Manley Labs TUBES RULE 300B User Manual

MANLEY

LABORATORIES, INC.

OWNER'S MANUAL

THE 300B

PREAMPLIFIER

MANLEY LABORATORIES, INC.

13880 MAGNOLIA AVE.

CHINO, CA. 91710
TEL: [phone]
FAX: [phone]

email: [e-mail]

http://www.manleylabs.com

CONTENTS

SECTION PAGE

INTRODUCTION 3

MAINS CONNECTIONS 4

CONNECTING YOUR PREAMPLIFIER 5

FIGURE 1 FRONT PANEL 6

FIGURE 2 TOP PANEL 7

FIGURE 3 BACK PANEL 8

OPERATIONAL NOTES 9

SPECIFICATIONS 10

WARRANTY 11

WARRANTY REGISTRATION 12

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.

MAINS CONNECTIONS

Your preamplifier has been factory set to the correct mains voltage for your country. The
voltage setting is marked on the serial badge, located on the rear panel. Check that this com­plies with your local supply.

Export units for certain markets have a moulded mains plug fitted to comply with local require­ments. If your unit does not have a plug fitted the coloured wires should be connected to the
appropriate plug terminals in accordance with the following code.

GREEN/YELLOW EARTH terminal
BLUE NEUTRAL terminal
BROWN LIVE terminal

As the colours of the wires in the mains lead may not correspond with the coloured marking
identifying the terminals in your plug proceed as follows;

The wire which is coloured GREEN/YELLOW must be connected to the terminal in the plug
which is marked by the letter E or by the safety earth symbol or coloured GREEN or GREEN
and YELLOW.

The wire which is coloured BLUE must be connected to the terminal in the plug which is
marked by the letter N or coloured BLACK.

The wire which is coloured BROWN must be connected to the terminal in the plug which is
marked by the letter L or coloured RED.

DO NOT CONNECT/SWITCH ON THE MAINS SUPPLY UNTIL ALL OTHER CON­NECTIONS HAVE BEEN MADE.