SKU: 72003354785

Doepfer A-101-1 Vactrol Filter

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Description

Doepfer A-101-1 Vactrol FilterDoepfer A 101 1 Vactrol Filter Eurorack Module For Sale. This module is part of the extensive Doepfer A 100 Modular product line. We're a Doepfer dealer. If you're looking to buy a system, monster case, or large lot of modules, please contact us. This item is new in box, carries the manufacturer's warranty, and ships free within the continental US. All photos shown here were provided by the manufacturer, along with the following product description:

Doepfer A-101-1 Vactrol Filter Eurorack Module For Sale.
This module is part of the extensive Doepfer A-100 Modular product line.

We're a Doepfer dealer. If you're looking to buy a system, monster case, or large lot of modules, please contact us. 

This item is new in box, carries the manufacturer's warranty, and ships free within the continental US. All photos shown here were provided by the manufacturer, along with the following product description: 

This is the first vactrol based module in the A-100 system. A vactrol is a combination of a light depending resistor (LDR) and a LED (light emitting diode) both put into a small light-proof case. Increasing the LED brightness causes a decrease of the LDR resistance (e.g. the light controlled voltage module A-179 is an application of a LDR). This effect can be used in circuits that require variable resistors to obtain the desired function (e.g. VCFs, VCAs, VC phasers, VC trigger delays, VC slew limiters, VC Envelope Generators, VC LFOs, VCOs and many more). The advantage of vactrols compared with other solutions (e.g. OTAs, diodes, transistors or FETs as variable resistors) is that they behave like a normal Ohm resistor and can handle high voltages without causing distortion. This is probably the reason why the sound of vactrol-based circuits usually is described as soft or mellow. Disadvantages are theexpenditure and consequently the expenses and the not exactly defined coherence between LED current and LDR resistance. For each vactrol the LDR resistance decreases when the LED current increases but mechanical and electrical tolerances cause that each vactrol will behave a bit different (e.g. because of the differences in alignement and distance between LED and LDR, different brightness of the LEDs at the same current).

Module A-101-1 is a special multitype filter based on an idea by Nyle A. Steiner (published in Electronic Design, issue  25, December 1974, page 96 ff). The circuit uses the standard non-inverting amplifier filter design. Different filter types (low pass / LP, band pass / BP, high pass / HP) are realized by injecting the audio signal into different points of the circuit and using a common output for all filter types. One may feed three different audio signals into the filter simultaneously. Each signal is filtered correspondingly (LP resp. BP resp. HP) and the sum of the three filtered signals appears at the output. Of course it is possible to feed the same signal to all three inputs. In this case one obtains different combinations of LP/BP/HP according to the settings of the three input attenuators for LP/BP/HP. Even a Notch filter is possible (not available in the original design). The filter inputs are normalled, i.e. the BP input is connected to the LP jack socket provided that no cable is plugged into the BP socket (same applies for HP/BP inputs). 

In contrast to the original circuit vactrols are used instead of diodes as variable resistors for frequency control of the filter. Due to the"crooked" response of vactrols the filter has not an exact frequency control standard (like V/Oct). The inevitable tolerances between different vactrols will lead to an individual sound of each module and individual resonance behaviour. Even the resonance control is realized with vactrols. Consequently this parameter is voltage controlled, too. Resonance can be increased up to self-oscillation. Resonance and consequently self-oscillation may vary with the filter frequency because of vactrol tolerances.

A special feature of the module are the two audio outputs. Out 1 is the output of the original circuit. In the original circuit by Nyle A. Steiner the output level was distinctly dependent upon the resonance (higher resonance = higher output level). Out 2 compensates this behaviour by the usage of an additional vactrol that is connected in series to the vactrol that controls the resonance. This additional vactrol forms an attenuator (or simple VCA) that approximately compensates the level increase for higher resonance settings.

Two LED displays show the current frequency and resonance setting. The LEDs are connected in series to the LEDs inside the vactrols and show consequently the LED illumination inside the vactrols.

Width: 16TE / 16HP / 80.9 mm
Depth: 50 mm (measured from the rear side of the front panel)
Current:
+30mA (+12V) / -30mA (-12V)

 

 

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SKU: 72003354785

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GoRetro Girl
Boise, US
★★★★★ 5
Makes the Sink Area All the More Organized
Color: Silver With Towel Rack - 9.25″, Color: Silver With Towel Rack - 9.25″
At first glance I'm sure most people might think this kitchen accessory is kind of silly; a caddy for your sponge and dish soap? But honestly, it makes the kitchen area look at the more organized and keeps things in place. I sprung for the model with the towel holder because I always feel weird about bacteria sitting in the wet microfiber cloth that I use for cleaning the kitchen countertop and my dining table. The little dowel allows it to dry very quickly. The holder can be configured in a few different ways to accommodate your cleaning items. I like that it's wide enough to comfortably hold the large bottle of dishwashing soap I buy and it's the perfect width for Sponge Mommy/Daddy sponges. I've had it less than a week and haven't had to wash it yet, but it seems like it will hold up well in the dishwasher and won't rust. Since I don't have any sponges on a handle, I may use the removable compartment for those (that you can see on the left in my photo) for other kitchen tools.
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Reviewed in the United States on April 7, 2026
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Leena E.
Los Angeles, US
★★★★★ 5
Un mess your kitchen sink mess
Color: Black - 9.25″
Just the exact right thing to gather all the sink doodads into one place. There is a little divider that is movable so you can adjust the sponge holder to your brand of sponge. AND it has a drain spout for the water run off. Very sturdy and handy sink catch all.
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Reviewed in the United States on May 29, 2026
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Melissa11
Alexandria, US
★★★★★ 5
Great for organizing sink
Color: White - 9.25″
We had one of those suction cup sponge holders, but if you have tile that is not completely smooth, it falls down. This does not have that issue because it just sits on the counter or if you have a large sink lip, on there. You can move the inside pieces around which I was really surprised about because I thought it was all in one piece. Being able to move them around is great because then you can adjust it for your own soap dispensers, etc to fit your space. I like that it comes in a ton of colors. We got the white and it blends into our kitchen and looks really nice. This organizes our dish soap, sink drain cover, and sponges nicely and gives it all a space to go in. The tray on the bottom is silicon and removable which is great. I wish I had bought this thing years ago because it's great.
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Reviewed in the United States on April 9, 2026
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Sabina Boo-Rivera
Boise, US
★★★★★ 5
Great deal. Great product. Simple and efficient.
Color: Black - 9.25″
It is very simple to put together and it feels sturdy and I like how it looks. I know everyone's sink is different but it fits mine PERFECT. I'm really happy with this purchase. Good price good value. I don't see why you wouldn't buy it if this is the style you were looking for.
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Reviewed in the United States on April 29, 2026
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KIMBERLY
Los Angeles, US
★★★★★ 5
Spicy racks
Item Package Quantity: 2, Item Package Quantity: 2
I bought these as I needed to organize my spice cabinet. I was using a lazy Suzanne and the spices kept falling off them. These fit perfectly in the cabinet,I attached them using the command Velcro stickers that come off easy. I am in an apartment. They are strong enough to allow the shelves to slide out.
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Reviewed in the United States on May 20, 2026

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