P1 Audio Processor User Manual Safe Sound Audio Model P1 Audio Processor User Manual Safe Sound Audio, UK
Page 2 User manual P1 Audio Processor P1 Audio Processor Features Advanced audio compressor with peakride which utilises multiple side-chains allowing the compressor to ‘ride’ the crests of the audio so that control of fast audio peaks, especially vocals, may be as fast as desired whilst release from compression compliments the natural decay of the audio waveform. Exceptionally low levels of ripple distortion.
P1 Audio Processor User Manual Contents P1 Audio Processor Features Safety Information; READ THIS FIRST Quick Start Guide Audio Connector wiring information Detailed Operational Guide Power on Typical audio connections +48V Phantom Power for microphones Setting the input gain Overload warning Setting up the output gain High pass filter Expander operation peakride compressor operation peakride compressor theory Limiter with dynamic threshold control How the P1 limiter manages dynamic range Answers to some
Page 4 User manual P1 Audio Processor Important Safety Information : Read this first! There are dangerous voltages present within the unit. Do not open the unit and refer all servicing to qualified service personnel. The lightning flash with arrowhead symbol, within an equilateral triangle, is intended to alert the user to dangerous voltages within the unit.
P1 Audio Processor User Manual Page 5 This unit must be earthed. This unit should only be connected to a mains supply of the type marked on the rear of the appliance. Take special note of the required mains voltage. The IEC mains connecting lead originally supplied with this unit has been fitted with a 3A mains fuse. Always replace with a fuse of the same rating. (UK plugs only) This unit is fitted with an externally accessible fuse. Always replace with a fuse of the same type and rating.
Page 6 User manual P1 Audio Processor Quick Start Guide After reading the important safety information, you may wish to ‘plug and go’.
P1 Audio Processor User Manual Page 7 The unbalanced INSTRUMENT input (2 pole ¼” jack plug) has priority over the MICROPHONE input. The balanced MICROPHONE input (3 pole XLR plug) has the lowest priority. The connector wiring follows normal audio convention. Details are given later in this manual.
Page 8 User manual P1 Audio Processor HI PASS FILTER The switchable high pass filter has a -3dB point at 80Hz and a slope of 18dB per octave. PEAK INDICATOR Lights when the main signal path (before the limiter) comes within 3dB of clipping. EXPANDER Variable threshold expander with a fixed expansion ratio of 1:3, fixed attack time of around 3ms and variable ‘follow-audio’ release time. COMPRESSOR WITH peakride A sophisticated multi side-chain compressor with variable threshold, attack and ratio.
P1 Audio Processor User Manual Page 9 Adjust the preset output gain control (screwdriver adjustment) until the desired recording level is shown on your recording device metering; best to allow 1dB below 0dBFS. MAIN OUTPUT The balanced main output is fed via the preset level control described above to a 3 pole balanced ¼” jack labelled ‘LINE OUT (BAL)’. An LED bargraph shows the output level prior to the output gain control.
Page 10 User manual P1 Audio Processor Audio Connector wiring information Note: All connector wiring information refers to the cable end connecting to the P1 audio processor unless otherwise stated. BALANCED MICROPHONE INPUT Any standard balanced XLR-3 to XLR-3 microphone cable should be suitable.
P1 Audio Processor User Manual Page 11 It is also possible to feed this input from an unbalanced source which may be the case when feeding the P1’s line input from some keyboard instruments or unbalanced sound card outputs. If you want to use an ‘off the shelf’ cable then use a standard unbalanced line level cable (guitar cable) with standard ¼” 2-pole jacks at either end. If wiring your own unbalanced cable we suggest the following wiring arrangement which will give better noise and hum rejection.
UNBALANCED INSTRUMENT INPUT Any standard unbalanced ¼” to ¼” 2-pole instrument (guitar) cable should be suitable. If wiring your own use standard ¼” 2-pole jack plugs for both ends wired as follows; INSERT POINT A ‘Y’ type cable is necessary to access the processor’s insert point. The ideal cable type is a twin ‘figure 8’ unbalanced cable. These are available ‘off the shelf’ but if wiring your own, a typical wiring scheme is shown below.
