Fender made a gradual transition away from the tweed circuits. Many of the
early 60's amps had tube vibrato, which unlike tremelo, actually changed the
pitch of the notes, not just the amplitude. These vibrato circuits required
many tubes, so Fender eventually replaced them with simpler tremelo
circuits, which just modulated the pitch of the notes.

The mid-60's was Fender's famous "blackface" period, named for the black
face of the control panels of the amps. The preamp circuitry was markedly
different from the 50's tweed era. Instead of having two gain stages before
the EQ, the blackface amps positioned the EQ right after the first gain
stage and before the volume control.

Another important change was the inclusion of a reverb channel on many of
the blackface amps. The reverb channel tapped a tiny portion of the signal
just after the second gain stage, fed it to a 12AT7 tube set up as a
miniature power tube, which in turn powered a spring reverb tank. The signal
was taken from the spring reverb, re-amplified with a gain stage, and fed
back into the reverb channel just before the third gain stage.
stage1--EQ--volume---stage2-----RESISTOR-------stage3----->
| |
| |
| |
> REVERB CIRCUIT^
These blackface amps had a cleaner, brighter sound than many of the earlier
tweed Fenders. This was due to many factors. Repositioning the EQ between
stages1 and 2 made it harder for the first stage to overdrive the second, as
EQ circuits tend to "eat" a lot of signal. The large 3.3. Meg Ohm resistor
between stages 2 and 3 also reduced signal strength. The use of higher B+
voltages made for a stronger, cleaner sound in both the preamp and the power
amp. The power tubes were fixed biased, so they didn't compress the sound
the way cathode biased tubes do. The EQ circuit had a more pronounced
midrange "cut" than most of the 1950's tweed amps. Finally, many of the more
powerful Fender amps from this period used solid state rectifiers, which
make the amp produce a sharper sound with faster tracking of transients
(sudden increases in volume, like from plucking a string hard).

The signal path remained all tube, so the sound was still quite warm. The
Fender Deluxe Reverb amp from this period, with its slightly lower B+
voltages and tube rectifier, has an excellent rock and blues sound. It has a
beautiful, shimmering clean sound at lower volumes, and a wonderfully fat
distortion when cranked. (turned up loud). Not quite as rough as a Marshall,
but great for blues and blues-rock.

CBS bought Fender in 1967, and within a year or so was making horrible amps.
CBS changed the circuitry of many of the tube amps, and musicians did not
like the sound of the new Fender amps. CBS also changed the control panel
from black to an ugly silver, and as a result these CBS amps became known as
silver faced Fenders. CBS did reverse many (but not all) of these circuit
changes when they realized musicians hated the new amps.

Changing a silver face Fender back to a blackface circuit usually involves
modifying the driver/phase splitter circuit back to blackface
specifications, removing two 2,000 pf caps just before the power tubes, and
possibly the hardest part, re-routing the wires (they physical placement of
wires) to reduce oscillation. This cannot always be done successfully.

An example: the AB763 circuit is a blackface Twin (the one most say sounds
better), and the AA769 and AA270 Twin circuits are examples of the "silver
face" Twin. One of the differences is that the 12AT7 driver tube of the
blackface Twin uses an 82K resistor on one tube plate, and a 100K resistor
on the other plate. The silver faced Twin's used 47K plate resistors, which
provided less gain.

Mesa Boogie Amps

These evolved out of Randall Smith's experiments with Fender amps. While
there were many techs at the time experimenting with increasing the gain of
both Marshall and Fender amps, Randall took the concept further than most.
He added tube gain stages to the end of Fender preamps; and between the
preamp and the power amp, he added a master volume. This allowed players to
push the preamp tubes deep into distortion, yet send just a tiny portion of
this distorted signal to the power amp. So at low master volume settings,
the power amp ran (operated) clean. Previously, a distorted amp had both
preamp and power amp distortion, as there had been no master volume to "dam
up" all the preamp gain. Master volumes allowed players to get distorted
preamp sounds without loud, distorted power amp tones.

