Aphex 1100MKII Class A 2 Channel Tube Mic Preamp

APHEX 1100MKII Details ^top

This superbly crafted new breed of advanced tube microphone preamp reaches far beyond mere technical excellence to deliver sound that is uniquely involving, compelling, and real. Our incredible new 2 channel Model 1100 gives you up to 20 dB more headroom than conventional preamps, allowing you to record hotter tracks with the highest possible digital resolution. This unprecedented amount of headroom, combined with an EIN of -135 dBu, allows you to take more gain without the pain of overload distortion or noise.

MORE GAIN - NO PAIN
To achieve this amazing performance, we developed new proprietary circuitry:
Discrete Class A Bipolar PNP Solid State Front End
Second Stage Reflected Plate Amplifier™ Tube Circuit
Sweepable Low Frequency Cancellation Filter (LoCaf™)
MicLim™ Limiter on the microphone input itself makes the 1100 virtually crashproof
Drift Stabilized™ A/D Circuitry eliminates the need for high pass filtering in the digital domain
Third stage Reflected Plate Amplifier Tube Circuit Discrete Class A Impedance Balanced Output Stage
Compare this to any other mic preamp — you'll understand the benefits of 'More Gain with No Pain'.

MORE REASONS THIS IS A GREAT PREAMP
Front panel peak headroom meter and function controls
Precision three-turn output level attenuator
Full featured AES/EBU digital audio output
Noiseless muting via rear panel Mute Jack
Ramped 48-volt phantom power circuit
Linear, internal low-noise power supply
20dB pad and Phase Reverse are switched by bifurcated gold-contact relays

THE PATH TO MORE GAIN
MicLim™ CIRCUIT
A custom designed optical attenuator, located directly on the mic input line, smoothly limits the microphone's output signal according to the MicLim peak detector's control current. Since attenuation comes prior to preamplification, the proprietary MicLim can increase the Model 1100's effective headroom by typically 15 dB. MicLim detects the preamplifier's output signal and instructs the input attenuator to proportionately reduce the microphone's output level just enough to prevent clipping. MicLim has no effect at all when the preamplifier's output level is not approaching clipping. NOW WITH A NEW IMPEDANCE SELECTOR for use with microphones with low output (source) impedance.

Tunable, low-cut servo filter — LoCaf™
This unusual design meshes a tunable second order (12 dB/octave) low-cut filter into the nodal intersections of the first and second amplifying stages in a so-called "servo" configuration. This servo affects only the frequencies below the low-cut corner frequency, contributing nothing to the audible signal. Imposing the servo filter in such a manner gives the preamp about 20 dB more overload headroom in the low-cut range compared to conventional techniques. Additionally, the added subsonic headroom afforded by the low-cut servo filter eliminates the need for MicLim to respond to subsonic signals, eliminating the undesirable effect of limiting the input signal in response to excessive subsonic energy. The low-cut shape follows a Butterworth response slightly modified to improve the transitional phase.

Tube, discrete Class-A differential second stage
The unique, Aphex patented "Reflected Plate Amplifier" tube circuit is configured as a single-triode differential opamp to further enhance the preamplifier's common-mode rejection. This novel circuit topology subtly imparts the tube's sonic warmth and character while retaining a long and stable operating life.

Ultra low noise, transformerless, discrete Class-A, bipolar PNP, variable gain, differential input stage
No outer feedback is used, eliminating the possibility of any dynamic interaction with the microphone's self-impedance. The input impedance remains passive, providing an optimal load for any microphone. The solid state, Class-A PNP bipolar design achieves high common-mode rejection with extremely low noise, wide bandwidth, and low distortion at all gain settings. Robust input overload protection assures that all performance features will be ratained indefinitely. The gain is adjustable in 4dB precision steps from 21 to 65 dB.

Series-Shunt, optical soft-mute attenuator
The second-stage output signal passes through a specialized series-shunt optocoupler circuit to provide a soft mute without adding distortion or noise.

Tube, discrete Class-A output stage
An Aphex petented "Reflected Plate Amplifier" tube circuit is configured as a low distortion triode buffer having a very low output impedance and high output current drive. The maximum output level of +27 dBu into 600 ohms meets the needs of any professional application. Matched-impedance balancing assures top performance whether driving balanced or unbalanced lines. A rear panel switch is assigned to insert a 12 dB low impedance pad into the output line for systems based on IHF (semi-pro) operating levels. Rear panel XLR 3-pin and 1/4 inch phone jacks are both provided for balanced output.


