User guide

TECH NOTES

SWITCHING ON

The power switch is located on the right hand corner of the front panel. When one first turns on the power the LED

next to the switch is red, indicating "mute"- after about twenty seconds it turns green and audio can pass. This

prevents thumps or pops during warm-up and shut-down. The circuit is smart enough to ignore short black-outs. The

audio does not normally pass through the relay involved - the relay, when muted, simply shorts the output. Do not

switch on and off rapidly in succession as this is not good for the power supply. A recent update added high voltage

shunt regulators so that AC power variations were not reflected to the output. We also added output transformers.

TUBE LIFE

As with all tubes, their quality degrades with age. This is due to cathode emission, a natural process found in all

tubes. Excessive increase in noise (hiss) can indicate the need to replace a tube. Usually, the 5814/12AU7A will be

the one to try first as this is the tube in the gain stage. The 6414 is the output tube. Microphonics are a natural

occurrence found to some extent in all tubes. We try our best to select the least microphonic tubes possible.

TUBE SUBSTITUTION

This circuit has been optimised around the 5814 and the military 6414 tube types. We also believe these are the best

tubes for your unit. Replacement tubes can be obtained from Manley Laboratories. However, if you're stuck in a

pinch, the following tubes are approved substitutes for this unit:

For the 5814: 12AU7WA, ECC82 (exact substitutes)

For the 6414: 12AT7, ECC81, 12BH7A (not exact substitutes, but they will work fine with a little less current output)

CUSTOM VERSIONS

For mastering use, we also build a custom version of the Manley MID Frequency Pultec EQ which has

1/2dB switching BOOST and CUT controls replacing the continuously variable controls found in your unit. We also

build a Mastering Version of our Pultec EQP1-A.

SERVICING and TUBE REPLACEMENT

High voltages are present in this unit when powered and for 10 minutes after power is removed due to the slow

discharge of the high voltage capacitors. Before opening the top, remove the mains cable and let the unit "sit" for

about 10 minutes. Even then it is good practice to only use one hand in any high voltage gear and/or use rubber

gloves. Do not touch the circuit board or and resistors and capacitors as there may be some charge still remaining.

Wiggling the tubes slightly back and forth helps when removing or inserting them. Given these precautions, replacing

tubes is as easy as changing a light bulb. There is a metal tube shield over the 5814, Twist it slightly counter-

clockwise to remove it. It is used to reduce hum and light pick-up. Replace it after changing the tube.

6414

output tube

5814

input tube

EQ SECTION

POWER

TRANSFORMER

MIT Multicap

output capacitor

Gain make-up

amplifier