A magazine reviewer once wrote the following about the Manley 250's: "In triode mode a pair of Manleys produces a remarkably three dimensional soundfield that is both convincing and seductive. When switched into tetrode mode, the Manleys have the brawn to deliver a full symphony orchestra directly into your living room." "When I listened through the same cut through the triode mode tube amps, I cried. Yup, tears ran down my cheeks while I bounced up and down, waving my arms, physically buffeted by the raw emotion of the music. Emotion- that essential component at the very core of great music. The Manleys pass through that emotional information, but the (solid-state amps) don't." Tried and true: The Manley 500 and 250 Watt Monoblocks are our most powerful push-pull production-models. Both the circuit design and the selected componentry have been refined over years and years of development. Reliability that you can depend upon combined with musical accuracy and emotional authority is what these amplifiers promise- and deliver. They are able to switch operation modes allowing the listener to choose between the sonically seductive qualities of triode and the more powerful Ultra-Linear configuration. We use big, beefy reservoir capacitors in the high voltage supplies giving plenty of instant energy for dynamic performance of transient peaks and bass impact and weight which often exceeds that of rival solid-state amplifiers. We run high voltages on the plates of the output tubes but operate them at lower current which will result in their longer life. Although each output tube has its own bias-adjust, We carefully fit each amplifier with computer-batched tubes for optimum performance. The bias adjustment pots and measuring points are conveniently located behind the oval front panel insert.
To avoid a heavy power drain when the cold amplifier is first switched on, we conceived a "Soft-Start" mode which also functions as an "Ever-Warm" position allowing the amplifiers to be always warmed up for pleasurable listening. Each amplifier only consumes 30 watts of power in Ever-Warm mode. A blinking green LED reminds the user that the amplifier is in warm-up mode because as all the power supplies are at half-voltage, the amplifier will still operate at half power when the Ever-Warm mode is engaged, so the user should use the MUTE switch when in this mode.
The front-panel mute switch and angled-back chassis make it easier to hook up the interconnects, speaker cables, and IEC power cord.
In our own in-house magnetics department, our R&D team completely redesigned all of our output transformers in 1998 with the goal to reclaim that luscious rich mid-range of our vintage designs. In 2013 we reworked the output transformer to operate the output stage in Ultra-Linear mode which is a great sounding balance between the detail of triode and the brawn of Tetrode. We also specifically set out to achieve a deeper bottom register at higher power with lower distortion. Hours and hours of listening tests, measurements, and fine-tuning brought an exciting and stunning result to our ears. We hope you will agree.
ALL-TUBE monoblock design: uses 10 x Tungsol EL34B output tubes
Driver Stage: High current double 12BH7EH (x2) Electro-Harmonix Russian
Input Tube: Tungsol 12AT7 large plate
BALANCED & UNBALANCED inputs: RCA and XLR jacks (switchable)
MUTE switch: on front panel
TRIODE / Ultra-Linear output mode switching: on front panel
SOFT-START turn on mode: minimizes in-rush current by first powering up amplifier to half voltages
EVER-WARM mode: for standby keeps tubes warmed up at half voltages
MANLEY Precision Output Transformer: designed and wound at Manley Labs
Front panel bias measurement and adjust: Concealed under the black oval insert
Output Tube Standing Current: 27.5mA
Set Bias for: 275mVDC measured across each bias tip jack to ground
Large filter / reservoir capacitors: 3800uF x 2
Angled rear of chassis: provides for easy connections
WBT binding posts: CE compliant for European models
Input Sensitivity RCA: Triode = 1.637 V, Tetrode = 1.837 V for full power
Input Sensitivity XLR: Triode = 3.2 V, Tetrode = 3.6 V for full power
Input Sensitivity Triode: 174mV for 1 watt into 8 Ohms
Input Sensitivity Tetrode: 146mV for 1 watt into 8 Ohms
Gain Triode: 30dB
Gain Tetrode: 32dB
Input Impedance RCA: 116 kOhm @ 1KHz
Input Impedance XLR: 270 kOhm @ 1KHz; 20 kOhms @ 20KHz; 38 kOhm @ 20Hz
Actual Output Impedance Triode: 0.538 Ohm
Actual Output Impedance Tetrode: 0.465 Ohm
Optimum Speaker Load: 5 Ohms
Damping Factor Triode: 14.8
Damping Factor Tetrode: 17.2
S/N Ratio Ref 1W into 8 Ohms: -80 dB; -90dB A-WGT
Dynamic Range: 93dB
FLAT frequency response: 10 Hz - 30 KHz continuous
Full Power Tetrode: 250W @ 1.5% THD into 5 Ohms
Full Power Triode: 100W @ 1.5% THD into 5 Ohms
Power Consumption: 30 Watts in "EVER-WARM" mode
Maximum Power Consumption: 815 Watts at full power
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:
Mains Fuse 100-120VAC operation: MDA 10 Amp SLO-BLO Ceramic Time-Delay fuse
Mains Fuse 220-240VAC operation: MDA 8 Amp SLO-BLO Ceramic Time-Delay fuse
B+ Fuse: MDA 1 1/2A SLO-BLO Ceramic Time-Delay fuse
Badge Illumination: Units produced before 4/2003 use 8V, 0.3A "Fuse-Lamp" 1/4" X 1 1/4"
- Serial numbers after N250188 use LED illumination which probably won't burn out
Power Cord: Detachable IEC standard. Appropriate power cord supplied for destination country
Unit Dimensions: W=19" x D=13" x H=9" each
Unit Weight: 68 Lbs. each
Shipping Weight: 73 Lbs. each