Humming cam-corder mic
Identifying antique microphones
Seck mixer support
Multi-room home audio
How to use a compressor / limiter
Spare drivers for Yamaha NS10MS monitors
Where can I get a new turntable drive belt?
Where can I get user manuals?
How to clean clogged mic grilles

 
Q1 I recently purchased a ATR97 Microphone for use with a Sony 80X Mini cam. The microphone works fine but I am getting a constant humming noise that detracts from the noise I wish to record. Because I have to record from several locations there is a 50m length of cable from the microphone to the cam corder. Most of this is usually wound up around a cable reel. I have tried earthing the microphone cable both at the microphone and the cam corder ends but it only makes the humming worse. I cannot use the built in microphone of the cam corder because the nearby road traffic noise is distracting. As I record for hours at a time I use a mains power connection for the cam corder. Any suggestions? Many thanks in anticipation. G.D.

Q2 I like your web site, which I've visited a couple of times now. I do a bit of amateur recording as a hobby but I've never seen a microphone like the one Jack McIvor uses in "Stiff". Can you tell me what type it is and is it an antique? Yours faithfully, M. Duffy (Scotland)

Dr Know's reply: Thank you for your comments and we're glad you like our site. The big old mic in the photo is actually a theatrical prop which has a cunning space inside to hold a slim condenser such as AKG C451, C460, SE300, Audio-Technica PRO37R, ATM33a, etc giving quality performance with retro looks.
However for "Stiff" we only used it as a prop since all the cast were wearing ATM73 head mics. A pre-programmed digital echo and band pass filter was added to give the effect of an old "tannoy" system.
[added Jan 2008, see our expanding range of original classic and vintage microphones for hire or sale.]

Q3 We are a company located in Austria, specialising in repairing professional audio devices. Recently we got a Seck mixing console - unfortunately without any schematics. It would be great, if you have some drawings - or information where to get them. I'd like to thank you for your efforts, with best regards.      M.M.

Dr. Know's reply: As you probably know, Seck were taken over many years ago by Soundcraft and much of the Seck design went into the Spirit series consoles. Unfortunately, Soundcraft don't support Seck products and we are not aware of any specialist Seck support companies.
We have limited tech info and compatible parts available. We have two types of new replacement power supplies available from stock. We often have  secondhand stripped down parts available. More detailed information and prices can be found on our data sheet www.gbaudio.co.uk/data/seck.htm 
I have now added some schematic and circuit drawing links on this data sheet for all the people who keep asking about Seck mixers. I hope this helps you. Let us know how you get on.

Q4 I read your web site with interest and wondered if you could help me with a query I have regarding my home audio set-up? I would like to install pairs of speakers in four different rooms and am looking for a simple (and cheap!) way of controlling volume in each room independently. Do I need to buy a separate amplifier for each room or is there a product on the market which will do this for me? Any help or guidance would be much appreciated! Many thanks,  S. J.

Dr. Know's reply: You are obviously someone who either loves his music or can't be without the radio. There are simple switching devices around £20.00 that can switch between four pairs of speakers from one amplifier but these do not vary the volume and you will need to be careful about the total load impedance presented to the amplifier. You will need to check the impedance of each set of speakers (will they all be the same or will they be different pairs?) and work out how to combine them safely. As a rule of thumb, most (but not all) domestic speakers are 8 Ohms impedance each. Most modern amplifiers will be fine driving a total load of 4 Ohms ie two pairs wired in parallel. If you want to control some of the volumes separately and/or run all four rooms simultaneously, you will need either a four channel power amplifier (eg Yamaha XM4220) or an extra stereo amplifier (eg Denon PMA250SE), fed from the pre-amp output of your main amp. This will allow you to run two pairs of speakers from each amp so you will be able to vary the volume in two stereo zones. If you really want to vary the volume in each of the four rooms separately, you will need a separate amplifier for each room ie four stereo amplifiers or a six channel power amplifier plus your existing amp (eg Yamaha XM6150).

Q5 Please can you help me I have a Drawmer DL221 compressor and it is my first time to use a compressor and I cannot get a good vocal sound out of it could you give me some information on settings because I have not got a clue. yours R.

Dr. Know's reply: Try this out first with a music source such as CD or MD or sampler.
Set the threshold and gain to zero. Set the other three controls to the left. Set the meter switch to VU and the function switch to bypass. Sound should be passing through, unaffected.
Now switch the bypass to Norm. If everything is wired up right you should hear things about the same.
Threshold determines the level at which the compressor starts to affect the sound. So the higher you set this, the less effect. the lower you set this, the more effect.
Ratio sets the proportion of sound compressed. 1:1 is no compression, 3:1 or 4:1 is usually a good vocal setting although light, breathy vocals will need a higher level. Infinity:1 is a maximum "brick wall" limiter.
The Attack and Release determine how quickly the compressor acts and de-activates on the sound, so you can experiment with these to balance leading edge dynamics and decays with compression or limiting control. These controls can give you some artistic control of the sound, making the compression sound more or less natural/seamless.
The Gain control is just a way of compensating for any loss of signal level caused by the compression or limiting. It operates after the compressor circuit.
Using the Bypass switch will allow you to compare levels against the dry sound.
The LED meter shows the amount of gain reduction (GR) or you can switch it to VU to see the actual level passing through.
If you use compression over a stereo source, switch the Stereo link. This makes both channels trigger simultaneously.

Q6 Hello,  First of all your site is great, it helped me a lot. I would like to order a NS10M part that is L.F. JA1801... Regards K. C.

Dr. Know's reply: No problem. Even though Yamaha, in their infinite wisdom, have discontinued the ubiquitous NS10MS, we have spare bass drivers, tweeters and crossover networks available @ £49.95 + VAT each by mail / email / telephone order. Check out the full specs on our NS10MS data sheet.

Q7 Where can I find a new drive belt for my beloved old Dual record deck?    C.B.

Dr. Know's reply: We have a large range of replacement drive belts available @ £10 each by mail / email / telephone order. See the chart and measurement guide on our Drive Belt Data Sheet

Q8 What would be the cost' Canadian ' for the operational manual for the Yamaha EMX 150 mixer , I just purchased one at a used item sale.  J.W.

Dr. Know's reply: Thank you for your enquiry. You can download a copy for free.
Use the link from our Technical Reference Library: www.gbaudio.co.uk/info.htm#Manual
(Here you will find free links for most manufacturers' user manuals)

Q9 Question is, do you have any sprays / fluids or services for cleaning clogged up microphone heads of the round mesh variety? Or can you point us in the right direction? Yours sincerely S.B.

Dr. Know's reply: Remove the grille from the microphone and wash with hot water and detergent, using an old toothbrush or nail brush. If the grille is very clogged up, leave it to soak a while in the soapy water. If it is rusted, scrub all the rust off with a small wire brush and then seal the bare metal with a coating of enamel paint or plastic sealant spray. Take care not to get the spray on the foam inside the head. If they are really bad, it will probably be easiest and safest to just replace them.

hi, just bumped into your web site (through a search on some microphone specs i think) and its really nice. if more people actually put up some useful information on their sites then the web would be a better place...  a.f. brussels