Attenuator question - upgrade worthwhile??

byteme · « **on:** 12 Jun 2003, 05:31 pm »

Hey,

I've got preamp using a WL B100K (100 kohms) attenuator. Would it be worthwhile to "upgrade" it to a DACT or Goldpoint knob?

What is involved if I would? 3 solder joints only or would there be more soldering??

mgalusha · « **Reply #1 on:** 13 Jun 2003, 02:11 am »

IMO this is an "it depends" question. If your existing volume pot is quiet and tracks well then it may not be a big improvement.

Many low cost pots don't have very good tracking between channels, especially at low levels. In addition low cost carbon based pots usually become noisy over time. The DACT and Goldpoint attenuators both use ELMA switches which are very good. Both use discrete resistors, the DACT uses surface mount while the Goldpoint uses leaded resistors allowing you to choose your flavor.

The downsides are of course the cost and the fact that you only have 24 discrete levels. In some systems this may not give you fine enough control.

Installation is usually quite simple. Three connections per channel. In some cases you may have to drill the mounting hole larger.

Mike

randytsuch · « **Reply #2 on:** 13 Jun 2003, 05:13 am »

Just one more word of advice if you are going to do this.

A stepped atteneutor is probably larger than the pot it is going to replace.
I would measure how much room you have in the preamp, and make sure it's going to fit.

Randy

TG · « **Reply #3 on:** 13 Jun 2003, 12:07 pm »

If you're considering the Goldpoint you can save a bit by buying a kit rather than an assembled attenuator. All you need to do is add the resistor array. Not at all difficult, just a bit tedious

- makes a nice simple project for a rainy afternoon while listening to some nice tunes.

I'd second the comment about the size issue, particularly with the Goldpoint ladders - BIG devices.

Cheers

Malcolm Fear · « **Reply #4 on:** 14 Jun 2003, 10:26 pm »

I use a DACT stepped attenuator. It is not much bigger than a standard pot. In my AKSA GK-1 pre amp, it makes a huge difference over a chaep pot.

Dan Banquer · « **Reply #5 on:** 22 Jun 2003, 10:55 am »

There are two main reasons why the discreet stepped attenuators are better and make a big difference.

1. The tracking error is very low. Tracking error ( for those who don't know what it is) is the difference in resistance between the left and right channel on the attenuator. Using standard 1% metal film resistors one can easily achieve a maximum difference of 0.05 db difference between left and right. Typical audio volume pots have a difference of somewhere between 1 db and 2 db. Reducing the mismatch will decrease the need for equalization and yes that always seem to sound better.

2. Most audio volume pots typically use a carbon film or carbon composition material. Carbon has much higher thermal noise, than metal film resistors. So if things are sounding a bit quieter to you that makes sense to me.
I have been using them for years, they work great.

ABEX · « **Reply #6 on:** 22 Jun 2003, 10:04 pm »

And which do you use Dan? I was thinking about changing the Attenuator in my FT Audio Passive,but I need to figure out the Gain issue before I do that .

One person changed his out and cannot even go to 9o'clock because of the Gain using a DACT. Have to settle on the amps to use first.

I want to use 2 amps for 3-way Speakers in order to find a good balance between the Mid\High Drivers and Bass Drivers. Was initially going to get an outboard 3-way XO,but then I would be running into other issues like parts quality and matching to get the best out of the drivers. I do see the benefits,but the parts have to match the drivers capabilities I think. Caps,Inductors and Resistors must be the best as far as synergy is concerned and none of the Active Manufactures have cost effective designs to allow you to do that.So I will try it another way.

Do you have any suggestions for what are the better stepped Attenuators to use for both apps?

Just some thoughts!

Dan Banquer · « **Reply #7 on:** 24 Jun 2003, 12:34 pm »

I make my own. It's a 20K attenuator.
I am going to do some shameless marketing for a minute. The SCPA 1 pre amp I make allows to adjust gain for different amp sensitivities. It has a maximum of 12 db difference in gain between channels. I think this might help you in biamping your speakers, and it also comes with a discrete attenuator for very low tracking error. See the R.E. Designs web site for more info. I'm also giving some very good discounts these days.
If this does not suit your needs than give me a call in the evening and maybe I can help you get to a solution.