Any gigging musician who uses an acoustic
electric guitar in live performance situations knows that getting an
excellent sound with even the most expensive instrument is next to
impossible. Most well recorded acoustic guitars are not piezo type
acoustic electrics, they are usually quality acoustic guitars with
expensive mics in front of them going through expensive preamps, EQ's
and possibly compression. Several gigging friends and myself have
auditioned dozens of hybrid acoustic electric guitars and available
electronics packages in a quest to find an A/E preamp that actually
lives up to it's hype. To date we haven't found one example that didn't
have severe drawbacks. Personally, I like to use Ovation
acoustic/electrics on stage for no other reason than they are fairly
bullet proof and resilient to humidity and bar cheese. After owning a
guitar shop for years I can tell you that I never heard a really good
sounding Ovation. The plastic, space starved bodies simply don't allow
many of the frequencies that an acoustic guitar produces to develop. The
early ones had finish on the tops that was so thick it caused cracks in
the wood as the finish shrank. The thick finish also didn't help the
sound.
Most players try to EQ the missing frequencies into the sound. That
approach is really doesn't help much and the reason is simple. It is
difficult for the EQ to accentuate parts of the spectrum that are *not*
there to begin with. Since the guitar isn't producing the frequencies
that are audibly missing, the EQ is only actually boosting frequencies
near the passband that it is centered at. EQ's don't *add* frequencies
to the program material. This leads to over EQ'ing and over EQ'ing leads
to phase problems which makes an acoustic guitar sound honky and more
electric. Another problem with most acoustic on-board preamps is the
output swing is small due to power supply constraints of using small
batteries.
In the 70's a company called Alembic took on a similar problem with a
decidedly different approach. Alembic wanted to develop a great bass and
found that the industry type instrument electronics that were standard
for years just weren't up to par with what was happening sound wise in
recording studios at the time. Alembic decided to design electronics for
the bass more like studio gear was made. One of the differences with an
Alembic bass is the external power supply (there are batteries but they
don't have the same v as the external supply). Alembic also used low I
pickups fed into beefy FET's and the EQ section was based on a 5534 IC
just like you would find in recording consoles of the day. The sound of
those basses is without equal.
It is this same approach that we implemented when designing
the AEEQ-1A. This unit is basically a high quality discrete FET
recording console preamp feeding a complete Pultec EQP-1A equalizer. The
units run on an internal +-24V well filtered power supply. The
combination of the much lower phase shift of the LC EQ, and the
24V rails make this unit a stunning live performer. It turns the sound
of even the anemic acoustic electric into a HUGE room filler.
Here is a photo of the prototype that was built several years back. Since
then we have started building them into 2 space cases using the
Vintage
Windings EQ-1A Filter unit. The circuit is fairly simple. This example
has optional input/output transformers. The input is switchable to the
transformer (w/ an XLR or 1/4" balanced input) which goes directly to
the EQ, or the front 1/4" input can be routed through a 500K pot to the
FET input preamp (a separate Forsell Opamp) through another 500K pot,
then on to the EQ. This setup maximizes the Pultec EQ portion as the
unit can be used as just the standard Pultec EQ when the preamp section
isn't needed. The input transformer can be eliminated but I wouldn't
eliminate the quality output transformer, even for guitar (it provides
gain in this circuit and it helps with noise).
This is a great DIY project for the guitar player who wants a killer
sound !!
Please
e-mail for details. Note: The
Pultec EQ project can be found
here.
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