P1 Audio Processor User Manual Page 13 BALANCED LINE OUTPUT Any standard ‘off the shelf’ balanced line level cable should be suitable. If wiring your own, at the P1 end use a standard ¼” 3-pole jack plug wired as follows; It is also possible to feed this output to an unbalanced destination which may be the case when feeding the P1’s line output to some unbalanced PC sound card inputs. In this case use a standard ‘off the shelf’ unbalanced line level cable.
Page 14 User manual P1 Audio Processor MONITOR INPUTS The P1 has the option to accept either unbalanced or balanced monitor inputs which allows standard cables to be used in both cases. The monitor inputs will most commonly be fed from a stereo output of the recording device or PC sound card. Unbalanced connection : plugs into the jack labelled ‘MONITOR INPUT L/R (UNBAL)’.
Quasi balanced connection : plugs into the two jacks labelled ‘MONITOR INPUT LEFT (BAL)’ and ‘MONITOR INPUT RIGHT (BAL)’. If feeding from an unbalanced monitor output and wiring your own cable, we suggest the following wiring arrangement which will give better noise and hum rejection. (Note that the sleeves of the two 3-pole jacks at the P1 end are intentionally left unconnected.) Balanced connection : plugs into the two jacks labelled ‘MONITOR INPUT LEFT (BAL)’ and ‘MONITOR INPUT RIGHT (BAL)’.
Page 16 User manual P1 Audio Processor Detailed operational guide POWER ON With the IEC mains cord securely fitted to the rear of the unit, plug the P1 into a suitable mains power source taking special care to ensure the mains voltage is as indicated on the rear panel. Note that a UK 240V AC supply is suitable for powering a unit marked ‘230 VAC’ Check that the front panel green PWR LED is lit.
P1 Audio Processor User Manual Page 17 TYPICAL AUDIO CONNECTIONS The diagram below shows a typical application of the P1 audio processor in a recording set-up. Three audio input types are provided for, these are; Balanced microphone input, for use with either dynamic or phantom powered condenser microphones. Balanced line level input, for use with any line level source such as keyboards and the outputs of certain guitar and bass effects units which offer a LOW IMPEDANCE line level output.
Page 18 User manual P1 Audio Processor Although it is possible to connect sources to all the P1 inputs simultaneously, only one will function at any one time; The balanced LINE input (3 pole ¼” jack plug) will always have the highest priority. The unbalanced INSTRUMENT input (2 pole ¼” jack plug) has priority over the MICROPHONE input. The balanced MICROPHONE input (3 pole XLR plug) has the lowest priority.
P1 Audio Processor User Manual Page 19 circuitry to help protect the microphone amplifier from damage in this case but it’s impossible to protect in all circumstances so you have been warned! Most professional balanced dynamic microphones will not be damaged through the accidental application of phantom power. SETTING THE INPUT GAIN This is done independently of any output level setting and independently of any record level setting in your recording device or PC sound card.
Page 20 User manual P1 Audio Processor Overload warning Although not usual, it is possible for a very high level audio source to overload the P1’s input stage. The red PEAK LED will light when the input level is 3dB below the maximum signal level which the P1 can handle.
P1 Audio Processor User Manual Page 21 SETTING UP THE OUTPUT GAIN The P1 limiter takes care that the maximum audio level through the processing chain is carefully monitoring and controlled without having to adjust any settings. However you do have to adjust the output gain control so that the maximum level from the P1 (after the limiter) matches the desired maximum recording level. There are two ways to do this; by using a test signal, or by trial and error using any dynamic audio source.
Page 22 User manual P1 Audio Processor Adjust the P1’s input gain until the red LIM LED just lights. Now set your recording device to monitor the incoming test audio signal level on its record meter. If your recording device has a recommended input level setting for best audio performance, then set this first according to their recommendation. If there is no recommendation then we suggest you set it to its maximum setting.
