Triodes & "Fake" Triodes
by Steve Deckert
most dangerous thing you can do if you're really serious about conjuring
up a good hi-fi system is to draw assumptions. In audio I have found
that the popular opinion is usually never correct when it boils
right down to it.
people ask what the difference is between Pentodes or Triodes, and
what's the difference between a "real" triode like the
300B and a Pentode that's wired in triode... always followed with
the question, which is better?
only there was a definitive answer, but there is not. I've heard
all three sound wonderful and terrible based on the following variables:
circuit, the power supply design, the types of capacitors used,
the quality of your source and cables, speakers, room acoustics,
quality of your hearing, and subjective personal preference. These
variables can be applied to every question in audio ending in the
phase "which is better?".
true triode tube has advantages and disadvantages like anything
else in this game, as does a pentode, output transistors etc. Which
is better depends on which one will compliment the variables in
the most desirable way.
large factor as to which is better is really the issue of negative
feedback, used to keep solid state amplifiers and pentode tube amps
stable and low in distortion. Triodes have a different operating
character in that they do not require negative feedback resulting
in a usually more transparent sound with greater clarity and better
the negative feedback off most pentode amplifiers yields a power
curve that rises with impedance. Since most speakers have an impedance
that climbs with frequency, the pentode will put out more current
as the frequency increases. The result of this is a thin dry ultra
fast sound with lots of spank. A monster that makes some recordings
sound interesting for the first time, and most everything else sound
are far more efficient than triodes and with the same bottom line
can usually produce 5 times more power. That makes pentodes and
solid state transistors a partially monetary issue. So, as an example,
if you have speakers that are marketed for handling large amounts
of power with low distortion, you can bet they require large amounts
of power to reach their potential. In such a case, with say a well
damped room, and some easy rather laid back soft dome tweeters,
a Pentode may sound overall better because of the extra power and
the other side, if you've gotten more sensitive (sensible) speakers
you would know that they are higher in fidelity, more expensive,
and harder to find than normal speakers. But in such a case, the
higher sensitivity also means higher transient speed, much more
resolving power with the potential to unmask layers and layers of
additional detail and crucial harmonics that make the difference
between real and recorded sound. In a system like this, more pressure
is on your source and cables again because of the much higher resolving
power of the speakers. You can and will hear everything that's wrong
with any one part of your system and or recordings. This is high
fidelity. In this world, the difference between negative feedback
and no negative feedback amplifiers is as obvious as listening to
your stereo with your fingers in yours ears and then taking them
in this world, because of the resolving power of your speakers and
the higher quality supporting gear required, bells and whistles
become setbacks from a sonic standpoint, and the shorter your signal
path is the less chance of contamination. Suddenly we want simple
circuits with part counts in the single digits and this is where
tube amps typically (but not always) excel. Within the tube camp,
the Triode will almost always sound far superior and far more natural
with the correct timbres and harmonics. In the inefficient system
it may and probably would sound dull, soft, and be in a state of
constant clipping which because triodes clip so gracefully would
be interpreted as a lack of clarity until such a point where the
poor thing blasts off and sticks in your ceiling with smoke coming
out of its ass.
my opinion, if a man wishes to set up a personal listening room
in his home with the serious intent of creating a perfect 3 dimensional
soundscape with perfect frequency balance the top of the audiophile
food chain is single ended triodes and either expensive high quality
full range horn speakers, or electrostatic or planer magnetic panel
speakers. And I'll confirm a secret that you've probably heard before...
You've never experienced PUNCH or dynamics until you've sat inside
this combination. The detail and speed is breathtaking and if you
compared it to huge conventional speakers of you choice, boasting
multiple woofers, massive solid state amps, and even a subwoofer
with it CRANKED you wouldn't be close.
of us, with the restrictions of family and budget are content to
just have the pollution free sound at lower levels on smaller more
more "which is better".... (Same answer coming) A REAL
triode or a pentode wired as a triode? Right now, especially after
the newfound popularity of the 300B and perverted prices of some,
it is popular to be in the "real triodes are better" camp
and snub you nose up at anything else. Fact is, the reasons covered
above and the differences between pentodes and triodes are unchanged
regardless of whether or not you use a true triode or wire up a
pentode as one. So, if we eliminate the politics from the equation
we're left with only the resulting sound. So, which "sounds
better"... same answer- same variables as discussed above.
there is difference in sound between wiring a pentode as a triode
and a true triode, yes. Is there is difference in one brand or type
of triode and another, yes. All tubes sound a little different,
so by the shear fact that a pentode wired as a triode and a real
triode are different tubes you are certain to hear differences.
