[David_Gardiner]

If you write songs and play the keyboard you're obviously going to want to record the instrument and your vocals, which seems like a simple task but turns out to be a bit more involved than it looks.

I thought it would be easy to make straightforward recordings of vocals from a condenser mic with piano backing from a Yamaha keyboard. But unless you want to record the output of the Yamaha's built-in speakers as your backing (which is hardly hi fi!) you're going to need some way to combine piano and microphone and also give a headphone output, so that you can hear what you're playing, because once you connect anything to the 1/4" jack socket that is the Yanaha's output socket the internal speakers of course go silent. Also you want to keep the vocal track and the backing track separate until you combine them carefully, perhaps altering the levels and adding a bit of reverb to the vocals or whatever. You don't want your vocals mixed with the output of a couple of nasty 4" speakers behind plastic grilles.

Now I'm perfectly aware that there are all manner of amplifiers and mixers on the market that can solve this problem, but if I have good sound editing software in the computer and don't need any of the other facilities such equipment provides it seems like a lot of money to fork out just to be able to perform such a basic task.

If you have played around with Yamaha or other keyboards you'll also know that you can't simply join the two stereo channels together at the output socket – this produces horrible distortion. You have to combine them 'gently', through resistors, and I have found by experiment that two 4.7k components give a clean output without attenuating the signal too much. In fact it's useful to have a measure of control of the amplitude after the combining resistors also, so that you can get the level of the Yamaha signal more or less the same as that of the microphone, making it simpler to record on software such as Total Recorder or Wavepad. I also included a 180 ohm resistor in series with each headphone output to protect the output stage of the Yamaha in the event of an accidental short circuit when pushing in or pulling out the jack and to make the signal passed on to the computer independent of whatever headphones might or might not be plugged in.

The unit I ended-up with provided a clean signal from the keyboard of roughly the same amplitude as the microphone as well as a comfortable sound level in the headphones.



Depending on the microphone you're using and how loud you want your headphone monitor you may need to adjust the value of R1 in the diagram. The higher the value the lower the amplitude of the signal passed on from the keyboard. The microphone signal is passed through unalltered, and needn't go through this little box at all, except that it's convenient to feed the two channels into a twin lead that in my particular case goes to a computer in the room next door to avoid fan noise while recording. The little box (about 7 X 5 X 2 cm) and all the components came to about £13 from Maplins. I haven't included the earth wiring on the diagram – obviously if you build the unit in a plastic box you need to run an earth lead between the earth terminals of all the sockets. The resistor values in the prototype are: R1 2.7k, R2 180, R3 180, R4 4.7k, R5 4.7k.

[Boydie]

I could really be missing the obvious here but why aren't you simply recording your piano output and microphone output onto different audio tracks?

If you have the PC and audio interface you can get free software (eg Audacity) to record onto different tracks, which seems a MUCH simpler and cheaper solution

[David_Gardiner]

That's exactly what I'm doing, but if you make a direct connection to the keyboard you immediately mute the internal speakers so you can't hear what you're playing. In addition to still needing the headphone output to hear what you're playing (the one that is now occupied in feeding the computer), the keyboard gives a stereo output only, but you want to feed it into a single channel to record, so you also need to convert the keyboard's stereo signal into mono so that it can be fed into a single stereo channel at the computer end. That requires the two resistors R4 and R5, because if you short circuit the two stereo channels from the headphone socket directly together you get extreme distortion. Finally you need the two channels you're feeding into the computer (keyboard and mic) to be at least reasonably similar in amplitude if you're going to record them as a single stereo signal, and R1 performs that function. This little box solves all those problems.

[Boydie]

I think you are misunderstanding the process of multi-track recording

The "normal" practice would be to do the following:

If you want to keep the STEREO spread of the the keyboard you need to record it to 2 tracks within your recording software and pan one hard left and the other hard right - STEREO is made up of a left and right channel

Many DAWS (Digital Audio Workstations) and multi-track recorders now allow you to have a single STEREO channel, which simplifies this process

To hear what you are playing you would connect your headphones to your audio interface and either use "direct monitoring" (where you hear the signal of the keyboard prior to it going in to the computer - the advantage is you get no latency and the disadvantage is you don't hear any processing within your DAW) OR monitor from your DAW, which may introduce some latency so you may need to tweak your system depending on how powerful your PC is and how good your audio interface and drivers are

Once everything is recorded you can balance your signals (volume, amplitude) and also do other things like use EQ, compression etc. - this is the process referred to as "mixing"

Once you have a mix you are happy with you can export it as a WAV, MP3 etc. to share with others

I think you would find this set-up MUCH more useful as the flexibility of recording things to separate tracks could really pay off - eg if you complete a song but someone changes the lyrics you only need to re-record the vocal (or only part of it)

If more parts are added at a later date (drums, percussion, harmonies etc.) it will be easier to mix everything together if everything is on separate tracks


If your approach is working for you then fine - I have added this in case people wanting to get in to recording think they have to get a soldering iron out and need an understanding of electronics

[David_Gardiner]

With respect, I don't think you read the first part of my post, where I explained the problem I was addressing. If you just want to sit at the keyboard, sing a song and record it (vocals and keyboard on separate stereo channels) using a standard PC which has one stereo input from which to record, this is a very simple and cheap way to do it. I'm not talking about multi-tracking or laying down extra tracks with different 'voices' or anything like that, just making a straightforward good quality recording of somebody singing and playing the keyboard. You're talking about something quite different. Of course you could add more tracks afterwards if that is what you want to do, but that isn't the process I'm talking about.

[Boydie]

Fair enough

I would still say a multi-track approach would be better if you already have the kit

If this meets your needs (and you are handy with a soldering iron) then this is clearly an ingenious solution and is certainly cheaper than buying a multi-input audio interface