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 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.
fancy power cord
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.
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.
walnut and copper turntable
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
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
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.
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. schematiccost:$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 painted black and the top,bottom,and
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.
This is one of those 'for fun' projects, there are many good headphones already out there
but I still decided 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.cost:$18.71
stereo tube amplifier
click on image for larger view
I've always liked the sound of a tube amp.Whether they recreate or create a sound is still up for debate.I like the smooth midrange and the silky treble,though the bass is usually a little too sloppy for my taste.While the mainstream audio people have been using solid state for decades, audiophiles have stuck with tubes.Here is my modest little 39 watt push pull tube amplifier.Click here for pictures of the construction.Design is basic and straight forward- 1 12AX7 is the predriver and the phase splitter,this goes into a EL34 push-pull output wired in 'ultralinear' mode.The bias for tube each can be set
by a pot and meter on the chassis.
The chassis is copper and the base is walnut.
Click here for schematic.
click here for pictures of my stereo room
click here for my collection of charles rodrigues cartoons
Click on the picture to see video of my hifi equipment.
The goal of all inanimate objects is to resist man and ultimately defeat him.