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Tim Williams[_3_] Tim Williams[_3_] is offline
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Default Tube mono-block amp with SIX 6L6 outut tubes

Well, yeah, it just scales. More in parallel, more (total) bias and load
current, lower load impedance.

By the time you get to 8 or 10 or more, you should probably be asking
yourself if a one of those fancy DSP pedals plus a class D amp is cheaper
(not to mention more efficient, as we start running into the limitations of
a 120V 15A circuit around this level..), or at least another tube type with
better economy of scale (i.e. a transmitter tube of some sort), give or take
whether we're talking production here (6L6s are still around, if ****ty --
the cheap ones that is) or one-offs from NOS.

Heh, funny, come to think of it, that matched tubes are very common, and
independent grid bias is reasonably common, but independent grid drive level
is not at all common. Really all that matters is balance at the OPT, for
magnetic reasons. The more tubes you wire in parallel, the less critical
their matching is (assuming independent variables, and assuming any
individual does not exceed its plate dissipation rating).

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/

wrote in message
...
I found a schematic of a stereo amplifier containing TWELVE 6L6 audio
output tubes. But aside from sharing the power supply, it's two
mono-blocks with each having SIX 6L6 output tubes. Unfortunately, I was
not able to get any real detailed information on this.

I compared it to several guitar amp schematics which use FOUR 6L6 tubes
in push-pull parallel, and this is very similar. It just has 3 tubes on
each side of the phase, rather than two. The plates are all wired
together and cathode / grid components are duplicates to each tube.

They did use as bias adjust potentiometer on each tube, which I have not
seen on the guitar amps.

Obviously the purpose is to increase wattage output.

I'm not intending on building this, but it's interesting and makes me
wonder if someone could use EIGHT 6L6 tubes, or TEN?
(Of course adding more tubes mean bigger audio output transformers and
heftier power supplies.

Another question that comes to mind is the impedience of the primary on
the audio output transformer. Assuming I could find a transformer that
would handle the wattage, would the impedence be the same as those used
with FOUR 6L6 tubes, or would that change since there are two more tube
plates connected in series.

Anyhow, looking at this schematic makes me think that any PPP amp with
FOUR tubes could have more output tubes added, as long as power supply
current is available and a suitable audio output transformer is
obtainable.