Manley ENHANCED PULTEC EQP1-A EQUALIZER - Manual (Page 8)

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 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 5814/12AU7Awill 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 Enhanced 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 Mid Frequency EQ.
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 to prevent a shock. 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. It
is there to reduce both hum and light pickup. Turn it slightly counter-clockwise to remove it. Do not touch the circuit
board or any resistors and capacitors as there may still be some charge remaining.
8
6414
output tube
5814
input tube
EQ SECTION
POWER
TRANSFORMER
MIT Multicap
output capacitor
Gain make-up
amplifier