The X-Y capsule amplifier was discontinued in February 2021.

The X-Y microphone capsule amplifier is a microphone “body” that supports the X-R series interchangeable microphone capsules and capsule heads. The X-Y has a flexible power scheme, and may be configured to run on +12-48V phantom, internal A23, rechargeable Li-ion battery, or external DC power.  The X-Y capsule amplifier is available in mono, stereo, and three- or four-channel configurations.

The X-Y amplifier mounts to a standard 5/8″-27 thread microphone clip via its XLR output connector.  The X-Y amplifier may also have a 1/4″-20 thread mount.

Input Configuration

The X-Y has several options for input configuration:

• fixed mono with single RCA input
• fixed end-address stereo with dual RCA inputs
• fixed end/side-address stereo with three RCA inputs (2x left plus right)
• fixed left-center-right with three RCA inputs
• TB4M input to support interchangeable capsule heads
  • stereo: 120º
  • three-channel:  90º
  • four-channel 2D surround:  90º
  • four-channel 3D (ambisonic):  120º

Capsule connection

The X-Y is supplied with female RCA input(s).  X-R capsules with male RCA plug output may be directly attached to the X-Y amplifier, or extended via RCA adaptor accessories or extension cables.  A complete range of stereo and surround recording techniques are thereby enabled; including coincident, near-coincident, and spaced stereo; as well as combination of coincident and spaced microphone pairs, binaural, Blumlein, 2D, and 3D (ambisonic) surround.

The X-Y capsule amplifier may be supplied with a TB4M input connector, which allows connection to the interchangeable capsule heads.  The interchangeable capsule head output uses a TA4F connector with the following pin configuration (3D surround):

pin 1:  white RCA jack, left (front left up),
pin 2:  red RCA jack, right (front right down)
pin 3:  black RCA jack, front (back left down)
pin 4:  yellow RCA jack, back (back right up)
chassis:  ground

The TA4F output pins on the capsule head are routed to the XLR output pins on the X-R or X-Y capsule amplifiers with XLR-5-M (-3-M) output, as follows:

pin 1(1):  ground
pin 2:  black
pin 3(3):  white
pin 4:  yellow
pin 5(2):  red

Mono compatibility for stereo amplifier

Stereo versions with XLR-3-M output may be used as a mono balanced microphone; the unused input should be terminated to reduce system noise.

Stereo versions with XLR-3-M output may also be used as a mono microphone with two capsules attached when connected a single microphone channel.  This will mix the signal from the two capsules to the single channel with opposite polarity between the two capsules.  This technique can be used in live sound reinforcement to cancel ambient sound and thus increase gain before feedback of the microphone system.

Custom features

Gain control

The X-Y offers an optional seven-position switch (three-position for three- or four-channel input versions) for gain control.  The gain switch may be set with either a spindle or a screwdriver slot (3mm flathead).  Standard gain settings are from 0 to +18dB for the seven-position switch, and 0dB to +16dB for the three-position switch.  If desired, mono and stereo versions may also be supplied with the three-position switch, and all versions may be built with fixed gain only.  Custom gain settings may be selected within the +27dB maximum range.

Note that use of gain will reduce the maximum SPL handling of the microphone system: for example, with a standard X-R capsule at +18dB gain, the maximum level is 114dBSPL.

Output level may be further increased by +6dB with the electrically-balanced output option (mono and stereo versions only).  This additional gain does not reduce maximum SPL handling.

Special amplifier functions

The X-Y amplifier is available with a range of special encoding/decoding functions, including:

• electrically balanced stereo output
• mid/side encoding to two- (mid and side) or four-channel (left, right, mid, and side) output
• left/center/right mixing to left and right
• left/center/right with side encoding

Many special functions are also available using custom output cables, including Blumlein format (dual bidirectional at 90º) for the 2D surround head and center channel or dual stereo pair mixing.  Please inquire for details and specify function in order comments.

Stereo recording

Various stereo recording angles may be achieved by using RCA adaptor accessories between the capsules and capsule heads.  The capsule spacings and stereo recording angles with each adaptor are as follows (click on spacing for image):

Spacing/ Stereo Recording angle	Capsule on head	Coincident with RA adaptor	Coincident with Y adaptor	With Y adaptor	With male & female adaptors
90º fixed mount, standard capsule	9cm card: 142º hyper: 90º	2cm card: 180º hyper: 105º	0cm card: 180º hyper: 109º	14cm card: 120º hyper: 81º omni*: 180º	16cm cards: 113º hyper: 78º omni*: 165º
90º, standard capsule	8cm card: 147º hyper: 92º	3cm card: 177º hyper: 103º	0cm card: 180º hyper: 109º	13cm card: 124º hyper: 83º omni*: 180º	15cm card: 117º hyper: 80º omni*: 165º
120º, standard capsule	9cm card: 114º hyper: 67º	N/A	N/A	16cm card: 93º hyper: 59º omni*: 127º	19cm card: 86º hyper: 57º omni*: 114º
180º, standard capsule	11cm card: 73º hyper: 27º omni*: 123º	N/A	N/A	19cm card: 62º hyper: 25º omni*: 91º	22cm card: 58º hyper: 25º omni*: 84º
90º, short capsule	6cm card: 158º	0cm card: 180º	1cm card: 180º	12cm card: 128º	14cm card: 120º
120º, short capsule	7cm card: 122º	N/A	N/A	14cm card: 98º	17cm card: 91º
180º, short capsule	9cm card: 77º	N/A	N/A	17cm card: 64º	20cm card: 61º

