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Avalon 737

Test & Review

Would you like to acquire a quality preamplifier in your professional studio or in your home studio, in order to ensure perfect and precise mixing? You can opt for the Avalon 737 preamp. What can make this preamp so special compared to other preamps in the market? Discover in this guide our complete test as well as our opinion on the Avalon 737.

Avalon 737 test and review

🎤 by Kevin Jung

Summary of the Test 👇

The signals generated by a sound source are not always strong enough to be faithfully reproduced in an audio recording. A preamplifier is necessary to increase the gain of the signal and make it more suitable for the operation of the device on which it is received.

The efficiency of processing an audio signal is not the same from one preamplifier to another. The Avalon 737 proves to be more efficient than other preamps in this regard. You will discover through this guide why this preamp is the best choice for your recordings.

Avalon 737 preamp review
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Presentation of the Avalon Design brand

Avalon Design thrived in the manufacturing of studio equipment under the leadership of Wynton Morro, its chief engineer, during the 1980s. The company was originally based in Sydney, Australia before moving to California, United States to gain more scale .

Avalon Design experienced its first successes as a manufacturer of preamps such as the 737. The brand also impressed Prince with the quality of its equipment. Such recognition was far from trivial for the company at the time, especially as it still needed to launch.

Avalon 737 Preamplifier Overview

The Avalon 737 is one of the best-selling preamplifiers in the audio equipment industry worldwide. Its popularity was built in particular with the Hip-Hop and RNB scene. He has in fact used to record the titles of artists such as Jay-Z, Dr.Dre and Beyoncé.

Class A and high voltage technology Avalon Design did not stop at the transistor in the design of the devices, however. Many preamps from this brand also feature tube circuitry .

The Avalon 737 preamplifier aligns with this philosophy by presenting hybrid technology , but in an approach all its own. Classic hybrid circuits have tube stages (like the SPL Goldmike 9844 tube preamp ) and transistor stages that operate simultaneously, which is not the case with the 737.

Avalon 737


The Avalon 737 combines a compressor and stereo equalizer in its housing. The entire device has also been equipped with two parallel signal paths . This opens up the possibility of operating the processor with active stages based on class A transistor stages.

The Avalon 737 can in fact be transformed into a tube machine at the press of a single button. The transistor stages are replaced where necessary by tube circuits in the signal path. The manufacturers of the Avalon 737 also describe this architecture under the term “ Twin Signal Path ”.

Build quality of the Avalon 737 preamplifier

6mm thick brushed aluminum faceplate . The large aluminum rotary buttons are sufficiently spaced on the front for comfortable use. The saturated appearance of the rotary switches for filter frequencies and stereo input selection contrasts with the clarity of the relays. The smooth switching of the level regulators to the zero position also reinforces the quality impression of the Avalon 737.

All the connection interfaces of the Avalon 737 are on the back of this studio equipment. The only exception is the connection of unbalanced instruments with an impedance of 1 megaohm . It is then easier to connect the 737 to other peripherals such as an electric guitar even if it is rack mounted. The required phono input signal can be chosen with a rotary switch . However, it is not possible to record instrument and microphone signals at the same time.

The balanced microphone input has an impedance of 850 ohms which can be increased internally to 2200 ohms if necessary. The manufacturers specify in this respect that they used only high quality Lundahl transformers toroidal transformer and certain capacitors of the device were also created especially for the audio interface.

Avalon 737
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The two-stage amplification section of the circuit of this preamplifier consists of 2 E88CC tubes manufactured in Russia by the company Electro Harmonix . Another tube of the same type is installed in the compression section while a fourth serves as an output stage . All components are soldered meticulously and cleanly on the boards.

Relays with silver contacts remove the compression and equalization sections of the signal tracks . This function is defined under the term hard bypass . Some relays activate phase inversion, phantom power, low pass filter, hi-gain function and internal sidechain on demand. Others change the order of the compression and EQ sections.

