HAMPTONe

TMPS: Field calibration of our Tube Microphone Power Supplies

FILAMENT ADJUSTMENT:

Our current TMPS have two independent regulator circuits for the filaments (assuming a dual), allowing fine adjustment of each mic. Once complete, the mics should be labeled and used with the appropriate output on the supply if you want it calibrated as close as possible. In general, they will be very close and interchangable. On single supplies, there will only be the circuit on the left. We set these under load, so they will be very close, but it is always best to verify this under the load of your microphone, especially with tubes like the VF14m or AC701k.

The pictures below show the test points and voltage readings for an AC701 (TMPS2-KM54), as well as the trimpot location to fine adjust them. Be careful not to bend the leads on the power resistors in the post filter, they are raised off the board for better heat dissipation.

COMMON TUBE FILAMENT VOLTAGES:

AC701k = +3.95VDC @ 0.1A

6072A = +6.3VDC @ 0.15A

EF86 / 6267 = -6.3VDC @ 0.2A (u67)

EF14 = +5.0VDC @ 0.4A

*Filaments should be adjusted very close to maximize tube life*

(pictures shows a dual KM54 supply, with AC701k tubes)

(measurements must be taken under load, with no load Vf=18.2vdc)

CABLE COMPENSATION FOR FILAMENT

In an ideal world the filament measurements would be taken inside the mic, through the cable, because there is typically 20-50mVDC voltage drop in the cable. We generally adjust the supply +0.03VDC to compensate for this if we don't have the actual mic during burn in. The pictures above show the voltage "uncompensated" to avoid confusion.

PLATE ADJUSTMENT:

In general this does not need to be done because of the small current draw. Adjust the Plate supply after the filament(s) have been adjusted. There is only one regulator circuit for the plate (hi voltage) supply because the current draw on this supply is less than 2-3mA. Next to the trimpot in this picture is a zero ohm resistor (one black band) which is the hi voltage test point. The voltage for this supply was 120vdc. If you are unsure what the test values should be, we will provide those for you. No compensation is required for the plate voltage.

THE MOST COMMON PLATE VOLTAGE = 120VDC (MOST VINTAGE TUBE MICS)

OTHERS:

U67 = 210VDC

U47/VF OR EF14 = 105VDC

M49 = 110VDC