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Saturday, December 3, 2016

Q. What's wrong with my patchbay?

By Hugh Robjohns
Neutrik 48 Jack patch bay.
I have a Neutrik quarter-inch jack patchbay that I'm having problems with. The unit is only a few months old but already I seem to be suffering from poor connections, with signals being quiet or not coming through properly and becoming distorted. I have isolated my outboard and tried different cables to check if the problem lies with these, and all roads lead back to the patchbay. Are there any methods for cleaning the contacts in patchbays or fixing them? The patchbays I had before never had any of these problems and I was using them for over four years.

SOS Forum Post

Technical Editor Hugh Robjohns replies: It is very unusual for a patchbay to become unreliable in such a short time. I presume there is no obvious environmental problem such as excessive dust, damp or smoke? Dust, damp and smoke tend to work together, gathering on the socket contacts to form a sticky residue which acts as a high-resistance layer, giving the kind of problems you seem to be experiencing. It helps if you can make sure the faceplate of the patchbay is vertical in the rack, rather than horizontal or sloping, as this minimises the risk of dust falling into the sockets, and that the room is kept dehumidified and well ventilated.

Another related cause is dirty (tarnished) plugs. This used to be a real problem in professional studios using PO316 or bantam patch cords which employed brass plugs, but tends not to be an issue with the plated domestic quarter-inch plugs used in most home-studio rigs. Professional studios using brass patch plugs often use a mechanical burnisher to clean and polish the plugs, along with an aggressive cleaner for the sockets, but the equipment is designed to be cleaned in this way. The plated domestic plugs and sockets are often quite soft in comparison and will wear out very quickly if treated this way, so gentle hand cleaning with a mild metal polish or contact cleaner — Deoxit or Servisol, for example — might help. Don't get too enthusiastic though: excessive rubbing with an abrasive cleaner will quickly damage or even remove the plating, making your problems a whole lot worse! A quick wipe over with one of the gentle cleaners mentioned above every month or two should keep everything in good order, if surface contamination is the problem.

Another likely problem, probably the most likely, in fact, is that your patch cables are of a non-standard size. Some of the cheaper Chinese-made moulded patch cables are fitted with locally made plugs that are slightly undersized and don't conform to the correct quarter-inch specifications. Consequently, they sometimes don't make reliable contact with some types of socket. The solution here is obvious: try patching using good-quality leads (ideally with Neutrik jacks on the end), and see if that works any more reliably.

Published June 2005

Thursday, December 1, 2016

Q. Do I need to use a compressor before my soundcard?

By Sam Inglis
Alesis Nanocompressor.

If I limit using a Alesis Nanocompressor when recording into my Emu 1820 soundcard, can I still limit the final mix with, say, Waves' L1 Ultramaximizer without any problems? I thought that you should only limit once, and then you have to unlimit before limiting again. Is this true or will the Nanocompressor cause no problems? I've set a threshold of just under 0dBFS and a ratio of 100:1. The attack is fast, and the release 200ms. Soft-knee and peak-sensing modes are active.
I am using the compressor to drive the A-D converters on the Emu 1820. Will this cause me any problems when limiting later to record to CD-R? Or should I just compress slightly at 2:1 with a -9dB threshold and fast attack and release times when recording at the input stage?

Thomas J

Features Editor Sam Inglis replies: I'm afraid there is no such thing as 'unlimiting'. Once you have applied dynamic processing such as limiting or compression to a signal, there isn't an awful lot you can do to reverse it. However, it's not uncommon to apply multiple stages of compression. Compressing an entire mix is also very different to compressing an individual signal within the mix, both in terms of what you're trying to do and the settings you would use.

Some people like to use a hardware compressor before the A-D converter, if it has a specific 'sound' that they can't get later using plug-ins. However, in normal use, there is absolutely no need to use either a compressor or limiter to 'drive' the A-D converters.

You only need to use a limiter on the way into the soundcard if you are dealing with wildly unpredictable levels and there is a possibility of a rogue peak exceeding the headroom you've left. In general, it would be much better simply to leave more headroom at the input of the A-D converter. The dynamic range of a modern A-D converter is huge, and there is no need to push your input signals anywhere near clipping in order to get good sound quality.

So, in short, unless your input signal levels are hugely and widely variable, or you particularly like the sound of the Nanocompressor, I'd simply remove it from the signal chain altogether, and turn the preamp gain down.

