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Old 01 April 2010, 01:23   #1
Charlie
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My latest little monster...

Isn't she pretty?

-ugly-

It's amazing what you can do by raiding an old PCB, adding a couple of caps, part of a ribbon cable, and some Super-glue.


The other end

(LM324)
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Old 01 April 2010, 02:48   #2
Zetr0
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wasit do?
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Old 01 April 2010, 03:03   #3
gulliver
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I am just guessing it might probably be an audio amplifier by hijacking the lm324 from an old/useless device.
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Old 01 April 2010, 03:10   #4
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Quote:
Originally Posted by gulliver View Post
I am just guessing it might probably be an audio amplifier by hijacking the lm324 from an old/useless device.
hmmmmmm

not an amplifer persay' as there is only caps for cleaning, transistors would normally be used.

I think its more a "left / right and ground audio out" to a 3mm stereo jack- but thats just an edumacated guess =)


so charlie.... wasit do?
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Old 01 April 2010, 04:39   #5
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Originally Posted by Zetr0 View Post
hmmmmmm

not an amplifer persay' as there is only caps for cleaning, transistors would normally be used.

I think its more a "left / right and ground audio out" to a 3mm stereo jack- but thats just an edumacated guess =)


so charlie.... wasit do?
Zetr0, transistors are not always required. He is already using an operational amplifier, the lm324, thus no transistors needed.
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Old 01 April 2010, 04:47   #6
coze
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nope, it's teh secret nintendo GC emulator for teh Mamiga
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Old 01 April 2010, 05:15   #7
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My guess: audio out taken from the internal Amiga to a proper external speaker system before the RCA connectors..
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Old 01 April 2010, 11:09   #8
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The prize goes to rkauer!

I'm tired of listening to muffled sound on my speakers because of over-aggressive filters, so thought. 'Why not grab the outputs direct from the LM324?'

A little while later...
Crystal clear stereo in all it's glory.

Um, confession time. It might not be an Amiga.
I guess the same would apply?
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Old 01 April 2010, 11:27   #9
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That would be an Acorn A3000

TC
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Old 01 April 2010, 12:09   #10
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That would be an Acorn A3000

TC
Bahhh, Outed!

Maybe one could say some of my retro-interests are a bit, um 'nuts'?

Last edited by Charlie; 02 April 2010 at 00:20.
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Old 01 April 2010, 13:21   #11
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I KNOW, it's a plasma LCD
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Old 01 April 2010, 14:54   #12
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Quote:
Originally Posted by gulliver View Post
Zetr0, transistors are not always required. He is already using an operational amplifier, the lm324, thus no transistors needed.

I fail =(

I even know the lm324 is an op-amp....

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Old 01 April 2010, 16:22   #13
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This is pretty cool.. What are the voltage ratings and microfarad value of the caps?
Can this be done on Amigas too, or are there no need? I guess the Amiga 1200 doesn't mess with the sound in the circuit anyways, ... or does it?

Last edited by 8bitbubsy; 01 April 2010 at 16:28.
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Old 01 April 2010, 23:59   #14
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I bet the same 22uF from the mobo. 25V or a bit more, looking the size of they.
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Old 02 April 2010, 00:30   #15
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Pretty good guess again.
The Caps in the photo are 100uF, 50v because that's what I had to hand. My less-than-expert guess would be anything from 10uF, 16v to that would do.

If memory serves me correctly the Amiga also has a sound filter that I think is under software control - how you switch it off, I've no idea.
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Old 02 April 2010, 14:02   #16
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That's the LED sound filter. It's usually turned off, so no worries about that.
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Old 04 April 2010, 18:29   #17
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Charlie, don't use anything less than 35V rated on the audio circuit.

It uses +12 and -12V, so the sum is 24V.
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Old 06 April 2010, 01:10   #18
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Audio is +/- 12V, so you'd say an absolute minimum of 24V if you didn't know any better, but engineering best practices say allow an additional 50% voltage on caps , so the real minimum is 36V on the caps. Rkauer wins.
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Old 06 April 2010, 03:32   #19
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Fatality!
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Old 06 April 2010, 14:39   #20
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Quote:
Originally Posted by TheCorfiot View Post
That would be an Acorn A3000

TC

I did it on an A5k to bypass the sound filter, its known 'trick' for machines
after A3k.


Chris
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