Audio Attenuators > Networks

Audio Attenuators and Networks

Step-type Rotary Attenuators

These designs have been standards for over 50 years and continue to be the step-type rotary of choice for leading manufacturers of audio consoles for the broadcast industry.

Decade Attenuation Networks

Chosen by industry and military as preferred standards for lab and production work is your assurance that these instruments are accurate and reliable for your audio and digital signal measurements.

Product Data and Selection

Shallco offers a broad selection of rotary step-type audio attenuators for broadcast and recording industry applications.

Accuracy:

Individual resistors are to an accuracy of 1% for all values above 10 ohms, unless otherwise specified.

Frequency Response:

Attenuators designed for audio have no appreciable change in level from 0 to 20kHz.

Insertion Loss:

Ladders of 1:1 impedance ratio, 6 dB; 1:2, 2 dB. "T" and "H" attenuators of 1:1 impedance ratio, 0 dB. For unequal impedances, the loss is a function of the impedance ratio.

Direction of Rotation:

Increasing attenuation with counterclockwise (CCW) is standard and will be supplied unless otherwise specified or requested.

Construction:

Heavy duty solid silver alloy contact surfaces, solid silver alloy wipers and silver alloy slip ring surfaces are standard. A unique "torsion " wiper design provides low uniform contact resistance for millions of trouble-free operations. The rotor is pinned tothe shaft.
Both the mechanical detent and electrical circuit are shielded and enclosed. The shaft is of 0.250 diameter stainless steel.

Mountings:

Both bushing and two-hole mountings are available for most any design.

Ladder Circuits

Monaural and stereo ladder types are best suited for consoles that require cueing and low noise at minimum cost. Nominal insertion loss for a 1:1 impedance ratio is 6 dB. Standard types are available in 20 and 30 step designs with step increments of 2 dB and 1.5 dB respectively. Tapers include audio to off w/cue, audio to off, linear and linear to off.

"T" and Bridged-T Circuits

Both "T" and bridged-T attenuators provide accurate adjustments in signal level with zero insertion loss. Increments from 0.1 dB to 2 dB are standard with ranges of 10, 20, 30 and 45 steps in most impedances. In addition to parameters and the devices listed in our online catalog we can provide custom designs for special applications. All devices are manufactured with precision film resistors of ± 1% accuracy and are housed in shielded enclosures. All terminations are solder lug type. Bridged-T type devices are lowest in cost and are equally as accurate as the "T" for all but the most stringent applications. Our applications engineer can recommend the best and most economical device for your application. Standard impedances are 600 ohms but others are readily available. All units are equipped with detents.

Bridged-H Circuits

Bridged-H attenuators provide all the features of the Bridged-T types but in a balanced circuit. These devices consist of two bridged-T attenuators on a common shaft. Therefore, the cost of a balanced unit is about two times the cost of the bridged-T type and should be used only in balanced line applications. Both 20 and 30 step designs are available in various step increments. Standard impedancesare 600 ohms. All units are equipped with detents.

Potentiometer

Potentiometer step-type attenuators are provided in 20 and 30 step designs in 2 dB and 1.5 dB step increments respectively and are available in audio and linear tapers. The resulting attenuation curves are based upon infinite impedance loads. The standard impedance range is from 5000 ohms to 100,000 ohms. Resistors are film type with ± 2% accuracy. Units are available with or without detents.

Fixed Pads

Fixed pads are available in "T" and "H" configurations from 30 to 600 ohm impedance with losses to 90 dB. Pads are equipped with precision film resistors housed in shielded enclosures. Terminations are solder lug type.

Tapped fixed pads are available to allow field adjustments when adjusting or matching audio signal levels. Ranges are up to 40 dB in 1.0 dB steps. VU meter multiplier networks are available for extending meter ranges.

Branching input and output networks are available for combining or splitting signals. These are available in both "T" and "H" circuits with ratios of 1:10 and 10:1. Standard impedance is 600 ohms. Resistor accuracy is ± 2 %.

Unmounted Decade Attenuators, Audio

The Series 2500 Decade Attenuators are step-type precision networks designed for use in measuring equipment. These units are adaptable for use in noise meters, audiometers, transmission sets and attenuation etworks. The frequency characteristics are essentially flat from zero to 50kHz. For best results, it is recommended that power input be limited to 0.5 watt or less. Accuracy: 0 to 60 dB, +/- 0.5% +0.05 dB; >60 dB, +/- 2% measured at 1kHz.

Series 2500

Type	Steps	dB/Step	Range	Detents	Deg. Indexing	Deg. Rotation	Case Dia. & Depth
2509	10	0.1	1 dB	yes	15	150	2.25 x 2.063
2509	10	1	10 dB	yes	15	150	2.25 x 2.063
2513	10	10	100 dB	yes	15	150	2.25 x 2.063

NOTE: Attenuation increases with CCW rotation.

Unmounted Decade Attenuators, High Precision Audio/Video

Series 1790 Decade Attenuator units are precision devices designed to operate over a frequency range extending into the low rf spectrum. Each unit is carefully shielded and is provided with a grounding lug. The electrical circuit employs switches using a low loss dielectric, solid silver alloy contacts and low capacitance wiping blades. The use of low reactance resistors and a carefully designed circuit reduces frequency discrimination to a minimum. These devices may be specified whenever accurate control of attenuation are important at a constant impedance. Accuracy: 0 to 60 dB, +/- 0.25% + 0.03 dB; >60 dB, +/-0.5% at 1 kHz.

Series 1790

Type	Steps	dB/Step	Range	Detents	Deg. Indexing	Deg. Rotation	Case Dia. & Depth
VT-1790	10	0.1	1 dB	yes	15	150	2.75 x 2.813
VT-1791	10	1	10 dB	yes	15	150	2.75 x 2.813
VT-1792	10	10	100 dB	yes	15	150	2.75 x 6.375

NOTE: Attenuation increases with CCW rotation.