Radio Design Labs HD-MA35U
35 Watt Mixer Amplifier - 4/8 Ohm Outputs

OUR PART #  HD-MA35U


The Radio Design Labs HD-MA35U is a four input audio mixer amplifier for systems demanding the broadest range of features and the highest energy efficiency. Two output power amplifier zones, 35 watts (Zone 1) and 4 watts (Zone 2), are driven from high-efficiency Class D amplifier stages. The mixer and amplifier sections all normally shut down (standby “sleep” mode) when audio is absent and automatically turn on when needed. The Zone 1 amplifier output level may be VCA controlled using various optional RDL remote controls, or by industry standard 0 to 10 Vdc or 0 to 10k ohm controls. This output drives 4 ohm or 8 ohm speakers. The output impedance is switch-selectable on the rear panel. The Zone 2 amplifier output drives an 8 ohm speaker and/or 600 ohm telephone equipment.

The HD-MA35U has four inputs that are common to both mixers. Inputs 1 and 2 accept balanced mic or line level sources. Inputs 3 and 4 accept unbalanced mono or stereo line-level sources.

  • Input 1 is switch-selectable MIC or LINE. Phantom voltage (IEC standard 24 Vdc) is switch-selectable for the microphone input. The line input is transformer isolated and accepts balanced or unbalanced, high or low impedance audio sources. A gain trimmer is provided to set the input preamplifier to the optimum gain for the installation.
  • A paging source is normally connected to Input 1. This input is equipped with push-to-talk terminals and with an adjustable threshold VOX circuit with LED threshold indicator, either (or both) of which may be set to duck (“fade down” or “mute”) inputs 2, 3 and/or 4 by 25 dB when a paging signal is active on Input 1. The attenuated inputs fade up to normal volume when the paging message is finished. A rear-panel trimmer allows the start of the fade-up to be delayed from 2 to 6 seconds.
  • Input 2 is switch-selectable MIC or LINE. Phantom voltage (IEC standard 24 Vdc) is switch-selectable for the microphone input. The line input is active balanced and accepts balanced or unbalanced, high or low impedance sources. A gain trimmer is provided to set the input preamplifier to the optimum gain for the installation.
  • An RDL Dual-LED VU meter is provided on the rear panel to indicate proper gain adjustment for Inputs 1 and 2. Correct input gain adjustment insures adequate mixer stage headroom.
  • Inputs 3 and 4 each provide unbalanced stereo RCA input jacks, summed to mono.

RDL HD-MA35U Features:

  • Four inputs with individual front-panel volume controls
  • Bass and Treble tone controls
  • Designed for background music with paging and music-on-hold
  • Master volume VCA controlled with remote adjustment capability
  • Manual or automatic (VOX) priority ducking
  • Balanced inputs and amplified outputs on detachable terminal blocks
  • Unbalanced inputs and outputs on RCA jacks
  • Includes power supply
  • Automatic sleep mode meets strictest energy saving standards

RDL HD-MA35U Specifications:

  • Amplifier Zones (2):
    • Zone 1 (Main): 35 W RMS, front-panel mixer (user controls)
    • Zone 2: 4 W RMS (8 Ohms), rear-panel mixer (trimmers)
  • Audio Inputs (5):
    • 2, balanced, mic or line switch selectable on terminal blocks
    • 2, unbalanced stereo summing inputs on RCA jacks
    • 1, unbalanced amp in on RCA jack
  • Gain Adjustments (2): Inputs 1 and 2: Rear-panel single-turn trimmer
  • Maximum Input Level:
    • Mic Inputs: -9 dBu
    • Balanced line inputs: + 20 dBu
    • Unbalanced Inputs: + 5 dBV (+11 dBV, one input)(for 1% THD+N at output)
  • Phantom Voltage: 24 Vdc (IEC 61938: 2013), switch-selectable for each mic input
  • Ducking/Muting Actuation: Automatic (Input 1 VOX: rear-panel adjustable signal threshold with LED indicator) or Manual (contact closure to ground)
  • Ducking/Muting Release Delay: Rear-panel single-turn trimmer, adjustable 2 to 6 seconds
  • Ducking/Muting: Switch-selectable for inputs 2, 3 and/or 4, 25 dB ducking attenuation, nominal
  • Effects Loop: Unbalanced RCA jacks (preamp output from main mixer, input to power amplifier)
  • External RDL Module Power Output: 24 Vdc, 100 mA maximum, ground-referenced
  • Input level (to cross compressor threshold equaling 23 W amplified output):
    • Mic Inputs: -50 dBu (2.5 mV), (front panel and rear trimmer at max.)
    • Balanced line inputs: -21 dBu (70 mV), (front panel and rear trimmer at max.)
    • Unbalanced Inputs: -15 dBV (180 mV), (front panel and rear trimmer at max., both inputs driven)
  • Noise (line or amplified outputs): 
    • Mic or Balanced line inputs: -70 dB (below compressor threshold at max gain)
    • Unbalanced Inputs: <-75 dB (max gain)
  • THD+N: < 0.5% (1 kHz at compressor threshold, main amp output); < 0.1% (line output, main)
  • CMRR:
    • Mic inputs: > 50 dB (50 Hz to 120 Hz)
    • Balanced line inputs: > 80 dB (50 Hz to 120 Hz, transformer-coupled input)
  • Compressor: Threshold 2 dB below rated output, automatically adjusting attack and release times
  • Frequency Response (mixer):
    • Mic to line output: ±1.5 dB (40 Hz to 25 kHz)
    • Balanced line input to line output: ±1 dB (20 Hz to 20 kHz)
    • Unbalanced line input to line output: ±0.5 dB (20 Hz to 20 kHz)
  • Frequency Response (amplifiers): ± 1 dB (50 Hz to 20 kHz)
  • Tone Controls: ±10 dB @ 10 kHz, ±9 dB @ 100 Hz (front-panel) with center detent
  • Audio Outputs (2): -10 dBV nominal (316 mV), dual mono unbalanced RCA (main mixer; FLAT or EQUALIZED, switch selectable on rear panel); 0 dBu nominal balanced, terminal block (zone 2 mixer)
  • MOH Output: 0 dBu nominal (775 mV), 600 Ohm transformer-isolated, 16 dB headroom
  • Power Amplifier Outputs (2):
    • Zone 1 (main, <1% THD+N): 35 W RMS (4 Ohms), 32 W (8 Ohms) on detachable terminal block (switch-selectable 4 or 8 Ohm impedance)
    • Zone 2: 4 W (8 Ohms, on detachable terminal block)
  • Indicators (9):
    • Front-panel: Signal present (4; 1 per input, green), Compressor activity (red), Power (bright=on, dim=standby, blue)
    • Rear-panel: dual-LED VU meter (for inputs 1 and 2, green/red), Ducking/muting threshold (yellow)
  • VCA: Zone 1 (main) master level (with switch-selectable input 1 bypass), 0 to 10 Vdc control, RJ45 (compatible with RDL VCA wall controls)
  • Front-panel controls (7): Zone 1 (main) mixer level controls (4, inputs 1 through 4), EQ (2, bass and treble), Power (momentary pushbutton, toggle on/standby)
  • Rear-panel controls (22): Gain trimmers (2, input 1 and 2), Mic/Line switch (2, input 1 and 2), Zone 1 line output pre/post-EQ switch, Effects loop bypass switch, Sleep (standby) mode delay (4 binary switches), Input 1 ducking/muting detector sensitivity trimmer, Phantom voltage switches (2, input 1 and 2), Ducking control switches (3, to duck inputs 2, 3, and/or 4), VCA paging bypass (includes or excludes input 1 from master VCA control), Zone 2 mixer level controls (4, inputs 1 through 4)
  • Efficiency Standard: “Energy Star® Program Requirements for Audio/Video” Version 2.0
  • Sleep Mode Power Consumption: < 1 W (amplifier and included power supply)
  • Sleep Mode Delay: 10 minutes to 2 hours (switch-selectable in 10 minute increments)
  • Sleep Mode Disable: Selectable
  • Active Mode Delay: 2 seconds (nominal) after input audio detected
  • Audio Detector Threshold: -80 dBu mic (at max input gain), -55 dBu balanced line (at max input gain), -42 dBV unbalanced
  • Ambient Operating Environment: 0° C to 50° C Maximum; 20° C Recommended
  • Power Supply (included): 100 to 240 Vac, 50-60 Hz, 50 W; 24 Vdc output to amplifier chassis
  • Dimensions (HxWxD): 3.5" x 8.5" x 10" (8.89 x 21.6 25.4 cm)
  • Weight: 5.6 lb.(2.5 kg)
  • Package Type: Cardboard Box
  • Package Dimensions: 17.75" x 9.125" x 3.9375"
  • Shipping Weight: 8.105 lbs.
  • WEEE weight: 6.395 lbs.
  • Tariff code: 8518.50.0000
10.4" Rack Mount for HD Series Products
Radio Design Labs HD-HRA1 10.4" Rack Mount for HD Series Products
RDL's HD-HRA1 mounts one RDL HD series product. Mixer amplifiers may be mounted forward for user control, or may be recessed securely behind a filler panel (sold separately). This adapter fits 10.4" racks.

