Crescendo duo

Dual-Channel Microphone Preamplifier with 120V technology

Crescendo duo combines the precise sound that German Rundfunk-Technik is famous for with the innovative SPL 120V technology.
The internal operating voltage of 120 volts allows Crescendo microphone preamplifiers to break completely new ground. This results in microphone preamps that sound detail-rich, vivid and equally honest.

Crescendo duo lets microphones shine in a whole new light – 
because they have never been amplified like this before.

The Undistortable

Thanks to the SPL 120V technology, it is almost impossible to overdrive this microphone preamplifier.

Crescendo duo is a dual-channel microphone preamplifier with 120V technology.
Both channels feature the same range of functions. Besides phantom power (48 V) for condenser microphones, polarity reversal, a high-pass filter and a PAD switch, they provide the possibility to adjust the VU meter to display very high levels – so they leave nothing to be desired. The gain can be adjusted comfortably and precisely via a 12-step switch. With the switchable output control, the output level of the Crescendo duo can be perfectly adapted to following AD converters. Two outputs per channel allow the signal to be sent to two different devices in parallel. In addition to the extensive feature set and the outstanding technical characteristics, Crescendo duo convinces with a sonic authenticity that is second to none.

“The Crescendo duo is a microphone preamp of the absolute master class. Anyone who is making acoustic recordings and wants to capture every mic detail without any noise will find this top preamp to be the perfect partner.”

48 V

The 48V switch activates the required phantom power of 48 volts for the use of condenser microphones.


With this switch the level displayed in the VU meter can be adjusted by -10 dB. This is very handy to display high levels.

How does Crescendo sound?​

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“If you are looking for a two-channel preamp for the most important signals of a session at that moment – from voice and vocals to supporting acoustic instruments such as acoustic guitar or strings to the drum overheads or the stereo main microphone in orchestral, choir and organ recordings – the SPL Crescendo duo does the job superbly.”


Activating the polarity reversal switch turns the polarity of a microphone signal by 180°.


A high-pass filter with 6 dB per octave reduces subsonic noise below 120 Hz.

Mic Gain

The gain is adjusted by a 12-step switch. The pre-amplification ranges from +18 dB to +70 dB.

Crescendo duo – Lyrics: "if not, winter" by Sappho

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The switchable output control allows level adjustment to subsequent devices. The control range is +/- 10 dB. This results in a total gain of 80 dB.


By activating the PAD, the input sensitivity can be reduced by 20 dB. This allows the preamplifier to be ideally adapted to high level input signals. Tip: With PAD activated, Crescendo duo is also ideal for line-level input signals.

Built-in Output Splitter

Both microphone preamps have two parallel outputs each. An additional external signal splitter for back-up systems during a recording session is therefore no longer necessary.

“Its sound has an extremely noble, gentle character, which lends depth and transparency to a recording. Especially in genres like jazz and classical music the Crescendo duo should be very popular, because it transmits the dynamics of a performance very well and offers so much headroom that distortion is not an issue at all.”

Classical Gropius guitar, recorded with the SPL Crescendo duo

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The 120V technology

The 120V technology is our reference technology. The 120V technology is unique in the world. It operates at a DC voltage of 120 volts. This is four times that of IC-based semiconductor op-amps.

The highest possible audio quality requires the highest possible audio operating voltage.

The 120V technology works with +/-60 V. To be able to handle such a high voltage, we have developed special proprietary operational amplifiers that can operate with a DC voltage of +/-60 V: the SPL 120V SUPRA operational amplifiers.
This high voltage would destroy conventional components and operational amplifiers.

The 120V technology achieves exceptional technical specifications and sonic benefits. Technically, in terms of dynamic range, signal-to-noise ratio and headroom. Sonically, in terms of richness of detail and an absolutely relaxed listening experience.

By the way, the “120V” in the name of the technology has nothing to do with the local mains voltage from the mains power socket. This is about the operating voltage inside the device with which the audio signals are processed.

The mains voltage from the mains power socket is transformed to the required secondary voltage in the device’s internal linear power supply with toroidal transformer. Rectifiers convert this AC voltage into DC voltage required in the audio device.

The idea for SPL 120V technology and the SUPRA operational amplifier based on this technology were developed in the 1990s by SPL founder and chief developer Wolfgang Neumann.

With the goal of building the best mastering console ever, this basic technological philosophy then took shape for the first time – thus the SPL MMC1 Mastering Console for Galaxy Studios saw the light of day in 2000.

SPL MMC 1 in the “Galaxy Mastering Studios”
SPL MMC 1 in den “Wisseloord Studios”

The outstanding sonic and technical features quickly got around in the scene – so further orders were not long in coming.

Besides the MMC 1, another legendary product with 120V technology was created with the PQ, the “King of Parametric Equalizers”.

Since that time, 120V technology has been the foundation for all SPL premium products. Meanwhile, not only for mastering applications, but also for the, studio or hifi use.

SPL PQ – Modell 2050

What exactly is that?

And what does it do?

Good questions need good answers.

And that’s what the 120V technology video gives you.

