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Old 13th May 2017, 11:49 am   #41
mhennessy
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Default Re: How to cure a noisy Bardwell amplifier?

78xx rather than 75xx for positive linear. The xx represents the voltage - 05 in this case. The letters are manufacturer-specific, so can usually be ignored (Google the whole part number if in doubt).

Yes, the inductor is the most reliable indicator. That's needed to store energy during the switching cycle.

A 7805 is self-contained little IC, and only really needs a couple of caps for stability - though sometimes you can even get away without them. Rather than order a pre-made kit, I'd encourage you to experiment with one, simply because you'll learn more (and have more fun) that way. Obviously if this was a job for a customer where time is money the advice would be different, but this appears to be a home project, and whatever the end result, the real value in DIY projects is the lessons learnt
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Old 13th May 2017, 11:50 am   #42
ms660
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Default Re: How to cure a noisy Bardwell amplifier?

Sorry about that, not typing straight!

Lawrence.
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Old 13th May 2017, 6:56 pm   #43
Sound Man
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Default Re: How to cure a noisy Bardwell amplifier?

I see that you live at Loughbrough, you can get a 5v Regulator from Maplin Electronics. The part number is QL31J.

David
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Old 13th May 2017, 6:57 pm   #44
indigo.girl
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Default Re: How to cure a noisy Bardwell amplifier?

Quote:
Originally Posted by mhennessy View Post
A 7805 is self-contained little IC, and only really needs a couple of caps for stability - though sometimes you can even get away without them. Rather than order a pre-made kit, I'd encourage you to experiment with one, simply because you'll learn more (and have more fun) that way. Obviously if this was a job for a customer where time is money the advice would be different, but this appears to be a home project, and whatever the end result, the real value in DIY projects is the lessons learnt.
Thanks mhennessy and Lawrence - I've just ordered 10 chips for 99p - will have a play when they arrive. Have found this simple circuit on the internet to stabilise the chip. Does that look about right. Also, do I need a heat sink?
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Old 13th May 2017, 7:38 pm   #45
Biggles
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Default Re: How to cure a noisy Bardwell amplifier?

It all depends on what current you need to draw through the regulator chip. You could just try it without a heatsink and check to see if it gets too hot. Be aware that the heatsink tab on the 7805 is not isolated electrically and is normally at 0v, if the standard configuration is used. Use a 1 to 10 microFarad in parallel with a 0.1 microFarad capacitor across the input and outputs and 0v to reduce potential noise.
Alan.
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