Usually ships in 7-14 business days.
Need it sooner? Call us!
HD Series Filler Panel with Lens
Radio Design Labs HD-FP2L HD Series Filler Panel with Lens
RDL's HD-FP2L mounts in front of an HD series product to allow viewing while preventing user adjustment or tampering. Lens is removable during setup.

Usually ships in 7-14 business days.
Need it sooner? Call us!
HD Series Amplifier Rear Cover
Radio Design Labs HD-BP1 Back-Pack HD Series Amplifier Rear Cover
RDL's HD-BP1 back-pack mounts to an RDL HD series mixer/amplifier to prevent user access to the rear panel. The back-pack holds the power supply and provides a completely closed back for the installed amplifier.

Usually ships in 7-14 business days.
Need it sooner? Call us!
HD Series Filler Panel
Radio Design Labs HD-FP1 HD Series Filler Panel
RDL's HD-FP1 fills an unused half of a rack adapter or mounts in front of an RDL HD series product to prevent user adjustment or tampering.

Usually ships in 7-14 business days.
Need it sooner? Call us!
HD Series Amplifier Security Cover
Radio Design Labs HD-ASC1 HD Series Amplifier Security Cover
RDL's HD-ASC1 mounts to an RDL HD series mixer/amplifier to prevent user adjustment or tampering. The power button and associated indicators remain accessible with the HD-ASC1 installed.

Usually ships in 7-14 business days.
Need it sooner? Call us!

Radio Design Labs HD-MA35U
35 Watt Mixer Amplifier - 4/8 Ohm Outputs

OUR PART #  HD-MA35U

Product Information:

The Radio Design Labs HD-MA35U is a four input audio mixer amplifier for systems demanding the broadest range of features and the highest energy efficiency. Two output power amplifier zones, 35 watts (Zone 1) and 4 watts (Zone 2), are driven from high-efficiency Class D amplifier stages. The mixer and amplifier sections all normally shut down (standby “sleep” mode) when audio is absent and automatically turn on when needed. The Zone 1 amplifier output level may be VCA controlled using various optional RDL remote controls, or by industry standard 0 to 10 Vdc or 0 to 10k ohm controls. This output drives 4 ohm or 8 ohm speakers. The output impedance is switch-selectable on the rear panel. The Zone 2 amplifier output drives an 8 ohm speaker and/or 600 ohm telephone equipment.

The HD-MA35U has four inputs that are common to both mixers. Inputs 1 and 2 accept balanced mic or line level sources. Inputs 3 and 4 accept unbalanced mono or stereo line-level sources.

  • Input 1 is switch-selectable MIC or LINE. Phantom voltage (IEC standard 24 Vdc) is switch-selectable for the microphone input. The line input is transformer isolated and accepts balanced or unbalanced, high or low impedance audio sources. A gain trimmer is provided to set the input preamplifier to the optimum gain for the installation.
  • A paging source is normally connected to Input 1. This input is equipped with push-to-talk terminals and with an adjustable threshold VOX circuit with LED threshold indicator, either (or both) of which may be set to duck (“fade down” or “mute”) inputs 2, 3 and/or 4 by 25 dB when a paging signal is active on Input 1. The attenuated inputs fade up to normal volume when the paging message is finished. A rear-panel trimmer allows the start of the fade-up to be delayed from 2 to 6 seconds.
  • Input 2 is switch-selectable MIC or LINE. Phantom voltage (IEC standard 24 Vdc) is switch-selectable for the microphone input. The line input is active balanced and accepts balanced or unbalanced, high or low impedance sources. A gain trimmer is provided to set the input preamplifier to the optimum gain for the installation.
  • An RDL Dual-LED VU meter is provided on the rear panel to indicate proper gain adjustment for Inputs 1 and 2. Correct input gain adjustment insures adequate mixer stage headroom.
  • Inputs 3 and 4 each provide unbalanced stereo RCA input jacks, summed to mono.