The corresponding tactile switches light up when active. They can therefore be used comfortably even in unfavorable visibility conditions. The VU meter in the center of the front panel is also illuminated without dazzling to be easier to read.

The Avalon 737 preamp technology is modern enough to match the performance of a home theater amp or headphone amp . This is at least the case for sound reproduction, because the absence of modern connectors such as a USB port complicates direct connection to a computer. An external sound card is essential for this purpose.

The device also does not have RCA ports, which is inconvenient as it can help in connecting to multiple devices. A USB to XLR port audio cable can still be used for connecting the preamplifier to a turntable . The Avalon 737's technology can then be used to amplify the signal from a record player when playing vinyl records.

However, we must look for more creative solutions to use the Avalon 737 preamplifier with an audio and video device such as a television. It is more conclusive if necessary to connect the television to a surround sound system which will in turn relay the signal to the preamp.

Avalon 737


Also consult our guide : Beyerdynamic M130 . This guide brings you the complete review of this dual ribbon microphone. You can also discover in this guide our opinion on the sound quality produced by this microphone.

Features of the Avalon 737 preamplifier

Avalon technicians equipped the 737 with 11 potentiometers , 7 push buttons and 6 level regulators. A notched potentiometer in the neutral position at the input adjusts the gain to a maximum level of ±8 dB . A switchable boost gain also boosts the audio circuits by 10 dB .

Another central detent potentiometer adjusts the output level from -20 to 6 dB . Compressor and equalizer can be activated separately. There is no global bypass switch for these two components.

The order of the dynamics unit and EQ in the signal path can be reversed with the press of a button. The equalizer can thus refine the compressor signal or distort the frequency response of the input signal before it reaches the compressor.

Just like the AMS Neve 1073 DPX preamp , the Avalon 737 is a preamplifier with Class A circuitry for amplification and monitoring. This circuit can further , microphone and instrument signals analog tube technology for the 737 design.

The channel strip combines three signal processing modules in a 19-inch format housing. It consists of a preamplifier , an optocompressor and a four-band parametric equalizer . The Avalon 737 can thus act upstream for analog monitoring (like the Genelec 1032 CPM monitor ) with an audio sequencer such as the Studio One 5 . It is a good alternative or complement to the channel strips of an audio mixing console.

Minimalism is the key word in the design of the Avalon 737. No superfluous elements should alter the signal. The 737 can still provide some leeway for sound manipulation with its EQ, compressor, and tube preamplifier.

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The primary function of the Avalon 737 audio system is as a recording channel , but it is also suitable for mixing or mastering . In particular, it can refine specific vocal tracks and enrich a bass drum with harmonics. This audio hardware can also distort the signal of a snare drum thanks to its strong compression and versatile equalization.

The Avalon 737 demonstrates its effectiveness in mastering when connected to another device using a Link socket . Compression sections are coupled to ensure identical compressor characteristics for both channels. The channel strip with the highest ratio is automatically the master and transmits the settings to the second device. The hands of the two VU meters then move at the same time to display the compression .

The optocompressor comes with sophisticated settings to satisfy the most seasoned audiophiles. The threshold is adjustable to ±20 dB for a ratio of 1:1 to 20:1 . The attack can also be set between 2 and 200 ms for a release of 0.1 to 5 seconds and gain makeup between 0 and 10 dB . All these settings are accessible through continuously adjustable potentiometers.

The box also contains two equalization bands for sidechain signal processing . Generous amplitudes of ±15 dB for an LF band of 60 to 1000 Hz can be obtained using Bell filters. The latter are also favorable to obtaining a gain of ±15 dB on a high frequency band of 0.6 to 10 kHz .

The compressor is carefully positioned to handle multiple tasks in addition to traditional full-range compression. It adapts flexibly to the most subtle corrections. This includes removing a minimum of compression on the very energetic bass area.

The Avalon 737 preamp even has an SC list to directly check the EQ setting of sidechain filters . This simplifies fine tuning in addition to allowing the direct use of the two equalization bands for signal processing .

