GK-1/Dact

stvnharr · « **on:** 27 Apr 2004, 01:19 pm »

Has anyone incorporated a Dact attenuator into their GK-1?
Or, does anyone other than Malcolm have experience with a Dact based passive pre-amp with their Aksa?

PSP · « **Reply #1 on:** 27 Apr 2004, 05:27 pm »

I used a DACT as a passive attenuator for a few months before I built my TLP. The DACT was built into the same chassis as my 55N, and I used an extender rod to keep the DACT very close to the input RCAs near the rear of the chassis. In this build of the 55N the amps and heatsinks were built onto the sides of the enclosure at the rear with the amp boards jutting out toward the DACT, so signal leads (26.5 awg Vampire cast copper magnet wire) were very short. I don't know what else I could have done to optimize things for the DACT.

That said, the system sounded very, very nice. Absolutely quiet, very detailed, very correct, very refined, very polite... too polite for my taste.

When I put the TLP into the system (even though, at that point, with the TLP in the same chassis as the 55N I had a little hum) there was a very noticable increase in engagement and muscle. I noticed that I was listening a lot more and that--while at work during the day--I was thinking a lot about getting home and listening some more... all signs that the Audio drug has become even more powerful...

When the music is sweet, I want to hear sweet. But when things get rough and nasty (think Tina Turner's lead into Proud Mary) I want to hear rough and nasty. The TLP did both of these very, very well. My GK1 is under construction, by the way.

Whether a DACT passive will work for you depends on what elements of music engage you most.

Good luck,
Peter

stvnharr · « **Reply #2 on:** 29 Apr 2004, 02:38 pm »

I have finally had the time to do a thorough search here about my question, and there was a lot of reading contained.

Peter, did you use the 20K Dact in your passive?
Everything I read points to use a 10K in a passive.
But Hugh seems to recommend and design for 20K in TLP and GK-1.
So, is it possible to configure a 10K for later use in GK-1?

SamL · « **Reply #3 on:** 29 Apr 2004, 09:44 pm »

10K DACT should be fine if you will be doing a little mod to make it into stepped attenuator.
Have a look at this post.
http://www.audiocircle.com/index.php?topic=4880.msg41839#41839&highlight=dact#41839

PSP · « **Reply #4 on:** 29 Apr 2004, 10:11 pm »

I used the 20k DACT. I discussed this at some length with Hugh. If I remember correctly, he suggested that some CDPs might be too heavily loaded by 10k (possibly costing dynamics). Since at the time I was considering buying the TLP (which uses 20k) I went that direction.

Please post your results if you build a passive.

Peter

stvnharr · « **Reply #5 on:** 30 Apr 2004, 04:03 am »

Sam, Peter,
Thanks for the replies. I think I have enough information to go on from here, should I desire. I'll definitely post results if I build anything.

Malcolm Fear · « **Reply #6 on:** 2 May 2004, 12:39 am »

I used the DACT in my GK-1. I then turned it into a shunt. The difference was quite significant.

JohnR · « **Reply #7 on:** 2 May 2004, 12:54 am »

If you don't already have an attenuator you could get a shunt kit from goldpoint. Don't think it costs any more than a DACT, perhaps less.

Larry · « **Reply #8 on:** 2 May 2004, 04:32 am »

Quote from: Malcolm Fear

I used the DACT in my GK-1. I then turned it into a shunt. The difference was quite significant.

You can't turn a series attenuator into an authentic shunt attenuator.

Larry · « **Reply #9 on:** 2 May 2004, 04:36 am »

Quote from: JohnR

If you don't already have an attenuator you could get a shunt kit from goldpoint. Don't think it costs any more than a DACT, perhaps less.

