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Manley Labs Neo-Classic 300B Line Preamp

1 Review

Neo-Classic 300B Line Preamp

Our most esoteric product is THE 300B PREAMPLlFIER. This is the first and only preamp to feature these classic tubes. 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 the 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...
  • 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
  • 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: changeable with power transformer re-wiring and fuse value change.
  • Mains Voltage Frequency: 50~ 60Hz
  • Dimensions: W=19". L=13". H=3 1/2"
  • Shipping Weight: 28 Ibs.
  • Ratings & Reviews

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    Once the unit was in place and the tubes inserted (nice touch to have numbered orange dots on the tubes and the appropriate sockets so no mistakes could be made) along with the well written and humorous user manual, I was ready to fire it up. This is my first piece of Manley gear and besides being well built there is just something about the look of this unit maybe retro or classic yet elegant – can’t quite put my finger on it. I had to place it on the top of one my equipment racks as this unit generates some serious heat, but then again why would one want to hide all those beautiful glowing tubes? Associated equipment a pair of Quicksilver Horn Mono Blocks and a pair of Klipsch La Scala II, yes I know horn loaded speakers so all the audiophiles can dismiss this review since I obviously have no ears. I believe some of the controversy of horn speakers involves equipment pairing and the type of music one listens too but that’s a story for another day. Digital is an Oppo, turntables Project Xtension 10 and a VPI Aries 3. This unit replaced a BAT VK3si that I have had for years and I do consider it a very good preamp. I was concerned about noise, but this turned out to be unfounded as the Manley was dead quiet. I principally listen to vinyl but usually warm things up with some CD’s. I found with the Manley that I was actually enjoying the CD’s for a change the Manley was bringing the best out of that format. With vinyl the first thing that struck me was the soundstage being very deep, huge filling the room. The different instruments were clearly placed and detailed. There was a new found clarity a very natural direct presentation. I found the hi frequencies to be soft with a gorgeous mid-range and nice controlled tight bass. Overall I have found myself listening to more and more music with no fatigue truly a wonderful sounding piece of equipment. I am still running the stock tubes and in direct mode, but I do have some replacements waiting to roll into place at some point.