Play Video


Most audio devices work with an internal operating voltage of +/-15 volts and can thus process a maximum input level of +21.5 dBu. If a DAC, for example, has an output level of +22 dBu at 0 dBFS, level peaks of the music material would already cause overloads in the input stage of the device.
All components in the audio device often operate at their limits. The result is an unsteady sound that causes stress and faster ear fatigue.

SPL devices with 120V technology can handle input levels of +32.5 dBu thanks to the higher internal operating voltage of +/- 60 volts – thus offering 12 dB more headroom. All components consequently operate continuously in the optimum operating range. The result is a very pleasant, natural and relaxed sound experience. So you can enjoy your music in every detail.

These diagrams clearly show the superiority of the 120V technology in comparison to other circuits with lower, common operating voltages.

Crescendo duo – Café del Mundo

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Looks great, feels great – and lasts for a lifetime

The Crescendo duo has a 4 mm thick, black anodized aluminum front panel and aluminum knobs milled from solid. The housing is made of high-quality steel and is powder-coated in elegant black.

Sounds good

With all SPL devices we develop not only according to plan, but also by ear. Many important components are installed on the circuit boards using Through-hole technology. This way we can ensure that we can use the best sounding components.

Crescendo duo – Microstudio

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Home is where the heart is

That’s why we manufacture all devices in our own production facility in Niederkrüchten on the Lower Rhine, Germany.

Crescendo duo v1 or v2?

With the new revision v2, the Dual-Channel Microphone Preamplifier with 120V technology Crescendo duo receives a facelift in the new design of the SPL Studio series.

Besides the black faceplate the housing has also got an update to the next level.

Since Crescendo duo v1 is already pushing the envelope, the only technical change in v2 is different steps of amplification on the big “Mic Gain” switch. There now is a large choice of medium amplification values.

What’s the difference?

  • Crescendo duo v2 comes with a new faceplate design in black.
  • Crescendo duo v2 comes with a different and improved housing.
  • Crescendo duo v2 comes with more steps of values for medium amplification on the big “Mic Gain” switch.

The product page describes the product features of the Crescendo duo v2. More information about the first hardware version is available in the corresponding manual.

Download: Manual – Crescendo duo v1

The current manual of Crescendo duo v2 is available for download at the bottom of this product page within the section “Manuals”.


Play Video
SPL Crescendo duo - introduction, overview and further information
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Lyrics: "if not, winter" by Sappho @ microstudio
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Best Stereo Preamps for Classical Guitar? SPL Crescendo duo
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Recordings from microstudio: guitar
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Classical guitar recording with the SPL Crescendo duo
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SPL Crescendo duo – Café del Mundo

Other Microphone Preamplifiers

Crescendo 8
Eight Channel Microphone Preamplifier with 120V Technology
Channel Strip
Channel One Mk3
Channel Strip
Track One Mk3
Channel Strip
GainStation 1
Class A & Tube Microphone-/Instrument Preamplifier
GoldMike Mk2
Dual Channel Microphone & Instrument Preamplifier


Replacing fuses and voltage selection

The replacement of fuses and the switching of mains voltages must only be performed by qualified technicians. Fuses must only be replaced with fuses of the same type and specifications.

Play Video
Replacement of defective fuses for 115V
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Replacement of defective fuses for 230V
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Changing the mains voltage from 115V to 230V
Play Video
Changing the mains voltage from 230V to 115V


Analog input & output; XLR (balanced)

Maximum output level
32.5 dBu
Input impedance
Output impedance
75 Ω
Frequency range (50 dB Gain, -3dB)
20 Hz – 100 kHz
THD + N (10 Hz – 22 kHz, 30 dB Gain)
0.0036 %
THD + N (10 Hz – 22 kHz, 70 dB Gain)
0.32 %
Noise (A-weighted, 150 Ω, 30 dB Gain)
- 89.2 dBu
Noise (A-weighted, 150 Ω, 70 dB Gain)
- 51.7 dBu
Equivalent Input Noise (EIN, 70 dB Gain, 150 Ω)
-121.7 dBu
Common mode rejection (1 kHz, 30 dB Gain)
79 dB

Internal Linear Power Supply with Shielded Toroidal Transformer

Operating voltage for audio electronics
+/- 60 V
Operating voltage for relays and LEDs
+ 12 V

Mains Power Supply

Mains voltage (selectable, see fuse chamber)
230 V AC / 50; 115 V AC / 60 Hz
Fuse for 230 V
T 0.5 A
Fuse for 115 V
T 1 A
Power consumption
max. 17.7 VA

Dimensions & Weight

W x H x D (width x height x depth)
482 x 88 x 300 mm
19 x 3.46 x 11.8 inch
Unit weight
6.1 kg
13.45 lbs
Shipping weight (incl. packaging)
7.5 kg
16.54 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.

Product Condition


Brand-new product from the current product portfolio.


Demo, exhibit or return item.
In original packaging, incl. manuals and full warranty.
Only slight to no signs of use.


Demo, exhibit or return item.
In original packaging, incl. manuals and legal warranty.
In some cases clear signs of use, which are documented in photos.


"New Old Stock"
After discontinuation of a product still available new products with full warranty.


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


Aufgrund von Covid19 sind derzeit keine Events geplant.