The 60-watt Fender Super 60 was produced from
1988–1992. Photo courtesy of mercurymagnetics.com
I have a stock Fender Super 60 head
and recently purchased a second one
without tubes. I want to do something
different with the second head
and was wondering if there’s any way
to modify it to get a JTM45 sound.
Do you have any suggestions?
This could be an interesting project, but I do
need to preface it by saying there’s really no
way to transform your Fender Super 60 into
a Marshall JTM45 without, well, gutting the
entire amp and starting from scratch! While it’s
fun to note that the original Marshall JTM45
was actually a design that Ken Bran “borrowed”
from Leo’s Bassman (which in turn had
its origins in tube design manuals published
by RCA), different transformers with different
voltages and impedances, as well as substantial
differences in the circuitry will prevent us from
getting an authentic JTM45 sound and feel.
That said, there are quite a few changes
you can make to the spare Super 60 that
should give you a very different and very
useable amp to complement your existing
stock model. While there are many more
complicated ways of modifying the amp, I’ll
recommend changes you can make without
cutting circuit traces or replacing pots, which
are mounted in this amp’s circuit board.
One more point regarding the circuit
board: The circuit traces in these amps are far
from the best quality and can be easily damaged,
so try to execute the changes carefully.
Hopefully you’ll only need to do them once.
Go online, grab a schematic for Fender’s Super
60 series tube amps, and let’s get started.
We’re going to begin at the input stage
and work our way to the output. First, let’s
change the components in the cathode
circuit of V101. Remove R102 and C101
(1.5k and 10 μF respectively) and replace
them with an 820 Ω resistor and a 250 μF
capacitor. Although most of the resistors in
this amp are 1/4 watt, I’d recommend using
1/2-watt resistors wherever and whenever
possible for better reliability. While they
are physically a bit larger and may possibly
need to be elevated off the board a bit due
to hole spacing, as long as the solder joints
are sound this should not present a problem.
As for the 250 μF cap, anything 5 volts
or higher will work fine—just be aware of
the polarity and orient the cap properly.
Next remove C102 (.0047 μF) and replace
it with a .022 μF 400V or greater. Finally
remove C1 (.022 μF) and replace it with a
500 pF cap. This can be of either silver mica
or ceramic persuasion, and voltage is not an
issue as no DC voltage is present here. That
takes care of the input stage, so we’ll move
to the tone stack next.
While the changes to the input stage will
affect the amp’s gain and body, the tone stack
is where the most noticeable change will take
place, as it is the circuit most responsible for
shaping the amp’s sonic signature. First, remove
R10 (100k) and C4 (100 pF) and replace
them with a 56k and 250 pF unit, respectively.
Again, here you can use a silver mica or ceramic
cap, but be sure it’s at least 400V DC.
Next remove C6 and C7 (0.1 μF and
.047 μF) and replace them each with a 0.022
μF 400V. These changes play the biggest role
in taking the amp from the American camp
to the British camp. I employed this mod in
a rotary “MF” (Marshall/Fender) switch on
an amp I built for Stevie Ray.
Finally, remove C106 (22 μF) and R111
(3.3k) and install an 820 Ω resistor in the R111
position, leaving the C106 location empty.
Now we’ll move on to the phase inverter stage.
Start by removing R134 and R137
(470k) and replacing each with a 1M resistor.
Next remove R153 (680 Ω), replacing
it with a 470 Ω, and R136 (6.8k), replacing
it with a 10k.
Now remove C124 and C125 (.022 μF)
and replace each with a 0.1 μF. Here, I prefer
using 600V to 630V DC caps as the voltages
are a bit higher. (Excluding the 250 μF cathode
cap, it’s fine to use 600V to 630V caps
for all the caps I’ve mentioned. That’s what I
use in all the amps I build, along with 1-watt
resistors. It’s the best way to ensure failure-free
performance.) Finally remove R138
(6.8k) and replace it with a 4.7k.
There you have it. This should give you
a normal channel that definitely has a foot
planted in JTM45 tone. While I did not specifically
address the characteristics of the Super
60’s distortion channel, it too will definitely
have a more British tonality, and you may
notice a bit of increased gain as well. A bonus!
(Assuming that’s what you’re looking for.)
As far as tubes are concerned, since the original
JTM45 came equipped with KT66s, the
British version of the American 6L6, I thought
I’d leave the Fender’s 6L6s intact, alleviating
the need to convert to an EL34-based output
stage. To do that properly, you’d have to install
an appropriate output transformer, which
would require substantially more money, time,
and effort. I would have suggested changing
the 6L6s to a pair of KT66s in the amp, but if
memory serves, the Super 60 doesn’t provide
sufficient tube spacing for these behemoths!
One other tube position to consider
would be the phase inverter (V102). The
stock tube in this location is a 12AT7, but
if you’d like to get a bit more drive or push
out of the amp, try installing a 12AX7, as
the JTM would have had.
Now I hope you can get some super
leads from your Super 60.
Warning: All tube amplifiers contain lethal
voltages. The most dangerous voltages are
stored in electrolytic capacitors, even after the
amp has been unplugged from the wall. Before
you touch anything inside the amp chassis,
it’s imperative that these capacitors are discharged.
If you are unsure of this procedure,
consult your local amp tech.
is one of
the godfathers of the
low-wattage amp revolution,
co-founded and was
the principal designer for
Budda Amplification. Jeff recently launched EAST
Amplification, and he can be reached at