look no further.  You just found it.  The performance easily exceeds other high-end phono preamps at a small fraction of the price.

Circuit Details:

Our design philosophy is to use simple, easy to build circuits, that employ innovative features which minimize cost and achieve performance levels that exceed the most expensive equipment on the market.  This is evidenced by the success of all of our products.

The most important parameter to optimize in a tube phono preamp is noise.  It is the most difficult to eliminate.  The most critical element in reducing noise is the first gain stage.  We have achieved very low noise performance by utilizing the 6C45pi tube.

The 6C45pi Tube:

This is a heavy duty Russian military tube that is unlike any other.   At the plate current levels used, it has more than twice the transconductance of the commonly used 6922 tube.  Also, gain is 65% higher.  These two factors combine to yield a much lower noise figure than is possible with any other current production vacuum tube.  The first stage employs cascoding for lowest possible noise.

Passive Equalization:

The RIAA equalization is obtained with a passive network that is direct coupled to the first stage.  It has been precisely tuned to give a very accurate playback response.  No feedback is used in this design because it simply is not required.

Second Stage:

The second stage utilizes a 12AX7 arranged in a current source loaded configuration.  It is the perfect tube for this application.  The first stage boosts the signal level high enough that it easily exceeds the noise floor of the 12AX7.  Only two stages are used because every intervening tube in the signal path will add noise.  This design uses the minimum number of tubes in the signal path.

The preamp will operate on 115V-60 Hz as well as 230V-50Hz used in Europe and Asia.

Total Performance:

These design features produce a noise figure of at least 75 dbA.  This is outstanding for a tube phono preamp and exceeds conventional designs by at least 10 dbA if not 15.  Gain is a whopping 52 dB.  Consequently, the preamp can be driven by all but very low output moving coil cartridges.  Step-up transformers can be added for these types of cartridges.  Contact us for details as moving coil cartridges require special consideration when mated to a transformer.  Connecting the Phono Preamp to the Grounded Grid Preamp creates a combined gain of 64 dB of very low noise amplification.  By the way, the thing sounds pretty darn good.

Easy Assembly:

The circuitry is contained on two circuit boards, one for the power supply and one for the preamp.  Very little point-to-point wiring is required.  Assembly time should be less than 6 hours.  

Power Requirements

Specifications:

Signal to Noise Ratio: Greater than 75 dBA.

Gain:  54 dB.  

Max Signal Out:  20 volts RMS.

Output Impedance:  1000 ohms.

Input Impedance:  47 k Ohms.

Tube Compliment:  4-6C45Pi, 2-12AX7A

Dimensions Overall:  15'W by 11'D by 4 1/4'H.

115V or 230V, 50-60Hz, 25 watts.

Weight:  10 pounds.

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Transcendent Phono Preamp