Ian Iveson wrote:

"Paul D. Spiegel" wrote

Chris, remember that these posters are discussing guitar amps, not
hi-fi. They may like the distortion products created by the wrong
tube
performing at a non-linear operating point. It certainly isn't
what the
circuit designer intended, but whether they like it or not is
totally
subjective.

This is a popular but questionable view.

All musical instruments are easy to modify. You can put tin cans in
your piano, use a broken read for your saxophone, and put a dent in
your trumpet. Your new sound may excite for a while, but the novelty
soon fades and becomes irritating.

Clearly, orchestral instruments are standardised. Where the score
says "piano", it assumes a concert grand, not an upright stuffed
with tin cans. Some may argue that this is simply because the music
itself is externally specified, and so an orchestra is to some
extent like hi-fi: the aim is reproduction.

But there is more to it than that. Orchestral instruments were
developed over centuries. This refinement was opposed to
standardisation which therefore cannot explain it. Each instrument
was developed to have a sound that was *just right*, on its own and
in many combinations with others. This correctness was not just
subjective to the taste of its designer; it was and is a matter of
general, i.e. *social* perception. There is no such thing as private
music. It's a social movement with its own life that transcends the
individual artist, who can only contribute and develop, not invent.

Hence the iconic sounds of Hammond organ, Fender guitars, Marshall
and Fender amps. They produce the right basic palettes of sound,
with reasonable reliability.

A good guitar amp has a standard repertoire. Effects can be added,
but these are also generally standard.

Messing willy-nilly is unlikely to result in a musical sound.
Historic movements don't happen by chance. God doesn't play with
dice.

Designing an amp for mere reproduction is quite trivial. Producing
one that gets the performance *right* is much harder. This is true,
IMO, of both hi-fi and instruments.

So stick with the AU7 and play some proper music.

cheers, Ian

I hope your not in the same terse mood you had the other evening,
and I risk bringing up the subject of longtail pair
driver-phase splitters again.

The original poster says he has a guitar amp where
12AX7 is the specified tube for phase splitter.
We could assume its configured as an LTP,
and there is probably some NFB applied to one of the two inputs to the
LTP, since this is a common practice with LTP guitar amp drivers.

If 12AT7 or 12AU7 are just plugged in, they will sort of work,
but the amount of FB applied if any will be reduced, and the
balance of the drive voltages to each output tube will not be as close
as with 12AX7.
If anything, the sound at low level will be slightly warmer, since
there will be more 2H in the output signal, at least at low levels.

I doubt there is any harm in replacing 12AX7 with other tubes such as
12AT7, 12AU7,
12AY7, etc.
But the circuits of guitar amps do use different biasing and loadings so

that fairly optimal operation points are used for the driver LTP PI.
Subbing other tubes to get the same amount of correctness in working of
the subbed tube
means the loads and FB should be altered to suit.

The sound changes are anyone's guess, and I have difficulty co-relating
what musos say about the sound of their amps and the engineering.
But at least I can say a Vox AC30 with 4 x EL84 in pure class A
will sound warmer than a pair of 6L6 biased for near class B.


Fidelity is the enemy of the electric guitarist. All the musos I know
loathe a dry flat lifeless sound of an accurate amp, with SS amps
heading the list of loathability.
The heavy rock and rollers and heavy metals artistes like to
run with 40% IMD since the tubes are in heavy overdrive.
I would think that the choice of PI tube wouldn't make much difference.
I sure can't hear much difference, and it leaves me reaching for the
ear plugs when I ever am trapped into attending a "gig".
I don't like the ear damage effects of modern music venues.
The jazz guitarist, such as George Benson, relies on his amps to give
a kind of warm sound, well, that's ho I hear it from recordings
I have which I bought 20 years ago, and he's not into heavey clipping,
he exploits the musicality of the mildly distorted triodes
well before clipping starts.


Nearly all these dudes like to boost the hell out of the HF content of
the string information.
Without brightness, and presence, there is dullness, since the
jazz guitar and solid body electric guitar has truly dull sound when
played without an amp, since there is not the
more finely made wooden diaphragm to resonate that is a marvel
in a well made acoustic guitar used by say John Williams.

The pop and jazz players all like something that puts some magic into
what they are playing,
so that their musical talent, ( if they have any at all ) comes out
adorned with slightly or grossly tubaceous atifacts.
Reverb is somewhat important ihmo.

About all of what Ian has suggested about music and evolution of
instruments
is about right, and for hundreds of years the formal orchestra
instruments were inched
up to where they are now.
Then came electricity, and pickups, amplifiers, and eq-ing of the sound,

and effects, and musical expression has exploded to include genres
which would have been impossible in 1920.

Much of the "new music" is just noise by noisy boys, but
all ages precipitate the gems and throw out the trash.

Some of the black blues music from the 30s and 40s underpins
much of the modern pop music which is the majority of music
listened to today.
Some of those dudes get their music across best with simple note
playing,
simple picking styles, and there wasn't any real need to
have all the modern "featurisms" of the modern performance
to sing about how ****ed off one was about one's lerve life,
which was and remains is the predominating concern of people
young enough to try to clumsily relate to the opposite sex,
driven unmercifully by their primal urge to ****, attenuated by
vice and virtue ridden life decisions, fickle dispositions and consuming
emotions.

The electric guitar was able to cry their pains of hurt, desire, lust,
whatever, all by itself. Not to mention a saxophone.
If any music sums up western nation cultural expectations,
and the power of being with all our machines, its the electric guitar.


Of course the same personal relations subject matter was sung about in
1750
when guests in fine houses gathered to sing at the parties they held,
gathered around around the harsicord which was something jangly and
tinny,
and which appealed to youth of the day.

Steel strings would have been expensive for the poor in 1750, being the
product
of the industrial revolution.
So for centuries, gut strings dominated string instruments.

Later on the largely socially oppressed black in america could
at least afford 6 steel strings to moan the blues with some rythym,
and jazz got off the ground, all because of modern materials advances
and the invention of fast syncopation and rythym, a legacy out of
africa.

Last month I sat delighted while a woman played an electrified
concert harp. The complexity, and skill required to
play it is far greater than what most pop musicians could ever play.
The music she played was composed for the instrument, and
was used for some film soundtracks.
At times a bow was inserted between strings, to allow some
deep bass to be played along with what was running in the
"effects" box with many switchable effects used during the piece,
and always the music twisted and turned and wove us into its journey,
not boring us with repetition, or by peurile lack of ability.
There was zero reliance on tube amps to entertain us;
What entertained the audience of a thousand souls
was the training of the artiste, her discipline, and her natural
affinity
to make music, music composed to require and her abilty to let
music reach our souls without projection of her own
personal romantic disposition, devoid of the
pop musician's tiresome egotistical presense, which becomes a PITA
after a certain age afasiac.

Obviously, I am over 35, and have a mind, but at 20 I thought the Stones

were ok, and I liked Dylan, and the folk music that was around,
and the jazz, and the classical, except opera, which I thought
was pretentious.
The message often mattered most with the pop music and folk.
Butr when I listen now to the Stones on Beggar's Banquet I am bored,
embarrassed even, and I don't need to be reminded that
""I can't get no satisfaction"", and think now,
what's wrong with this jerk that he can't get no satisfaction?

All the Rap musos are wasting their time talking words of "music" to me,

and the lyrics simply have me thinking some serious growing
up has to be done, if they are ever to become honourable men,
and no amount of biasing of a 12AX7 phase inverter will ever pull these
kids out of the musical quagmire they are in.

Patrick Turner.