Manley 300B Preamp Original Version 1996 - 2001 - Manual (Page 3)

INTRODUCTION
THANK YOU!...
for choosing the Manley Laboratories "The 300B Preamplifier". Designed by David Manley, the 300B
Preamplifier uses the best available parts with the shortest, cleanest, signal path possible. This Preamp
features the 300B direct heated triode as the line and headphone driver. The 300B is typically used in
low power amplifiers as the only power tube. These amps generally deliver 5 to 9 watts single-ended and
cost from $3000 to over $100,000 Some of these amps sound very nice coupled with efficient speakers.
We build an amplifier that uses a pair of 300B's that can be operated single-ended or push-pull and
delivers up to 36 watts. We consider the 300B to be an extremely good tube for low power purposes.
Driving headphones and cables is a very good application for these tubes. Here is where the impedances
are not too low and the power requirements are not too high, however, these applications are near the
limits of where smaller triodes and dual-triodes are usable. We combine the classic 300B with another
classic - the 6SL7GT to provide the complete amplification stage. To complement this tube choice we
chose to use tube based rectification and regulation as well as our usual extreme filtering.
To complement our best sounding line driver to date, we used the techniques of the best passive
preamps. We used a 24 position gold contact Grayhill switch with metal-film 1% 1/2 watt resistors for a
superior audio attenuator and a widely separated ceramic switch for input selection. Also used were, gold
plated connectors, high purity copper wire, Mil-spec printed circuit boards with extra thick copper and
plating, and custom designed transformers.
The elegant front panel finish is a high purity plated gold that complements the electronics both visually
and in its long lasting outstanding quality. Please take a few moments to read through this manual, there
may be features and information about this preamplifier which you should familiarise yourself with.
Thank you again, and please enjoy!
GENERAL NOTES
LOCATION & VENTILATION
The Purist Preamplifier must be installed in a stable location with ample ventilation. It is recommended,
if this unit is rack mounted, that you allow enough clearance on the top and bottom of the preamp such
that a constant flow of air can flow through the ventilation slots. We also recommend that the
preamplifier be placed at least 10 inches away from its amplifier.
WATER & MOISTURE
As with any electrical equipment, this preamplifier should not be used near water or moisture.
SERVICING
The user should not attempt to service the preamplifier beyond that described in the owner's manual.
Refer all servicing other than tube replacement to Manley Laboratories.
SPECIAL NOTES
The 300B's are packaged separatly to prevent damage. You will need to carefully plug them in before
powering the preamp. Pay attention to the size of the pins to properly align the tubes before inserting.
The large pins go into the large sockets. It is difficult but possible to insert the 300B's wrong and damage
the preamp. Tubes may become loose during transit. Straighten and press down each tube before
plugging the preamplifier into the mains socket. Furthermore, do not touch the tubes after the
preamplifier has been switched on, as the tubes do become very hot during operation and should only be
handled after the power has been turned off and the tubes have cooled.