Re: 6CH6 voltage rating



Phil Allison wrote:

"Sander deWaal"
" Turneroid Autistic Fuckwit "

When you connect a 8ohm speaker to a 4 ohm tap outlet, the reflected
load seen by
the tubes doubles and there is much more class A.
The higher the load ohms, the greater amount of class A, less AB power
and also the lower the maximum tube currents.

Tubes tend to last longer.


Mebbezo, but it'll distort more with penthodes/tetrodes.
Might just be what geetah wankers want, though.

** It puts the whole OP stage at risk of arc over failure used like that.

Especially true of Marshalls and all similar EL34 based amps.

No Phil, you are wrong.

Changing the load from 4 ohms to 8 ohms will not place the tubes at
significantly greater
risk of arcing.

The speaker loads change across the F range and high value voltages
occur regardless
of the nominal Z of the speaker.

A typical combo speaker has a high Fs bass resonant peak maybe 50 ohms,
and then Z MIGHT
be the nominal Z at 200Hz, but then due to inductance Z rises with F
above,
so that at 2kHz, Z = 10 times the nominal Z.

So if the amp wants to arc, it will, regardless of whether 16 ohms, 8
ohms or 4 ohms is connected to
a 4 ohm tap.

Thus is is possible for high back emf voltages to be generated, but
nevertheless, with any
speaker, the tendency is less than if NO speaker is connected, because
the load needed to stop
the production of high back emfs isn't a low number of ohms.

The only guard against these high back emfs which might cause arcing is
to use diodes from each anode to 0V.

Usually most 6L6/EL34 based amps can be overdriven to hell without risk
of
insulation failure unless a fuctard has poured a beer down into the amp.

An exception was the Lennard amps of the 1960s which had an octet of
EL34 with Ea = 900V, and Eg2 = 450V,
and could make around 400 watts working into a load of around 2k5 a-a.

These had a nasty habit of arcing from the anode pin 3 to the earthy pin
2 on the tube socket,
and smoke during a big number wasn't unusual.
But for 1960 it seemed a great way for a band to make a big row in a
large hall
on a dance night.

I recall the experiences well when I was 18.

Now they have 8,000 watts, and the girls can't here you asking them for
a dance.

At such gigs, nobody has any conscious logical reasons for being
present.




Patrick Turner.

....... Phil
.

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