The Headphone Monitoring Amplifier for 500 Series.

500 Series double-slot module headphone monitoring amplifier with Phonitor Matrix for two

Create perfect mixes on headphones – thanks to the Phonitor Matrix.

The headphone output stage

The HPm delivers full headphone sound – twice!
The output stage of the headphone amplifiers is designed as a push-pull amplifier in Class AB mode. The bipolar transistors share the amplification of the positive and negative half-waves, which produces a higher gain and a higher output voltage than in Class A operation, where only one transistor amplifies both half-waves.

The output stage transistors are thermally coupled and thus run particularly coherently, which contributes to a consistent and stable sound image. The power supply has a buffer circuit with low source resistance, ensuring generous current reserves even when operating low-impedance headphones. Both headphone amplifiers provide an individual volume control.


The audio signal can be switched between stereo and mono. In the Mute position, the headphone
outputs are muted.

Phase Inverse Ø

With the phase inversion switch the phase the of the left or right channel can be inverted (180°).

Tip: M/S – Mid or Side?

By using the MONO and the phase invert switch in combination, it is possible to only monitor the
M or S signal. When “Mono mode” and phase inversion is active, only the S signal is played back.

If the phase inversion is switched off, the Mono signal corresponding to the M signal is played back. Separate monitoring of the M and S signals has become a standard for many mixing and mastering engineers.

The revolution in the headphone amplifier:
Phonitor Matrix

The Phonitor Matrix enables mixing and mastering engineers to create perfect mixes on headphones, which will translate perfectly to all types of stereo speaker systems.

Wie ist das möglich?

Music is normally produced and mixed for playback on stereo speakers.

Listening on headphones is different from listening on loudspeakers. The biggest difference is the
lack of crossing signals of the sound signal from the left speaker to the right ear and from the right speaker to the left ear. These crossing signals are missing in conventional headphone listening, because there are no signals crossing from one side of the headphones to the other. This results in an unnaturally wide stereo stage and sound sources are not played back at their correct position in
the stereo field.

The SPL Phonitor Matrix can correct this false stereo image with an analog circuitry.

The Phonitor Matrix parameters

The two main parameters of the Phonitor Matrix are Crossfeed and Angle:

Crossfeed determines the opening angle of the stereo image.
Angle determines the opening angle of the stereo image.


The “Crossfeed” parameter of the HPm is continuously adjustable via the crossfeed control.

Speaker Angle

The “Angle” parameter can be adjusted in three settings: 20°, 30° and 40°. The studio standard is 30°.

Center Level

To make the listening experience even more perfect, the level of the center of the stereo image needs to be attenuated when the Phonitor Matrix is active. This ensures that not only the position of all sound sources is correct but also their volume. With HPm, this parameter, which we call “Center” in the Phonitor Matrix, can also be adjusted in three settings. You can choose between an attenuation of -0.5dB, -1 dB or -1.5 dB. The standard for an authentic representation of the stereo image is -1 dB. During conventional listening on headphones, our brain can compensate a certain level of false playback representation – but this is very exhausting and leads to listening fatigue.

Summed up

The SPL Phonitor Matrix corrects the false representation of the stereo sound image, which makes it much easier to find the right decisions for mixing and mastering engineers. So nothing stands in the way of a successful and long mixing session on headphones.

Play Video
Everything you need to know about the Phonitor Matrix
Play Video
Everything you need to hear about the Phonitor Matrix

Phonitor Matrix

With the Matrix switch, the Phonitor Matrix (Crossfeed, Speaker Angle, Center Level) can be activated or deactivated.

Play Video
HPm 500 Series module at


Sound On Sound
Recording Magazin

Other 500 Series products

Transient Designer 500
Dual-Band De-Esser 500
Stereo Image Bigger Maker

Other Studio Headphone Amplifiers

Phonitor 3 DAC
Headphone amplifier, monitoring controller and DAC
Phonitor 3
Headphone amplifier and monitoring controller
Phonitor One d
Headphone Monitoring Amplifier
Phonitor One
Headphone Amplifier

Other Professional Fidelity Headphone Amplifiers

Phonitor xe
Headphone Amplifier
Phonitor x
Headphone Amplifier and Preamplifier
Phonitor se
Headphone Amplifier



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Input & Output; balanced

Maximum input & output gain
21 dBu
Input impedance
Output impedance
150 Ω
Common mode rejection
> 82 dB
Frequency range (-3 dB)
10 Hz – 100 kHz
THD & N (0 dBu, 10 Hz – 22 kHz)
0.03 %
Noise (A-weighted)
-92.3 dB
Dynamic range
113 dB

Headphone Outputs, 1/4" (6,35 mm) TRS Jacks

Tip = Left, Ring = Right, Sleeve = GND
Max output power (600 Ω)
+18 dBu
Max output power (300 Ω)
+15 dBu
Max output power (32 Ω)
+5 dBu

Dimensions & Weight

Double-spaced module for 500 Series
Unit weight
0.8 kg
1.76 lbs
Shipping weight (incl. packaging)
0.9 kg
1.98 lbs

Reference: 0 dBu = 0,775V. All specifications are subject to change without notice.


Calculation of VAT (value added tax)

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If your country cannot be determined via geolocation and you are not logged in as a user with the billing address of your country, the prices are displayed including the VAT of Germany (19%).

What does it actually mean …

In Stock!

The product is in stock in our warehouse in Niederkrüchten, Germany, and will be shipped the same or next working day.

We process the orders after receipt of the order and update the stock in the online shop regularly. If the product is no longer available at short notice due to high order volume, you naturally have the right to withdraw from the purchase (see Right of Withdrawal).

In any case, you will receive an e-mail with details of the delivery and the estimated delivery time.

Available soon!

The product is not in stock in our warehouse in Niederkrüchten, Germany. Usually it will be available again within 5 working days.

In any case, you will receive an e-mail with the details of the delivery and the estimated delivery time.

Of course you have the right to withdraw from your purchase (see Right of Withdrawal).

Currently unavailable.

This product is currently sold out and unavailable.

Was bedeutet eigentlich …

Auf Lager!

Das Produkt ist in unserem Lager Niederkrüchten vorrätig und wird noch am selben oder nächsten Werktag versendet.

Wir arbeiten die Bestellungen nach Bestelleingang ab und aktualisieren den Bestand im Online-Shop regelmäßig. Falls das Produkt wegen hohem Bestellaufkommens kurzfristig nicht mehr verfügbar ist, hast du selbstverständlich das Recht, vom Kauf zurückzutreten (siehe Widerrufbelehrung).

In jeden Fall erhältst du eine E-Mail mit den Einzelheiten der Lieferung und der voraussichtlichen Lieferzeit.

Bald verfügbar!

Das Produkt ist in unserem Lager Niederkrüchten nicht vorrätig. Gewöhnlich ist es innerhalb von 5 Werktagen wieder verfügbar.

Auf jeden Fall erhältst du eine E-Mail mit den Einzelheiten der Lieferung und der voraussichtlichen Lieferzeit.

Selbstverständlich hast du das Recht, vom Kauf zurückzutreten (siehe Widerrufbelehrung).

Zur Zeit nicht verfügbar.

Dieses Produkt ist derzeit ausverkauft und nicht verfügbar.


Due to Covid19 there are no events scheduled at this time.


Aufgrund von Covid19 sind derzeit keine Events geplant.