SKU: 72003354785

Doepfer A-101-1 Vactrol Filter

Sale price$171.00 Regular price$190.00
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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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Alice
Whiting, US
★★★★★ 5
Best dog toy!
Color: Multicolor/Alligator & Wild Duck, Size: Medium, Color: Multicolor/Alligator & Wild Duck, Size: Medium
Best dog toy! Most dog toys lady maybe a week or less but this one has been going strong for almost 2 months. Both the squeekers still work on both toys i purchased. My vizsla loves ti squeek and carry it around. We added an empty water bottle in the pocket cavity for some extra fun! Yes, we are still on the same water bottle! Fantastic durability.
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Reviewed in the United States on May 26, 2026
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Amy Jo
Carnegie, US
★★★★★ 3
Shows wear quickly
Color: Multicolor/Sheep & Cow, Size: Medium
These are cute but not holding up as well as I had hoped. Quality is ok and the Velcro has held up great. The fabric just isn’t as good as it could be. They are much larger than expected.
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Reviewed in the United States on April 28, 2026
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Rachel
New York, US
★★★★★ 5
Super Sturdy with hours of fun.
Color: Wild Duck, Hare, Squirrel & Alligator, Size: Small
I got the small ones that you cannot put a water bottle in. These toys have held up way better than expected. I am dog sitting a very rough with toys dog named Chunk. He tears up ever. Single. Toy my dog (Ted) has. I bought new ones just for chunk. These appealed to me with the no stuffing, They were cheaper, and have a squeaker. Everything chunk needed. They arrived on time and I thought I wasted my money. They were super soft, like too soft. They felt flimsy and weak. Like 5 minutes with chunk and they be dead. 2 hours with my dog and they would have a rip. So far 2 of them (I set two out) have lasted the whole weekend. The bunny looks very rough and disgusting, but no rips, the squeakers still work, and no random fluff everywhere. I am going to wash the bunny once chunk leaves. My very careful doggo Ted loves them too. He throws them up in the air and catches them, plays tug of war with them, and no rips. They are super sturdy. He can’t wait until Chunk leaves (chunk is 2 and Ted is 12-13) so he can play with them.
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Reviewed in the United States on April 26, 2026
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Amber B.
Port Orchard, US
★★★★★ 5
Loved it
Color: Brown/Wild Duck, Size: Large, Color: Brown/Wild Duck, Size: Large
He loved it so much, he destroyed it so we ordered another. I didn't realize that you can stick an empty water bottle inside. Again, the first one didn't last long, but he enjoyed it
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Reviewed in the United States on May 20, 2026
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Doug Jones
Grantham, US
★★★★★ 5
Very fun interactive toy
Color: Brown/Wild Duck, Size: Medium
This toy is very versatile. There's no stuffing yet it's very soft so it can be used as a tug toy. It also makes for a fun fetch toy because it has a cavity to put a water bottle. It gives your dog something that crinkles and can be pierced when bitten and easily replaced with another empty bottle whenever necessary. That is what really makes this toy the standout of all the ones offered by Best Pet imo. I don't expect this to last forever but once my pup gets bigger we'll probably get the large size for her because there's not too many all in one fetch and tug toys at an affordable price.
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Reviewed in the United States on May 15, 2026

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