This a
turntable that I built in the mid 90's.I decided to try something different from
my previous designs.The 25 pound platter is a 12" in diameter and 3 1/2" thick
piece of poured concrete.The plinth is a 15 1/2" square piece of marble 1/2"
thick sitting on top of another 15 1/2" square piece of marble with layers of
PORON® in between.This in turn sits on top of 4 plastic cone shaped
feet. The tonearm is a single point suspension.They give the best movement with
the least amount of friction, plus they are the easiest to make.The
counterweight is made from a large vcr flywheel. It has to hang low to keep the
arm from tipping over.The entire assembly sits on top of a column of solid steel
2" thick. There is no antiskating, only a small piece of foam is used at the
pivot point. This provides all the damping and the anti skating. The only thing
I don't like about my design, is that the arm only takes 'p' mount cartridges, I
dont know what I was thinking. The motor is a dc servo type. The meter isn't
just for looks, by monitoring it,I can see if there is too much friction from
the huge platter. The belt is a piece of elastic I bought at a fabric store. The
last enclosure is the solid state phono stage.
After reading about all those fancy power cords in the audio
magazines.I decided to design and build my own.The wire is braided 18 gauge
speaker cable.The blue box contains a power line filter,a MOV, and a neon pilot
light.I originally wanted a LED, but decided that it would introduce to much
noise into the circuit.Most people that have used the cord seem very happy with
it,although I'm a bit dubious about the effects that a power cord can have on
the sound of a stereo. cost:$36.34 This is one of my simpler projects.Construction is basic and straight
forward.I used 3 braided, teflon coated wires,two for the ground and one for the
hot.The outer casing is a shrink wrap and the ends are standard gold plated RCA
connectors. A clear, thicker shrink wrap is used where the wire and the
connector meet. cost:$23.12
Here is my latest, and probably my last, turntable
design.It's pretty conservative in comparison to other designs.The base is
walnut and the corner pieces are redheart and rosewood. The bottom is particle
board and the top is particle board with a thick sheet of copper bonded to it.
My original design called for a belt drive motor, but I found a direct drive
motor that was very stable,so I decided to go with it instead. The power source
for the motor is internal and is a very basic D.C. design. The power switch is
on the back and its only plays 33.33 rpm.The design doesn't call for any
permanent feet, so I'm free to experiment with different materials. I'm
currently using some spongy foam I found at a design and engineering show. It
does a very effective job of absorbing any vibrations. cost$66.74
This is my latest tonearm design.Like all my other
designs it is a unipivot. The arm is a piece of brass with a square cross
section,at first this may seem strange but who says that tonearms must be
round.The base is a flywheel from an old VCR.The weight that hangs down is also
a flywheel from a VCR. The only thing that is from a real tonearm is the
counterweight which hangs well below the pivot point.A small piece of brass
touches the center pole that the arm rests on.This prevents the arm from swaying
and provides enough friction so there is no need for any anti-skating.Two
mounting holes hold the arm to any turntable.This makes the arm very easy to
remove for repair or upgrade.VTA can be adjusted by shimming the mounting
plate.
cost:$12.44
This is my phono preamplifier.I went through many
different design ideas,but settled on a simple solid state opamp circuit(sorry
all you tube fans out there).I started by finding dozens of phono schematics on
the web as well as in magazines.I tried each one in my Micro-Cap program(a
computer program that analyses analog circuits).The schematic that yielded the
flattest response with the easiest to find parts was chosen(some of the
schematics required resistors and capacitors with very oddball values). schematic .The opamp was
an important factor in the design.I selected a Burr Brown OPA2132p dual opamp
that was recommended by many of my friends for its superior sound. Assembly was
done on a perfboard with a simple split power supply. cost:$44.21
I've known for years that a good clean voltage source
for your stereo does help with the sound quality, so I've decided to build a
simple power line conditioner.There are three outputs. The first output is an
isolated one which will be used for noisy products like cd players.The second
output is through a low pass filter(20KHZ),for products like turntables. The
third is a straight through with no filter,for high current products like
amplifiers.There is a generous sprinkling of MOV's throughout,and an analog
meter and the circuit that drives it,completes the design.Wiring is 8 gauge
speaker wire.The enclosure is made from walnut and the bottom is particle
board. schematic meter:I
really didnt need a voltmeter but I like meters.The meter is a zero center type
where the zero equals 120v.The circuit that drives it is quite simple.The 120vac
is stepped down to 12 volts and is rectified and filtered and sent to a voltage
regulator and a voltage divider.The meter simply reads the difference between
the two.Once adjusted the circuit is very accurate. schematic cost:$195.73
It seems that most audiophiles at one time or another have
built their own pair of speakers.Whether its for the fun and pleasure of making
it themselves, or the fact that store bought speakers have gotten very
expensive.My first pair I built was back when I was just a teenager,the speakers
weren't very good, but it was fun.Here is my latest pair, years of trial and
error and alot of research about speaker building on the internet has paid
off. concept:The basic concept is a simple one,to have a good sounding
speaker,that can play cleanly with good imaging.I also wanted a speaker that was
easy to move around and didn't physically over power a room with its size.A
small 2 way with a 6" woofer fit the bill perfectly.Any bass that is missing
will be filled by a subwoofer later. drivers:VIFA D17WJ-00-08 woofer
and VIFA D25AG-35-06 tweeter cabinet:Whenever I listen to a pair of
speakers,I can always hear a speaker cabinet vibrating, so when I built this
pair, I decided to have a cabinet that is as inert as can be made.All the sides
are 2 layers of 3/4" particle board glued together with house paint,the front
baffle has an additional layer of 3/4" mohaganey.The inside has plenty of
bracing,and there is a layer of mouse pads glued inside.You can't hear the
cabinet vibrating at all, unfortunatly, the speakers weigh 66 lbs a piece!!The
offset of the tweeter was calculated so the peaks and nulls of edge diffration
would be cancelled.A layer of felt around the tweeter also helps with the
diffraction problem.The back is paintd black and the top,bottom,and sides are
wrapped in black vinyl. crossover:The crossover is a simple 2nd order
linkwitz-riley with a crossover point at 2200hz.You can make the crossover very
complex (and some loudspeakers have very complex crossovers) but that adds quite
a bit to the cost. I also believe that complex crossovers detract from the sound
quality,also, if you have to correct driver problems with a complex crossover,
you shouldn't be using that driver in the first place. schematic EQ
box:In the past, whenever I would finish one of speaker projects, I would be
surprised how thin the bass was.I would be years before I found out that all
speakers loose 6 db in the bass.Most cheap speakers don't do anything about it
because it costs too much to compensate.More expensive speakers compensate in
the crossover but I have decided to include a small passive EQ that you place
before the amplifier. schematic sound:Overall
I'm pretty happy with the sound.With a very solid cabinet, I loose very little
bass energy,and as long as I don't push the little 6" woofer, I can produce a
very solid bass. The tweeter is a perfect mate.It has a very clean and extended
sound and can be used in much more expensive speakers.The imaging is good with a
very nice front to back as well as side to side
imaging. cost:$325.19
This is one of those 'for
fun' projects, there are many good headphones already out there but I tried to
make a pair for myself.The design is very limiting,no crossover, enclosure or
driver compliment to worry about. Just buy a pair of headphone elements and hope
for the best.The sound is pretty good a little thin in the bass but there is
quite a bit of detail in the mids and treble.They are also pretty comfortable
and with some practice they are easy to adjust to fit your head.All parts are
scratch built except for the ear cushions and the cord.
