| Dr Z. Amplifiers - The KT-45 and some Route 66, Z-28 and Delta 88 tips |
| Last updated 09 AUG 2004 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
There are a number of Z amps I use. They are all different, and most
folks know I use a Ghia, Mazerati, and MAZ for blues, rock, country, or
whatever need arises, as I prefer the lack of pedals and more of the
output section distortion and touch. BUT ... sometimes you need a
clean amp, and sometimes Pedals and Hard Rock is the order of the
day ... this is KT-45 territory and what I will use then. Just like a Hiwatt
is cleaner than a Marshall, the KT-45 has that Hiwatt clean, and much
more pedal friendly than any Fender BF or Marshall amp ... plexi or
later. This may be "the" hard rock pedal amp if that is your style.
folks know I use a Ghia, Mazerati, and MAZ for blues, rock, country, or
whatever need arises, as I prefer the lack of pedals and more of the
output section distortion and touch. BUT ... sometimes you need a
clean amp, and sometimes Pedals and Hard Rock is the order of the
day ... this is KT-45 territory and what I will use then. Just like a Hiwatt
is cleaner than a Marshall, the KT-45 has that Hiwatt clean, and much
more pedal friendly than any Fender BF or Marshall amp ... plexi or
later. This may be "the" hard rock pedal amp if that is your style.
This is the Doctor Z KT-45 amp. Some interesting aspects of this amp.
This amp was originally intended to be a "kit" amp, hence the "KT"
designation. After a lot of thinking, the good Doctor felt that the only
way he could assure build quality and really stand behind the amp, was
to build it himself, rather than offer this as a kit.
In testing of this amp, some interesting things were noted. The first,
even before turning the amp on, was the power cord.
This amp was originally intended to be a "kit" amp, hence the "KT"
designation. After a lot of thinking, the good Doctor felt that the only
way he could assure build quality and really stand behind the amp, was
to build it himself, rather than offer this as a kit.
In testing of this amp, some interesting things were noted. The first,
even before turning the amp on, was the power cord.
This is the best I could do, trying to make a BIG "Z" on
the floor. This shows a few things about this cord. For
one, it is LONG! Not the usual five or six footer you see
on most amps. Half of this cord is still behind the
cabinet!
Having a cord that can reach across a long stage run
without extension cords, is a blessing.
This cord is also very heavy guage, hence my poor
attempt at forming this into a prettier "Z".
It reminds me of the old story when Aspen Pittman
(Groove Tubes founder and President) was at Acoustic
Amps before his GT days. Acoustic Amps had a really
long cord as standard. Acoustic management wanted
to save a few bucks with a shorter cord. Aspen
protested, but Acoustic asked Aspen, "how many
fewer amps do you think we will sell because of a
shorter cord"? Aspen replied, "you won't sell one less
amp, but with that sort of thinking, you will be out of
business in two years". They were out of business
within two years.
This cord to me, just presents to me, the builder's
basic thinking and approach to their product. This cord
to me, sort of said a lot more than many might expect.
the floor. This shows a few things about this cord. For
one, it is LONG! Not the usual five or six footer you see
on most amps. Half of this cord is still behind the
cabinet!
Having a cord that can reach across a long stage run
without extension cords, is a blessing.
This cord is also very heavy guage, hence my poor
attempt at forming this into a prettier "Z".
It reminds me of the old story when Aspen Pittman
(Groove Tubes founder and President) was at Acoustic
Amps before his GT days. Acoustic Amps had a really
long cord as standard. Acoustic management wanted
to save a few bucks with a shorter cord. Aspen
protested, but Acoustic asked Aspen, "how many
fewer amps do you think we will sell because of a
shorter cord"? Aspen replied, "you won't sell one less
amp, but with that sort of thinking, you will be out of
business in two years". They were out of business
within two years.
This cord to me, just presents to me, the builder's
basic thinking and approach to their product. This cord
to me, sort of said a lot more than many might expect.
The good Doctor has been around for 15
years. The Z amps are all very unique
designs, not copies or mods or other amps.
One aspect to this is in his amps where the
EF86 tube is used in the front end. I think
this will be a great place to mention this, as
this amp uses an EF86 in it's front end.
