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Old 26th July 2010, 04:01 PM   #1
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Default 80's boomboxes - how did they power the amps?

I'm looking at some old 80's ghettoblaster/boomboxes which could play really loud just running of 8 D cell batteries (12V)

How did they power the amplifiers in these days? I don't believe there was SMPS in these days, so what did they do then?

Reason I'm looking into this is to give old ghettoblasters "new guts", running class-d into improved drivers...

Thanks for the feedback.
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Old 26th July 2010, 04:09 PM   #2
maxw is offline maxw  United Kingdom
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They are powered by STYLE!

Seriously though, I don't know the answer, but post some pics of your work when finished!
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Old 26th July 2010, 04:47 PM   #3
paulb is offline paulb  Canada
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Probably 4 ohm speakers, amp driven into clipping. Distortion makes music sound loud when it isn't really. Car radios could play really loud back then too, and only on 13.8V.

Last edited by paulb; 26th July 2010 at 04:51 PM.
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Old 26th July 2010, 04:58 PM   #4
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Don't forget about the high Qts paper cone drivers with decent efficiency.
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Old 26th July 2010, 05:10 PM   #5
AP2 is offline AP2  Italy
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Unfortunately or..fortunately, the power is not an absolute measure.
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Old 26th July 2010, 06:40 PM   #6
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Actually just 1 or 2 watts sounds pretty loud. I don't think class-d will give you any noticeable benefit in this situation.
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Old 26th July 2010, 07:10 PM   #7
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Upwards of 8-10% THD
+ battery life measured in minutes.
+ very aggressive tone controls
+ fairly low-fi sources to begin with, i.e. commercial radio, cassettes, 8-tracks
(maybe 55-60 db SNR

Square waves are LOUD.
No one said they sounded good, but they're attention-grabbingly LOUD.

Ask your local commercial FM station.

Or worse, commercial AM station.

regards

art
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Old 26th July 2010, 07:40 PM   #8
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I have a dead 90's one,TEN size D cells.Bi amped stereo (4 channels) 7.5 watts each,and my dad swears 'its the best music system ever bult'.I never got the chance to have a listen,but i hope i'll get it back to life.
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Old 26th July 2010, 08:03 PM   #9
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They are almost mythical, aren't they? Well I'll get a hold of an old lasonic l-30m soon... Click the image to open in full size.

I'm far from an electronics guy myself (only slapped together a UCD amp, that's it) but I'll open it up and post some pics of the guts - we'll know soon enough what's in there.

What I'm thinking is just to put some very small class-d amps in there, some rechargeable batteries (don't know what type yet) and see if I can connect a portable MP3 player to it.
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Old 26th July 2010, 08:09 PM   #10
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Quote:
Originally Posted by paulb View Post
Probably 4 ohm speakers, amp driven into clipping. Distortion makes music sound loud when it isn't really. Car radios could play really loud back then too, and only on 13.8V.
I've had a few on hand that were LOUD even before clipping. You're right with impedance - i've seen custom 3.2 ohm jobs on one. Also the drivers were wound with as small of a space as possible between magnet and coil (i forgot the technical word but i'm sure you know what i mean), and also they used as thin wire as possible. 2 more watts than what they were rated for and the speakers would blow.

This is how they could get upwards of 95dB/W AND also the reason why the speakers' voice coil would invariably start rubbing against the magnet if played too loud for too long.
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