HERRON AUDIO VTPH1
Owner's Manual

Herron Audio Vacuum Tube Phono Preampli�er Herron Audio Vacuum Tube Phono Preampli�er

Owner�s Manual Owner�s Manual

Installation and Operation
The operation of the Herron Phono Preampli�er is straightforward. As with any �ne audio component, careful set-up and integration into one�s system is important for optimum performance, safety, and reliability. Please read through the following set-up instructions completely prior to operating the unit. Procedure: 1. Position the unit in a well-ventilated area on a �rm, stable surface, away from equipment that generates alternating magnetic �elds such as motors, transformers, etc. Magnetic �elds of this type can introduce hum into the signal path. 2. Connect the phono leads to the phono preamp left-to-left and right-to-right. Connect the phono ground bleed wire to the ground connector of the phono preamp. 3. Plug the line stage leads into the output, left-to-left and right-toright. 4. Plug the power cord into the phono preamp. Make sure it is �rmly seated into the IEC socket prior to inserting the plug into an AC outlet. 5. Plug the power cord into a 120 volt (U.S. spec units) AC outlet. 6. Power up the unit by switching on the power switch. 7. Observe the LEDs for the appropriate operation (see the Front Panel Indicators section). Listen carefully for the click of the automute engaging the outputs. 8. Once the unit is powered up and operating, place the line stage input selector switch to a position selecting an unused or deactivated input. 9. Power up the rest of the system with the line stage input selector positioned to select any input not otherwise in use other than the phono preamp. With the volume control of the line stage set at its lowest position, select the phono preamp. Gradually increase the volume control until a normal listening level is reached.

Cartridge Loading
The Herron Phono Preampli�er is available in different con�guLOADING RESISTORS rations to suit the type of phono cartridge being used. User adjustments are minimized to simplify operations. For moving magnet units, the input impedance is set at 47,000 ohms in parallel with 100 pF (grid to plate capacitance of the �rst 12AX7 multiplied by the gain�the "Miller Effect"). For moving coil units, optional
Optional cartridge loading resistors shown at input connector terminations of the FET ampli�er board.

internal cartridge loading resistors can be soldered to the input

connectors, as shown, in parallel with existing 47,000 ohm resistors on the FET ampli�er board. Loading resistor switch contacts would compromise performance at the small signal levels that are generated by a moving coil cartridge. The cartridge loading resistors may be changed by the user, dealer, or factory, with values appropriate to speci�c cartridge requirements. CAUTION CAUTION CAUTION CAUTION CAUTION CAUTION

When changing cartridge loading resistors, the phono stage should be unplugged and left off for a minimum of 30 minutes prior to opening the unit, to insure that hazardous voltages in the power supply have time to discharge before entering the unit. Loading resistors should only be changed by technically quali�ed personnel. Care needs to be taken during this procedure in order to prevent damage by static electricity to the �eld effect transistors in the moving coil input stage. A grounding wrist strap is highly recommended. Keep the cartridge load resistor leads short, as shown, to prevent hum pickup. Install the grounding lug under the top screw at the rear of the chassis when reinstalling the cover.

!!!!

Please read the Owner�s Manual completely BEFORE operating the unit.

eight

nine