An authentic shunt attenuator can be constructed using the shunt kit from goldpoint. However, you cannot use the series attenuator to construct a shunt attenuator though you can make a fake shunt wiring scheme by adding a shunt resistor, which is not the same as the shunt attenuator.

stvnharr · « **Reply #10 on:** 2 May 2004, 05:04 am »

Malcolm,
Eventually I will put the Dact into my GK-1, but it's a real long story!

stvnharr · « **Reply #11 on:** 2 May 2004, 04:14 pm »

Just had a long session at the goldpoint site. Does anyone have experience with the goldpoint attenuators? One testimonial preferred the gpt over the dact, of course that's why it's in the testimonials.
Hm, choices choices

Malcolm Fear · « **Reply #12 on:** 2 May 2004, 11:14 pm »

Hi Larry
I thought what I had done, was to make a shunt attenuator out of a DACT.
I stuck a resistor (Riken Ohm) in the signal path and wired the DACT backwards (signal into pin 3, pint 1 and 2 joined together and going to earth). If it is not a shunt, then what is it? I was told it was a shunt, and have been calling it that for some time. I would appreciate your thoughts.
regards

Larry · « **Reply #13 on:** 3 May 2004, 09:37 am »

Hi, Malcolm,

Followings are the two types of attenuators. A series type stepped attenuator is a series of resistors forming one "long" voltage divider while a shunt type stepped attenuator, a voltage divider is formed with the (constant value) input-to-output resistor, and one ground resistor selected by the rotary switch position. They have distinct rotary switch constructions.

To overcome the weakness of series type where the signal has to flow through multiple resistors and solder joints, a shunt resistor is used with the series type to "improve" the signal route by purists. (The same can apply to potentiometers as well.)

However, from the figures you can see that they are still different in terms of number of resistors involved and signal routes, no matter how the shunt resistor is connected to a series type.

Series type stepped attenuator:

Shunt type stepped attenuator:

Larry · « **Reply #14 on:** 3 May 2004, 09:55 am »

Quote from: stvnharr

Just had a long session at the goldpoint site. Does anyone have experience with the goldpoint attenuators? One testimonial preferred the gpt over the dact, of course that's why it's in the testimonials.
Hm, choices choices

There are two things in a stepped attenuator that may affect sound: rotary switch and resistors.

I understand that both Goldpoint and DACT use the same rotary switchs from Elma. Therefor, the difference between the two would be in resistors used.

DACT starts to produce attenuators with surface mount resistors and some purists decide not to like it and prefer Goldpoint with which they can continue using separate resistors of their choice or building attenuators with various values from different resistor sets.

Some people may have other reasons to like or not like something.

stvnharr · « **Reply #15 on:** 4 May 2004, 03:27 am »

The differences between the two seem to be small in sound performance.
Dact can be motorized, goldpoint can be customized.

It's a wonderful world.

kyrill · « **Reply #16 on:** 5 May 2004, 12:04 pm »

Hi
There is another approach possible for the best volume regulator, (much) more transparent and if done well with no compromises, it seems.
See http://www.audio-consulting.ch/Wiring.jpg
See: http://www.stevens-billington.co.uk/page102.htm
See: http://www.audio-consulting.ch/DIYPot.htm
Very favourable reviews over the internet

stvnharr · « **Reply #17 on:** 12 May 2004, 04:56 am »

Larry,
Are you still using Goldpoint shunt that you wrote about a year ago?
What is the value?
I would think that 25k attenuator would match the 22k of the pot in GK-1, but don't really know, that's why I ask.
Goldpoint certainly seems better value than Dact.

Seano · « **Reply #18 on:** 13 May 2004, 02:32 am »

Quote from: kyrill

There is another approach possible for the best volume regulator, (much) more transparent and if done well with no compromises, it seems.
See http://www.audio-consulting.ch/Wiring.jpg
See: http://www.stevens-billington.co.uk/page102.htm
See: http://www.audio-consulting.ch/DIYPot.htm
Very favourable reviews over the internet

That may well be true but the cost is, put simply, plain stupid. Why on earth would anyone want to (or for that matter, consider) pay more for their volume control than they did for the entire amp that it controls?

In kit form, the copper wound transformer and the pot is nearly AU$800. For some extremely dopey reason, the made up unit is more like AU$8000.

Besides all examples I've seen still use an Elna pot......should be getting something far more esoteric for that sort of cash.

kyrill · « **Reply #19 on:** 13 May 2004, 09:02 am »

It is all about listening . Is the price worth the update?

By the way there are several transformer companies who let you specify yr. own trafo. So you can "clone" a little trafo. But the iron of the trafo plays a role too. But the manufacturer will help you with the best sounding one..The empty Elma switch can be ordered at different addresses.
Probably for the same price you will have a silver one.