A lot of rock and blues players didn't like this sound, as they felt it was
too one dimensional and "stiff", compared to the more complex sound of a
whole amp (both the preamp and power amp, and the speakers) distorting.
Nevertheless, for every player who didn't like this sound, it seemed that
there was another who loved the high gain saturation these Mesa Boogie amps
got. Another complaint was the Mesa's clean tones, while quite similar to
Fender's, didn't sound as natural or rich as the clean sound of say, a 1965
Fender Twin.

Through the 1970's and 1980's, Mesa continued to refine their Boogie amps,
from the original Mark I's, to various Mark II's, Mark III's, and finally,
the Mark IV, which is a much more complex amp that the original Mark I.
These amps are all "Boogie's"-they all share the use of pre-distortion EQ.
The EQ is positioned just after the first gain stage. There are subtle and
not so subtle differences in the tones of all these amps, but they come from
the same general "family" of circuits. Boogie amps are thought to have a
smooth, very compressed, "L.A. studio player" tone.

Mesa's newer "Dual Rectifier" amps are not of the classic Boogie design, but
instead are much more like Soldano amps. They have the EQ newtork at the
*end* of the preamp, just like Marshall, Soldano, Bogner, VHT, and other
"British" style amps. These products have a more aggressive tone that's more
suited to grunge and metal.
Marshall's 1970's Master Volume amps

Beginning in 1974, Marshall rolled out their new master volume amps.
Marshall began making them in part as a response to Mesa's Boogie amps, and
in part to give rock players what they were asking for: Marshall crunch at
lower volumes. Marshall kept the EQ at the end of the preamp, and simply
added a gain stage so that there were 3 stages of gain before the EQ, not 2
as in the previous Marshall amps. [Marshall kept making the old style,
non-master volume amps throughout the 1970's.] With the gain set high and
the master low, this gave preamp only distortion. For sure, it sounded like
a Marshall, but not the same as an old non-master volume head cranked to 10,
which had both preamp and power amp distortion, a tonally more complex brew.
Nevertheless, it was a reasonable compromise for many guitarists.
Early JCM-800's with diode clipping

By the early 1980's, Marshall was producing amps that mixed tube and
transistor distortion. The transistor distortion was accomplished by adding
"diode clipping" circuits among the tube preamp gain stages, which gave the
amps a lot more distortion, but sacrificed warmth. The tubes before the
diodes helped to push guitar signal into the diodes, where they were clipped
(distorted), and the tubes after the diodes both amplified and "warmed up"
the sound somewhat. These and later Marshalls had a bright, buzzy
distortion, especially at low volumes. When cranked up loud, the power tubes
would begin distorting, thickening up the sound to reduce the harsh, thin,
buzzy distortion. Another unsual (for Marshall) feature was that the EQ was
positioned early in the preamp, just after the first gain stage. This would
be changed on later JCM-800 models: moved to after 3 gain stages, just like
on the 2203 amps. And the new 4210/2205 amps sported (had) an effects loop,
something new for Marshall. This allowed guitarists to put their delay
pedals after the preamp distortion for cleaner delays. Finally, Marshall
used a post phase inverter master volume for these amps. Marshall would
later change back to a master volume after the EQ (but before the phase
inverter) much like the 2203 amps.

Some metal players loved these new Marshalls, whereas many older rock and
blues players hated them.

The 1980's marked a confusing period for Marshall, as they were
simultaneously still making 1. non-master volume amps: circuits 1987 (50
watt model) and 1959 (100 watt model), 2. 1970's style Master volumes
(circuit 2203-all tube signal path), and 3. the new models with tubes and
transistor distortion mixed, like the 50 watt 4210.

Many players call all 2203 style master volumes JCM-800's, but these 2203
amps were being made long *before* Marshall began calling their amps
JCM-800's. Also, there were JCM-800's being made which used diode clipping,
and thus were *not* the older style 2203 circuit.

