The Vintage Windings OS-3 Old School 3 Band LCR Equalizer
The BEST 3 Band Equalizer Module Available!!

The Vintage Windings Old School 3 Band Toriodal Inductor Based Equalizer Module is simply the best sounding EQ on the market today. When used in combination with quality gain opamps and high end input and output transformers the VW-OS-3 will perform as well or better than the best equalizers from any era.
One of the first things that many customers of our Pultec EQP-1A style coils contact us about is obtaining inductors for a midrange EQ. Once they have experienced what a good MPP toroid does for the high end of an EQP-1A they want the same smooth sound for the mids and lows. The cost of building an EQP-1A and MEQ-5 just to get full range equalization is very high and time consuming. Why not build what you really want from the start? The Vintage Windings OS-3 provides 3 glorious bands of fully toroidal LCR based filtering. This is a top of the line, no holds barred three band equalizer that has no equal. Sure there are excellent inductor based equalizers out there. Most use pot core inductors (why this is a bad thing) and all of them cost multiple thousands of dollars. The Vintage Windings OS-3 along with quality gain makeup amps and transformers will give the same thrills for a fraction of the cost of comparable production equalizers.

Why is the VW OS-3 different from other inductor EQ's on the market? It was engineered for DIYer's and technicians whom are looking to build a better sounding EQ than they can buy. There is no equal. On the OS-3 there are no shared components. Each frequency has a dedicated capacitor and winding tap. This means two things that you don't get with virtually any other manufacturer.

1) Accuracy. Vintage Pultec's, and most modern manufactured inductor EQ's share several coil taps and capacitors to make some frequency points. This means that some frequencies are only close to the original intended frequency. If the shared winding was a bit off that will create two inaccurate frequency points. The Vintage Windings OS-3 nails every frequency dead on with no pot core drift.

2) There is no need for expensive two deck multi-switches. Single deck switches are used for this EQ.

100% Handmade one at a time in the  USA!!

Description:


The OS-3 is a true Old School Turret Board Equalizer Module. It can be used in a variety of circuits. Here is the basic one we have been building these with. The circuit is in it's most basic form. Adding adjustable bandwidth can be done simply by changing the resistors* coming from the switch poles to 2.5K pots (lin). A high frequency shelving filter can be included with the addition of several caps and a fourth multi-switch. The 10K Linear Frequency pots can be replaced by resistor arrays on switches for very precise adjustment.

Here is the Vintage Windings OS-3 Module:



Here is the OS-3 in a circuit:



OS-3 Specs:

All capacitors are high quality Polypropylene Capacitors. Sprague Orange Drops were used for values they manufacture.

The module is assembled on a high quality turret board. This is a passive module and there will be a loss in db if it is inserted in a line circuit without added amplification. It is designed to be placed between the inputs of an opamp however there are other options for how it is used.

High Frequency:
MPP Tapped Toroid Inductor - Large core that is impossible to saturate when used at a standard line level.
8 Frequency Points (Pultec) - 3K, 4K, 5K, 7K, 8K, 10K, 12K, 16K
(Note: a 20K frequency point can be added for additional cost)

Mid Frequency:
MPP Tapped Toroid Inductor - Same as above.
8 Frequency Points (Pultec) - 700, 800, 1K, 2K, 3K, 4K, 5K, 6K

Low Frequency:
Ferrite Tapped Toroid Inductor - A ferrite core was chosen here for economical reasons. High perm toroid MPP cores required to make the higher inductances needed for the low end filters are very expensive and hard to source. A very beefy ferrite core is used here. The larger core will not saturate and will not be as affected by temperature as a smaller ferrite would.
7 Frequency Points - 60, 100, 200, 300, 500, 700, 1K

*The resistors between the coils and the switches along with the internal dcr (Q actually) of the coil determine the slope (bandwidth) of an LCR circuit. The narrowest bandwidth is obtained with no R on the pole. Most designers add a small resistor (220 - 500 ohms) adjusting the bandwidth to taste. The resistor can be replaced by a 2.5K pot for an adjustable bandwidth as in the high end of the Pultec EQP-1A. The same can be done with the mid and low frequencies.

The OS-3 can be used inside of other circuits without input and output transformers. For quality stand alone equalizers input and output transformers are highly recommended. Vintage Triad HS-56v's are great and several modern line transformers sound absolutely fantastic with these.

Op-Amp choice - What ever you like tube or ss. Generally, well designed higher voltage opamps will yield the most satisfying results. We use John Hardy opamps in many projects because they sound excellent. However, there are many choices on e-bay that will work fine. Standard high quality IC's will also work on the cheap (like 99.9% of gear out there....but that defeats the purpose here!).

The Vintage Windings Old School-3 Equalizer Module can also be used in instrument amplifiers. The venerable Ampeg SVT uses a Toroid Coil for it's famous midrange. Here you have all three bands covered in superb LCR filtering. As a personal note I use one in a preamp for my bass rig. E-me if you want more info.

Introductory Price Only $499.99 !!


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