On Jan 28, 10:03*pm, "GRe" wrote:
"Patrick Turner" wrote in message
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[...]
The vast majority of users are technically illiterate, through no
fault of their own.
They cannot be blamed for buying ARC and other major "reputable" brand
names of audio gear while thinking they can use it without special
mains arrangements to get reliability if the mains voltage is 13.7%
above the labelled input mains voltage on the unit they buy, ie,
252Vrms instead of the labelled 220Vrms.
Obviously (on paper) ARC's operate within spec even at .au supply.
VT200 Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
990W at rated output; 1200W maximum; 680W at idle.
(not from the manufacturer's site)
Unfortunately, ARC designers do not realise their idiocy of
"theoretical on paper functionality".
You are right about the mains power draw with VT200; its quite high to
maximise the class A1 working, but I will always keep saying that
biasing multiple 6550 tubes with just one fixed grid bias voltage and
allowing Pda to be 31W and allowing B+ to be just above the electro
cap working voltage in a box where temperatures rise dangerously on
hot summer days where we often get 35C room temp is a recipe for
trouble. Here I am fixin' trouble, right?
VT200 MKII Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
990W at rated output; 1200W maximum; 680W at "idle".
Complete spec, see:http://www.audioresearch.com/vt200.html
VM220 Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
620W at rated output; 900W maximum; 400W at "idle".
Complete spec, see:http://www.audioresearch.com/VM220.html
So where is any recomendation to adjust the bias currents to comply
with a safe reliable Pda?
There is none. All too often I find hi-end makers are much too
optimistic.
The damn hi-brow makers AND low brow makers SHOULD ensure that users
are made aware of the pitfalls of incorrect mains voltages. But they
all know any mention of anything technical or of any possible negative
outcomes is detrimental to sales figures. They think its better users
burn their gear to bits, with an attitude of utter carelessness about
their customers.
A bit hard to find but ARC actually say something about it, quote:
"Factors which can shorten tube life include inadequate
ventilation,
The VT200 and VM220 have adequate natural ventilation without reliance
in any fan, although the VT200 does have a fan, just one, but because
tubes quickly drift away from being a matched quad at purchase, the
practice of using one bias voltage applied to 4 x 6550 means that Pda
may average say 31Watts, but may vary between 20W and 45W, and OP
tubes mysteriously just expire thermally because there is insufficient
bias monitoring let alone any visual indication of bias current
condition or any active protection circuits to turn the amp OFF when a
6550 begins to conduct excessive Idc. Not IF, but WHEN, ok
overdriving loudspeakers at continuously high
volume levels,
What a meaningless statement this one is!!!!!!!!!!!!
Just exactly what is meant? Where are the technical terms.
Will ARC over heat their tubes if driven for 1 hour in a room at 35C
with mains at 250Vac, and with an 8 ohm resistance or other reactive 8
ohm load and at any level up to clipping with a sine wave?
Assuming all speakers have a region where actual Z is below the
nominal, how do their amps cope with a 6 ohm resistance load connected
to the 8 ohm terminations and run at clipping indefinately?
severely fluctuating A.C. line conditions (e.g.
sagging line voltage during summer peaks of air-conditioning
demand),
Again, wheat is meant? If the mains voltage was at 250Vac with no air
con or room heating etc, then with air con or room heating or someone
welding in the garage, maybe mains might drop 10% which should not
affect the amp adversly although ther max PO will fall and clipping
will occur at a lower PO level.
Sudden RISE in mains voltage from 250V to 270V could spell disaster
though.
or severe interference pulses or electromagnetic
interference.
Again, where do they quantify the the interference?
Seems to me they are desperate to blame amp failure on something other
than their own shortcomings.
Power-conditioning products such as line filters,
isolation transformers and the like may or may not help sonic
performance, particularly when used with power amplifiers;
Haha ha, wht a load of ********. The aforesaid products are used
specifcally to help control imperfect mains supplies.
But of course few known power conditioning devices would affect any
linear PSU or the sound of any amp such as made by ARC.
contact your dealer for professional advice. A dedicated 15-amp
or 20-amp A.C. circuit for your power amplifier is the most
effective solution for power-starved audio systems".
Power starving is seldom a problem in a modern domestic situation in a
western country.
Here we easily have at least 10A capable domestic power wiring with
240V which allows 2,400Watts of draw and one will find Vmains falls
less than 5%.
Obviously, in the USA one should have the same 2,400W capability so
one might want 20A x 120V circuits.
I've never had any trouble running a pair of my 300W monoblocks with a
total of 24 x 6550 tubes. No special wiring was needed.
I don't expect anyone to agree with me about what ARC and many other
makers should do about their designs.
All these makers are severely egotistical and believe that their ****
don't stink, but I know both theirs and mine does stink, and I have
nothing to loose by pointing out to all their products could be
improved greatly. I include circuitry in my creations to prevent
clouds of smoke, the other guys don't bother.
Patrick Turner.
Regards,
Gio