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Stepped Attenuators



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Description

The audio volume controls CT2 is a high quality stepped 24-position attenuator. It was designed for maximum sonic quality, accuracy and reliability. This makes them equally suited for audiophile applications and for professional applications.

The DACT CT2 attenuator is available in 10, 20, 50, 100 and 250 kOhm. This makes it equally suited for audiophile applications and for professional applications. The series resistor networks consist of 23 non-inductive, low noise, SMD metal film resistors. The layout of the PC board and the choice of SMD resistors have reduced the signal path to a minimum length (typical five times shorter than conventional stepped attenuator designs with leaded resistors). The PCB design combined with the special resistors also account for the very low series inductance and the very low stray capacitance. The result is a bandwidth beyond even the most demanding audiophiles requirements.

There has been special care taken to ensure the durability of the CT2. Therefore, all contacts and PCB traces are gold plated to prevent any corrosion. As a result, the CT2 will maintain its specifications after long time of use even in hot and humid environments. The rotary switch itself is a gold plated high precision switch manufactured in Switzerland.

DACT CT2 gold plated contacts.
DACT CT2 gold plated contacts.

CT2 is now available with 1 deck (mono), 2 decks (stereo) and 4 decks (balanced stereo)..

DACT CT2 rear view showing SMD resistors.
DACT CT2 rear view showing SMD resistors.

Features

  • Low noise, non-inductive, metal film SMD resistor network.
  • Compact design.
  • Entire signal path gold plated.
  • Shorter signal path than conventional attenuators with leaded resistors.
  • Reduced inductance and stray capacitance.
  • Improved sonic quality.
  • Gold plated contacts and connectors on DACT audio switches.
  • Improved accuracy - 0.05 dB tracking and 0.05 dB attenuation accuracy.
  • Improved reliability.
  • Increased bandwidth.
  • Reduced distortion, less than 0.0001%.

Typical Applications

  • Passive pre-amplifier (volume control).
  • Volume control in audiophile amplifiers.
  • Volume control in professional audio and A/V equipment.
  • Upgrading hi-fi and A/V audio equipment.
  • Reference audio attenuator.
  • Test equipment attenuator.
  • Wide-band attenuator.

Downloads

Adobe AcrobatDownload DACT CT2 Datasheet (122 KB)
PDF files use Adobe Acrobat® Reader®, which is available here if required.

Circuit Diagram

DACT CT2 circuit diagram.
DACT CT2 circuit diagram.

Dimensions and Outline

DACT CT2 dimensions and outline.
DACT CT2 dimensions and outline.

Specifications

  • Number of steps: 24
  • Bandwidth (10 kOhm): 50 MHz
  • Channel matching: +/-0.05 dB
  • Attenuation accuracy: +/-0.05 dB
  • THD: 0.0001 %
  • Mechanical life, min. 25,000 cycles

Approximate Dimensions (mm)

Dim.

Description

CT2

CT2

(2 decks)

(6 decks)

A

Distance between terminal sets

14.5

3 x 14.5
2 x 20.0

B

Mounting plane to first terminal set

14

14

C

Total build-in depth

42

112

D

PCB width (bottom)

9

9

E

Total height when mounted on a PCB

36

36

F

PCB diameter (click-house for CT2)

32

32

 

Maximum Ratings

Note

Parameter

(conditions / comments)

Value

Unit

CT2

1

Switching capacity

(resistive load)

2V/2A
 24V/0.6A
  42V/0.4A

AC/DC

1

Power dissipation

(each resistor)

100

mW

1

Operating ambient temp. range

-25 to +70

deg.C

1

Storage temperature range

-40 to +85

deg.C

 

Mechanical Characteristics

Note

Parameter

(conditions / comments)

Value

Unit

CT2

Number of positions

24

indexing angle

15

deg.

Switching function

Shorting

Gold plating, contacts

(hard-gold)

3

um

Gold plating, wiper

 (hard-gold)

8

um

2

Mechanical life

> 25,000

cycles

Switching torque

1.5

Ncm

Nut tightening torque

Max. 300

Ncm

 

DC Electrical Characteristics

Note

Parameter

(conditions / comments)

Value

Unit

CT2

Total resistance range

10,20,50,100,250, 500 (500:CT2 only)

kOhm

3

Total resistance accuracy

(new)

0.1

%

Attenuation steps

(source output
   impedance = 0),
  (load input impedance = infinite)

0,2,4,6,8,10,12,14,1 6,18,20,22,24,26,28, 30,32,34,38,42,46,5 0,60,infinite

dB

3

Attenuation accuracy

(new)

+/- 0.05

dB

3

Matching accuracy (tracking)

(2 decks)

+/- 0.05

dB

4

Contact resistance

(new)

Max. 0.01

ohm

Contact capacitance

(adjacent contacts)

1

pF

Series inductance

(10 kOhm, input to ground)

Max. 0.2

uH

 

AC Electrical Characteristics

Note

Parameter

(conditions / comments)

Value

Unit

CT2

4

-3dB bandwidth

(10k, A = -6dB)

50

MHz

5

Noise voltage

(10k, input to ground pin)

12.8

nV/Hz

6

Total harmonic distortion

(A = -6dB, fo = 1kHz)

Max. 0.0001

%

Notes

  1. Exposure to maximum rating conditions for extended periods of time may affect device reliability.
  2. One cycle is defined as a full rotation from one end stop to the other and return.
  3. Typical values at +25 deg. C ambient temperature. Output (pin 2) unloaded.
  4. Measuring probe input capacitance 1 pF.
  5. Theoretical value for an ideal 10k resistor.
  6. Measured with Panasonic Audio Analyser VP-7722P.

Reviews

Click here for a review by Hi-Fi World Magazine. Note: Outside link.

Click here for a review by EnjoyTheMusic.com. Note: Outside link.

Click here for a review by Audio Electronics. Note: Outside link.

Click here for a review by Stephen Chen, Audiophile Society of NSW. Note: Outside link.

Note: Note that all various resistances are priced the same for each model. xxxk refers to the resistance 10k, 20k, 50k, 100k or 250 kOhm.