8-Channel Mic / Line Switcher

The AB-8 is an 8-channel, balanced, bi-directional signal switcher, 1 in - 2 out or 2 in -1 out per channel.

  • Eight channels of balanced A - B switching for line, mic or MIDI signals.

  • Each of the eight channels can be individually switched or assigned to a Master Control circuit.

  • Master switching is controlled through front panel pushbuttons, optional footswitch or automatically triggered by loss of signal on channel one of A input.

  • Can be configured as two inputs to one output, one input to two outputs or a mixture of both.

  • Multiple units can be ganged together under Master Control of the first unit or through control Voltage input.

  • Indicator lights show status of each channel.

  • AUTO SWITCH functions automatically switches to redundant copy of backing tracks for live performance.

  • AUTO SWITCH has sensitivity and hold time controls to accommodate input signal levels from -20dB to +20dB

  • Easily switch from tracking to mixing in recording setups.

  • All signal paths revert A to Common when AC power is removed.

  • Internal DIP switches configure ground path switching and DC Voltage blocking requirements.

LM2U and LM2B
Level Matching Devices

These handy boxes can be used to match consumer grade audio devices (-10dB) to pro equipment (+4dB). These units convert the level and provide the conversion from balanced to unbalanced operation and vice-versa.

Each unit features:
  • XLR, TRS mini and RCA phono jacks
  • Level controls
  • Active circuitry, power by Whirlwind PS24 supply (included)

Model #s:
LM2U and LM2B

Frequency Response 20-20 kHz at unity gain, .1 dBv
Total Harmonic Distortion +noise < .0015% 20-20kHz at unity gain; < .0024% 20-20 kHz, +4 to 10 levels
Phase Shift < 11.4 degrees 20-20 kHz; < 2 degrees 100-4 kHz
Dynamic range 95.7 dB @ .1% thd
Total Gain 40 dBv
Range of level pot -40 to + 40 dBv
Maximum Input level +17 dBv
Input Impedance 20 k Ohms balanced
Maximum output level +17 dBv
Output Impedance 100 Ohms unbalanced
Noise at 20 dBv of gain -87.4 dBv 20-20 kHz
Noise at unity gain -103.4 dBv 20-20 kHz
Noise at 40 dBv of gain -68.1 dBv
Power consumption 34 mA DC max.
Stereo Separation 94 dB at 20 kHz; 110 dB at 1 kHz; 120 dB at 20 Hz


The ISO-2 is a two channel isolation box and line balancer.

As an isolation unit, use it to isolate lines to press and video feeds or on-stage power amps. It's a handy hum and buzz fighter for broadcast or live sound applications.

As a balancer. it converts unbalanced lines from CD players, tape decks, etc. to balanced for long cable runs.

Each channel features:

  • XLR or 1/4" input
  • Ground-lift button
  • Polarity reverse button (Channel 2 only)
  • Whirlwind's own TRSP-600 transformers ensure flat frequency response and low distortion.

Model #: ISO-2
Frequency Response: 20Hz-20kHz 0.5dB at +10dBm input
Maximum Input Level: +28dBm
Input Impedance: 600 Ohms
Output Impedance: 600 Ohms


Sometimes a ground lift isn't enough to do the job. The ISO-8 is a valuable part of systems
where different pieces of gear are connected across long lines. Many of our customers use it
to isolate drive lines to on-stage power amps. The perfect hum fighter in field broadcast or
live sound applications, the ISO-8 provides eight channels of high-quality line level isolation
to eliminate hum and buzz from interacting gear. Unbalanced outputs are an invitation
to system noise.
The ISO-8 provides both balancing and isolation to stop noise at the source.
Each channel features a ground-lift switch, and our own TRSP-600
transformers ensure flat frequency response and low distortion. It's handy
to keep an ISO-8 "in the rack" for emergencies. Available in XLR (ISO-8) or with 1/4" TRS jacks (ISO-8Q).
Frequency Response: 20Hz-20kHz 0.5dB at +10dBm input Maximum Input Level: +28dBm Input Impedance: 600 Ohms Output Impedance: 600 Ohms

IMP PAD 10, 20, 30, 40

Input a line signal into a mic pre or match levels between two pieces of 

gear with these precision in-line H-pads. Available in 10, 20, 30, and 

40dB attenuation versions, a set of Imp pads is a necessity for every 

complete audio toolkit.

Input Impedance (3-pin female XLR): 1k Ohms Output Impedance (3-pin male XLR): 150 Ohms


The phase reverse offers a temporary solution to fix a miswired mic or 

cable. This female-to-male XLR 3-pin inline device reverses the 

connection of Pins 2 and 3 between the connectors, which flips the 

polarity of a balanced audio signal.


Ideal for troubleshooting ground problems, this female-to-male XLR 

3-pin inline device disconnects pin 1 between the connectors. It isolates 

the ground of a balanced audio signal without requiring you to cut the 

cable's shield wire.


Some mixers have high impedance inputs that don't work with 

standard low impedance microphones. This inline impedance-matching 

transformer is the solution for making that connection.


This is a professional quality compact transformer in an XLR male/female tube for quick fix line isolation. The shield is lifted from input to output. Our ISOXL outperforms the industry leading inline isolation transformer . Give us a call to find out more!


The Canare BCJ-XJ-TRB (XLR-F to BNC) and BCJ-XP-TRB (XLR-M to BNC) adapters 
are a cost-effective solution for long cable runs over coaxial cable as 
opposed to the attenuation of twisted pair at digital frequencies. 

The adapters provide impedance matching between 75 Ohms and 110 Ohms, 
electrical isolation, transition of balanced/unbalanced circuit, and 
reduction of hum and noise. 

1ST Audio USA
2844-46 Dewey Avenue
Rochester, NY 14616
(585) 621-6270
Please call or email for Prices
e-mail - dave@1staudiousa.com

1ST Audio USA