SPL Dynamaxx 9735 Stereo Compressor


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SPL isn’t a well-known brand in the UK but has a high profile in Europe. The company sells a wide range of pro-audio equipment, from channel strips, tube devices & headphone amplifers to high-end monitor controllers. The name of the company is Sound Performance Laboratory and, as you’d expect from a German company, it offers high-quality products

On the face of it the Dynamaxx compressor is a straightforward stereo VCA compressor. However, SPL has used experience gained in the development of the Transient Designer and SPL Exciter to make the Dynamaxx a bit special. They started with state-of-the-art 2181 VCA chips from THAT Corporation and added dual sidechain inputs with level LEDs. They then added a Soft Limit function to provide a soft-knee compression mode, an Effect Compression mode with a fixed release time, Decompression mode for expansion and a noise gate

Each channel has its own sidechain and controls: Compression sets the amount of compression, similar to a threshold control – Gain allows post-compression gain make-up and Noise Gate sets the gate threshold. In addition there are four switches – Soft Limit, Effect Compression, De-Compression and Active (system in / out). For stereo operation, the Stereo Couple switch links the gain control of the two channels for accurate stereo tracking. Attack & release times, and gate operation, are program-dependent

According to SPL: “Though auto attack and release functions are nothing new, in the DynaMaxx design, the time constants are automated in a very musical way. DynaMaxx adaptively optimizes all time constants in real time during processing… This ensures both very musical and truly set & forget operation”

Paul White, writing in Sound on Sound: “Once again, SPL have come up with something that’s both effective and simple to use, yet just a little bit quirky to keep things interesting… I particularly like the ease of use, the smoothness of the processing, and the overall high quality of the signal path. The DynaMaxx sums up what we have come to expect from SPL of late — a combination of cleverly applied technology and deceptively flexible features, combined with an easy-to-use interface”

Key features

  • Two channel or Stereo Couple mode
  • Individual controls and sidechains for each channel
  • Soft Limit button
  • Effect Compress button
  • Decompress setting to expand over-compressed signals
  • Variable noise gate on each channel
  • Super-clean THAT 2181 VCA chips
  • Balanced inputs & outputs
  • Excellent build quality with high-quality components

The Dynamaxx turns out to be just as good as I hoped. It’s capable of subtle compression, with the kind of transparency that makes you reach for the bypass button to see if it’s actually doing anything. It’s super-clean, but can deliver pumping compression, and downright naughtiness, on demand. Soft Limit changes the sound completely and Effect Compression, as the name suggests, pushes the Dynamaxx further towards the naughty end of the scale

In a similar way to the TK BC1 in one of my other auctions, the Dynamaxx takes an ordinary concept to another level. It’s not a traditional attack / release / ratio / threshold compressor, it goes way beyond that. Like the SPL Transient Designer, it’s capable of changing the way you look at compressors. I like it because it’s different, it sounds great and it’s not just another bland VCA compressor

With a high-pass filter in the sidechain the Dynamaxx will make a great bus compressor capable of a wide range of colours

Inputs & outputs are on XLR connectors and jacks and the sidechain inputs are on jacks. Gain reduction is via THAT 2181 VCAs and all time constants are automated except in Effect Compression mode. Operating level is +4 dBm and the 9735 has a Gain control for post-compression gain make-up up to 20 dB. Gain changes are shown on 20-segment LED bargraphs and each input, noise gate & sidechain has an LED indicator

Mains input is a standard IEC mains socket with a 120 / 240 voltage selector and a ground lift switch. IEC mains cable supplied on request

Standard 19" 1U device suitable for all 19" racks. 120 / 240 Volt switchable with a standard IEC input. UK, Euro or US power cable supplied on request

Product page


Owners manual


Sound on Sound Review


Gearslutz Review


Release Time Review (in German)



In excellent condition with just a few signs of use. Tested & working 100%. Photos show the compressor for sale