re off topic, I think. 5AR4/5AS4 etc

[Murray Grandy]

It's amazing what you miss when you're trying to go the cheep route. Of
course I am aware of these differences and they make sense. Just didn't
think. Guess that is why 5AR4's sell for several times the cost of 5U4's and
other similar rectifiers. I was going to use the 5AS4 in a Dynaco ST-70.
Guess I will look for the real thing. Thanks to all for the great info.
Murray
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The 5ar4 cathode is indirectly heated - meaning it takes 15-30 seconds to
start working - the 5as4 filament is the cathode - heating up in a few
seconds.  5ar4 is a good idea as the other tubes in the piece of equipment
have warmed up and will be ready to draw current when the rectifier warms
up.  The prevents the high voltage from attempting to rise to a much higher
value as it would with a directly heated rectifier or solid state diode -
therefore stressing the filter condencers until the other tubes have warmed
up sufficently to draw current.

Regards,

Bill Riches, WA2DVU
Cape May, NJ

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