So, if you hear someone talking about a "JCM-800", he could mean an all tube
2203 master volume circuit (first produced in the 1970's, and which Marshall
continued to make in the 1980's). Or he could be talking about one of the
newer circuits with diode clipping, first made in the 1980's. You could ask
him "What model number are you refering to?". Or "Are you talking about the
2203 circuit with an all tube signal path, or the circuits with the mix of
diode clipping and tube distortion?" If he says something stupid like "All
JCM-800's are the 2203 circuit! No JCM-800's have diode clipping!", then you
can tell him he's full of shit. (i.e. he's either lying or just plain
ill-informed) You can say, "Marshall's 50 watt combo (model 4210) and 50
watt head (model 2205) both use diode clipping. Just look in the "History of
Marshall" book.

Marshall's later JCM-800's

Marshall modified the new design, and a 1988 schematic for the 2210 (head)
and 4211 (combo) amps show an extra tube gain stage after the diode
clipping. The diode clipping itself had been altered to a more complex
arrangement-more like a diode bridge rectifier, and the EQ was repositioned
to after the third gain stage. Much like the 2203 amps.

For Marshall's 25th Anniversary, they came out with the Jubilee amps,
favored by Slash or Guns and Roses, and recently reissued as the "Slash"
amps. These are among the most popular JCM-800 amps, which is somewhat
ironic, as they probably have to greatest use of diode clipping. Which at
low volume, to my ears, makes the amps sound too trebley. When cranked,
however, they can get an aggressive, yet warm tone. Listen to any Guns and
Roses record, or the guitar solo in "My Mama Said" by Lenny Kravitz. You'll
notice Lenny's rhythm guitars sound edgy and bright, but when Slash starts
his solo, his tone is thicker and meatier with less high end "buzz" and more
"throat." It could well be the EL34's being overdriven.

Marshall's JCM-900 amps continued to rely on pretty much the same formula as
the later JCM-800's. There were lots of differences (some of which added
gain), but the basic style remained the same: two gain stages in series,
diode clipping, third gain stage and EQ and master volume. Some JCM-900 amps
used IC's (transistor opamps) for additional gain. Some claim that Marshall
began using lower quality components in these JCM-900's, which reduced
reliabity. I've heard complaints that the output transformer blows up more
easily at high volumes than the output transformers used in earlier Marshall
amps.

Marshall designed these amps with the late 1980's metal players in mind, so
they have a lot of gain and thin, buzzy transistor clipping mixed in with
the tubes. Some amp techs find old JCM-900's used for low prices, and peform
extensive modifications to these amps to convert them either to the 1960's
style circuits (#1959, #1987), or the 1970's #2203 circuit. These mods are
not cheap, but they give the amp a warmer all tube sound.

Doug Hoffman makes some point to point wired boards perfect for converting
some JCM-900's to an early Marshall/tweed Bassman circuit. It still requires
a lot of work, but less so than making the boards yourself.

Bogner "FISH" preamp (Brown Channel) Marshall 30th Anniversary (Lead
Channel)

As many rock and metal players' tastes matured, they began realizing that
while they loved the *amount* of distortion the new Marshall amps had, they
didn't like the *quality* of it. They wanted the aggressive tone of Marshall
amps, but with more underlying warmth, much like Eddie Van Halen's sound.
Eddie had led people to believe that his Marshall amp had been heavily
modified, so that seemed the natural route for other guitarists to take.

Old Marshall heads from the 1960's and early 1970's were used for both their
stock sound, and the fact that their construction made them very easy to
work on. Newer amps used printed circuit boards, which were hard to modify.

