Goldpoint SA4M-47 passive 'preamp' winging its way to Marco Towers...

[lurcher]

I kind of follow where you're coming from Nick, and certainly agree that the numbers don't tell the whole story.

I was simply responding to the idiocy of someone who, in no uncertain terms, was TELLING me that the cables I had were too high a capacitance for use with my passive preamp, when the idiot in question clearly had no idea what the capacitance measurements were for the cables I was using!! With complete ignorance, he just blurts out any old shit to further his stupid agenda

Anyway, all I indisputably *know*, because I trust my ears, is that I can clearly hear (although it's far from disastrous) the deleterious sonic effect of moving from using 0.5m interconnects, to 1m ones, with the Goldpoint - and I suspect that's got far more to do with passives, in general, by their very nature, preferring the shortest lengths of cable possible, than anything relating to the 'bodged' capacitance value of the Klotz cables I'm using.

However, I'm more than up for being proven wrong on that one, as at the end of the day I'm far more interested in ensuring that my system sounds as good as it possibly can, than winning an argument on a forum!

Marco.

All I am saying is that that cable could be a problem with a high value passive. Yours is low value, so less likely. A high value passive should be inside the amp its feeding, so cable length doesn't matter. But a low value passive will place more demands on the source. Its all down to showing that there is often engineering behind what gets called synergy.

If you are driving long cables, a resistive passive is a bad choice. if not, not.

[Marco]

All I am saying is that that cable could be a problem with a high value passive. Yours is low value, so less likely. A high value passive should be inside the amp its feeding, so cable length doesn't matter. But a low value passive will place more demands on the source. Its all down to showing that there is often engineering behind what gets called synergy.

If you are driving long cables, a resistive passive is a bad choice. if not, not.

In reference to the bit in bold, less likely, but still possible? The fact of the matter is I can clearly hear the difference between half metre and one metre cables, when used with both the Goldpoint and Tisbury passives I've tried.

Don't get me wrong, we're not talking massive treble roll-off and the whole sound falling apart - far from it - just the music not *quite* being as purposeful and involving as it should be. The effect, although low-level, is definitely there, and enough for me to want to use the shortest cable lengths, as I like things to be as optimised as possible.

So, two things:

1) What's the difference between a "high-value" passive and a "resistive" one? What is meant by "high value"?
2) Have a look at the spec and construction of the Belden cable I linked to earlier, and give me your opinion if you think it's liable to be lower capacitance than the Klotz MC5000s I'm currently using, the spec of which you've already seen.

Marco.

[awkwardbydesign]

I think science comes closer than the other two (though of course it began as a branch of philosophy). I'm not sure what, if anything, religion brings to the party.

I think that makes my point for me!
And I used to look in the window of an ecclesiastical supply shop in Victoria many years ago. Lovely fabrics! And I still use some of their incense.

[lurcher]

Ok, well a couple of things:

1. The input capacitance of the amp will also have to be added, but of course that will be constant with cable length, but the combination may push the -3dB point where its audible. Without knowing what is at the front of your amp I could only guess at what the capacitance of that is.

2. "What's the difference between a "high-value" passive and a "resistive" one? What is meant by "high value"?" High value as in the -3dB point becomes audible. F-3 = 1 / ( 2 * Pi * R * C ), where R is in ohms, and C in Farads. My point about the "resistive" is not a high low thing. A inductive preamp such as a AVC or TVC behaves differently, at the worst (highest volume) the output impedance is the same as the source impedance. With a resistive, the source doesn't matter so much, its the value of the passive that sets the resistance.

3. 39 and 85 is less than 55 and 95, so, yep its a bit less.

4. I do have a hourly rate :-)

[anthonyTD]

My own personal reasons for using Switched attenuators were founded a long time ago,the main one being Accuracy,over conventional pots etc, Therefore i needed a good Switched attenuator that not only performed well sonically, but was reliable, and would fit into the space i had available, i also knew the switch type that DACT use as i had used versions of it too in earlier products, those were the initial reasons for choosing the DACT type, however, i also believe that the small footprint of the components lessen the problems that can be associated with larger, conventional resistive elements, ie; contact areas of the resistor material to connection ends, and the affect vibration has on each type etc. As for one type being sonicaly better over the other, well, that is always going to be subjective, as Marco has found by replacing certain material types in his experiment, however, in my opinion, the positives of switched attenuators on the whole, made from either surface mount, or conventional resistive elements[what ever the material] compared to conventional pots are always apparent to me.

Can I just point out that I have not said there is anything inherently good or bad about surface mount as opposed to leaded resistors sonically. I am sure a good SMD component will sound better than a poor leaded one and vice versa. What I was arguing again was:

1. Just because they are small and you can pack many more into the same space as one 5W resistor, doesn’t mean the signal is somehow fooled into thinking its a single resistor

2. I would be very surprised if 20 1k resistors in series sounded as good as one equal 20k resistor.

3. If a manufacturer happens to make a change that is simpler for them and lower cost, be wary when then then claim the change was done for reasons of the sound.

4. There are probably no absolutes in audio

[anthonyTD]

While we are on the subject,
As Nick has stated, depending on the impedance, or resistive value used in the attenuator, in conjunction with the input impedance, and capacitance of the amplifier used, it is posible to perceive a diffrence in sonics between a 1 mtr, and a half mtr interconnect, as Marco has found. Passive preamps, what ever the type, conventional, or switched will always be much more susceptable to cable length,and type in comparison to a preamp where the attenuator is actively driven.

[struth]

I am now using a supposedly low cap low res nordost flat cabke between tvc and amp. Have to say it did make a difference although whether it was the capacitance or not i wouldnt know...they were kindly supplied by Carjay and although a bit awkwarx to use as they are springy they are a metre long. I will when i change things round try a half metre set to see if i hear any differences. I should have some of the same cable somewhere.

[Ali Tait]

Fair enough, though I'm not sure how they enable us to make sense of the universe.

Might as well be comfortable whilst trying to..

[Gazjam]

Ali knows his frocks...

[The Black Adder]

Marco... What are you doing about the phase invert using the passive? The Croft (as it's being used as a phono stage) outputs are inverted yet the Pi outputs aren't.

Just wondered.