P1 Audio Processor User Manual Page 23 The 1kHz square wave signal was chosen to ensure that the recording device metering gives an accurate indication of the PEAK level being fed to its recording input. Many ‘peak’ reading meters still have a finite ‘integration’ time so they will display correctly the peak level of the more usual tone based test signals but under represent the actual peak voltage value of very dynamic audio.
Page 24 User manual P1 Audio Processor set this first according to their recommendation. If there is no recommendation then we suggest you set it to its maximum setting. Now adjust the output gain on the P1 using a flat blade screwdriver until the desired maximum recording level is viewed on the record meter. We suggest you set a maximum level of 1dB below 0dBFS.
P1 Audio Processor User Manual Page 25 HIGH PASS FILTER The high pass filter (sometimes called a low cut filter) affects only low frequency sounds below what’s called the turnover frequency which in the P1’s filter is set to 80Hz. When switched into circuit, it will reduce the level of all audio components below 80Hz progressively at a rate of 18dB per octave, so for example a 30Hz tone would be reduced in level by 18dB compared to the 60Hz tone level.
Page 26 User manual P1 Audio Processor THE EXPANDER Expanders reduce audio gain when the audio level falls below the expander threshold setting as shown in the diagram below; The P1 expander is a simple to use with a single knob to set the threshold. As the audio input falls below the threshold, its gain is reduced progressively from 0dB (no gain change) up to a maximum gain reduction of 20dB (called the expander depth). So loud sounds are unaffected but quiet sounds get quieter.
P1 Audio Processor User Manual Page 27 Hold time is how long the expander waits before operating when the input level falls below the threshold setting. The P1’s hold time is programmed to follow the natural dynamics of the audio signal. Short duration audio phrases have a short hold time whereas long audio phrases have a longer hold time. Release time is the time it takes the expander to reduce the audio gain as the input level falls below the threshold setting.
Page 28 User manual P1 Audio Processor We will now detail some common uses of the P1 expander. In each case remember to set the input gain correctly before switching in the expander. As a effects unit noise reducer : You have a really favourite classic guitar effects peddle but it has a very high background noise level. So record your killer guitar track as normal, then playback the recorded track through the P1. Switch in the P1’s expander and start with the THRESHOLD setting at the -60dB setting.
P1 Audio Processor User Manual Page 29 setting. This should have no audible affect. Now turn up the threshold control slowly so you lose as much as the background noise as possible without losing the natural decay of the vocal phrases. Make sure you turn up the threshold control far enough so that the background noise doesn’t drift back during very quiet or silent passages.
Page 30 User manual P1 Audio Processor THE peakride COMPRESSOR Compressors progressively reduce the gain of an audio signal as its input level rises above the compressor threshold as shown in the diagram below; The compressor threshold is the level point in dB above which the audio gain will be reduced. On the P1 this can be varied from 0dB to -40dB. The red LED bar graph shows how much the audio gain has been reduced and is calibrated in dBs.
P1 Audio Processor User Manual Page 31 to replace this ‘lost’ level and in the case of the P1 this is done automatically; the amount of make-up gain applied being related to the threshold and ratio settings. The use of compression when recording both vocals and instruments is a very powerful way of achieving the desired ‘live’ sound and so is often used at the track laying stage as it can actually improve the quality of the performance given by the artist.
Page 32 User manual P1 Audio Processor the start of a vocal phrase then try decreasing the attack time (turn the knob clockwise). If you feel that the vocal performance is still a bit uneven, try increasing the ratio control until you get a more even result. Be careful not to go too far or you will kill all the dramatic effect which the vocalist is trying to achieve.
P1 Audio Processor User Manual Page 33 clockwise). This will allow some more of the initial note attack to sneak past the compressor. Now try experimenting with the ratio control. Lowering the ratio will restore more of the ‘natural’ dynamics of the instrument which may be appropriate for some mixes. Using such high levels of gain reduction (with the associated high gain make-up) can sometimes raise the background noise level of some instruments to an undesirable level.
Page 34 User manual P1 Audio Processor Many instruments and vocalists have a natural vibrato which finds it’s way into the compressor control side-chain causing the gain to move up and down in sympathy. This is extremely undesirable and causes high levels of non-linear distortion. The P1’s peakride design overcomes these problems by the use of three separate control side-chains which act in the time domain (rather than in the frequency domain of a multi-band compressor).
