Diode Bridge Compressors
After the popularity of our Diode Bridge Compressors Shootout review and the love received from the interview with Dave Derr of Empirical Labs on the Distressor (and him talking about aspects you may not have known about it) we thought it would be wise to get a Diode Bridge Compressor expert designer (Tim Farrant of Buzz Audio) to chime in with some extra info on this style and proffer some wisdom that you may not realise you can do with them, or remind you what you can do with (in our opinion at least) one of the most sonically interesting types of compressors.
Knowledge is power, so here’s some, to help you out. And we’d recommend playing with the shootouts in the Diode Bridge Compressor Reviews in conjunction with this interview to really enhance your experiential understanding. Imprint this stuff sonically in your brain and it will stay with you for a long time.
1 - What is unique about the character of a Diode Bridge style of compression and how it works vs other designs (VCA, Opto, FET)?
Tim Buzz Audio - I guess it's the distortion it generates and this creates the harmonics. Optical compressors are generally low distortion due to the LDR low speed, and VCAs are designed to have as low distortion as possible. FETs and diodes are similar in that you are operating them at very low signal levels to take advantage of their non-linear transfer region. Of course how you design the side chain circuit is going to have a huge impact on how it works with real audio, and every diode bridge compressor is different in this regard.
2 - What is special and particular with the new radio steel laminated transformer you created for the DBC-20 and DBC-M and why you did you create this rather than use a different type of readily available transformer?
Tim Buzz Audio - Actually, it is a cheap transformer we had made for use in lo-fi public address applications! But by carefully implementing it into the circuit we can get a good frequency response and it adds some saturation as the input level gets up. The main reason for using it is the low price, it does not add significantly to the cost of the DBC-20, but is does add the vintage vibe!
3 - How do you think people can get the best out of the DBC (for clarity or colour) - e.g. which stages are best to drive?
Tim Buzz Audio - As I said above, the transformer does tend to saturate as the input level gets up, so pushing and feeding plenty of input signal will add more colour.
4 - How does the adaptive ratio design of the DBC benefit how it compresses vs other compressors - what other ones is it similar to in this regard?
Tim Buzz Audio - There are many famous compressors that operate like this, the most notable would be the Fairchild 670. Basically the thing has a wide "soft knee" characteristic. The DBC will move from a low 2:1 ratio right up to 20:1 depending on how hard you drive it. So if you think about it, this type of operation is perfect if you want control a vocal, as the louder they get, the more of a "clamp" you need. It is also useful on complex material if using fast attack to control transients, the compressor hits the transient at a high ratio but leaves the average level alone. An adaptive ratio also makes the unit easy to use - one less decision to make!
5 - Why did you choose the particular diodes you have in the DBC, and how different would alternate diodes make the unit sound?
Tim Buzz Audio - We use Schottky barrier signal diodes and I chose these because they have the sound I wanted which was a bit more punchy than standard silicon diodes. Plus they also have very tight manufacturing tolerances so we do not need to match them, which saves labour and helps keeps the cost of the unit down.
Hear the Buzz Audio DBC-20 Diode Bridge compressor below.
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If you want to discuss or make any requests about Diode Bridge Compressors, or any gear you'd like us to make a shootout of please join our Facebook Group and sign up to our mailing list at the bottom of the page.
And here is a useful extra expert reading from Dave Hill of Cranesong on Compressors
If you want to know about the first ever Diode Bridge Compressor (and the grandfather of virtually all modern compressors) learn abut the U13 here