Guitarists and amp techs began adding master volumes and additional gain
stages. Some simply changed some of the resistor and capacitor values in
2203 amps to increase the gain of exisitng stages. Others took the more
radical approach of adding entirely new gain stages, which greatly increased
the amount of distortion. One of the more popular circuit configurations
that came out of this "hot modding" phenomenon was the "4+0" circuit: gain
stage, gain control, three more gain stages, EQ, master volume, then the
power amp.

Not all of the modificiations sounded good. In fact, many great sounding
stock amps were butchered into amps which were noisy, unreliable, and bad
sounding. Guitarists found that it's not hard adding gain-what is hard is
making the gain and resulting distortion sound MUSICAL.

Some of the more talented amp techs with sharp (good) ears were able to
create some good sounding circuits. One was a Mr. Reinhold Bogner, whose
"FISH" preamp was popular in the early 1990's. Unlike Boogie amps, each
channel was almost completely independent. The highest gain "brown" channel
used the 4+0 configuration, the two other distortion channels (Strato and
Shark) used the lower gain 3+0 circuit. The Brown and Strato channels are
very similar to Marshall circuits, with a shared Marshall style EQ after the
gain stages. The Shark channel is a lot like a Vox AC30's Top Boost channel
with an extra gain stage. Even the EQ on this channel is very Vox like. It
doesn't completely capture the Vox AC30 sound, of course, because its
lacking the AC30's power amp and speakers, which are a very important part
of the Vox sound.

There were also other amp techs who either modified Marshalls to the 4+0
style preamp, or began making their own amps and preamps with this type of
circuit.

Marshall eventually decided to use some of these ideas for it's 30th
Annivesary amp (model #6100). While the amp does use some solid state
devices, most of the preamp uses an all tube signal path. Gone are the diode
clipping circuits common to the JCM-900 and many JCM-800 amps.

The lead channel uses a 4+0 circuit. It is unusual in that after the second,
third, and fourth stages, there are "cathode followers". Cathode followers
are usually one of the two triodes in a 12AX7 set up to lower the impedance
of the signal. Some amp techs claim cathode followers add more "crunch" to
the sound. It is normal for a Marshall style circuit to use a single cathode
follower just before the tone controls, but not after each gain stage.

Soldano lead channel

Michael Soldano is the person who made the super high gain Marshall sound
famous. Some of the Marshalls he worked on he modded to the 4+0 circuit, but
for his SLO-100 amp, he added a fifth gain stage to make a 5+0 circuit. It
is debatable as to whether or not this extra gain stage is really needed, as
four gain stages is usually enough for very saturated distortion sounds.

Unlike most Marshall amps, Soldano amps use 6L6/5881 power tubes instead of
EL34's. Other makers of high gain British sounding amps, have decided to
stick with EL34's, or offer a choice of EL34's or 6L6/5881 power tubes. One
reason for this is that in the late 1980's and early 1990's, it was becoming
hard to find good EL34's. Luckily, in 1996, we have more choices for this
famous tube. Svetlana's new Gold Top EL34's have been getting very positive
reviews in the press and on the Internet, and even Marshall, which had
switched to 5881's for many of its amps, has decided to go back to EL34's
for many models. Svetlana claims their Gold Top EL34's are modeled after the
famous Mullard EL34's used in most of Marshall's 1960's amps. They also
claim that the Gold Tops are able to withstand higher voltages than the
older Mullards, which is good news, as some of the newer EL34's cannot take
the higher voltages found in old Marshall amps.

Peavey EVH 5150

As I've already stated, this amp uses 6 gain stages before the EQ. A 6+0
arrangement. Unlike many other high gain Marshall style amps, there is no
cathode follower before the tone network, so the EQ is fed high impedance
signal from the plate of the 6th gain stage, not a low impedance signal from
the cathode of a cathode follower.

This amp's circuitry is very similar to the Soldano SLO-100. Mesa's Dual
Rectifier amps (Dual Rectifier, Trem-o-verb, and DC series amps) also have
similar lead channels to the SLO-100. These Soldano, Peavey, and Mesa amps
don't sound exactly the same for a variety of reasons: the physical layout
of components (lead dress), the quality and type of the components used,
some circuit differences, etc.