P1 Audio Processor User Manual Page 35 attack, especially to provide adequate control of certain vocal styles, and the usual consequence that the whole vocal phrase then suffers from over compression. It is often difficult to achieve the attack speed without the undesirable over compression. The P1 compressor achieves this by altering the ratio of the compressor dynamically.
Page 36 User manual P1 Audio Processor The P1 limiter with dynamic threshold control Considering that almost half of the processing power in the P1 is dedicated to the limiter, it doesn’t exactly have a high profile on the front control panel, so what’s it all about? Let’s start with the basics; All digital recording systems have a maximum signal level which they can handle. If you go above this level then digital audio clipping will result and it sounds truly awful.
P1 Audio Processor User Manual Page 37 But can’t I just record in such a way that this maximum audio level is never reached? In theory, yes you can; if you are very careful and record well below the maximum permitted level of your recording system; but as so commonly happens, you set up the levels carefully during rehearsal but when the actual recording takes place, the vocalist has turned from shy retiring folk singer to the rock legend from hell! And the once in a lifetime performance is ruined by digi
Page 38 User manual P1 Audio Processor being exercised and this only happens when you pump in the very highest audio level which the converter will accept before digital clipping. This level is called 0dBFS. So, allowing our 12dB safety margin, a quiet vocal phrase may only be peaking 20dB below this maximum safe level (down at -32dBFS).
P1 Audio Processor User Manual Page 39 microphones can be in excess of the recording system’s practical dynamic range. In addition, the digital clipping caused by overloading an A/D input is very difficult to rectify. Have a look at the diagram below. High quality condenser microphones have a useful dynamic range in the region of 120dB, where measured from the highest signal handling level (let’s assume a maximum acceptable distortion of 0.1%) down to the microphone’s noise floor.
Page 40 User manual P1 Audio Processor However the P1 has three very useful ways to manage the high input dynamic range available; It has a very high quality dynamically variable threshold limiter to protect the soundcard against unexpectedly high levels which would lead to digital clipping. It has an additional 14dB of input headroom so that unexpected high input levels do not level clip within the P1.
P1 Audio Processor User Manual Page 41 Answers to some common questions; Q. Why don’t 24 bit soundcards achieve their theoretical 144dB dynamic range in practice? A. The highest audio signal level which most 24 bit A/D chips can handle is around +7dBu limited by the +5V supply voltage which these chips are designed to run from (not to be confused with the soundcard’s maximum input level which is often much higher but this is simply fed through an analogue level attenuator to the actual A/D chip).
Page 42 User manual P1 Audio Processor signal handling limit of +21dBu. There wouldn’t be much point in protecting the digital recording chain if we could accidentally clip the P1’s own circuitry. The P1’s maximum output level is also set to achieve the best distortion performance through the THAT VCA chip which is at the very heart of the limiter. Lowest distortion is achieved at or below +2dBu and is still very good at the +7dBu limit we have set. Q. You talk about levels in dB and in dBu.
P1 Audio Processor User Manual Page 43 ‘natural’ threshold (which we call 0dB) and this allows the limiter to use a much gentler control side-chain to ensure that the maximum permitted level is not exceeded. As the threshold is set according the dynamics of the input audio, it allows a higher useful dynamic range to be passed on to the recording device than traditional limiter designs and at much lower levels of distortion.
Page 44 User manual P1 Audio Processor The monitoring facilities We’ve designed the P1 to provide the kind of monitoring set-up which is most commonly required during track recording and overdubbing. If you have enough replay outputs from your recording device then one stereo output of your recording device will normally be dedicated to your main monitor loudspeakers and a second stereo output will be available to feed to the P1’s monitor inputs.
P1 Audio Processor User Manual Page 45 If working from balanced stereo monitor outputs, then connect as shown below; During track laying or overdubbing you require to hear both the already recorded tracks plus the new source which you are recording. The P1 has an on-board monitor mixer to allow you to do this. The headphone volume control sets the overall monitor level fed to the headphones and the MON SOURCE level control allows you to set the level of your new source material within the monitor mix.
