The DAV Electronics S.I.P.P. is a high quality M-S Image Processor and Parallel Insert Mixer. It allows the engineer to use outboard processors in ‘parallel’ by allowing any desired mix of wet and dry paths using a continuously variable blend control.
The source is fed to a single input and then split into two:
The dry path represents the original source which can then be blended with the with the ‘wet’ path which consists of the same source routed to a balanced insert point. The user can connect any piece of outboard, or indeed pieces of outboard to the wet path to achieve a variety of effects.
The most common application for this technique is in the implementation of ‘parallel compression’. This technique allows low-level parts of a signal to be brought up, while retaining the transients in the source. It works particularly well on drums and vocals as well as across the mix in both mixing and mastering applications. Other common uses include distortion as a parallel effect but in fact any process could prove to be creatively useful.
The most essential element of any parallel process is that the phase relationship between the original source and the processed parallel remains intact. Digital Audio Workstations allow users to route signals out via D/A and A/D converters and mix the returning audio with the original. Many also compensate for the conversion delays induced in doing so.
But the process can be subject to what is referred to as ‘inter-sample delays’ whereby the returning audio is subject to delays which are less than the value that can be represented by a single sample. Therefore the returning audio can be say, half a sample out of time, and no amount of compensation or nudging regions in the digital realm can perfectly align the two.
Engineers have traditionally avoided this problem by sending a ‘dry’ signal out of a second converter pair and returning it alongside the processed one. The S.I.P.P. avoids this problem by doing the splitting and subsequent summing in the analogue domain. It is also a valuable tracking tool, before the signal has ever reached the digital recorder. As the S.I.P.P. splits the signal into two, it can also be used as a one to two, or two to four line level splitter. This is achieved by using both the main output and the insert send as outputs, while the parallel process is in bypass.
So say for example you were tracking a vocalist using a compressor in the traditional way, but weren’t quite sure that the compression worked everywhere in the song, you could connect the compressor to the insert send, the compressor output to a second A/D converter channel and bypass the parallel process. That way you’d be printing both a compressed and uncompressed vocal to the DAW with no need for an external mixing desk.
The S.I.P.P.’s ability to split a signal can also allow it to be used to feed an equalised signal to a compressors sidechain. The original source is fed to the S.I.P.P.’s input. The insert send is connected to an eq, and the return of the eq to a compressor sidechain input. The parallel process is bypassed. The output of the S.I.P.P. is then connected to the compressors audio input. Now the sidechain can be EQ’d without the need for a separate EQ’d source to be sent from the workstation.
Equally it can be used as a pair of two to one line mixers by using the standard inputs and insert return points as inputs. The blend controls the adjust the relative balances between the sources. For example if you wanted to blend snare top and bottom mics together, compress them and record to disk as a single file, you could feed the snare top to the input, the bottom mic to the insert return and blend to taste. The resulting output would feed the compressor.
To take this idea a step further, the output from channel one could feed the input to channel two, allowing you to parallel compress or distort the blended snare mics. The S.I.P.P can also be used as a high quality stepped attenuator. If you want to run your preamps ‘hot’ for sonic reasons, as many API users like to do, but you don’t want to risk overloading your converters, you can use the S.I.P.P.’s stepped gain control to allow you to do this.
Just because the parallel path is there, it doesn’t mean you have to use it. With all knobs detented the S.I.P.P. allows you to easily recall settings which is essential when using the S.I.P.P. in a mastering capacity or simply recalling a mix.
The DAV Electronics S.I.P.P. Features:
Frequency response: 10Hz - 50KHz ± 0.25dB
Inputs & Outputs: All Balanced
Distortion: Less than 0.01% Typ, 0.001% 1KHz @ +20dBu o/p
Clipping level: +29 dBu
Noise: 20 microvolts [-110dB ref +20 dBu. Bandwidth 10Hz-18KHz input loaded 150 ohms, 32dB gain].
Connectors: IEC mains, XLRs on rear
Dimensions: 19" 1U rack mount.
Depth = 150mm
Gain range:-5dB to +6 in 1dB steps