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Old 8th April 2011, 06:24 PM   #11
anilva is offline anilva  India
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Quote:
Originally Posted by Bksabath View Post
Anilva
maybe you have a bunch of wires running to close and parallel to each other.

Could you trim the excess off and keep suply output and imput avay from eah other and crossing at 90.
Thanks. Will try the rewiring.

Quote:
Originally Posted by bobodioulasso View Post
If you draw twice as much current as standard F5 you need more filtering caps.
I did not think on these lines at all. Makes sense.
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Old 8th April 2011, 06:42 PM   #12
anilva is offline anilva  India
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Originally Posted by jackinnj View Post
Third -- You might want to consider a ground loop breaker if the above don't work.
what is this? Is this 'ground lift switch', in which case I tried and failed.
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Old 9th April 2011, 12:45 AM   #13
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Quote:
Originally Posted by bobodioulasso View Post
If you draw twice as much current as standard F5 you need more filtering caps.
If you have, or can borrow a 'scope, I'd look for ripple on your power supply rails (look for AC voltage on the DC rails). If this is the problem, additional filter caps (double what you currently have) can help solve.

In addition, is your transformer sized properly for this amp design? Suitable VA capacity?
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Old 9th April 2011, 02:18 AM   #14
anilva is offline anilva  India
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Quote:
Originally Posted by CanAm Man View Post
If you have, or can borrow a 'scope, I'd look for ripple on your power supply rails (look for AC voltage on the DC rails). If this is the problem, additional filter caps (double what you currently have) can help solve.

In addition, is your transformer sized properly for this amp design? Suitable VA capacity?
Well, I dont have access to a scope. I will try with increased filter cap size.

The toroid is rated at 600VA. Runs quietly. No problem. Supply rails are at 22.7 VDC on load.
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Old 9th April 2011, 02:21 AM   #15
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600 VA should be more than adequate.

I'd try doubling your power supply caps (just temporarily solder them to your existing power rails), and see if that cures your problem. Good luck....!
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Old 9th April 2011, 03:35 AM   #16
eyoung is offline eyoung  United States
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You can lift the ground on one input small ~10 ohm after you've tried everyting(SP) else and see if that will do the trick . the long and winding Hafler DH200 thread has a wealth of info in it...required reading.

Regards, Elwood
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Old 9th April 2011, 07:19 AM   #17
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The standard PSU capacitance is definitely not enough in this case.
I can tell because i experimented such an implementation.
Lower the bias to half value and you will see hum disapear.
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Old 9th April 2011, 09:52 AM   #18
AndrewT is offline AndrewT  Scotland
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Far easier to reduce output bias to make the amp into a normal ClassAB. Then the Hum will be measurable or not.

You can measure the hum on the output.
You can measure the Ripple (almost=Hum) on each supply rail.
Do this with high bias and with low bias.

Once we have those numbers we can estimate whether the capacitors are too small, or are damaged, or are empty cans.
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Old 9th April 2011, 01:27 PM   #19
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Or simply simulate using psud2 and look at ripple figures
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Old 9th April 2011, 07:21 PM   #20
anilva is offline anilva  India
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Thanks for all the tips. Lot of things to digest and try. Will go step by step and see the changes. Will record the impact for further postings.

Cheers.
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