Malcolm Stewart

The actual microphone capsule, within the dotted lines on the left of your diagram, requires power to work the FET amplifier. (A FET (Field Effect Transistor) is used because it has the best characteristics for these types of microphone which have a very high impedance - i.e. take very little current.) This power is supplied via the 10kohm load resistor, although I wouldn't describe it as a "load" resistor in this application. The 1 microfarad capacitor stops the DC voltage from the supply upsetting the amplifier (triangle with "Output" as label), and passes the alternating signal from your microphone to the amplifier's input. If you've got little experience in this area, please do try to stop electrostatic voltages from damaging the electrical components when you're assembling things. For example, try not to wear nylon clothing, and if possible have all your components on a conducting metal surface e.g. aluminium foil, on which your forearms can rest. Also, do make sure that your soldering iron is electrically SAFE. I'd advise Googling for "ESD" and "static safe working". e.g. http://en.wikipedia.org/wiki/Electrostatic_sensitive_device http://www.hakko.com/english/static/pages/esd.html Damage from static discharge may be instantaneous, or it may weaken the component, and problems will arise later. Hope I haven't worried you, but a few basic precautions should help you have it working first time.

I'm here because of buying and using several Minidisc recorders over the years. However, last February after some research, I bought a solid state Sony PCM-D50, and can't see myself ever using Minidisc again. Most of my recording is in daylight where the easily seen display of the PCM-D50 is a huge bonus. My two later Minidiscs displays are useless in anything like daylight, and the display on my NH900 has failed. The other advantage is that I no longer have to use Sony's Sonic Stage to upload my files to my PC. Obviously when not using the excellent built-in microphones on the PCM-D50, my techniques are very similar to using Minidisc, so where is the best place to post?

My set-up uses two Yoga lapel style mikes inside wind-reducing Rycote furry covers mounted each side of my baseball cap, and very close to my real ears. From each mike there's a short mono lead to a combiner socket which I clip to my shirt or jacket. The stereo output from this is plugged into an inline socket connected to the ex-earphone lead. To refresh my memory, I've opened the inline socket attached to the lead from the cheap head/earphones, and there's 3 wires. There's a common earth, and colour coded enamelled signal leads. These are only insulated by the heat soluble enamel, hence the compact size. I can plug the gold-plated stereo connector directly into my Minidisc or into the battery box, as preferred. (As this lead is carrying DC to power the mikes, I guess it's more susceptible to noise from minor corrosion or tarnish, and the gold plating is a bonus.) Hope I've made it clear. NOTE: I've now moved from Minidisc to a Sony PCM-D50 solid state recorder. It's bigger than Minidisc, but I can see the screen easily, it's intuitive to use, and since getting it, I've not used my Minidisc recorders at all. There's simply no contest. (It's what the Minidisc interface should have been!)

I'm in the UK, and I've often found that the most cost effective route for buying the slim cable for microphones etc. is to buy cheap iPod style earphones, and then to cannibalise them simply to get the gold plated plugs and slim cable - not available elsewhere. I made a dummy head mic set-up some time ago, using my own head; and going from ordinary plated plugs to gold plated types acquired from earphones dropped the handling noise quite noticeably.

Thanks - I've posted a similar note in the Hi-MD forums.

Went to check my NH900 last night and found that its display is dead. At first I thought it was simply a dead battery, but plugging in my RM-MC40ELK showed that the unit was working apart from the display. Just wondering whether this is a common fault, and whether it's worth asking Sony to repair it. Fortunately, I have other Hi-MD units (MZ-RH10 & MZ-RH1) but the MZ-NH900 was the only one with a display visible in normal daylight, where I tend to do my bird & dummy head recordings. A Google search suggests that there are a few old units still waiting on dealers' shelves, so I think I'll go down that route.

Went to check my MH900 last night and found that its display is dead. At first I thought it was simply a dead battery, but plugging in my RM-MC40ELK showed that the unit was working apart from the display. Just wondering whether this is a common fault, and whether it's worth asking Sony to repair it. Fortunately, I have other Hi-MD units (MZ-RH10 & MZ-RH1) but the MZ-NH900 was the only one with a display visible in half-decent daylight.

You should be OK. The microphones I used in reply #286 (above) were bought as mono lapel mikes, with an omni response. The stereo aspect shouldn't make much difference. I bring my two leads together into a stereo plug where it goes into the battery box. HTH

At last, some time after making my battery box, I've used it "in anger" for the first time, and it didn't disappoint. I went to the NDF in south Birmingham (UK) last weekend, and recorded some of the percussion demos from a seat about 20-30 feet away from the stage. I used a pair of Yoga omnis, with the output of the battery box feeding directly in to the Line input of my RH1. I was in luck. When I checked what I thought was the best track for peak level, I found that it peaked just 0.6dB below max level. I'm very pleased with how the resulting CD sounds on my HiFi system, and am surprised at how clean it is compared to many of my CDs.

Hi Mike, Maplin do a range of affordable microphones, and if you can visit one of their stores, I think you'll find one of them has the lapel clips that you are looking for - albeit in a kit with a microphone. HTH Malcolm Milton Keynes

Congratulations - these things happen! I remember making up a simple microphone extension lead, and checking at every stage; so how did I get left and right reversed! Let's hope your recordings go well.

When I was making my battery box and binaural stereo microphone set-up, I bought cheap stereo earphones (from Maplins) and cannibalised them so that I could get gold plated stereo plugs and lightweight cable at a sensible price. With the voltage supplied to the mike capsules, the low noise gold plated connection made a big difference in handling noise. The screening may not be good enough for use in a building where mains fields exist, but in the countryside it's fine, and environmental noise from distant motorway traffic, aeroplanes, and helicopters is my main problem.

For fishstyc I was going to make the same point. Occasionally, the noise level has been so low that the automatic Track marker has kicked in. Can't remember which Hi-MD recorder I was using. (On the contrary I have found it quite difficult doing wild-life recordings of, say, birds, very difficult without picking up distant road noise, aeroplanes etc.)

Thanks for the clarification. I've never used any of the equalisers so completely forgot what impact they could have on the ear-phone output. As for me, I'm now asymmetrically deaf so feed the output of my MD players into a SoundProfessionals headbanger amplifier with an attenuator lowering the input of the left channel. Works quite well (apart from the increase in bulk and cabling!), and I can probably hear better stereo via 'phones than naturally with distorting hearing aid. Years ago, my hearing was good enough for me to sit on a HiFi listening panel! Not anymore. (And it's hereditary, not induced by rock concerts etc.)

I've knocked up a battery box (as per this thread) and using the same small omni microphones, all I've noticed is how clean the recordings are, albeit at a lower level than via the mic input, naturally. (RH-10 and RH-1) Connecting the battery box output to the mic-input is OK. The 9V only goes to the mics themselves, and the output is isolated. There's no amplification in the battery box. Whether the electronics in the mic gives a little more gain with the higher voltage, I've no idea. Extra bass often comes from having the mic closer to the sound source - something which a higher dynamic range may encourage. I suggest you just get the parts and give it a go. I'm sure you won't be disappointed. If you then find that you are concerned about the frequency response, there are plenty of tools available for dealing with that when you've uploaded to your PC.