The EF86 / 6267 of today, is frankly, a crap
shoot when it comes to it's output and specs.
I have always been leary of EF86 based
amps, as finding a good EF86 is the key to
having these amps not only sound good, but
also having them not be noisy and
microphonic. An EF86 is a very high gain
pentode. It has a gorgeous distortion
character, much different than a triode such
as a 12AX7. In some earlier Vox amps, this
was the magic in some of them. (Frankly I
prefer the AC30/4 over the AC30/6TB myself).
An EF86 can have a gain much higher than
the "100" of a 12AX7, in the order of 400-2000
depending on the circuit. This high gain can
make them very touchy to say the least. In
my Victoria Sovereign, picking a "good" EF86
is critical, as it seems to be in a Bad Cat or
Matchless amp also. A decent EF86 is good,
a great EF86 is magic. Spend the $60.00 or
so for a great one, it will be worth it.
One of the first things I noticed when I
plugged in the KT-45 was it's lack of
background noise. In looking deeper later
into the circuit design, it was found that
once again, this was very unusual and
unique.
This amp was not too fussy about the EF86 in
V1. I even took known bad examples and
tried them, and to my surprise, they worked
pretty nicely, where they were just about
unusable in my other EF86 based amps.
Using an NOS 6267, there was though, more
"good stuff", more harmonic content and a
much more open sound.
On a Strat on the neck pickup, the amp set at
about noon on all three controls, and the
guitar volume at about 8, there was chime
and life from a simple chord. Working my
way up the fretboard, one note at a time, a
few less than optimal spots were noted, as
would be the case in most any "off the shelf"
amp. Tracing the stock tubes, it was noted
that the stock GT-E34Ls #6 tubes were fine
and had a great dynamic match, but V2, a
Sovtek 12AX7LPS was somewhat
unbalanced. This was replaced with a
SAG-AX7-MPI and the issue was resolved.
Later, a Raytheon NOS 12AX7 that was an MPI
and a Tung Sol 12AX7 MPI were also tried.
This is the phase iverter, so any of the MPI's
worked nicely in the same manner. With the
old LPS vs the MPI, after one hour at 50
watts output into a load at a 400 Hz tone, the
output transformer temerature dropped 12
degrees with the MPI.
The bottom line here seems to be, that
current new EF86 tubes work great in these
amps, so that is one area of possible
concern that you can toss out the door.
After seeing and hearing how the good
Doctor has implemented the EF86 into his
designs, it makes me jump at the chance to
try the Z-28 (6V6 based) and Route 66 (KT-66
based) amps. I am already aware of the
Route 66, and have many clients that use
this amp, but would like to spend more time
with this Dr. Z masterpiece.
These are amps that use the EF86 in a way
where all of the great attributes of this tube
are put into play. All the gain you may need,
pentode character, and not needing many
stages of dual triode cascading gain (and the
noise) to reach a target gain level. It is so
refreshing to have the joy of playing an amp
that is so versitile, responsive to guitar tone
and volume controls, and touch sensitive.
In this day of complex front end amps, some
of which have more "features" than tone,
these amps are a breath of fresh air, without
going the vintage or tweed routes. These
are unique designs from Doctor Z, so don't
have too many preconceived ideas up front
... these amps may surprise even the most
dihard critic.
Thanks to the good Doctor for using a super
tube in a super way.
years. The Z amps are all very unique
designs, not copies or mods or other amps.
One aspect to this is in his amps where the
EF86 tube is used in the front end. I think
this will be a great place to mention this, as
this amp uses an EF86 in it's front end.
The EF86 / 6267 of today, is frankly, a crap
shoot when it comes to it's output and specs.
I have always been leary of EF86 based
amps, as finding a good EF86 is the key to
having these amps not only sound good, but
also having them not be noisy and
microphonic. An EF86 is a very high gain
pentode. It has a gorgeous distortion
character, much different than a triode such
as a 12AX7. In some earlier Vox amps, this
was the magic in some of them. (Frankly I
prefer the AC30/4 over the AC30/6TB myself).
