STEPS to HEAVEN

Andrew Harrison and Ketan Bharadia step out with Danish Audio Connect's CT1 stepped attenuator.

CT1 audio attenuator

A volume control is one necessity that even the most hair-shirt purist could not forgo.
Balance control -expendable; tone controls - unnecessary; but control over music's volume - essential.
Problem is that in most applications a potentiometer (variable resistor) will be used directly in the delicate signal path.  This can have potentially  disastrous effect on sound quality.

Nowadays any ¢G500+ amplifier worth its salt should have at least an Alps Blue pot fitted, its metallised,  conductive plastic track offering audible advantages over the most basic carbon-track variant.  But beyond the potentiometer lies the stepped attenuator.

This uses a multi-way rotary switch with a 'ladder' of high-quality  discrete resistors making up its rungs. You move up and dawn the ladder to change volume by simply turning the knob.

Danish Audio Connect make one such device, their ¢Gl05 CT1 Audio Attenuator with  its 24 steps. We tried their 250k ohm version in our World Audio Design KLPP1 valve line and phono pre-amp as well as in front of some DPA amplification (although 10k ohm would be a more normal value here).

Hooking up the CT1 instead of a DPA 50S pre-amplifier was certainly  chucking it in at the deep end as the DPA is already a seriously good pre-amp thanks to its extremely high-grade Penny and Giles pot.  Used as  a passive volume control and connected directly to DPA's 50S power amp, there was just about enough volume but we had to use most of the attenuator's travel.

Our first impression was of a 'stripped-down' sound that initially lead us to think that something was missing.  Further listening showed that the DPA pre, in contrast was actually laying a thin veil over the sound.

Another bonus with the CT1 was an increase in the boogie factor. rhythms had greater conviction and transients were that bit more precise and snappy.  Subtle details previously overlooked made themselves felt - tonal colours were more realistic and sound staging that much more focused, with images firmly located. After this promising start, next up was the KLPP1.

A few wafts of multi-core flux later and the re-tweaked KLPPI was mated up to a Chord SPM 400 power amp for auditioning.  One ability of this attenuator that's very obvious is its truly crystal clarity.
The spaces in a sound stage between the various images were clearer and more open, as if a fine coating of mush had been peeled off them.  The top end was more extended and a little sweeter, while lower down bass and midrange had lost some of their slightly tubby cuddliness in favour of a drier, more detailed character.

The CT1 'invisibility' was its finest asset. if you're accustomed to cheaper pots, you might think the CT1 a touch grey and lean when you first encounter it. Give its sound a chance to sink in though, and you'll wonder how you never noticed the blatant colorations of less elevated volume controls.

There are other claims made for the CT1 by the manufacture on top of the purely sonic; increased reliability, lower distortion and better tracking accuracy between channels. The reliability factor I am not inclined to question given the superb build quality and use of gold-plated contacts on precision wafers sourced in Switzerland.  And precise channel matching comes from the high-tolerance surface mount Metal film resistors.

Danish Audio Connect CT1 attenuators are available in 10k ohm, 20k ohm, 50k ohm, 100k ohm and 250k ohm values. With a four-wafer version for balanced audio applications priced at +/- ¢G165 each.

HI-FI WORLD SUPPLEMENT              APRIL 1998