LM4780 PCB's, need suggestions - Page 2

Redshift187 · 20th June 2009, 01:38 AM

It sounds great, but I've never built anything else to compare it to. I chose my own components based on quite a bit of research and leaned toward good value. I used 2x 15,000 uF caps on the power supply board (1 board for 2 channels, really abusing the power supply when I turn it up all the way) and 2x 1,000 uF on each amp board. I compared a couple of different power supply setups. You can read about it here:
Breaking all the rules, a "custom" bridged story

In a couple of weeks I will have built a LM3886 DC servo design to compare it to.

AndrewT · 20th June 2009, 11:59 AM

is it really a 29-0-29 transformer?

Measure the input mains voltage and the output secondary voltage with the secondaries unloaded.

Calculate the unloaded voltage for the nominal mains input voltage.
This answer is the rated voltage times the regulation factor of the transformer.

Vac unloaded = Vac Rated * [ 1 + regulation ] * Vac mains actual / Vac mains nominal.

Now calculate the Vac unloaded for maximum tolerance mains supply voltage (in the UK this is 254Vac for a 240Vac supply).

Use this to determine the worst case voltage that will be applied to the rectifier.

20th June 2009, 11:59 AM	#12
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	is it really a 29-0-29 transformer? Measure the input mains voltage and the output secondary voltage with the secondaries unloaded. Calculate the unloaded voltage for the nominal mains input voltage. This answer is the rated voltage times the regulation factor of the transformer. Vac unloaded = Vac Rated * [ 1 + regulation ] * Vac mains actual / Vac mains nominal. Now calculate the Vac unloaded for maximum tolerance mains supply voltage (in the UK this is 254Vac for a 240Vac supply). Use this to determine the worst case voltage that will be applied to the rectifier. __________________ regards Andrew T.

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20th June 2009, 01:38 AM	#11
Redshift187 diyAudio Member Join Date: Aug 2008	It sounds great, but I've never built anything else to compare it to. I chose my own components based on quite a bit of research and leaned toward good value. I used 2x 15,000 uF caps on the power supply board (1 board for 2 channels, really abusing the power supply when I turn it up all the way) and 2x 1,000 uF on each amp board. I compared a couple of different power supply setups. You can read about it here: Breaking all the rules, a "custom" bridged story In a couple of weeks I will have built a LM3886 DC servo design to compare it to.

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