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Old 14th January 2012, 06:51 PM   #381
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Quote:
Originally Posted by Chris Goldring View Post
I wish i had a THD analyzer
The distortion figures are high enough that if you have a scope and oscillator
you can cobble together a circuit which compares the input signal to the
inverted output signal and by tweaking the relative amplitude and finding
the midband frequency where you get the best cancellation you can see
the distortion pretty clearly.

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Old 14th January 2012, 07:05 PM   #382
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Nice to have you here, sir.
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Old 14th January 2012, 07:05 PM   #383
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lay my hand on the heatsink 10 seconds before huting is it ok for dissipation ?
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Old 14th January 2012, 07:08 PM   #384
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Originally Posted by juanitox View Post
YEEPEEEEEEEE YEAHHHHHHHH , wonderfull , merveilleux ,c'est Formidable!!!!
Awesome!

What do you mean by too much gain?

As for hum, does it go away when you unplug the input? With 100+ dB speakers some is too be expected, but I'm sure we can get it under control.
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Old 14th January 2012, 07:17 PM   #385
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Originally Posted by juanitox View Post
lay my hand on the heatsink 10 seconds before huting is it ok for dissipation ?
Sounds reasonable. The chip temp is what matters most, of course. At 17V, 2.77A, you're pushing it. What is your supply voltage and resistor value?
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Old 14th January 2012, 07:25 PM   #386
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i have a 40V 800VA transfo and i make fig 10 with lm337 negative bias. my load resistor is 12ohm and 8 ohm speaker
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Old 14th January 2012, 08:02 PM   #387
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my First Solidstate Amp , Thanks Michael !! ..

Click the image to open in full size.

Click the image to open in full size.
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Last edited by juanitox; 14th January 2012 at 08:07 PM.
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Old 14th January 2012, 09:13 PM   #388
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Very nice. Congratulations!

Your Vds seems a bit high. I notice your load resistors are quite small and must be really hot inside the case. Could you measure the voltage across them when the amp is fully warmed up (30 minutes or so)? While you're at it, measure your power supply voltage. Also, what's the PCB in the lower left? Thump relay?

And for your hum issue, in addition to my previous question, which word best describes the noise: hum, hiss, or buzz?
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Old 14th January 2012, 09:31 PM   #389
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yes the module is a sofstart.. power supply is at 50,5V voltage drop across the loads resistors (10 + 2ohm) is 32V

i'v got 16V and 2.68 amp ..

the resistor 200W variable resistor is too hot, i will change it for a 800w thick film.

the hum is a transformer noise , i ithink ringing in the case and in the speaker ..
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Old 14th January 2012, 09:42 PM   #390
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Originally Posted by juanitox View Post
i'v got 16V and 2.68 amp
That sounds closer to the mark. You'll probably want to move your load resistors to the top so they get some air. If you switch to the big thick film types, don't foget they must be attached to a large heatsink.

If it sounds like mechanical hum, it could be that your transformer is running too hot with the load resistors inside the case.

Have you had a chance to listen, or is the hum too bothersome?
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