A Mad Professor Selects Speakers
This month we talk to Björn Juhl, amp and extremely low distortion – clean is an unde-
What’s the process for creating a new amp?
pedal designer from BJF Electronics and fea- fined term – to high gain was played through
tured Scandinavian boutique amp and effects the MP101, which ran a Red Fang/Private
company, Mad Professor. Jack cabinet. The most desirable settings
were with all tone controls at noon. I have
suggested to many CS- 40 owners to try mul-
tiple speaker arrays. Achievable sounds are
nearly limitless, so the importance of speak-
ers is immense.
Are you trying to find a niche or emulating
something similar on the market?
Mad Professor offers two amplifier models.
The CS- 40 came about after heavy persuasion from Harri Koski at Custom-Sounds (also
marketing and management for MP). He
wanted a 40-watt amplifier that took pedals well. In focusing on just one amplifier, I
wanted to produce my sound and include
options I was asked for as an amp technician. One inspiration was avoiding sounds
of amplifiers less fun to play – what do you
expect from a former amp repair guy? The
vision was creating versatility and a more
pleasing sound that might differ for each guitarist. The MP101 was designed from CS- 40
user feedback. They desired fewer controls,
more output power and two channels. We
wanted simple tone control. Extra attention
was required for the treble so a few peaks
could be controlled.
Do you aspire to create a certain tone
when designing the amp?
Yes, absolutely! Sound comes first.
How big is the speaker’s role in amp design?
Speakers provide half the sound and many
signatures are possible. The balance in
response, power handling and efficiency we
desired proved difficult to find in modern
speakers. We tried many and some blew up!
In the Eminence booth at the Musikmesse a
few years back, I found a couple of possibilities. I felt a Red Fang or a combination of
Red Fang and Private Jack would work well.
From this, a 4x12 cabinet was born. Certain
speakers are best for particular sounds, but
may only allow a few amp settings. The 4x12
Red Fang, and especially the Red Fang/
Private Jack combination, lend maximum use
of the CS- 40’s controls.
When introducing the MP101 at NAMM,
many guitarists exercising multiple playing
styles best demonstrated that a specific
speaker array is desirable. Everything from
Do you design the amp around the speaker
or design the amp and find a speaker that
Ideally, I find the speaker first. I’ve also been
in positions where the speakers used for tuning couldn’t be used in production. It can
be a daunting task to find complementary
speakers. One may be close, but requires a
change in the amplifier. That means back to
the drawing board! It’s a breeze to design an
amplifier that takes advantage of limits set
by a specific speaker. Designing an amplifier
without having the speaker is a headache
because it involves compensating controls
for too many unknown variables. We can easily surmise that the speaker more drastically
changes the sound than any other part in the
amp. Which is easiest to change, the amp or
speaker? Sometimes a speaker exhibits qualities that warrant rebuilding the amplifier to
eliminate inferior parts. If the speaker is right
you don’t need much of an amp to achieve
How do you go about finding the right
speaker? What factors do you consider?
I like listening and hearing for myself first.
I consider tonal balance and how treble is
handled under the heaviest distortion and
maximum power. It’s no fun when a speaker
can’t handle the amp’s hardest working
point. There are also details to find with
Do you prefer custom designed or off-the-
If possible, off-the-shelf – it makes life easier
for the consumer wanting direct replacements. If off-the-shelf doesn’t work for a
specific application, then custom is more
attractive. In fact, I’m currently designing a
preamp/power amp intended for a custom
speaker supplied by Eminence.
How do you decide the power of the amp?
The power requirements of an amp depend
on where and how it will be used. Other
considerations are weight and size. We
assume sometimes the amp will be run at
maximum power. I believe in using parts that
accommodate each other. The amplifier must
produce in the loudest clubs, but should also
be useful at low volumes. It’s then a question
of the preamp and getting compression and
playability regardless of level. An amplifier
must have limits. For example, it must fit in
the trunk of a Volvo P1800 and weigh no
more than can be comfortably carried walking one block in any major city. Then there
are limitations on power. There are solid-state solutions, but the amplifiers I design
are generally tubes.
What features of the each amp please
The CS- 40 puts the control in the hands of
the musician’s imagination and hearing, making it possible to fine-tune a desired sound.
The MP101 is more about simplicity and raw
power. I think it’s neat that I was allowed
to set the range of sounds to my ear. I also
used the ears, skills and input of studio guitarist Sebastian Nylund. Oh, and I enjoy playing it, too.
For more information on Mad Professor
please visit mpamp.com.
Anthony “Big Tony” Lucas
is a guitarist and Senior Lab Technician at Eminence
Speaker LLC, where he specializes in guitar-speaker
design and customer support. Big Tony has been with
Eminence for over 10 years and is responsible for many
well-known guitar speaker designs.