The Manley Reference 350 watt monoblocks were built at the old VTL factory back before the Manley-VTL split-up that took place in 1993. They were at the time Manley's second-to-largest models in the Designer's Reference Series. They were 8-output tube designs. The 350's were usually ultra-linear configured (although some units were fitted with triode-tetrode switching) and used either GE 6550A's before 1990 or KT90's after 1990. The Input tube was always the 12AT7A or 6201. Some early models used the 12BH7A for driver tube although most of the actual production models used 6350 driver tubes. Those two tube types have the grids and cathodes swapped on the pinout so make a big note that the 6350 and the 12BH7A are NOT interchangeable without reworking the circuit board! Flanking the driver tube there were two additional readout test points and an additional trimpot for the driver AC balance adjust. See below for picture of how to set this.

The earliest units had yellow power switches and black transformer hats. Lower serial number also indicates age...usually, there is a date written on the power transformer bobbin inside the unit.

Manley 350's had a sheet-metal chassis and stainless-steel covers. Cool features of these amplifiers included the adjustable "slope" and "feedback" controls that allow the user to select different feedback capacitive and resistive values respectively. Here's an explanation about what Variable Feedback (resistive) is all about. Changing the capacitor in the feedback loop changes where the high frequency rolloff of the amplifier starts. Bigger capacitor will make the amplifier's super-sonic roll off earlier. Also handy were the front panel mounted bias readout tipjacks and tube readout selector even though one still had to address the top deck of the amplifier to make the actual bias adjustments. Many of the later Manley 350's had MIT-Multicaps. And some of them even had TRIODE / TETRODE switches.

We still do perform warranty service on these old monsters, so if you need help with yours, please get in touch.




  • Output 8 x 6550 (before 1990) or KT90 (1990-1993)

  • Driver 6350

  • Input l x 12AT7WA

  • Input sensitivity for full power, feedback set at:

  • MAX 1.8 Vrms

  • STANDARD 1.44 Vrms

  • MIN 1.2 Vrms

  • Input Impedance: 82 kOhm

  • Output load impedance: Factory set for 5 Ohms nominal

  • RCA Unbalanced input

  • Power Output: 380W 3%T.H.D. feedback MAXIMUM

  • 376W 3%T.H.D. feedback STANDARD

  • 360W 3%T.H.D. feedback MINIMUM

  • Front Panel bias measurement with Top Deck Bias adjust

  • Variable Feedback 3-position switch

  • Variable SLOPE: 20 KHz, (Ref. to 0dB @ 1K)

  • +1 dB slope MINIMUM

  • +0.97 dB slope STANDARD

  • +0.88 dB slope MAXIMUM

  • Mercury Magnetics power & output transformers

  • S/N ratio: better than -90 dB

Specifications subject to change because they just might.

  • Power consumption: enough to occasionally trip circuit breakers on turn-on

  • 300 W Quiescent

  • 900 W Full Power

  • Large filter / reservoir capacitors

  • 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:

  • Mains fuse: 120v operation use 10A SLO-BLO; 220v use 5A SLO-BLO

  • B+ fuse use 1.5A SLO-BLO

  • Dimensions: bigger than a bread box: W=19, D=10, H=8.5 inches

  • Shipping weight: more than I can lift, about 80 lbs