Published June 2005

Wednesday, November 30, 2016

Q. Is it worth recording at a higher sample rate?

By Hugh Robjohns
CD burning.
I've recorded several songs in 24-bit/48kHz. When I went to burn the CD, the application I'm using for burning (Nero) did not recognise the files. I had to convert them to 16-bit/44.1kHz first. So does it make a difference in the audio quality of the final CD tracks to record at the higher rates when it's then converted back to 16-bit/44.1kHz? Maybe it's not worth getting a fancy audio interface after all?

SOS Forum Post

Technical Editor Hugh Robjohns replies: If your end format is destined for a 44.1kHz sample rate — the standard audio CD format (the 'Red Book' standard) is 16-bit/44.1kHz — there is no point in recording at 48kHz in the first place. There is no significant quality gain involved in using a fractionally higher sample rate (48kHz is only eight percent higher than 44.1kHz), and the technical losses and time involved in sample-rate conversion aren't very constructive either.

I would recommend recording your material at 24-bit/44.1kHz and then truncating and re-dithering the finished tracks to 16-bit as the final stage before burning the CD. There is a useful advantage in recording your original material with 24-bit resolution, as this increases the dynamic range available to you. This translates into greater headroom and a reduced risk of overloads and transient clipping.

If you want to start with higher resolution source recordings, possibly with an eye to releasing the material on high-resolution formats in the future, then you have a choice of sample-rate options. Obviously, sample-rate conversion will be needed for a CD release, and many argue in favour of recording at 88.2kHz as this is double 44.1, making the down-sampling relatively simple.

In the early days of sample-rate conversion this made a significant difference to the resulting sound quality, but modern sample-rate converters appear to handle non-integer conversions with no loss of quality at all, and a 96kHz sample rate is more widely used in high-resolution formats. In my opinion, there is very little to be gained in going to higher sample rates, so I would use 24-bit/44.1kHz for a CD-only release (reducing to 16-bit/44.1kHz at the last possible stage), and 24-bit/96kHz for everything else.

Published June 2005

Monday, November 28, 2016

Q. What kind of ear plugs should I wear at gigs?

By Hugh Robjohns
Some generic attenuating ear plugs manufactured by Sensorcom.Some generic attenuating ear plugs manufactured by Sensorcom.

I've been coming home from gigs recently with my ears ringing and I'm worried about damaging my hearing. I think it's definitely time to invest in some kind of (preferably unobtrusive) ear protection, but what kind of ear plugs should I be looking at? I still want to be able to hear what's going on but keep my ears out of danger at the same time. I guess I can't wear earplugs when I'm actually performing, but at least I can reduce the chances of permanent damage when I'm watching the other bands. What's your advice?

Patrick Bailey

Technical Editor Hugh Robjohns replies: Hearing damage is directly related to both sound level and length of exposure. So, even if you don't want to wear ear plugs when you're performing, consider wearing them when you're rehearsing, as well as at gigs — it has been suggested that musicians often do more damage to their ears during the many hours of rehearsal than in the comparatively short time they spend on stage.

I would recommend investigating the options for good-quality ear plugs that reduce the overall level of sound but maintain an even spectral balance so that you can still hear everything clearly, although the overall level is reduced. Disposable solid-foam ear plugs won't give you this even balance and will adversely affect your enjoyment of the music. You can often find suitable generic ear plugs in the good musical instrument and equipment retailers, sold as 'musicians' earplugs', and available in different strengths (amounts of attenuation). Obviously, the greater the number of dBs of attenuation, the better overall protection they offer.

However, for a really comfortable and long-lasting solution, I would recommend making an appointment with a good audiologist who will be able to take ear moulds and make earplugs to your precise specifications that will be comfortable to wear for long periods and easy to clean and look after. Custom-made earplugs will cost more, but considering that hearing damage is irreversible, if you value your ears the cost should be irrelevant!

More information and advice is available from the RNID (www.rnid.org.uk). The web site of their ongoing 'Don't Lose The Music' campaign (www.dontlosethemusic.com) is aimed specifically at musicians, DJs, clubbers and concert-goers and is linked with two hearing protection specialists — Advanced Communication Solutions, or ACS for short (www.hearingprotection.co.uk), and Sensorcom (www.sensorcom.com) — who can produce custom-fitted ear plugs.
Some custom-moulded ear plugs, manufactured by Sensorcom.Some custom-moulded ear plugs, manufactured by Sensorcom.

Published June 2005