The following is the text from the User Guide for the new AVA Vision adjustable phono preamplifeir.
Vision Adjustable Phono Preamplifier User Guide
Introduction
Thank you for your purchase. We think this special and sophisticated new and unique RIAA phono preamplifier will please you.
Your new Audio by Van Alstine Vision Adjustable Phono Preamplifier is a brand new multi-purpose direct-coupled split passive EQ very high performance solid-state phono preamplifier. It is designed with high current buffered output circuits to handle long cables, complex tape loops, and other difficult loads.
The Vision Phono Preamplifier is user adjustable for either MM or low output MC cartridges, and provides for adjustable cartridge loading and gain.
The circuits we designed have very low DC offset or drift. Thus all coupling capacitors have been eliminated from the direct signal path. It is built in our new custom 7” x 5” x 2.5” inch chassis. The isolated internal linear analog power supplies are fed by a small 120V to 16V AC step down “wall wart” transformer, keeping all high level AC and noise out of the preamp chassis.
The AVA Vision Phono Preamplifier is shipped with the internal dip-switches set for a standard MM cartridge as a default setting unless you have instructed us of your preferred settings at time of order.
Make all adjustments with your preamplifier turned off.
Each phono channel has a ten-position dip-switch. Pushing down on the raised nub of each switch position will turn that switch on or off. There will be a small click as the raised nub is pressed down and engaged.
When each switch position is pressed down at its number end, that switch position is ON.
If you ordered the Vision phono section for use with a normal output moving magnet cartridge it will be delivered with all ten switch positions per channel turned off. This is the normal 20dB gain default setting for moving magnet phono cartridges.
Just in case you loose the setup instructions below, they are also printed on the inside of the preamp cover, making it very hard to loose them. ☺
Note that the switch positions closest to the grey-shielded input cables are positions 1.
For use with a low output moving coil cartridge each channel should be set as follows as a starting point.
Set switch positions 1 and 2 to ON. This adjusts the cartridge input conditions for MC cartridge
Set switch positions 4 to ON. This sets phono gain to the normal +60 dB for MC cartridge
Set switch positions 9 to ON. This sets phono input load to 100 ohm.
Switch positions 3 ON instead of 4 increases the MC gain by 6 dB
Switch positions 5 ON instead of 4 decreases the MC gain by 6 dB.
Switch positions 6 through 10 set alternate MC input loads.
Position 6 ON is a 1000-ohm load
Position 7 ON s a 475-ohm load
Position 8 ON is a 220-ohm load
Position 9 ON is a 100-ohm load
Position 10 ON is a 47-ohm load
Positions 7, 8, 9, and 10 all turned ON at once provide a 30-ohm load.
Make sure all unused switch positions are turned off.
Make sure the settings on both channel's switches are set identically.
Please call us at 651-330-9871 for help if you have any questions.
