They are not glued, but about a decade or so ago when I was mucking
around in one they were very difficult to get off. At this age the
attempt may break the posts off the pots. It would still be useable
but you'd need a key or a screwdriver or something to adjust it.
It may just be better to be glad the thing works. I know two people
with that model, the one modified and the other stock.
But now that you got me started, that EQ is poor for music. IIRC those
were actually discrete component OPAMPS and on the 60 HZ, which I
would've liked to extend the response of down to DC, it simply isn't
possible. That's OK, when they use like a 33uF and I replace it with a
470, it is close enough.
I have this old Soundcraftsman that I would really like to get a power
transformer for. Now that's an EQ !. And it uses coils in the tuned
circuit. Now that you got me started, the design of the old unity gain
except for shunting either source or degeneration with passive tuned
circuits has an advantage. The is when you use two adjacent controls
in the same direction (boost or cut) the tuned circuits begin to act
as if they are in paralell, giving less of a double hump in the
response curve.
This is going to get deep, get your waders on. Decades ago there was a
very accurate method of measuring frequency response. It fed a speaker
a single tick, and through fast fourier transform it was able to plot
the entire frequency response curve of a speaker. It was abandoned
because it was too accurate.
For a couple of decades cheap speakers were being passed off as high
fidelity and how they did it is simple. To make the response curve
look better they began using bands of pink noise, and a wide spectrum
mike. The problem was the bass, an FFT would accurately show the
possible +-10db variations in the lower ranges.
Now remember that the cone is still moving, being an inductive load
fed by a constant voltage, the problem is cancellation, and
nonlinearity of the magnetic field and/or compliance or the woofer's
suspension. This means that tons of THD are produced at the
frequencies reproduced less efficiently by the system.
Now, abandoning the FFT method and going with the pink noise, they are
checking for say 60Hz, but appearing in the output with this method
are the distortion components, 120Hz, 180Hz, 240Hz and so forth. This
all added up makes the curve look flatter, but it is not. I don't know
about anybody else, but for a 60Hz input, for a frequency response
curve, I would only want the 60Hz output to count in the results.
So anyway, back to the price of beans in Chile. This sparked my
curiousity and I promptly got out the square wave generator and the
oscilloscope. After some experimentation seeing what the controls did
to a 1Khz square wave I understood how the FFT works. Not the complex
math involved, but at least the concept. The FFT method was touted as
having the great advantage of not requiring an anechoic chamber to
take the test, true, a speaker would read pretty much the same in an
open field or in a phone booth. That is an exageration though, the
mike had to be a certain distance away.
Over the years I came to realize the one should just get good speaker
if one can afford them, and that is what I did. I got the Boston
A150s. This was over ten years ago and after all the abuse people with
their own stereos still come to hear things on MY stereo. And I just
found out recently that the midrange has the biggest magnet in the
system, not the woofer. At $400 for the pair used, which was MSRP I
whipped out the money after hearing them.And they were ten years old
almost at the time !. Go ahead and think that I got fleeced, but come
and listen to them first. We are talking 20-20,000 within 3db and 0.7%
THD at one watt. Remember, one watt is pretty loud for most people.
Some purists shun tone controls altogether, but not me. In fact I
designed but never built perhaps the best set of tone controls ever.
Bass turnover continuously varible from 44-480 Hz and +- 18db range.
Yes it is dangerous ! Midrange was pretty much standard but the treble
was just as gnarly. Went from about 2Khz to 9Khz, and had the same
range. No, you do not crank these up.
It was designed in response to the industry's propensity for not
giving us the outer octaves. But I simply do not need it anymore.
At this point, even though I do use a boosted bass, when I run out of
power it doesn't clip just the bass, all frequecies pretty much clip
at the same point.
Now to the guitar. If you play an electric with distortion, with solid
state you generally can't play G type or C type chords. The problem is
that the second note in the chord is only 4 frets (½ steps) away from
the base, rather than 7. But it can sound good on tubes, or specially
designed circuitry.
That old sweet sound was also due to interaction of the soft output
stage with the output transformer as well as the speaker. They built
power soaks for people who wanted that sound but wanted to practice at
a lower level, but the results were not quite the same thing. Would've
been better to regulate the B+ to the output stage.
I don't know if FETs would react the same, but they might, or at least
be very close.
The best thing I did though, was to start using two amps. One clean
and one all fuzzed out. You can just about make one guitar sound like
two. If you place the amps across the room from each other, you
actually get a sort of stereo image out of it.
Time marches on. I got ripped off and did not have a guitar for a
while. Then I got so dismayed by the media that I not only stopped
watching TV, I actually stopped listening to music for years. That's
right, it is hard to fathom, but I did.
That had a very interesting result. I do not play copies or covers
anymore. Period. I've written three songs, well one and two almost
songs. I have switched to the acoustic, and use chordography that
would never fly on an electric, even clean. It just sounds better on
an acoustic. Mine even has a pickup, but I prefer to mike it.
My next step is to buy one of those newer ones with the advanced
internal pickups. You can play it on a stereo and it sounds like an
acoustic. I was very impressed the first time I heard one.
Good luck grinding the ax (a term we used to use for playing with
distortion, heavy metal).
Ummm, BTW, something just cropped up in my memory. You got that old EQ
which allows seperate adjustments for each channel, get two amps and
set them inversely. Don't run them tandem, feed both via a splitter,
then each out to it's own amp. Then you set, say the left 60, 1K and
10K down, the others up. On the right set the 250 and 3.5K down, and
the others up. You might like the effect.
I am not too crazy about these new amps with all the digital effects.
It is all taken out of my hands. I don't think that'll ever change.
Also sometimes I'll play on the old Fender amp and a bass amp at the
same time. That sounds pretty good too.
Have fun with it.
JURB
(as if it matters..)