Which is better?... Here's what I've found:
a pentode such as the EL34 where the screens are not tied together
internally, it is possible to wire it as a "true triode".
It is the only pentode I know of that is. The other ones have internal
connections on the screens that can't be changed so you end up with
a "Pseudo triode" as I've heard it called. The "Pseudo"
triode will retain some of it's pentode characteristics and be higher
in efficiency generating slightly more power from the same bottom
line. On the EL34 you can wire it both ways and observe the differences.
In fact we've got a product coming out soon that has this feature
built in allowing you to use your choice of two sockets, one wired
in true triode and one in a form of "pseudo triode" .
will say that when comparing a real triode with a pentode, even
an EL34 wired as a triode that there are certainly more opportunities
for complications and or artifacts in the sound with pentodes simply
because of the higher complexity of the tube design. Those extra
grids inside the pentode could cause complications if directly connected
to the plate as though they weren't suppose to be there. They would
certainly alter the emissions path and flow of electrons to the
the project I'm working on that has both options you can hear a
clear difference between the two, and because of this I have explored
the possibilities that exist with the extra grids available in a
pentode to a point where I have found that you can do some wonderful
things with them. By controlling the resistance between them you
can manipulate or stage the electrons and I imagine create subtle
phase relationships that would be frequency dependent. If you think
about it, this is the very heart of the single ended amplifier,
the output device itself, and with the pentodes extra grids you
can put yourself right inside the emissions path between cathode
and anode... that's where the action is.
have found the sonic relationship between making changes to the
resistance between the plate and each grid is a tool for sculpting
out a perfect sound stage when doing the final voicing on an amplifier.
In the case of our little project, the pure triode mode sounds real
good, typically up front and personal. But in the other configuration
the soundstage simply LOCKS-IN deep and wide, and the shimmering
trails of high frequency harmonics are much longer with a silkier
tone and far better balanced within the rest of the soundstage.
Size and space relationships within the soundstage become clearer.
is also something else to consider with all of this tech talk, and
that is the amount of space between the cathode and anode (plate)
of a given tube type. One of the secrets of our Zen Triode amp is
the EL84/6BQ5 tubes small glass envelope. The plate and cathode
are very close together. Having grids in-between the two and properly
wired close the gap even more. There is less gas in the tube which
may or may not effect things, but in any case the sonic result is
greater speed and potentially wider frequency response.
people consider the EL34 to be the big brother of the EL84, but
there is an obvious difference in speed that has to be dealt with
during the design stage of a good amplifier. In the case of our
SE84B amp, the tube is so fast that a tube rectifier was required
to slow down the power supply enough to effect a musical vs. anal
result. On our new project using EL34's, we've been spoiled and
are used to the speed of it's little brother and were unable to
effect the same sonic result with tube rectification from the same
bottom line. In this case, the tube is a little slower so the power
supply needs to be a little faster. Doing this gives results that
bring the signatures of the two amps much closer together, even
though the circuits are completely different.
just when you start to assume that smaller tubes are faster in all
cases, or make any assumptions about "what is better"
in relation to audio configurations you're just hopping on a Mary-go-round
which stops where it starts. Understand that every stereo is unique,
just like no two humans are exactly the same. Even identical stereos
are different because of the rooms they're in are different. And
even if they were identical stereos in identical rooms, no two sets
of ears would interpret it the same. You will never know for sure
what is better sounding between any given set of choices in audio
until you try them for yourself and see.
have chosen to use popular (but overlooked by the high end industry)
tubes that we use because they are cost effective and readily available.
I firmly believe that the art of amplifier design has very little
to do with the tubes you use. But that's only because so many of
our Zen amp customers have sold their triode amps with the high
dollar valves in favor of a tube costing around 5 bucks. This magic
little amp also uses what is considered to be by most assumption
makers "the worse sounding tube rectifier there is, a 5Y3GT!"
But there again... there's a rude lesson in it all somewhere.