Stepped Attenuators

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.

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

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

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

Circuit Diagram

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.