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300B Preamplifier
Introducing our most esoteric product, the 300B Preamplifier. As the first and only preamp to feature the classic 300B tubes, this device represents the pinnacle of audio innovation. Having designed 300B into small power amps for years, we have always admired the smooth, natural sound of this tube. The 300B provides optimal power and voltage swing for headphones and serves as an exceptional line driver, making it ideal for single-ended configurations.
Our design combines the historic 300B with another classic, the octal-based 6SL7GT, in the input stage. All triodes run in pure Class A operation, delivering unmatched audio clarity. To enhance this retro feel, we implemented vacuum tube rectification and regulation in the power supply, along with ample capacity. An innovative ripple rejection circuit filters out power supply noise, resulting in an incredibly low-noise preamplifier, perfect for headphone users.
The 300B Preamplifier features an ALPS audiophile volume control, gold-plated RCA connectors, high-purity silver wire, mil-spec printed circuit boards with extra thick copper plating, and custom-designed output transformers crafted in our own magnetics department.
For 2002, we reintroduced our classic "Manley-Blue" pewter grey color and updated the chassis for enhanced functionality. Whether you use headphones or loudspeakers, this preamp delivers unparalleled performance, setting a new standard for audio quality.
Notes for Current Version:
- Transformer Switch: Ensure the switch is set to "IN" to use the headphone jacks. For main line outputs, switch to "OUT" for optimal performance.
- SUB Out: This post-volume control output drives a powered subwoofer, matching its level with the preamplifier's volume.
This is a refined version of the 300B Preamplifier, originally produced from 1996 to 1999, now enhanced for superior audio enjoyment.
Manley Labs 300B PREAMPLIFIER
Basic Specifications
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)
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:
Dimensions:
W=19". L=13". H=11"
Shipping Weight:
28 Ibs.
Specifications to change because they just might.