Page 46 User manual P1 Audio Processor mute the feed of the record input from the recording devices monitoring output. The P1 is capable of generating high monitor levels so always switch the headphone level control to minimum when connecting headphones then turn up the level slowly to the achieve the desired monitoring level. Monitoring at high levels for sustained periods is not advisable.
P1 Audio Processor User Manual Page 47 Technical Specification MODEL P1 AUDIO PROCESSOR Size : 223mm wide by 44mm high (1U) by 225mm deep (excluding cable connectors) Weight : 1.8kg (4lbs) Power requirements : AC power to the voltage indicated on the rear panel 10%, 50/60 Hz. Mains Plug fuse : Rear panel fuse : Power consumption : 3A (UK plugs only) 20mm fuse, 250mA 250V 15W MAIN PROCESSOR AUDIO PATH Frequency response : -0.5dB points at 15Hz and 55kHz Distortion : < 0.
Page 48 User manual P1 Audio Processor EQUIVALENT INPUT NOISE FIGURES; Microphone : Line input : Instrument: 128dB (max gain with 150 ohms source) 100dB (unity gain) 105dB (max gain) BALANCED LINE OUTPUT Output noise : -93dBu RMS unweighted, measured 22Hz to 22kHz -95dBu RMS A-weighted, measured 22Hz to 22kHz Maximum Output Level (post limiter) : > +21dBu Output impedance : 50 INPUT GAIN RANGES Microphone input : Line input : Instrument input : 0dB to +70dB -10dB to +20dB 0dB to 30dB EXPANDER
P1 Audio Processor User Manual Page 49 PEAKRIDE COMPRESSOR Threshold range : 0dB to -40dB Attack time range : 60ms to 1ms Release time : variable from 90ms to 500ms (tracks the natural audio decay). Ratio : 1:1 to INF:1 Make-up gain : automatically set in proportion to the threshold and ratio settings. Gain reduction meter : calibrated in dBs.
Page 50 User manual P1 Audio Processor Fault finding Problem : Green Power LED does not light when unit is connected to the power source. Checks : Is there any visible or audible sign of physical damage to the unit? If so, immediately disconnect the unit from the mains supply and connect Safe Sound Audio for assistance.
P1 Audio Processor User Manual Page 51 Problem : I seem to be having problems setting up the output level control on the P1 to match my recording device to give a consistent result. Advice : Make sure that the expander and compressor on the P1 are switched OFF when your are setting output level control. Problem : I am connecting the P1 to another balanced audio device but I am still experiencing higher than desirable levels of hum.
Page 52 User manual P1 Audio Processor Customer Care If you have a problem with the unit and suspect it is faulty, then first follow the guidelines in this manual for set-up, operation and fault finding tips. If you still cannot get the unit to function as you expect then contact Safe Sound Audio for advice and if necessary we will issue a Returns Authorisation Number prior to you returning the unit to us for servicing. Under no circumstances attempt any repair by opening up the unit.
P1 Audio Processor User Manual Page 53 Safe Sound Audio will be responsible for the cost of shipping the repaired or replaced unit back to the customer including insurance of the unit during shipping. The warranty will be void if the unit has; Suffered physical damage. Has been connected to an incorrect source of mains power. Has been damaged due to liquid spillage. Safe Sound Audio shall not be liable for any special or consequential damages resulting from the use of this product.
Page 54 User manual P1 Audio Processor How to contact us By post : Safe Sound Audio 47 Broadgate Lane Horsforth Leeds West Yorkshire LS18 4AG UK Callers strictly by appointment By telephone : +44 (0)7866 574 522 By e-mail : info@safesoundaudio.co.uk On the web : www.safesoundaudio.co.uk Safe Sound Audio reserves the right to make changes and improvements to the design of this product without notice.
P1 Audio Processor Notes User Manual Page 55
Page 56 User manual © Safe Sound Audio 2010 P1 Audio Processor