An EF86 can have a gain much higher than
the "100" of a 12AX7, in the order of 400-2000
depending on the circuit. This high gain can
make them very touchy to say the least. In
my Victoria Sovereign, picking a "good" EF86
is critical, as it seems to be in a Bad Cat or
Matchless amp also. A decent EF86 is good,
a great EF86 is magic. Spend the $60.00 or
so for a great one, it will be worth it.
One of the first things I noticed when I
plugged in the KT-45 was it's lack of
background noise. In looking deeper later
into the circuit design, it was found that
once again, this was very unusual and
unique.
This amp was not too fussy about the EF86 in
V1. I even took known bad examples and
tried them, and to my surprise, they worked
pretty nicely, where they were just about
unusable in my other EF86 based amps.
Using an NOS 6267, there was though, more
"good stuff", more harmonic content and a
much more open sound.
On a Strat on the neck pickup, the amp set at
about noon on all three controls, and the
guitar volume at about 8, there was chime
and life from a simple chord. Working my
way up the fretboard, one note at a time, a
few less than optimal spots were noted, as
would be the case in most any "off the shelf"
amp. Tracing the stock tubes, it was noted
that the stock GT-E34Ls #6 tubes were fine
and had a great dynamic match, but V2, a
Sovtek 12AX7LPS was somewhat
unbalanced. This was replaced with a
SAG-AX7-MPI and the issue was resolved.
Later, a Raytheon NOS 12AX7 that was an MPI
and a Tung Sol 12AX7 MPI were also tried.
This is the phase iverter, so any of the MPI's
worked nicely in the same manner. With the
old LPS vs the MPI, after one hour at 50
watts output into a load at a 400 Hz tone, the
output transformer temerature dropped 12
degrees with the MPI.
The bottom line here seems to be, that
current new EF86 tubes work great in these
amps, so that is one area of possible
concern that you can toss out the door.
After seeing and hearing how the good
Doctor has implemented the EF86 into his
designs, it makes me jump at the chance to
try the Z-28 (6V6 based) and Route 66 (KT-66
based) amps. I am already aware of the
Route 66, and have many clients that use
this amp, but would like to spend more time
with this Dr. Z masterpiece.
These are amps that use the EF86 in a way
where all of the great attributes of this tube
are put into play. All the gain you may need,
pentode character, and not needing many
stages of dual triode cascading gain (and the
noise) to reach a target gain level. It is so
refreshing to have the joy of playing an amp
that is so versitile, responsive to guitar tone
and volume controls, and touch sensitive.
In this day of complex front end amps, some
of which have more "features" than tone,
these amps are a breath of fresh air, without
going the vintage or tweed routes. These
are unique designs from Doctor Z, so don't
have too many preconceived ideas up front
... these amps may surprise even the most
dihard critic.
Thanks to the good Doctor for using a super
tube in a super way.
The KT-45 was purchased as I needed a simple and
light amp with a lot of clean headroom. This amp has
just that, and more.
Most folks think of something like a Fender Twin
Reverb for clean headroom, a 6L6 based amp. EL-34
based amps are thought of more as hard rock amps.
This amp does both, as long as you are willing to put
up with a high sound level.
This is a class A/B amp that uses GT E34LS output
tubes. The Groove Tubes E34LS is NOT a
conventional EL-34. The E34LS is built on specific
GT tooling in the JJ factory, but is not the same tube
as the JJ version. On the GT version, looking at the
tube, you will see more plate mass and heat sink
wings on the plate assembly. The E34LS is a 30 watt
tube. Other EL-34 tubes are 25 watters.
The tone stack on this amp also controls gain. Turn
the volume, bass, and treble to the 3 o'clock
positions, and this is a very loud and powerful rock
amp with gorgeous distortion characteristics. Dial it
back a bit, and it is crystal clean - a country picker or
slide players dream amp.
Some folks say this amp is The Who "Live at Leeds"
tone. Others say it is Vox AC-30 meets HiWatt. What
I found, is the amp can cover each of these tones,
but can dial right into the Vox AC-50 tones, their
EL-34 based class A/B amp used by folks later than
the AC-30 amps when more volume was needed for
bigger venues.
An amazing piece of work.
light amp with a lot of clean headroom. This amp has
just that, and more.
