Manleys most esoteric product is THE 300B RC PREAMPLlFIER, now
featuring Radio Frequency Remora Remote Control! This is the first and only preamp to
feature the classic directly heated 300B Triodes. We had been designing the 300B
into small power amps for many years and have always had
great respect for the smooth natural sound of this tube.
However, a single 300B provides truly appropriate power and
voltage swing for headphones and makes a remarkable line
driver. Here is where the impedances are not too low and the
power requirements are not too high: ideal for this kind of
tube in a single-ended configuration. This was the genesis
of a new preamp.
We combine the historic 300B with another classic, the
large octal based 6SL7GT, for the input stage- all triodes
running in pure Class A operation. To complement this
'retro' feel, we implemented vacuum tube rectification and regulation
in the power supply along
with plenty of capacity. We also developed an additional
(and innovative) ripple rejection circuit to filter out
power supply noise making this an incredibly low-noise
preamplifier- especially critical for headphone users.
Complementing this lovely and rich sounding line-driver is a
motorised ALPS audiophile volume control, gold plated
RCA connectors, high purity silver wire, mil-spec printed circuit boards with extra thick
copper and plating, and custom designed output transformers
which we wind right here in our own magnetics department. It
all adds up...
For 2002, we returned to our classic and elegant
"Manley-Blue" pewter grey color and the chassis was reworked to
accommodate a few updates we had in mind.
In late 2008 we added the fantastic REMORA Radio Frequency Remote
Control for the volume up/down functions.
Whether you use
headphones or loudspeakers this preamp will deliver the
goods and spoil you for any other preamplifier.
otes for current version
not covered in the manual:
The transformer switch puts the output transformer in or out of
circuit. You HAVE TO have it switched to "IN" to use the
headphone jacks. It is recommended, in the spirit of "less is
more", to switch to "OUT" when using the main line
outputs.
The SUB out is a post-volume control output which can be used to drive
a powered subwoofer unit so that the level of the subwoofer follows
the volume level of the preamplifier.
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Features and
Specifications for the Manley 300B
Preamplifier
- Inputs: 5 stereo pair unbalanced
RCA jacks
- Outputs: 2 stereo pairs MAIN out
same as SUB out unbalanced RCA jacks
- RECORD output: 1 stereo pair
pre-volume control unbalanced RCA jacks
- HEADPHONE Outs: 2 front panel
1/4" headphone jacks
- Optimized headphone impedance switching: 30-400 ohms
to 300-4000 ohms
- MUTE: Selecting HEADPHONE operation mutes LlNE outputs
- Output Vacuum Tubes: 2 x 300B
Electro-Harmonix
- Input Tubes: 2 x 6SL7GT Electro-Harmonix
- Rectifier Tubes: 2 x 5U4GBEH
Electro-Harmonix or 5AR4 China (Do NOT use the Sovtek 5AR4!)
- Regulator Tubes: 2 x OD3 NOS
JAN USA
- Gain: factory set at 12 dB at max Volume
- Internal Variable Feedback: 8.5 dB
of global NFB is used @ 12 dB of gain, adjustable trim -1.7dB to
+1dB
- Noise Floor: typically -70 dB (1 Hz - 100 KHz)
- S/N Ratio: typically 105 dB (A WGT, 20 Hz - 20 KHz)
- Frequency Response: 5 Hz to 50 KHz
±1dB
- Channel-to-Channel Separation (L to R):
@1KHz 48 dB; @10KHz 35 dB; @20KHz 34 dB
- Channel-to-Channel Separation (R to L): @1KHz
50 dB; @10KHz 40 dB; @20KHz 37 dB
- THD: 0.08 % @ 1KHz at 1V rms out
- Distortion THD+N: -80 dB (.01 %) zero "crossover"
distortion, mostly 2nd harmonic
- Input Sensitivity: 250mV (-9.8dBu) yields 1V out
- Input Impedance: 100 Kohm Noble
volume control
- Maximum Input Level: 5.5dBu or 1.459 Vrms @ 1KHz, volume control
at maximum
- Output Impedance (LINE STAGE): 100 ohms
- Maximum Output Level: 17.2dBu or 5.636 Vrms @ 1KHz, volume
control at maximum
- Output Power (100 ohm Headphones): 1W (10 V RMS) (28
V P-P)
- Output Power (600 ohm Headphones): 1W( 25 V RMS) (70
V P-P)
- REMORA REMOTE: controls motorised
volume control UP/Down; uses 9V battery
- Power Consumption: 170 Watts (1.4 A @ 120VAC)
- Operating Mains Voltage: Factory set for 100V, 120V or 220-240VAC operation for
original destination country's mains voltage.
- Operating Mains Voltage: changeable
with power transformer re-wiring and fuse value change.
- Mains Voltage Frequency: 50~ 60Hz
- Dimensions: W=19" x
L=13" x H=11"
- Shipping Weight: 28 Ibs.
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The Gutz of the 300B Preamp on the QC bench running through a battery
of tests before burn-in.
We no longer use the stepped attenuator and have since
switched to a motorised ALPS remote. The Remora circuitry is not
in this photo.
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