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I have started to build a (slightly) updated version of the Korg PS-3200 synthesizer.
The PS-3200 was the last of three fully polyphonic, semi-modular analogue synthesizers offered by Korg in the late 70's. (See Ben Ward's excellent Korg PS site for detailed information, including user manuals.)
The concept of the PS-Synthesizers was different from other manufacturer's early polyphonic instruments. Instead of using a small number of voices and a clever keyboard assigning circuit, the "PolyKorgs" had a complete synthesizer circuit, hard wired to each key. That makes a total of 48 VCFs, 48 VCAs and 48 voltage controlled ADSRs even for the smallest of the range, the PS-3100. The largest of the range, PS-3300, even had 144 of these circuits.
The sheer number of synthesizer circuits called for an extremly economic circuit design, and it's a joy to look at Korg's design ideas which led to building blocks that almost did the same as in the better known "classic" synthesizers. And after many years of engineering and reverse-engineering electronic music circuits, I have learned to look at odd solutions not as "substandard", but as a source of creativity an individual character. Here's a list of some highlights:
Function Implementation Side effects
Single-Transistor Waveform Converter creates triangle, saw, pulse and PWM from saw input, using one (!) transistor, one diode and two resistors per voice, plus two global control voltages Pulse height also changes with pulse width
5-Transistor-VCF (Korg-35) A Voltage controlled 2-pole (Sallen&Key) LPF built from 5 transistors rather high CV feedthru
Single-Diode VC Resonance The dynamic resistance of a simple diode is used to alter the feedback gain of the VCF limited range of Q
"Expand" function instead of VCF Envelope modulation depth Instead of scaling down the ADSR with a VCA, the a variable portion of the Envelope is just clipped with a single diode. It's so remarkably close to ordinary VCA function that apparently nobody takes notice. At least I have not read about it anywhere.
At slow Atack times, the Envelope appears delayed at the VCF (no effect until th eclipping point is reached). Usefull for Brass sounds, and not easy to emulate with conventional synthesizers.
Minimum parts count Voltage Controlled ADSR Three transistors, 1/2 of a LM324 and one CD4007 per voice. Plus some more involved control circuit, shared by several voices Transistors must be selected in 13-tuples, not just in pairs.
ADSR detail (1):
One-opamp control logic 1/4 LM324 is used as Flipflop, which is dynamically set by Gate-ON, dynamically reset by Gate-OFF, statically reset when the attack peak voltage is reached, and whose set/reset sensitivity is altered by a CV Very odd "Hold" function, depending on the "Attack"-value. But very useful in practise.
ADSR detail (2):
Single-Transistor, exponential slope VC-Decay Using a single transistor per voice for VC Attack and Release is remarkable already, even though the A and R slopes are linerar. But the Decay slope is exponential, and this is achieved with a single transistor and two resistors per voice! The Decay time range is rather limited. No ultra fast Decay, and no ultra slow Decay either.
Single-Transistor VCA That's the "Korg standard" VCA, well known from other instruments like the MS-10.
727 How To Create an Antique Mirror Effect | Apartment Therapy DC
How To Create an Antique Mirror Effect
Mclain Wiesand, a Baltimore-based custom furniture company, has made a name for itself by producing handcrafted pieces that capture the feel of real antiques. One of the techniques they use for aging mirror is wonderfully simple and serves as the inspiration for this how to.
Creating an antique mirror effect is an inexpensive way to revamp a flea market find, or add a new layer of interest and depth to an ordinary wall mirror. Almost any type of mirror can be aged using this technique, including mirrored plexiglass.
â¢ Mirrored glass or plexiglass. Due to the type of paint applied to the reflective coating, inexpensive, craft-store mirror works wonderfully.
â¢ Latex or other gloves for hand protection.
â¢ Paint stripper. Most types work fine. For a less toxic product, Citristrip works well.
â¢ Plastic putty spreader or putty knife.
â¢ Modern Masters Metal Effects Black Patina. This patina solution is essentially an acid that eats at the reflective surface of the mirror. There are probably other products that work similarly, but Modern Masters products work well and can be found online or in most art supply stores or specialty paint stores.
â¢ 1â chip brush (or similar brush).
â¢ Silver paint of choice.
Step 1: (Image 2, above)
Wearing gloves, place mirror face down on cardboard or other protected surface in a well-ventilated area. Apply stripper generously to back of mirror and allow to sit for a few hours, or until paint can be easily removed with plastic scraper. It is not necessary for all of the paint to be removed; generally speaking, 80-90% should suffice. When paint has been stripped, wash mirror with soap and water and allow to dry.
Step 2: (Images 3 & 4)
Place stripped mirror face down on clean cardboard or other protected surface. Dip chip brush in Modern Masters Metal Patina Solution and gradually apply it to the raw reflective surface of the mirror. As mirror tends to age from the edges inward, it is best to apply patina solution in heavier amounts around the edges of the mirror. In a matter of minutes (or less), the patina solution will begin to eat away at the reflective surface. Other application techniques that produce nice effects are spattering and light directional brushing of patina solution. Continue applying solution until desired level of ageing is achieved. Rinse with water to neutralize the reaction and allow to dry.
Step 3: (photos 5 & 6)
This next step involves reapplying paint to the back of the mirror. The color paint you choose will be visible through the spots created by the patina solution. The dark areas of aged antique mirrors tend to be a dark silver-grey but depending on the silvering technique used, can range from gold to pale silver to black. One method that produced nice results is a combination of dark and light silver paints, applied randomly (per images). Apply paint until the reflective surface is completely covered.
509 A List Apart: Articles: Supersize that Background, Please!
With an advertising world keen to use every inch of a medium for brand or product experience, it is becoming increasingly popular to design websites with full-browser backgrounds. Using CSS, this can be achieved quite easily. Just drop a huge background image in a page with one line of code (Line wraps marked Â» âEd.):
background: #000 url(myBackground_1280x960.jpg) Â»
center center fixed no-repeat;
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