Re: ARC VT100 repair and test.



Bret Ludwig wrote:

Having the fan blow first onto the regulator that gets hot before
wafting around everything else is a good
idea. And indeed waft around is all you'd get,
because it would be difficult to direct air to all the output tubes.

I am in no hurry to copy the circuitry used in the VT100.

Considering that it is a harsh sounding amp this seems wise.

I cannot see why it should be a harsher sounding amp compared to any
other.
At low levels the THD is commendably low like nearly all other
PP amps with 4 x 6550/KT88 tubes.

At low levels, maybe a watt, the use of 8 ohms speakers connected to the 4
ohm outlet match
would halve thd and Rout, but in practice doubt many would hear any
difference.
Same goes for reducing the idle current of the output tubes; sure there is
less class A
but I defy anyone to tell the difference between Ia = 70mA and Ia = 50mA
at a watt of output.
A watt gives loud 90 dB levels into most modern speakers.

I think the purpose of the CF drive to the output grids with series R is
to give the amp
a soft clip sound. But the CRO shows it clips like any other amp.

The mysteries of ARC topology remain buried in the ether of invention...

Patrick Turner.





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