A/B Path Swich box for Sugden Headmaster.

[Hodges]

In a previous post I wrote about the difference between a ifi Zen DAC's performance at low volume and a ifi Uno. Initially I though about using a Uno specifically for low volume listening and the Z-DAC for normal listening. Alternatively, a passive tone control or some form of pre-emphasis. The big issue was however, how to do it neatly.

Eventually after some trawling on eBay, I found this little baby. However, instead of using it to switch between one audio source and another, I shall use a single audio source {My ifi Zen- DAC}, and switch between the A & B inputs - i.e., use the switch box in reverse mode. These will go to inputs 1 & 2 on my Sugden Bijou Headmaster.

The next stage is to break one of the switched paths and insert a degree of pre- emphasis - a high pass filter. At seventy five, I just love the internet.

There was a time in my career when everything had to be worked out and source material came from loads of volumes. Now, so much of the B - ache is eliminated and many more issues can be researched in parallel.

Essentially what I am trying to achieve is a degree of fixed treble lift to emphasize the detail lost at low volumes due to the ear's lack of sensitivity at low volume + an increasing degree of deafness in yours truly. At a later stage, I will probably add switchable levels of lift, but for now I will simply choose a fixed degree at a predetermined frequency.

For the moment, I intend to experiment with nominal pre - emphasis of 25, 37.5, 50 & 75 microsecond characteristics. I am not quite sure, exactly what it may eventually be. However, I need to ensure it doesn't create problems at the Spendors Main Driver - to - Celestion HF1300 cross - over frequency, which is circa 3.2khz.

However, I await the arrival of the switch - box + a few extra components which ''Fentronics'' have included free - gratis; much appreciated. So, in the mean time I pressed on with looking for some bits I safely stored for another project; just where I can't remember, and fell upon a box of components, long tucked away after a project came to an end. Nothing changes, timescales always stretch with me as I seem to spend more time looking for things than the job actually takes.