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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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18th Feb 2009, 12:41 pm | #1 |
Moderator
Join Date: Feb 2006
Location: Wembley, Middlesex
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Homemade Audio Mixer
Recently got out of the loft and offered on this site for free and going to Graham (Ilama)
I thought I'd post pictures on here and link it to the sets offered section and vice versa. Mods if this is against the rules please delete and let me know. I built this mixer back in 1977/1978, I was still in college at the time. It was once used as a mixer for turntables before i built my own disco unit in 1982 and was also used for sound at a couple of amateur plays. I'm afraid I don't have any circuits or notes for this, but will endeavor to answer any questions. I have taken a few photo's as its going to be my last memory of it before it goes to Graham who hopefully will be able to do something with it. These are pictures of the top of the mixer. At the time there was an electronics shop in London's Edgware Road called HL Smith, anyone remember them? In the early days (long before my time) they supplied chassis and valve amplifier kits, and in my days that cut and shaped aluminum to size and shape. You can take the top cover off but you have to undo every knob first!! More pictures of the underneath to follow. Here is a link to my thread in sets offered: https://www.vintage-radio.net/forum/...ad.php?t=37446 |
18th Feb 2009, 12:49 pm | #2 |
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Re: Homemade Audio Mixer
And here are some pictures of the underside.
All boards and modules were designed by myself, at first using one of those etching pens, drawing directly onto the copper clad board which was then etched. Then at college we used the black tape and black circles which were bought from Maplin. I think the power supply went through a revision the original transformer wasn't a toroidal. |
18th Feb 2009, 12:51 pm | #3 |
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Re: Homemade Audio Mixer
The last picture is the back of the unit which shows the smaller VU meter drive circuits on their plug in boards, each board carried the drive for 2 meters and led's.
Now can anyone guess what inspired that design? |
18th Feb 2009, 4:49 pm | #4 |
Nonode
Join Date: Dec 2002
Location: Coulsdon, Surrey, UK.
Posts: 2,132
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Re: Homemade Audio Mixer
Wow - that's one hell of an impressive home made item...
Well done that man ! Yes, I recall HL Smith - you could take in some measurments spend 1/2 hour pottering around the rest of the Edgware rd shops and come back and collect your new chassis from them - what a service ! The last time I saw their shop was in the late 90's - still there, all boarded up with assorted vegitation growing out of the gaps . Very sad ! As ever, supply and demand. Andy |
18th Feb 2009, 5:32 pm | #5 |
Dekatron
Join Date: Apr 2005
Location: North Wales, UK.
Posts: 6,921
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Re: Homemade Audio Mixer
Hi
That's quite a machine! You could have kept quiet and said it was a commercial unit in a home-made case and we wouldn't have been any the wiser. Were you a fan of the A77 by any chance? The layout of those presets looks quite familiar, except yours won't spring apart as soon as you look at them.... Glyn |
19th Feb 2009, 10:32 am | #6 |
Dekatron
Join Date: May 2006
Location: Invercargill, New Zealand
Posts: 3,457
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Re: Homemade Audio Mixer
Nicely done! My dad made a mixer in the late 70's, nowhere near as complex though. His was based on the ETI (Australia) "Master Mixer" which used the LM382 preamp chip, one per two channels, and metal can 741's. All on Veroboard, connected with looms of hookup wire all laced together!
He had 6 channels, grouped to three sliders, so he could pan left/right and use one fader for a stereo pair. How is your EQ done? Dad never built the ETI one, it used custom wound inductors. The casework is nice. He never did manage to get the hang of drilling holes in a straight line. I seemed to have inherited that trait |
19th Feb 2009, 10:39 am | #7 |
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Re: Homemade Audio Mixer
Hi Arjoll,
I think I used a version of the ETI design, I seem to remember using an LM380 or LM381. The EQ was done using home made wound coils, i cant remember how effective it was, my disco that i built much later used an 'electronic' coil based around some op amps. I also couldn't drill in straight lines, if you look at the knobs they've all got skirts on them! I was making provision for a compander as well which is why there are eight holes with nothing in them. I also put in an audio limiter which was based on my college project and was also my first project to be published in Practical Wireless June 1980. Later I'll start another thread on this. |