16
May
12

Bits & Pieces

I’ve called this post Bits & Pieces because it isn’t about electronic musical instruments, but a few modules I’ve recently made, not all of which are greatly interesting in themselves, but have a use in my set-up.  These are:

1. Extension speaker

2. Headphone Amp

3. Headphone/speaker select switch

These are not highly significant, but I’ve spent time making and using them, so I thought I might as well briefly describe them.

Bits & Pieces 3 General IMG_0899

First of all, as you can see, the aesthetic involved is a different one from the projects I’ve described before.  By and large, they’re designed for mono use – although the headphone amp, based on a TDA2822 chip, is for connection to conventional stereo headphones – and they have a deliberately ‘retro’ appearance to emphasise the simplicity of the lo-fi circuitry and sounds they’re used for.

The circuits are housed in old tobacco and sweet tins I found in my garage: they came originally from my Grandad’s shed, so are very likely older than the speaker.  (Except possibly the Altoids tin, which strikes me as being somewhat more modern, although I haven’t looked into it).

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1.  The speaker enclosure – I use the word ‘enclosure’  loosely here as in fact it has no back to it – is something I saw around the house as far back as I can remember: the late 50’s/early 60’s.  I think my Dad made it: I must ask him.  Somehow I seem to have inherited it; and all I’ve done to it is to replace the speaker itself, which had got damaged over the years, with a new one, which is full-range and 8 ohms impedence; and exchange the connectors on the end of the lead with 4mm banana plugs.

The main use of the extension speaker is to get a better sound from instruments with no line out.  To date I have two of these: the Cracklephone and the Touch-Radio.  Both of these have 4mm banana sockets on them, and the speaker leads terminate in banana plugs, so can be connected directly into these instruments.

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2.  The headphone amp I made some years ago, from a circuit diagram I now appear to have lost.

Headphone amp IMG_0900

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3.  The headphone/speaker switch was also found in my garage – possibly a car-boot acquisition: designed for stereo headphones, but used in this set-up only for mono signals, divided and fed to left and right.To avoid antagonising my neighbours too much, especially late at night, I have a pair of banana leads to connect the instruments to the headphone/speaker switch, via the sockets in the Altoids tin, which allows the headphones to be used in place of the speakers.

3 Boxes IMG_0901

I didn’t manage to show this in the photo, but the speaker leads from the instrument or amp are connected to the banana sockets on the left of the Altoids tin, the headphone/speaker switch connects via the small stereo socket (in) and large mono socket (out) on the front, and the speaker connects to the banana sockets on the right.

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The older Stylophones in my collection would benefit from the addition of speaker sockets: as referred to elsewhere in the blog, most models seem to have additional components in the line-out circuit (filtering out higher frequencies), which gives the line-out sound a different character compared to the tone from the internal speaker.

Much has been written on the Cracklebox, and how it is against the principle of the original design to add a line-out.  As I see it, it isn’t a violation of principle to use an external speaker in place of the one built in to the instrument itself: a wider range of volume and tone is available this way.  And that’s what these Bits & Pieces are about, I suppose: creating sounds in a live, old-fashioned, organic sort of way, in contrast to the modern, synthetic, digital way (also good, of course – just different!).

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andymurkin

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