Avalon 737


Focus on the sound quality of the Avalon 737 preamplifier

The three modules of the Avalon 737 offer a multitude of possibilities for modifying the sound . This is especially true when combined with the adjustable input and output stages and the additional high-pass filter . All modules can additionally be excluded from the signal path. The gain will then be modified by the input and output level regulators and controlled by the VU meter.

The Avalon 737 preamp immediately delivers a picture without the use of a compressor or EQ. The basic sound changes along with the volume when the gain regulators are pushed to a higher level. The tubes are in fact gradually led towards saturation.

The vocals and acoustic guitar sound natural and direct . The highs are accentuated with brilliance without being intrusive. Rather, they resonate in a light and refreshing way. Knocking and breathing sounds gain a proximity effect that becomes stronger as the input level increases. This creates increased harmonic distortions at the input amplifier.

Manipulating the input and output level setting leads to subtle differences in the basic sounds. The picture is balanced overall. It becomes more compact and energetic in the midrange without losing authenticity thanks to the tubes.

The sound quality of the Avalon 737 is even more diverse with vocals and guitar. This can be done by combining the corresponding signals with various compressor and EQ settings . The compressor action is almost inaudible on the vocals, making them more streamlined. The movements of the lips and the timbre are then revealed with more life and character .

Full Overview of the Avalon 737 Preamp
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Increasing the treble by 4 decibels to 32 kilohertz in the guitar recording drives the sound upwards. The sound of tapping with the right hand and the sliding of the left hand across the key are skillfully staged. A guitar with a worn set of strings may even sound like it had new strings when used with the Avalon 737.

The Avalon 737 preamp also delivers good performance with bass . The resulting sound is rich and well-rounded with moderate whirring at times and extreme at others. Compression maintains full control of the signal by reducing attack time .

Percussion instruments are not left out with the Avalon 737. The bass drum can be optimized without difficulty and obtains pleasant compression . The equalizer highlights the sound base of the bass drum in addition to highlighting the impact of the sticks on the membrane.

The snare sound becomes very experimental with extreme compression settings in the mix. The drum signal acquires some roughness after increasing the gain. Adding plenty of reverb to the snare signal also takes creativity to another level when using the Avalon 737.

The 737 overall refines the sound in a discreet way , which is a rare quality on power amplifiers. It covers the picture with a typically American sweetness. Other DSP units can hardly deliver the same result despite high-fidelity technology. This can be seen with preamps such as Cambridge Audio CXA 16 and the Thomann Universal Audio from or even a power amp from Rega Studios.

Avalon 737


By the way, you can also check out our test guide and review of the Channel Strip Dbx 286s preamp . This preamplifier has two specific and separate sections, which are used to pre-amplify the sound and process the signal. Check out the full overview of this preamp through the link.

The technical characteristics of the Avalon 737 preamplifier

The high-pass filter offers 11 switchable levels from 30 to 140 hertz with a slope of 6 decibels per octave . This allows it to effectively eliminate parasitic noise The four bands of the equalizer overlap to a large extent for a total value of 15 Hertz at 32 kHz . The two outer bands for treble and bass are designed as passive filters , in contrast to active filters for the midbands.

Four operating frequencies are available for bass, namely 15, 30, 60 and 150 hertz . The values ​​available in the case of high frequencies are 10, 15, 20, 32 kilohertz . They differ from each other by an adjustable gain of +/-24 decibels on the bass and +/-20 decibels on the treble.

The lowest frequency for using the bass filter is 15 hertz compared to 32 kilohertz for the treble filter. The frequency response below 20 kilohertz , such as on a subwoofer, is influenced by attenuation or boost of frequencies in this range. These modifications are subtle and result in very fine changes in the sound system.

Two quality settings are available for each of the middle bands, namely the “Wide” and “Medium” setting. The filter frequency ranges for the upper and lower midrange cover all frequencies in duplicate. It is thus possible to amplify or attenuate the selected frequency ranges to double a maximum of 16 decibels by adding the two filters.