RDL HD-MA35U Features:

  • Four inputs with individual front-panel volume controls
  • Bass and Treble tone controls
  • Designed for background music with paging and music-on-hold
  • Master volume VCA controlled with remote adjustment capability
  • Manual or automatic (VOX) priority ducking
  • Balanced inputs and amplified outputs on detachable terminal blocks
  • Unbalanced inputs and outputs on RCA jacks
  • Includes power supply
  • Automatic sleep mode meets strictest energy saving standards

RDL HD-MA35U Specifications:

  • Amplifier Zones (2):
    • Zone 1 (Main): 35 W RMS, front-panel mixer (user controls)
    • Zone 2: 4 W RMS (8 Ohms), rear-panel mixer (trimmers)
  • Audio Inputs (5):
    • 2, balanced, mic or line switch selectable on terminal blocks
    • 2, unbalanced stereo summing inputs on RCA jacks
    • 1, unbalanced amp in on RCA jack
  • Gain Adjustments (2): Inputs 1 and 2: Rear-panel single-turn trimmer
  • Maximum Input Level:
    • Mic Inputs: -9 dBu
    • Balanced line inputs: + 20 dBu
    • Unbalanced Inputs: + 5 dBV (+11 dBV, one input)(for 1% THD+N at output)
  • Phantom Voltage: 24 Vdc (IEC 61938: 2013), switch-selectable for each mic input
  • Ducking/Muting Actuation: Automatic (Input 1 VOX: rear-panel adjustable signal threshold with LED indicator) or Manual (contact closure to ground)
  • Ducking/Muting Release Delay: Rear-panel single-turn trimmer, adjustable 2 to 6 seconds
  • Ducking/Muting: Switch-selectable for inputs 2, 3 and/or 4, 25 dB ducking attenuation, nominal
  • Effects Loop: Unbalanced RCA jacks (preamp output from main mixer, input to power amplifier)
  • External RDL Module Power Output: 24 Vdc, 100 mA maximum, ground-referenced
  • Input level (to cross compressor threshold equaling 23 W amplified output):
    • Mic Inputs: -50 dBu (2.5 mV), (front panel and rear trimmer at max.)
    • Balanced line inputs: -21 dBu (70 mV), (front panel and rear trimmer at max.)
    • Unbalanced Inputs: -15 dBV (180 mV), (front panel and rear trimmer at max., both inputs driven)
  • Noise (line or amplified outputs): 
    • Mic or Balanced line inputs: -70 dB (below compressor threshold at max gain)
    • Unbalanced Inputs: <-75 dB (max gain)
  • THD+N: < 0.5% (1 kHz at compressor threshold, main amp output); < 0.1% (line output, main)
  • CMRR:
    • Mic inputs: > 50 dB (50 Hz to 120 Hz)
    • Balanced line inputs: > 80 dB (50 Hz to 120 Hz, transformer-coupled input)
  • Compressor: Threshold 2 dB below rated output, automatically adjusting attack and release times
  • Frequency Response (mixer):
    • Mic to line output: ±1.5 dB (40 Hz to 25 kHz)
    • Balanced line input to line output: ±1 dB (20 Hz to 20 kHz)
    • Unbalanced line input to line output: ±0.5 dB (20 Hz to 20 kHz)
  • Frequency Response (amplifiers): ± 1 dB (50 Hz to 20 kHz)
  • Tone Controls: ±10 dB @ 10 kHz, ±9 dB @ 100 Hz (front-panel) with center detent
  • Audio Outputs (2): -10 dBV nominal (316 mV), dual mono unbalanced RCA (main mixer; FLAT or EQUALIZED, switch selectable on rear panel); 0 dBu nominal balanced, terminal block (zone 2 mixer)
  • MOH Output: 0 dBu nominal (775 mV), 600 Ohm transformer-isolated, 16 dB headroom
  • Power Amplifier Outputs (2):
    • Zone 1 (main, <1% THD+N): 35 W RMS (4 Ohms), 32 W (8 Ohms) on detachable terminal block (switch-selectable 4 or 8 Ohm impedance)
    • Zone 2: 4 W (8 Ohms, on detachable terminal block)
  • Indicators (9):
    • Front-panel: Signal present (4; 1 per input, green), Compressor activity (red), Power (bright=on, dim=standby, blue)
    • Rear-panel: dual-LED VU meter (for inputs 1 and 2, green/red), Ducking/muting threshold (yellow)
  • VCA: Zone 1 (main) master level (with switch-selectable input 1 bypass), 0 to 10 Vdc control, RJ45 (compatible with RDL VCA wall controls)
  • Front-panel controls (7): Zone 1 (main) mixer level controls (4, inputs 1 through 4), EQ (2, bass and treble), Power (momentary pushbutton, toggle on/standby)
  • Rear-panel controls (22): Gain trimmers (2, input 1 and 2), Mic/Line switch (2, input 1 and 2), Zone 1 line output pre/post-EQ switch, Effects loop bypass switch, Sleep (standby) mode delay (4 binary switches), Input 1 ducking/muting detector sensitivity trimmer, Phantom voltage switches (2, input 1 and 2), Ducking control switches (3, to duck inputs 2, 3, and/or 4), VCA paging bypass (includes or excludes input 1 from master VCA control), Zone 2 mixer level controls (4, inputs 1 through 4)
  • Efficiency Standard: “Energy Star® Program Requirements for Audio/Video” Version 2.0
  • Sleep Mode Power Consumption: < 1 W (amplifier and included power supply)
  • Sleep Mode Delay: 10 minutes to 2 hours (switch-selectable in 10 minute increments)
  • Sleep Mode Disable: Selectable
  • Active Mode Delay: 2 seconds (nominal) after input audio detected
  • Audio Detector Threshold: -80 dBu mic (at max input gain), -55 dBu balanced line (at max input gain), -42 dBV unbalanced
  • Ambient Operating Environment: 0° C to 50° C Maximum; 20° C Recommended
  • Power Supply (included): 100 to 240 Vac, 50-60 Hz, 50 W; 24 Vdc output to amplifier chassis
  • Dimensions (HxWxD): 3.5" x 8.5" x 10" (8.89 x 21.6 25.4 cm)
  • Weight: 5.6 lb.(2.5 kg)
  • Package Type: Cardboard Box
  • Package Dimensions: 17.75" x 9.125" x 3.9375"
  • Shipping Weight: 8.105 lbs.
  • WEEE weight: 6.395 lbs.
  • Tariff code: 8518.50.0000
10.4" Rack Mount for HD Series Products
Radio Design Labs HD-HRA1 10.4" Rack Mount for HD Series Products
RDL's HD-HRA1 mounts one RDL HD series product. Mixer amplifiers may be mounted forward for user control, or may be recessed securely behind a filler panel (sold separately). This adapter fits 10.4" racks.

