Amplifying the Recorder

The chief limitations of the recorder for playing with other instruments and in concert are its lack of volume and the limited dynamic range. After playing  some trios I wrote for Recorder, Oboe and Horn, I found that even the quite strong "Modern Alto" recorder I was playing, doesn't really have the volume to play very effectively with such instruments. A fortuitous audience who happened by and heard us play quite enjoyed it, but to achieve fair balance, I was hard put to play loudly enough and they, especially the oboe, to play softly enough.

Faced with abandoning the whole idea of playing with other instruments, I finally abandoned instead my impractical accoustic puritanicalism and decided to amplify. The next question was how to do it in a manner sensitive to the delicate nature of the instrument.

Was I to cart around some hulking guitar amp, with heavy cables and extension cords? Or could I find something unobtrusive that would sit under my chair and run on batteries? Did I need a studio microphone on a stand? Should I buy a Philippe Boulton electroaccoustic recorder?, or cut a microphone hole in my current model? Or, could a condensor mic cartridge be placed just under the block inside the recorder without disturbing the accoustics?

I think what I've ended up with should be good not only for the trios, but to improve balance and make for good live performances of concerti with strings and works with other wind instruments. Now, if only I could play such things well enough to be worth listening to!


























Amplifier and Speaker

I wanted a compact one-piece solution. Because the instrument is an alto recorder, the speaker needs no bass and so can be quite small. This also means you don't need much power. One or two watts works; four or five could make enough sound for a good sized audience.

I first investigated the possibility of using good quality amplified computer speakers. They are small, cheap, elegant, good quality, four or five watts output, and many models can run on batteries. But I discovered there were problems. All have only line inputs. These are not much good with the low output of a microphone: a separate pre-amp is required to bring the microphone level up to line input level. Also, each of the pair contains batteries, but the voltages of the two sets of batteries is summed together: neither speaker can be powered independently of the other. Thus, this tantalizing, seemingly ideal solution does not quite work, unless one is prepared to make some extensive modifications to one of the units.

After some hunting through big, ugly guitar amps, I finally found in one guitar store a Danelectro "Honeytone mini-amp", about six inches square and three inches deep. It runs off a single nine volt battery - pefect to put unobtrusively under your chair. The power seems to be just around a watt. (There are no specs, but the 3" speaker's rating is two watts.) It has a pre-amp with variable gain (the control pot being marked "overdrive"), and makes the recorder loud enough to play nicely with the oboe and horn. I got a rechargeable Ni-Cad battery so I won't be running through batteries and getting paranoid about leaving the unit on during a break.

Microphone

If a microphone is very near the sound source, it doesn't need nearly as much amplification as otherwise. If it's a foot away, the amplification will also pick up your breathing, anything you say, and other unwanted noise, but if it's 1/2 inch from the recorder's window, you can turn the gain on the amp way down. For this reason, a studio mic near the recorder isn't the best choice; It's much better to have a microphone actually attached to the recorder. In my view, this is the essential difference between simply amplifying an instrument and having an electric instrument: with an electric instrument only (or at least mainly) the instrument sound is projected, not all the sounds near the player, one of which is the instrument.

At first, I used a lapel condensor microphone. It attached to a clip, which I tie-wrapped to the recorder so the microphone sat right beside the window. (Right in front of the window it gets "wind" noise from the airstream!) This arrangement worked quite well, but I didn't like the clip and the tie-wrap being stuck on the recorder when I wasn't micing it. Also, condensor mics need a source of voltage and this one took an expensive watch battery - just one extra thing to worry about. (On the other hand, if you're not into soldering and electronics, it's a very workable solution. I also found later you could simply hold the mic on with a rubber band and have nothing permanently fixed onto the instrument.)

So I got a condensor mic cartridge from an old cassette recorder and attached it to a light cable with a phone jack on the other end. These mics are quite small aluminum cylinders about 5/16" in diameter and in length with a felt cover on one end and solder contacts on the other. Again, they need voltage to operate. But instead of creating some complicated battery hookup arrangement to put between the mic and the amp, I opened the amp, removed the circuit board, and soldered in a 39K ohm resistor between the +9 volts and the mic input, providing so-called "phantom" mic power. Since this put +DC voltage on the input, I also reversed the input capacitor. The mic cartridge had much more output than the lapel mic, and seemed very flexible as to its voltage source: any resistor I tried from 2K to 270K worked just fine.

I tried putting the mic inside the recorder, just under the block. I just fed the cable in through the bell pushed it up. Inside the recorder is by far the loudest point. The sound inside also seemed to me much flutier than the sound as heard normally from outside. (Flutey recorder lovers take note!) Philippe Boulton's "electro-accoustic" recorder microphones catch this inside sound. The sound I got was so strong I couldn't turn the gain down on the amp enough to prevent it from distorting. (So, I pulled up one leg of the input capacitor in the amp and reduced the input signal to it by about 8 to 1 with a 270K and 39K resistor divider to ground.) The presence of the mic (or the wire) inside the recorder also seemed to upset playability of the third octave notes of my 2-1/2 octave recorder, though I might have found a better position if I'd tried, and even as it was, a two octave recorder wouldn't have been noticably affected.

I could have drilled a hole for the mic in the side of the head joint, but since I wanted my recorder's regular tone, I elected to place the mic outside. To mount it, I cut a "cigar box nail" short and tacked it in (after drilling a pilot hole) so I could hook the wire under it near the window and about 3/4" from the mic cartridge, which then simply sits on the end of the wire, just to the left of the window. See the photo: the grey wire is pushed between the nail and the wood ring, and then pulled down until the fatter black part (heat-shrink tubing) is snugly gripped in this narrow space. The nail is the only part that stays with the recorder permanently. While not as loud as inside, this very close micing hard by the window still lets you turn the input gain way down to eliminate most extraneous noise.

Pedal Volume

This arrangement worked very well for our trios. But, always the perfectionist, I've found a pedal volume control and hooked it between the mic and the amp. This solves the recorder's usual lack of dynamic flexibility, at the cost of an extra piece and a bulky cable to the amp. I can now go from a "full volume" forte with the pedal forward to a "piano" with it back, using just the unamplified accoustic power of the recorder. Crescendi and decrescendi should pose no problem. Except of course, for having to consider such things to begin with. Am I carrying the electronics idea too far? Some impressions should come from our next trio session!

Experimenter's Note: Computer Speakers

Computer speakers with four, five or six watts would have power to spare that the "honeytone" doesn't. I did try one experiment with a cheap computer speaker I had sitting around. After finding and removing a 33 ohm resistor that virtually shorted the input to ground (at least as far as a microphone is concerned), I did get a certain amount of sound out with the cassette recorder microphone cartridge, though not enough to do much. The microphone had to be within a couple of inches of the speaker with the volume control up full before there was any feedback. But it's not impossible that some of these units might have enough gain if a couple of resistors were changed, or if the microphone picked up the sound from inside the recorder, where the volume is loudest. That still wouldn't solve the battery problem. However, a determined person might work something out if there's enough room inside somewhere for the remaining batteries.