Avalon 737 test and review
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The lower midrange filter can be continuously adjusted between 35 and 450 Hertz using a specific knob. The range can be increased by a factor of ten to go from 350 Hz to 4.5 kilohertz . These same options can be applied to the high midrange filter. They can go from a range of 220 Hertz to 2.8 kHz to frequencies ranging from 2.2 Kilohertz to 28 Kilohertz thanks to the Mal-Dix mode.

The Avalon 737 optocompressor comes with standard settings for tuning. Firstly, these are the threshold from -30 to +20 dB and the ratio from 1:1 to 20:1 . This is followed by the attack time from 1 ms to 100 ms and the release time from 100 ms to 5 s .

Compression control is via an optocoupler circuit, which creates smooth, melodious compression. The Avalon 737 does not have a sidechain input to allow the compression module to be triggered by external signals. It is nevertheless possible to establish the compression according to frequency. An internal sidechain injects the middle bands of the EQ section on demand into the compressor channel.

The filtered signal is then excluded from the audio channel and provides stronger compression thanks to the enhanced frequency ranges . This will then reproduce the effect of a hissing attenuator. An internal routing relay to be activated with a key switch can additionally reverse the order of the compression and EQ sections. This provides more possibilities for processing sound.

The values ​​measured when using the Avalon 737 are very good overall. The frequency response is completely linear between 20 Hz and 20 kHz . The harmonic distortion rate is 0.02% when the input and output level regulators are in the zero position. Harmonic distortion increases when the gain is pushed to maximum. This is due to the harmonic distortion of the tubes which tends to increase proportionally.

Avalon 737


Common mode rejection is well below -70 decibels . The Avalon 737 therefore poses no problem for use with long microphone cables ( a condenser studio microphone to be precise).

The FFT spectra of the different settings proposed in the manual reveal quite pronounced harmonic distortions. These settings relate to the acoustic guitar, vocals and bass drum. The filters are also very flexible and allow the processing of the frequency response with great precision .

The optocompressor has a very gentle compression curve to process the signal efficiently. This is true even with a maximum threshold setting of -30 dB and a ratio of 20:1 . The signal-to-noise ratio for the microphone input is -84.5 decibels compared to -76.8 externally. The results are much higher for line input with values ​​-95.3 and 91.6 decibels .

The input sensitivity for microphones is very low, however. A microphone must provide an output voltage of 52 dBu to deliver +4 dBu to the output of the Avalon. You also need to have the gain regulator set all the way up and the high gain switch depressed.

The Avalon 737 is therefore ineffective with dynamic microphones or ribbon microphones. Most microphones of this type are not very sensitive. Moving coil microphones ( like that of the AKG P220 microphone ) would be more effective in this regard, although they may also in rare cases have reduced sensitivity.

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Our Overall Opinion

Overall Sound Quality

4,8 /5

Value for money

4,6 /5

Global mark

4,7 /5

Our opinion on the Avalon 737 preamplifier

It is now possible to find the 737 in the form of a plug-in for its virtual sequencers or DAWs. The plug-in is developed by Universal Audio and benefits from optimal emulation quality to reproduce the original quality of the Avalon 737. However, this plug-in cannot match the authenticity and sound quality to be obtained from the 737 in its physical form.

The design of the Avalon 737 preamp is a priori quite intimidating for beginner musicians. A music production veteran may be more comfortable with the operation of this device. However, it would be a shame not to choose this preamp solely because of its apparent complexity.

The possibilities offered by the Avalon 737 in terms of audio recording are difficult to replicate with other preamplifiers. The fact that it includes both a compressor and an equalizer in addition to the amplifier module itself is enough to justify it. It is the ideal device for revealing your creativity in audio recordings as long as you learn how to use it.

Avalon Design 737 Preamplifier Demo

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Avalon 737