Usually ships in 7-14 business days.
Need it sooner? Call us!
HD Series Filler Panel with Lens
Radio Design Labs HD-FP2L HD Series Filler Panel with Lens
RDL's HD-FP2L mounts in front of an HD series product to allow viewing while preventing user adjustment or tampering. Lens is removable during setup.

Usually ships in 7-14 business days.
Need it sooner? Call us!
HD Series Amplifier Rear Cover
Radio Design Labs HD-BP1 Back-Pack HD Series Amplifier Rear Cover
RDL's HD-BP1 back-pack mounts to an RDL HD series mixer/amplifier to prevent user access to the rear panel. The back-pack holds the power supply and provides a completely closed back for the installed amplifier.

Usually ships in 7-14 business days.
Need it sooner? Call us!
HD Series Filler Panel
Radio Design Labs HD-FP1 HD Series Filler Panel
RDL's HD-FP1 fills an unused half of a rack adapter or mounts in front of an RDL HD series product to prevent user adjustment or tampering.

Usually ships in 7-14 business days.
Need it sooner? Call us!
HD Series Amplifier Security Cover
Radio Design Labs HD-ASC1 HD Series Amplifier Security Cover
RDL's HD-ASC1 mounts to an RDL HD series mixer/amplifier to prevent user adjustment or tampering. The power button and associated indicators remain accessible with the HD-ASC1 installed.

Usually ships in 7-14 business days.
Need it sooner? Call us!
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