* omnidirectional capsules do not resolve a stereo recording angle of less than 180 º at less than 55cm spacing.  However, when used with the equalization disc, the resulting polar response becomes subcardioid at frequencies above 2kHz.  Thus, the recording angles shown for the omnidirectional capsule with equalization disc are derived for a subcardioid polar pattern.

Capsule mixing using RCA Y adaptor

Two X-R capsules may be connected to a single input with the RCA Y adaptor, which will mix the two signals from the capsules.  When used with an RCA extension cable, the Y adaptor mixes two discrete sources into a single microphone channel.  Also, the Y adaptor may be used to blend an omnidirectional capsule with a directional capsule.  This technique is especially useful with the acoustic low-pass filter, yielding a hybrid pattern with a directional high-frequency response and an omnidirectional low-frequency response.

Ambisonic decoding

When used on the four-channel 3D head, the short cardioid capsules have 4cm radius from the center of the head.  The capsule head output given above is “A” format.  This output must be mixed to “B” format (bidirectional response on three axes, plus omnidirectional) for further processing, using the matrix:

W (omnidirectional) = FLU + FRD + BLD + BRU
X (front to back) = FLU + FRD – BLD – BRU
Y (left to right) = FLU – FRD + BLD – BRU
Z (up to down) = FLU – FRD – BLD + BRU

The resulting ambisonic frequency response requires correction.  The recommended filters (low-frequency shelving, notch, and high-frequency shelving) to decode to B format are as follows:

W filters: +9dB shelf @ 120Hz; -7dB notch (Q=1) @ 5kHz, +9dB shelf @ 11kHz.

XYZ filters: +9dB shelf @ 120Hz; -11dB notch (Q=1) @ 4.5kHz.

Note that the low frequency shelving boost is not recommended for recording distances of less than 1m.

Output Configuration

The mono version has an XLR-3-M output; the stereo version is available with either XLR-3-M (unbalanced) or XLR-5-M (impedance-, transformer-, or electrically-balanced) outputs.  Three- and four-channel versions have an unbalanced XLR-5-M output.  Stereo electrically-balanced outputs will increase output level by +6dB, and have twice the current draw compared to the unbalanced, transformer-, or impedance-balanced output options.

X-R capsule outputs are inverse polarity.  The mono XLR-3-M output amplifier is configured to supply a noninverted signal on pin 2, and the inverted capsule signal on pin 3.  Thus, the X-Y capsule amplifier will yield positive polarity when connected to a balanced input amplifier via a standard XLR microphone cable.  When a mono X-Y amplifier is used into an unbalanced input device, pin 2 should be connected as the signal lead.

For the stereo XLR-3-M version, the left channel is routed to pin 3, and the right channel to pin 2.  These outputs are inverted.

An option for stereo noninverted polarity output is also available, which requires two additional amplifier channels and will thus double the current draw of the amplifier (noninverted outputs are also available with the transformer-coupled output option, which does not require additional amplifier channels).  The stereo noninverted or transformer output options may be preferred where the X-Y amplifier will be connected to an unbalanced input device.

The output pin configurations for XLR-5-M versions are as follows (inverted unless otherwise noted):

XLR output/ TB4M input pin	2/3	3/1	4/4	5/2
stereo (electrically balanced or transformer coupled)	left noninverted	left inverted	right noninverted	right inverted
stereo (impedance balanced)	75Ω to ground	left inverted	75Ω to ground	right inverted
stereo with mid-side encoding	mid	left	side	right
left-center-right (with side encoding)	center	left	side	right
left-center-right (with center mixing)	left+center	left	right+center	right
2D surround	center	left	back	right
3D surround (ambisonic)	back left down	front left up	back right up	front right down

Output cables

Custom output cables are available in a range of special formats to support stereo and multichannel output.  These cables are configured to route the X-Y output pins to pins 3 of the XLR-3-M outputs, with impedance-balancing components on pins 2.  This will result in positive polarity when connected to balanced XLR input microphone amplifiers.

When operating on internal battery or external power, the X-Y’s XLR output may be directly connected to any stereo unbalanced input with a miniplug output cable.  There will be no DC voltage present on the XLR output when phantom power is not present.

RJ45 output option

The RJ45 output requires Category 5e cable with shield, connected to a compatible RJ45-input device.  There is no internal battery option with the RJ45 input, so either phantom power or an external power supply of +9-12VDC must be used.

