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
FREQUENTLY ASKED QUESTIONS
What tubes should I get for my Manley 250's?
If you are retubing, we would suggest the stock original tubes; you can order a complete matched set on our webstore. For the output tubes, we use the Tungsol EL34B. For drivers we use EH 12BH7s. The 12AT7 input tube is very common, and we use the Tungsol version here. We are personally a little afraid of untested "new old stock" tubes at high prices. There may be a reason they have been kicking around for 30 years. And also as we run each and every tube we put in all of our gear through a battery of noise, operation, gain, and matching tests and purposefully select every tube specifically for best performance in that specific product and circuit, we think we are putting the very best tubes in Manley gear that we can possibly put in there.