Most folks think of something like a Fender Twin
Reverb for clean headroom, a 6L6 based amp. EL-34
based amps are thought of more as hard rock amps.
This amp does both, as long as you are willing to put
up with a high sound level.
This is a class A/B amp that uses GT E34LS output
tubes. The Groove Tubes E34LS is NOT a
conventional EL-34. The E34LS is built on specific
GT tooling in the JJ factory, but is not the same tube
as the JJ version. On the GT version, looking at the
tube, you will see more plate mass and heat sink
wings on the plate assembly. The E34LS is a 30 watt
tube. Other EL-34 tubes are 25 watters.
The tone stack on this amp also controls gain. Turn
the volume, bass, and treble to the 3 o'clock
positions, and this is a very loud and powerful rock
amp with gorgeous distortion characteristics. Dial it
back a bit, and it is crystal clean - a country picker or
slide players dream amp.
Some folks say this amp is The Who "Live at Leeds"
tone. Others say it is Vox AC-30 meets HiWatt. What
I found, is the amp can cover each of these tones,
but can dial right into the Vox AC-50 tones, their
EL-34 based class A/B amp used by folks later than
the AC-30 amps when more volume was needed for
bigger venues.
An amazing piece of work.
Carmen Ghia and KT-45. A great combination with
an A/B box, giving a wide range of tones from over
the top creamy leads of the Ghia, to the clean
headroom of the KT-45, to massive sound levels
by raising the volume level on your guitar using
the KT-45.
The KT-45 amp is also pedal friendly. This was
another big surprise in testing this amp.
an A/B box, giving a wide range of tones from over
the top creamy leads of the Ghia, to the clean
headroom of the KT-45, to massive sound levels
by raising the volume level on your guitar using
the KT-45.
The KT-45 amp is also pedal friendly. This was
another big surprise in testing this amp.
Getting ready for a recording session with the Z-28.
This amp did what the Fender Deluxe Reverb did and more. Doing a bit of
research and bench testing, this "22" watt rated amp had an output of 35 watts at
-10db input signal at 400HZ which was something of a surprise. The EF86 front end
was much more quiet than my Deluxe Reverb and more pedal friendly. The amp
runs on the edge of class A, even though it is a class A/B amp. A call in to Dr. Z
confirmed bias settings of 28-30 milliamps was indeed normal on this amp.
This amp did what the Fender Deluxe Reverb did and more. Doing a bit of
research and bench testing, this "22" watt rated amp had an output of 35 watts at
-10db input signal at 400HZ which was something of a surprise. The EF86 front end
was much more quiet than my Deluxe Reverb and more pedal friendly. The amp
runs on the edge of class A, even though it is a class A/B amp. A call in to Dr. Z
confirmed bias settings of 28-30 milliamps was indeed normal on this amp.
Various mics and mic placement were used. The GT-33 was selected after
another four or so mics were tried. This is one of the world's great guitar
mics or overhead mics used for violin or acoustic dobro. The only mic that
seems to excel over this mic may be the GT-44 in this particular application.
The mic was run into a ViPRE preamp at settings of MF (medium fast) for rise
time and transformer terminated at a 1200 ohm setting. This yielded much
lower noise than the API preamp which is not transformer input isolated, it is
a typical balanced bridge input device.
another four or so mics were tried. This is one of the world's great guitar
mics or overhead mics used for violin or acoustic dobro. The only mic that
seems to excel over this mic may be the GT-44 in this particular application.
The mic was run into a ViPRE preamp at settings of MF (medium fast) for rise
time and transformer terminated at a 1200 ohm setting. This yielded much
lower noise than the API preamp which is not transformer input isolated, it is
a typical balanced bridge input device.
First track was recorded with this off axis placement using the Dr. Z 2x10
cabinet. This cab yielded more defined and detailed results over the 1x12
cabs that were also tried. These cabs were the K&K ported cabs with
Celestion V30, 75, and 100 speakers. The Jensen P12R was also tried. A
Bogner 1x12 closed back cab was tried, as was a Mesa 1x12 half open back
with stock speaker and GT 1x15 cab.
cabinet. This cab yielded more defined and detailed results over the 1x12
cabs that were also tried. These cabs were the K&K ported cabs with
Celestion V30, 75, and 100 speakers. The Jensen P12R was also tried. A
Bogner 1x12 closed back cab was tried, as was a Mesa 1x12 half open back
with stock speaker and GT 1x15 cab.