With reference to the TB4M input connector, the RJ45 output pin assignments are:

1. pin 1 output
2. pin 1 impedance network
3. pin 4 output
4. pin 3 impedance network
5. pin 3 output
6. pin 4 impedance network
7. pin 2 output
8. pin 2 impedance network

chassis: ground

The RJ45 output uses a Neutrik etherCON Category 5e connector.  Neutrik etherCON Category 5e cables are recommended for the best possible connection and signal integrity.

Power Supply

The X-Y has a flexible power supply scheme that can be configured to support:

•     +9-52V phantom power
•     internal A23 battery (battery not included)
•     internal rechargeable 3.7V Li-ion battery
•     external battery via DC power port (+5-15VDC; +9VDC maximum to charge internal Li-ion battery)

The external power jack is 1.7mm ID, 4.0mm OD, center-positive.

The highest voltage supply will prevail between internal and external batteries.  Phantom power will prevail over internal or external battery supplies.

The X-Y contains a voltage regulation circuit that will generate a supply of +8-10V for the amplifier and microphone circuitry from the battery or external phantom power source.

The A23 battery is accessed by removing the thumbscrews and then the bottom panel of the case.

Due to space constraints, the fixed end/side-address stereo and left-center-right input operations are available in phantom-powered versions only.

LED indicator

Versions of the X-Y with internal battery option will have a dual green/red LED to indicate power source: red for phantom power; green for internal or external battery; yellow for internal low battery condition.  Note that if an external battery supply is used that is lower voltage than the configured internal battery type (with the internal battery removed), the LED may indicate yellow.  Thus, the LED cannot indicate external low battery condition.

Power monitor and battery charging

The X-Y monitors the current draw on its input connectors.  The X-Y amplifier circuit and microphone power supplies will activate when a microphone capsule is connected to any RCA input.  When a capsule is not connected, the amplifier circuit and microphone power supplies will shut down and the circuit will draw an idle current of 25μA.

The internal rechargeable Li-ion battery supplies 3.7V with 350mAh capacity.  An external power supply or battery between +5-9V (+5V recommended) is required to activate the recharge circuitry.  Charge time is approximately seven hours.  The LED will indicate red while charging and green when fully charged.  The X-Y with Li-ion battery is supplied with a USB charge cable.

If the X-Y is not to be used for longer than a week, an A23 battery should be removed to prevent discharge.  The internal rechargeable Li-ion battery is monitored by an internal charge regulation circuit, and thus may be left connected to an external power supply without damage from overcharging or loss of capacity.  If the Li-ion battery is allowed to fully discharge, loss of battery life may be experienced.  The Li-ion battery should be fully charged at least monthly.

X-Y stereo microphone amplifier specifications:

Phantom Power Input: +12-52V
External Power Input: +5-15VDC; minimum +12VDC required when internal A23 battery installed for operation on external battery.
External Power Input, internal Li-ion battery charging: +5-9VDC; +5VDC recommended.

Power supplied to capsules (minimum +16V phantom power): +10V across 6.8kΩ

Current, per channel, with capsule; unbalanced, impedance-balanced, or transformer-coupled output: 1.0mA
Current, per channel (mono or stereo), with capsule; electrically balanced output: 1.6mA
Current, idle, input not connected: 25μA (40μA for A23 battery)
Current, Li-ion battery charging: 50mA maximum

Autonomy, multichannel/stereo electrically-balanced, Li-ion/A23 battery: 25/10 hours
Autonomy, stereo/mono electrically-balanced, Li-ion/A23 battery: 50/20 hours

Input Impedance: 6kΩ
Output Impedance: 75Ω (each pin); 150Ω (dual XLR stereo output cable or RJ45 connector)
Recommended Preamp Input Impedance: 1.5kΩ or higher

Maximum Input Level, 0dB gain, phantom power, 1kHz @ 1% THD: +10dBV / 138dBSPL (standard capsule)
Maximum Input Level, 0dB gain, battery power, 1kHz @ 1% THD: +8dBV / 136dBSPL (standard capsule)

Total Harmonic Distortion, 1kHz @ 0dBV output, 0dB gain: less than 0.005%
Total Harmonic Distortion, 1kHz @ 0dBV output, +27dB gain: 0.025%
Total Harmonic Distortion, transformer output, 1kHz @ 0dBV: 0.1%
Total Harmonic Distortion, transformer output, 100Hz @ 0dBV: 2.0%

Frequency Response: 20Hz to 30kHz (-0.3dB @ 20Hz)
Frequency Response, transformer output: 30Hz to 20kHz
Equivalent Input Noise: -124dBV unweighted, -127dBA

Weight (typical):  100g (3.5oz)

Dimensions (without head):  111mm x 32mm x 25mm (4 3/8″ x 1 1/4″ x 1″)

Notice of FCC compliance

Pursuant to section 15.103(h), the X-Y is only intended to be operated on battery or phantom power.  The X-Y’s oscillator is disabled during operation with phantom power.  It is thus exempt from Part 15 of the FCC rules.  The X-Y qualifies for exemption as the highest frequency generated by the device is less than 1.705MHz, and it may not be operated from the AC power lines.  Use of an X-Y that is operated from the AC power lines is strictly prohibited under Part 15.