Update needed for heater bridge rectifier mod

[Greg.]

So, working on my friends 6550, I planned to tweak the heater supply for the ECF80’s as per the directions in the FAQ article. Unfortunately, apart from one resistor (and then only available on extended back order) none of the components suggested are now available from RS. Frustratingly, unlike Farnell, they do not suggest alternatives.

Any chance of bringing this FAQ thread up to date?
http://www.world-designs.co.uk/forum...ead.php?t=7643

Thanks.

[bob orbell]

I did this mod to mine many years ago, but to be honest Greg, there was no detectable improvement in the sound. BOB

[snowman_al]

Hi Greg,
I think the 'or equivalents' covers it pretty well. Specific makes or types are not important.

So plenty of choice out there, for example CPC Farnell have stock of
1N5820 = SC07427
4700uF 25 volt (105 degree) = CA05160
1.5 ohm 3 Watt W.W = RE04662

Alan

[Richard]

Originally Posted by bob orbell

I did this mod to mine many years ago, but to be honest Greg, there was no detectable improvement in the sound. BOB

Hi Bob, Yes indeed, it may be system or amplifier dependent. It was excellent on my Kit88 driving large transmission lines with noticeable (and measurable) lowering of hum (see Part 1 for the numbers) and a subjectively cleaner sound. If you use smaller speakers, or a phono stage rather than CD for example which already hums more than the improved amp, you may notice no difference.

There are 2 electrical improvements to be had for not a lot of effort/money; quieter rectification from using schotkies, and, lowering of ripple due to the improved passive filtration made possible from the increased voltage.

[Richard]

Hi Greg,

RS, all in stock,


1N5820G 774-3341 (G is Pb free) in 10's 25p each
4700uF 25V axial 707-6708 in 2's £2.29 each (or use a radial if it fits easier or is to hand)
1.5 Ohm 3W wirewound 151-574 in 5's 19p each

[Greg.]

Thank you. You guys helping me to be lazy when I was all set to search myself for alternatives today