Second track - mic moved away, position changed. ViPRE settings changed
to a 600 ohm termination. This brought up the level to the recorder quite a
bit which allowed the mic to be backed off. Capsule was switched to an
omni directional capsule which allowed more room acoustics for the second
track. At this 600 ohm setting of the ViPRE and the harmonics of the Z-28
with a Koa neck/body 'Strat", the sound was huge and mellow at a amp
volume level setting at 9:00. Amazing amp that captured the difference
between an Alder body guitar and a Koa body guitar big time.
to a 600 ohm termination. This brought up the level to the recorder quite a
bit which allowed the mic to be backed off. Capsule was switched to an
omni directional capsule which allowed more room acoustics for the second
track. At this 600 ohm setting of the ViPRE and the harmonics of the Z-28
with a Koa neck/body 'Strat", the sound was huge and mellow at a amp
volume level setting at 9:00. Amazing amp that captured the difference
between an Alder body guitar and a Koa body guitar big time.
At the end of the day,
the Z-28 is put away
with some of it's other
Z friends, a Fender
Pro Reverb and
Marshall JTM-45.
the Z-28 is put away
with some of it's other
Z friends, a Fender
Pro Reverb and
Marshall JTM-45.
A ViPRE to the left.
| To see a very nice review on the Z-28 and the Mazerati amps from the March 2004 issue of Guitar Player Magazine, CLICK HERE |
This was a post off the PRS gear forum by JWK
I don't get this. By my reckoning, the EF86 overloads way easier than the 12AX7 (and I'm sure you meant
to say dual triode). I don't have any direct experience with the EF86, but I have used a 6AU6 for an input
stage. Even more gain than the EF86 and gets squashed pretty damn easy. That sounded great with
pedals too, but of course you adjust the signal level from the little box, right? Don't take this the wrong
way. I'm just an amateur who likes to play with circuits. I'm hardly an expert and don't pretend to be one.
I still haven't figured out what makes an amp "pedal friendly". If you could explain how the EF86 doesn't
get squashed as easily as the 12AX7 I would appreciate it. Thanks.
This post brought up issues which I have wanted to address for quite a while in regard to the Doctor
Z amps that are grid biased; the Z-28. Route 66, and KT-45. My response is below, and there are
some tips in there, for users of these amps.
JWK ...........
Pentodes have a different overdrive characteristic than a triode.
Looking at a common 12AX7 made today, there are two sides of the tube, and these also do impact to
a slight degree, each other as a small factor. BUT ... a new 12AX7 at the more common voltages (250
plate and -2v bias) is "supposed" to have a gain of 100, a current output of 1.2 millamps, and a
transconductance of 1600.
The reality of today's 12AX7 is more on the order of gain in the mid 80s' TC at 1200-1400, but worst of
all, a current output of 0.6-0.7 millamps.
Now, even today's current EF85 pentodes, have a current output of 3.0 millamps, and a TC of over
2000. This is a stronger tube and also has a faster rise time.
Now, one can use an EF86 in many ways, and you can alrer the plate voltage, grid voltage, screen
voltage, and make the tube do different things. In a Matchless DC-30, the EF86 is used for gain, and
you can get gain of over 400 from these tubes easily. In the Z amps, they are used in a different way.
They drive current, and that is why they are quiet too.
The way the tone stacks work in the Z-28, Route 66, and KT-45 is very unique. If somebody ever says
that they had one of these amps and did not like it's tone (as opposed to power output or features), I
always seem to have found that it was due to them not using the tone controls over the wide range
they have.
These three amps almost have something of two volumes (bass and treble) and one "master" (the
volume knob). The tone stacks in these amps may be the widest and most effective of any amps I
have seen.
You need to use the tone controls on these amps, they will get you more diverse range than just
about any amp I can think of.
Also keep in mind, that in these amps, there is very little between your guitar pickup and the output
stage. Not multiple gain stages in one or more dual triode ... not a lot of R/C conponents and
resistors. This is why folks say these amps sound so open and big. Play something like a Route 66
for a while, and switch to a nice Marshall or Fender. The amps sound restricted or compressed in a
way. You became used to a more open design, and these are all great amps, all with great uses.
