Fender’s reissue ’65 Princeton Reverb includes
a 10” Jensen C-10R, a long-spring reverb tank,
a pair of 6V6 power tubes, and a 5AR4 rectifier
tube. Photo courtesy of Fender
I have a reissue Fender Princeton
Reverb. I play clean and always use
the Princeton in conjunction with a
5-watt Laney Lionheart 1x12 combo.
I configure these amps in stereo with
modulation pedals between them.
To beef up the sound, I’m considering
buying an extension speaker cab
for the Princeton. Searching online,
I can’t find any recommendations for
an extension speaker to use with the
Princeton. The Princeton’s rear panel
says the amp should have an 8 Ω load,
which confuses me. Am I supposed
to disconnect the Princeton’s internal
speaker? What I really want to do is
add a 12" speaker and use it in conjunction
with the amp’s 10" speaker.
Is this possible? I appreciate any advice
you can offer.
I selected your question because it has
caused confusion for decades. I hear this all
the time: What’s the proper way to use the
extension speaker jack on the rear panel of
most vintage Fender combo amps? For me,
the short answer is, there is no proper use
of those extension speaker jacks.
Let me explain.
On all Fender combo amps and heads
that have only two speaker output jacks
(main and extension) and no other impedance
setting controls or explanation of jack
functions (such as series or parallel, as on
some later Fender amps), the two jacks are
simply wired in parallel.
Now, the multiple speaker jacks on most
amps are typically wired in parallel, which
is not a problem for an amp with impedance-
selection capability, but this isn’t the
case with these Fender amps. The output
transformers on these types of Fender amps
have only one set output impedance, and
in the case of the combo amps, the output
impedance is optimized for the amp’s internal
For example, a Fender Deluxe Reverb
combo has a single 8 Ω 12" speaker, so
the output transformer is designed to
have a dedicated 8 Ω output. A Fender
Twin Reverb has two 8 Ω 12" speakers
wired in parallel to create a 4 Ω load, and
a transformer with a 4 Ω output. A Super
Reverb has four 8 Ω 10" speakers wired
in parallel to create a 2 Ω load. In each
case, the transformer output is matched
to the combo’s particular speaker load.
This produces the highest available output
power from the amplifier.
Once another speaker is added to the
equation, the impedance now becomes mismatched
and the power becomes reduced.
So for example, if you were to add another
8 Ω extension cabinet to the already
existing 8 Ω internal speaker, the output
transformer would then be presented with
a 4 Ω load and your 12 watts of available
clean output power would be reduced by
approximately 40 percent to 7.2 watts. Not
the result you were hoping for, I’m sure.
In addition to that, the transformer
becomes stressed because of the additional
load placed on it. In some amps, this can
absolutely lead to transformer failure, but
fortunately the transformers in most vintage
Fender amps seem to have been sufficiently
overbuilt to stand up to this abuse
for decades without fail. But now knowing
this, I’m sure that you can see adding an
extension speaker cabinet to your Princeton
Reverb will achieve the exact opposite of
what you’re looking for.
Yet I have a suggestion: Consider adding
some additional external power. There are
a couple of different ways you can accomplish
this, but we’ll focus on approaches
that hopefully let you retain the integrity of
the Princeton sound.
You need two things: First, a line-level
signal from your amplifier derived at the
output stage so it retains the tonal characteristics
of the amp, and second, an additional
power amp to amplify this signal.
You can accomplish this in a couple
of different ways. You could simply send
the signal from the external speaker jack
to any direct box capable of converting a
speaker-level signal to a line-level signal.
Unfortunately, most of the line-level outputs
on these boxes are available only as an
XLR connection, so you will also need an
XLR-to-1/4" converter, so the signal winds
up in a 1/4" format.
Another option would be to have the
external speaker jack on your Princeton
converted to a line-level output. This could
easily be done by any competent amp tech
in your area. I would strongly suggest adding
a control so the output signal level is
variable. This allows you to precisely adjust
the signal level going to your external amp
Now for the other half of the equation—
power. Here you have many
options, as well. One suggestion is to use
a small, portable power amp, such as the
Electro-Harmonix 44 Magnum. The size
of an effects pedal, this box produces 44
watts of power that you could then use to
drive your external speaker cabinet. This
would certainly give you enough additional
clean headroom and power for your
The other option would be to use another
small combo amplifier with a line level
input or effects loop return, possibly something
like the ZT Lunchbox amp. This way
you have power amp and speaker all in one.
There you have it! I hope this makes
your Princeton Reverb big enough for any
job. See you next time.
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