OTHER HIGH GAIN AMPS AND PREAMPS:

There are now many great sounding high gain amps, such as:

VHT Amplification:

VHT's products are like a combination of a hot rodded Marshall (modified for
high gain) and a Hiwatt. Some players claim that VHT's high gain sound is
the clearest and most focused of any hard rock or metal amp. The name of
their most famous amp, the "Pittbull" should give you an indication of the
sound. [Pittbulls are very aggressive, vicious dogs.] VHT amps get great
reviews in the guitar magazines.

Custom Audio Electronics:

CAE is most famous for their CAE 3+ preamp, which can be found in the racks
of a lot of famous guitarists. It is my personal favorite. I love this
preamp. It has an outstanding Fendery clean channel and two extremely rich
and aggressive Marshall like lead channels. CAE's lead sounds, while
definitely aggressive, seem somewhat more refined than the lead sounds of
other amps, like VHT, Bogner, and Egnater. CAE also makes a two channel 100
watt head that sounds great.

Bogner:

Bogner has stopped making the FISH preamp, and is now making just amps.
Their 100 watt Ecstacy is has been used by a lot of players, including Steve
Vai, and Brad Whitford. The Ecstacy is known for having a sound very similar
to old Marshall "Plexi" heads from the 1960's, but with more versatility.
The amp has a lot of switches, but it can generate both "old" and "new" amps
sounds. It also has the benefit of a terrific clean channel, much like a
1965 Fender Twin, but with more headroom.

Egnater:

Wonderful amps made in Michigan. Bruce Egnater, the company president and
chief designer, manufactures both super high gain, multi-channel amps and
lower gain amps more similar to vintage Marshalls and Fenders. Egnater amps
and preamps also get great reviews in the guitar press. I recommend checking
out (trying) their TOL 100 head, which has four channels.

Fat Boy:

This company isn't very well known. They make very good sounding amps which
are definitely worth trying if you have a chance.

Wizard:

The same story as Fat Boy-very good sounding amps worth listening to.

THE "RETROS" TREND

By the early 1990's, a lot of guitar players in the U.S. were tiring
of(becoming tired of/bored with) high gain preamp sounds. They wanted to
return to the sound of power amp distortion, which they percieved as
sounding more complex and dynamic than "sterile" high gain preamp
distortion. They felt high gain amps were 1. too "cluttered" with preamp
gain and 2. didn't deliver sounds that were as rich and "organic" sounding.
So, instead of adding even more gain stages, they wanted amps with *fewer*
gain stages, and no master volumes!

Some manufacturers like Marshall and Fender began reissuing their older,
classic non master volume amps. Some small manufacturers began making their
own version of older Fender amps, in part because they felt that Fender's
reissues used cheaper construction methods (printed circuit boards) that
didn't accurately capture the rich sound of the older amps, which were point
to point wired. Today, there are several manufacturers making Fender style
"tweed" amps, one of the most popular in 1996 being Victoria.

Fender and other companies such as Peavey, Carvin, Crate, and Mesa also
began offering new designs which they claimed offered a more "vintage" like
sound, with less preamp gain than their 1980's amps.

Some of the newer "vintage" style amp companies and amp designers include:
Matchless, (Tony) Bruno, (Cezar) Diaz, Victoria, Holland, Budda, Guy
Hendricks (Guy-Tronics), Naylor, (Kim) Hoffman, (Doug) Hoffman, Trainwreck,
Hound Dog, Dr. Z, Penn, Top Hat, Matt Wells, and Tone King. There are more
companies, and many, many more custom amp builders in the U.S., some of whom
do great work, some of whom just *think* they do great work but in reality
make overpriced shit. Always: TRY BEFORE YOU BUY!!!

