This is the Heritage Audio HA-609A . In a little under ten years Spanish company Heritage Audio has built up an impressive range of products inspired by classic Neve hardware attempting to hit the sweet spot between quality and price. As you would expect preamplifiers and EQs are well represented across the range but in this article, we are going to concentrate on another classic Neve design - The diode bridge compressor.

Part of the Elite Series the HA-609A is unmistakably a take on the Neve 33609, the current offering of the original 2254 from 1969. Originally commissioned as a more reliable alternative to Pye compressor/limiters, at a time before VCAs were available, Rupert Neve exploited the non-linearities of diodes to create a control element. By configuring diodes in a bridge format much of their inherent high levels of distortion can be removed. Although the low operating levels necessitated by this design presents its own challenges, this design went on to become the well known 2254. The 33609 is the current offering of this design from AMS Neve, although current it has been around since 1985!

Audio Examples

Here is an audio example without any talking. First here is the extract with the HA609A in bypass, as it’s a true bypass the transformers aren’t in circuit.

And here is the same clip with a 4:1 ratio, slow attack and 400ms release. The gain reduction was 3-4dB on the peaks.

This example is subtle, but listen to the way the back of the snare changes.

What Is A Diode Bridge Compressor?

Diode bridge compressors became popular in the late 60s and early 70s. They offered a faster response than optical compressors and lower distortion that FET designs. The introduction in the early 70s of VCA designs like the dbx160 eclipsed the diode bridge, making their moment in the sun brief, but for a significant number of users the control, speed and pleasing character of the diode bridge makes it a first call compressor, particularly on busses.

The HA-609A is unmistakably based on the 33609 but by taking advantage of modern manufacturing techniques it manages to deliver the same facilities without the price inherent in traditional labour-intensive production. One of the most obvious areas is the decision to use an external power supply. Diode bridge compressors already have a disadvantage when it comes to noise performance so keeping the power supply external must make life easier for the designer. The things which really matter to the sound remain in place. The design is an entirely discrete class A design and features no fewer than three Carnhill/St Ives transformers per channel. To deliver this kind of old-school construction and keep manufacturing in Spain is impressive. The HA-609A costs $1799, less than half a 33609!

Heritage Audio HA-609A

The HA-609A is clearly inspired by the Neve 33609 with a nod towards the Neve 2254. The panel layout and control set are almost identical to the 33609 but gains extra cool points by using the older Neve style skirted Marconi knobs. There are differences in the ranges available on the threshold controls but the ratio, attack and release times are identical to the 33609.

Dual mono or stereo linking are both available, though you need to be aware of what doesn’t get linked. The ratio and attack and release get linked in stereo use but the threshold and makeup gains don’t. Although in the video I operate the unit leaving the channel 2 threshold set as high as possible and letting the linking between the channels control both from the channel 1 threshold, I did this mostly for visibility reasons, so as not to obstruct the camera’s view. When driving the unit, not on camera, I found it most intuitive to control it using two hands setting identical levels on both sides. It just made more sense to me that way.

Pots And Switches

This is made easy by the use of detented pots and stepped rotary switches. On the subject of switches, the HA-609A has push switches instead of the metal toggle switches found on the 33609. I like toggle switches, particularity when it can be useful to operate two at once as in this case. Luckily the springs used in these push switches aren’t too strong, unlike my BAE 1073 which has buttons so stiff the unit will be pushed backwards if it’s not racked!

Unlike the 33609 there is no facility for an external side chain, something which doesn’t bother me but might bother some. Something which was never present on the 33609 but I’d prefer over an external side chain would be a high pass filter on the internal side chain to lessen the response to bass instruments.

HA-609A In Use

The sound of the HA-609A is immediately appealing. If you’re looking for that “thing” that the 33609 does on mixes then this unit delivers. I’ve used a real 33609 before but like many, the majority of my experience of diode bridge compression comes from Universal Audio’s excellent 33609 plug-in and the different but equally excellent Lindell Audio 254E. Everything that people attribute to the SSL bus compressor in terms of its cohesive glue can be said of diode bridge designs and in my opinion more so. Used sparingly, at 2:1 or 1.5:1 slow attack and at Auto 1 on the release (my favourite) it does the same job as an SSL bus comp but with more attitude and definitely more colour. I used to be an SSL bus comp person but in the last few years I’ve migrated to Neve style compression for anything guitar and drums based. You can use this on anything but for me, this is where it shines.

If my appraisal of the sound of there HA-609A has been presented in terms of how diode bridge compressors sound generally, that is deliberate. They have a distinctive and very attractive sound. If a hardware design were done badly there are potential negative aspects of this operating principle would make themselves known very quickly in terms of noise and distortion.

I am pleased to report that the HA-609A is done extremely well. Noise wasn’t an issue. Some distortion is the point of a unit like this and the analogue flavour this unit delivers is attractive and very useable. Build quality is reassuring and even the external power supply is at least an inline unit rather than a wall wart type and can accept a standard “kettle” C13 IEC lead rather than the fig 8 style IEC C7.

If you want a high-quality Neve style diode bridge compressor for under half what a real 33609 would cost the HA-609A won’t disappoint.