Just like guitars ... two are better than one .... it is the same with amps, if they differ.
The reason these amps are pedal friendly, is the EF86 in the way it is used in this amp, has loads of
headroom and does not go into distortion or compression as easily as a triode such as a 12AX7,
especially if that triode is driven hard, in which case the 12AX7 is even worse than in a lower gain
amp. The EF86 pentode has much more reserve in the Z circuit than even the EF86 in a Matchless
circuit ... very different application of the tube.
The big tip on the Z-28, Route 66, and KT-45 (and 6545 on the "45" side) .... is USE THOSE TONE
CONTROLS. These amps are VERY versitile.
I don't get this. By my reckoning, the EF86 overloads way easier than the 12AX7 (and I'm sure you meant
to say dual triode). I don't have any direct experience with the EF86, but I have used a 6AU6 for an input
stage. Even more gain than the EF86 and gets squashed pretty damn easy. That sounded great with
pedals too, but of course you adjust the signal level from the little box, right? Don't take this the wrong
way. I'm just an amateur who likes to play with circuits. I'm hardly an expert and don't pretend to be one.
I still haven't figured out what makes an amp "pedal friendly". If you could explain how the EF86 doesn't
get squashed as easily as the 12AX7 I would appreciate it. Thanks.
This post brought up issues which I have wanted to address for quite a while in regard to the Doctor
Z amps that are grid biased; the Z-28. Route 66, and KT-45. My response is below, and there are
some tips in there, for users of these amps.
JWK ...........
Pentodes have a different overdrive characteristic than a triode.
Looking at a common 12AX7 made today, there are two sides of the tube, and these also do impact to
a slight degree, each other as a small factor. BUT ... a new 12AX7 at the more common voltages (250
plate and -2v bias) is "supposed" to have a gain of 100, a current output of 1.2 millamps, and a
transconductance of 1600.
The reality of today's 12AX7 is more on the order of gain in the mid 80s' TC at 1200-1400, but worst of
all, a current output of 0.6-0.7 millamps.
Now, even today's current EF85 pentodes, have a current output of 3.0 millamps, and a TC of over
2000. This is a stronger tube and also has a faster rise time.
Now, one can use an EF86 in many ways, and you can alrer the plate voltage, grid voltage, screen
voltage, and make the tube do different things. In a Matchless DC-30, the EF86 is used for gain, and
you can get gain of over 400 from these tubes easily. In the Z amps, they are used in a different way.
They drive current, and that is why they are quiet too.
The way the tone stacks work in the Z-28, Route 66, and KT-45 is very unique. If somebody ever says
that they had one of these amps and did not like it's tone (as opposed to power output or features), I
always seem to have found that it was due to them not using the tone controls over the wide range
they have.
These three amps almost have something of two volumes (bass and treble) and one "master" (the
volume knob). The tone stacks in these amps may be the widest and most effective of any amps I
have seen.
You need to use the tone controls on these amps, they will get you more diverse range than just
about any amp I can think of.
Also keep in mind, that in these amps, there is very little between your guitar pickup and the output
stage. Not multiple gain stages in one or more dual triode ... not a lot of R/C conponents and
resistors. This is why folks say these amps sound so open and big. Play something like a Route 66
for a while, and switch to a nice Marshall or Fender. The amps sound restricted or compressed in a
way. You became used to a more open design, and these are all great amps, all with great uses.
Just like guitars ... two are better than one .... it is the same with amps, if they differ.
The reason these amps are pedal friendly, is the EF86 in the way it is used in this amp, has loads of
headroom and does not go into distortion or compression as easily as a triode such as a 12AX7,
especially if that triode is driven hard, in which case the 12AX7 is even worse than in a lower gain
amp. The EF86 pentode has much more reserve in the Z circuit than even the EF86 in a Matchless
circuit ... very different application of the tube.
The big tip on the Z-28, Route 66, and KT-45 (and 6545 on the "45" side) .... is USE THOSE TONE
CONTROLS. These amps are VERY versitile.