ABOUT THE DIGITAL SECTION
The A/D converter receives signal from the soft mute stage just prior to the analog output level control and triode output stage. This means you can use BOTH the digital and analog outputs independently, with full and proper calibration of both regardless of the analog output level settings. The analog and digital outputs respond equally to the input gain, low-cut filter, and all front end conditioning effects.

METERING
Each channel contains a 20-segment LED headroom meter, making it easy to optimize the performance of the preamplifier. The headroom meter is calibrated in decibels below clipping, where 0 dB is the analog clipping point. This coincides with the A/D converter's maximum input level, so the headroom meter also indicates the digital audio level accurately. Each channel contains its own independent controls over every function.

APHEX 1100MKII Specs ^top

- Aphex Model 1100MkII - Class A Tube Mic Preamp NEW FEATURES !
ANALOG AUDIO
EIN Gain = 65dB, input shorted, BW = 100Hz to 22kHz, EIN = -135dBu
Mute Function Optical soft switch, greater than 70 dB of attenuation
Low Cut Filter frequencies Off, 30, 36, 44, 53, 63, 77, 92, 111, 134, 162, 195 Hz
Low Cut Filter Type Second order Butterworth servo cancellaton technique - LoCaf™
Phantom Voltage +48VDC (can withstand a short curcuit to ground on both mic jacks indefinitely
Phantom build-out resistances 6.81k ohms to pins 2 and 3
Phantom ramp-Up/Down Slow ramp approx 5 seconds - eliminates turn on/off "thumps"
Preamp Gain 21 dB to 65 dB in 4 dB steps
Output match trim 3-turn precision potentiometer 0 to -12dB range
Maximum Output Level (MOL) +27 dBu unloaded; +25 dBu into 600 ohms
Maximum Input Level (MIL) +27 dBu minus preamp gain value plus pad value
THD Output level = +15 dBu, 0.09%; output level = +4dBu, 0.05%
IMD Output level = +15 dBu, 0.12%; output level = +4dBu, 0.08%
DIM Below noise floor at all possible measurement levels
Slew Rate 22V/usec
Analog Dynamic Range 97 dB to 101 dB depending upon preamp gain setting
Analog Output Noise -70 dBu to -74 dBu depending upon preamp gain setting
Analog Signal / Noise Ratio (SNR) 76 dB typical for ref level = +4dBu
DIGITAL AUDIO
Output Resolution 24 Bits
Output Sample Rate NEW 44.1, 48, 88.2, 96, 196 kHz selectable
Clock Source Internal low jitter crystal, external word clock, or external AES/EBU clock
any outside source up to 192kHz
Digital SNR 98 dB typical for ref level = 0dB(fs)
Digital SNR 80 dB typical for ref level = -18dB(fs)
FRONT PANEL CONTROLS
Preamp Gain (each channel) 21, 25, 29, 33, 37, 41, 45, 49, 53, 57, 61, 65 dB, switched
Low Cut Frequency (each channel) Off, 30, 36, 44, 53, 63, 77, 92, 111, 134, 162, 195 Hz switched
Line Output Calibration (each channel) 3-turn precision potentiometer 0 to -12 dB range
20 dB pad (each channel) on / off (switched by bifurcated gold contact relays immune
to noise, distortion, and dry contact diode effects)

Polarity (each channel) positive / negative
Test Tone (each channel) on / off
Phantom (each channel) on / off
Mute (each channel) on / off
MicLim™ (each channel) on / off
Clock Source NEW Internal / External - any source up to 192kHz
Internal Rate 44.1 / 48 / 96 kHz
Power on / off
REAR PANEL CONTROLS
Line Output Normal +4 dBu / -10dBv switch
Mute Jack Switchable via front panel pushbutton, or by a remote switch plugged in
OTHER SPECIFICATIONS
Power requirements NEW Universal Power Supply : 80 to 280 Volts 50-60 Hz 35 Watts
Dimensions 19"W x 1.75"H x 9" D 1 Rack U (482.6mm x 44.5mm x 228.6mm)
Front Panel Projections .75" max (19 mm)
Net Weight 8.2 lbs (3.73 kg)
Shipping Weight 10 lbs (4.5 kg)