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insonicbloom
PostPosted: Fri Feb 22, 2013 4:52 pm 
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just wanted to share this as much as possible - it's a pretty cool amp
and can power 12" speakers nicely

http://www.paulinthelab.com/2013/02/sparky-5-watt-amplifier-stripboard.html

I also just did a sound clip of it

http://soundcloud.com/pstevenson/sparky-sound-sample

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Last edited by insonicbloom on Wed Feb 27, 2013 5:36 pm, edited 1 time in total.

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culturejam
PostPosted: Sat Feb 23, 2013 12:03 am 
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That looks really cool, Paul. :D

I have a question: I was expecting to see pin 3 of the 741 referenced to virtual ground, but it appears to be connected to +12v instead. What's up with that?

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insonicbloom
PostPosted: Sat Feb 23, 2013 5:19 am 
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the first stage of the amp is a basic AC coupled amplifier which you can either use with a dual supply (like you're used to) or in my case you use bias resistors - the two 2.2M resistors bias the non-inverting input to about half the supply potential.
it's not an uncommon practice I think the FA-1 uses this method (I could be wrong, it's been a while since I looked that circuit)

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culturejam
PostPosted: Sat Feb 23, 2013 1:16 pm 
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Thanks. I'm not as familiar with the bias method you used. Always good to learn new things. 8)

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insonicbloom
PostPosted: Sat Feb 23, 2013 4:07 pm 
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well if you want to learn more about different uses for op-amps including the one I mentioned it's in this mini book http://www.amazon.co.uk/Operational-Amp ... 0859343359

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ChrisM
PostPosted: Sun Feb 24, 2013 11:37 am 
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culturejam wrote:
Thanks. I'm not as familiar with the bias method you used. Always good to learn new things. 8)

I think you might be confused because a non-inverting configuration is being used.

When you have an inverting setup pin 3 goes to virtual ground or ground (when using a bi-polar supply).

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jay66
PostPosted: Tue Feb 26, 2013 11:22 am 
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I'm not that good reading schematics but am I right this uses a 10k pot? Type A or B better?

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insonicbloom
PostPosted: Wed Feb 27, 2013 10:43 am 
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jay66 wrote:
I'm not that good reading schematics but am I right this uses a 10k pot? Type A or B better?


I used a B type but it won't harm it to try either.
yes it's a 10k pot

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insonicbloom
PostPosted: Wed Feb 27, 2013 5:36 pm 
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sound clip

http://soundcloud.com/pstevenson/sparky-sound-sample

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mrclean77
PostPosted: Wed Feb 27, 2013 8:10 pm 
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Saw the clip on FB earlier and was able to give it a listen. Good golly, miss molly....thanks for posting (the clip, but especially the project/layout)!

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jay66
PostPosted: Wed Feb 27, 2013 8:24 pm 
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insonicbloom wrote:
jay66 wrote:
I'm not that good reading schematics but am I right this uses a 10k pot? Type A or B better?


I used a B type but it won't harm it to try either.
yes it's a 10k pot



Thanks got it built just waiting on the IC's and 470uf cap. Also have a PWM built and waiting on the IC's.

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