Not all of these companies and people make Fender style amps. Some, such as
Matchless, and Bruno, make amps similar to original Vox AC30's. Budda is
famous for low watt amps that sound like a great Marshall from the 1960's.
Some make amps which are inspired by both Marshall and Vox sounds
(Trainwreck, Hound Dog).
KOREA, ASIA and EUROPE:

It is interesting that the trend toward vintage sounding amps is strongest
in America. It hasn't become as popular in Europe or Asia. I know an amp
tech in Germany and one in Sweden who both still love high gain preamp
designs. Nearly all of my guitarist friends in Asia still love high gain
sounds, even those who are now interested in vintage guitars.

I know a Korean rock band that bought a used early 1970's Marshall, and
couldn't get a sound they liked out of it. They said the sound too clean. I
told them they had to crank it up to "10" to get distortion from it, and
even then it might still not be distorted enough, they might have to use an
Ibanez TS-9 Tubescreamer to push the amp deeper into distortion. I also told
them they should get the amp serviced, replacing worn out old parts, like
the filter caps and tubes. Eventually, they decided the amp was too much
trouble-they couldn't crank it up to "10" because their neighbors would
complain, they didn't have enough money to have the amp serviced, and they
wanted an amp with more distortion. Vintage amps may be "cool", but they are
not for everyone!

I can tell you that an old Marshall, Vox, or Fender amp that has been
properly serviced, can sound fantastic, with some great distortion tones.
[Eddie Van Halen now claims that the Marshall amp he used for his early
albums was a completely stock Marshall, with no additional preamp gain. He
claims he simply turned up all the knobs to "10" to get his overdrive.] But
it takes some work, and you need to be able to play the amp near full volume
to get overdrive. Which not only makes your neighbors angry, it can destroy
your hearing!

If you do come to the U.S. to try some of the amps by Budda, Victoria,
Bruno, Tone King, Hound Dog, etc. make sure you are in a store that allows
you to test the amps at both low and high volumes. Try using a variety of
guitars with it. Try the amps with some pedals, too. IMPORTANT: Don't expect
the same sounds and "feel" from these amps as you would a JCM-900 or ADA
MP-1 preamp! While some of the vintage style amps can get suprizingly thick
overdrive, it's a mix of preamp, power amp, and in some cases, speaker
distortion. It's a new universe of sound to players used to modern amps. A
lot of the "magic" lies in the "in-between" sounds, being just on the edge
of distortion. Try varying your pick attack from light to heavy. Try
adjusting the volume knob on whatever guitar you are playing to hear all the
different "shades" and "colors" of distortion from the amp.

Realize that amps without master volumes may not be what you really need.
But you won't know this until you try several non-master volume amps. It
takes time for some players to get used to these products-time to adjust
your playing techniques and ideas about tone. Luckily, there are some
terrific amps with moderate to high gain and master volumes (CAE, Soldano,
VHT, Naylor, Egnater, Wizard, etc.).

THE RDIYS (Do It Yourself) TREND:

In America, guitarists are becoming increasingly knowledgeble about their
amps. It's like the 1970's, when guitarists realized they could modify their
guitars, by changing pickups and other parts to get custom sounds. In the
1990's, guitarists are doing similar things with their amps. This doesn't
always mean modification. Guitarists' increased sophistication about and
knowledge of amps means they are better able to choose among stock
(unmodifed) guitar amps. There are many more amps to choose from, and the
overall quality of sound and construction have increased in large part due
to guitarists learning more about amp sounds and construction.

But there are a growing number of American guitarists who are working on
their guitar amps. There are many new books explaining how amps work, the
history of famous amp companies and their products, and beginning in 1997,
there will be a new magazine published by Audio Amateur Publications, Inc.
for people who build, modify, and repair guitar amps and effects. There are
new kits for guitar amps and preamps.

Keep this in mind: WORKING ON GUITAR AMPS IS VERY DANGEROUS!! YOU CAN KILL
YOURSELF EASILY!! It's hard to kill yourself working on a guitar, but guitar
amps contain lethal voltages, some up to 600 volts DC. So think very, very
hard before learning how to do this work.

WORKING ON AMPS: THE EASY, SAFE WAY

Instead of working on amps yourself, you could pay a Korean technician
familiar with tube electronics to build you some preamps and amps. First,
try learning about tube circuitry. You can buy tube guitar amp books, and
you can read articles about amps on the World Wide Web. If you have a basic
understanding of how guitar amps work, then, when you decide to pay a Korean
amp tech to build you a tube preamp or amp, you will be able to communicate
with him about the kinds of sounds you want-and the circuits which make
these sounds.

It's one thing to say "I want more distortion." That is a very general
statement, and your Korean amp tech may not be familiar with modern guitar
amp circuits which create distortion. But if you tell him this: "I want more
preamp distortion. I want you to add more tube preamp gain stages. Because I
know, the more preamp stages, the more gain the amp will have. And more gain
leads to more distortion. I want you to make a preamp circuit like this,
using 12AX7 tubes: input--gain stage1---volume control--gain stage2--gain
stage3--gain stage4--cathode follower--EQ (bass, mid, treble)--master
volume---out" Then he will have a much clearer idea of how to help you. This
is much more specific information. More specific, detailed info:

An even better idea is to show him some schematics (circuit diagrams) from
some guitar preamps and amps. You can get many schematics from tube amp
books, and the World Wide Web. I have many high gain schematics at my web
page: http://www.Channel1.com/users/monadyne/Keenan/ Print out both the
GIF's for the circuits, and the text files which go with each circuit style
(1+2, 3+0, 4+0, etc.) You have to look for them, but they are there.

You'll need two kind of voltages, high "B+" voltages and low voltage to heat
the tubes. Tell you amp tech you'll need a high voltage power supply for the
B+ voltage, which can be anywhere from 200 volts up to 400 volts for a tube
preamp (Tell him "at least 3 milliamps per 12AX7S). You'll also need voltage
to heat the tube. Tell him you want 6.3 volts DC, rectified, filtered, and
regulated. At least 300 milliamps per 12AX7 tube. Tell him you want "bleeder
resistors" attached around the filter capacitors to safely discharge the
stored energy. 220K resistors will be okay. Tell him you want your amp or
preamp to have a "standby" switch that lets the tubes heat up using the 6.3
voltage supply, but keeps the high B+ voltage off. After 2 or 3 minutes,
then you can turn the standby switch to the "on" position, which turns on
the high voltage B+. Doing this will make your tubes last much, much longer.
Tubes should warm up first before any high voltage hits them. Applying high
voltage to cold tubes makes them wear out much faster.

And print out some of the articles from the world wide web that deal with
this material. Show these articles to him. Let him take them home and read
them.

You can then work closely with the engineer, because you'll have enough
electronics knowledge that you can "speak your engineer's language". You
don't need to know as much as your engineer, you just need to know a
moderate amount about tube circuitry. What you'll really need the engineer
for is protecting you from the high voltages. Your amp tech can implement
the ideas you have, actually building the circuitry in your mind. His hands
will be on the amp, your hands will be away from the amp. You'll just be
looking at him and the amp while he works. Keep your hands OFF of the amp.
Let your tech do the actual work! After a while, you may learn enough from
him to begin working on amps yourself. Have him teach you about safety.

Instead of just building a high gain tube preamp, you could have your
engineer build you a 5F6-A Fender Bassman. You can get parts for such a kit
from Doug Hoffman in Florida. Look for a link to his web page at the
"Ampage" web page, under "Manufacturers". Remember, a tube guitar amp ALWAYS
needs a speaker [or speakers] to work!! NEVER turn on an amp unless it has a
speaker of the correct Ohm rating attached, using speaker cable, NOT guitar
cords!!

Лень двигатель прогресса.