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

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Originally Posted by 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 :-)

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Ok, got all that. Cheers! Please forward the invoice for your services to my secretary, Grant. He's the one sat [over there] in the grey pencil skirt and stilettos, twiddling his hair :eyebrows:

Marco.

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Originally Posted by Marco

Ok, got all that. Cheers! Please forward the invoice for your services to my secretary, Grant. He's the one sat [over there] in the grey pencil skirt and stilettos, twiddling his hair :eyebrows:

Marco.

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Had to stop wearing wool:eek:

Hi Anthony,

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Originally Posted by 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.

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Interesting, and thanks for that. I knew you had very good reasons for choosing DACT attenuators, and so obviously considered that the SMD-type resistors they were fitted with didn't act as a significant bottleneck, which are also my findings :)

The bit in bold is a valid point, and something I hadn't considered... That's interesting. So not only do SMD-type resistors have shorter signal paths than conventional resistors, but they could also be less susceptible to vibration? Just shows you that blinkered absolutist thinking in audio doesn't get you very far! ;)

What's patently obvious, through listening, is that both DACT and Goldpoint switched attenuators are up there with the best, but like anything else, are built to a price, and as such, can be improved upon. You need to try some of these Z-Foil resistors, as they really are superb and almost as musically effective as the Obbligato Teflon tinfoil coupling caps you fitted to the Croft! :eek:

Marco.

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Originally Posted by anthonyTD

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.

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Indeed. We all know that passive preamps are much more sensitive to load, cable lengths and type. However, as I have found, they can be made to work very well when you partner them optimally! :cool:

Marco.

I believe the main issue with smd could possibly be in the quality of machine-soldering? Repairing an smd populated board is also tricky without the skills, tools and experience needed.

Me? I've been a pauper-coward and ordered a ladder type Dale attenuator to see what that does. Constant impedance on every step, the resistors have a good rep for basic types I think and if it's load of rubbish, I can say I've tried!

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Originally Posted by DSJR

I believe the main issue with smd could possibly be in the quality of machine-soldering? Repairing an smd populated board is also tricky without the skills, tools and experience needed.

Me? I've been a pauper-coward and ordered a ladder type Dale attenuator to see what that does. Constant impedance on every step, the resistors have a good rep for basic types I think and if it's load of rubbish, I can say I've tried!

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Good man. Then you can waste your life swapping resistors. :lol:

Hi Jo,

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Originally Posted by 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.

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When the Croft is being used as a phono-stage only, through the Goldpoint, then I leave things as normal, as the latter does not phase invert the signal. If I'm using the Pi, through the Croft (not the Goldpoint), then I would reverse the polarity of the speaker cables on the Copper amp, as the Pi doesn't phase invert, but the Croft does.

And if I'm using the Pi, through the Goldpoint (without the Croft), I leave things as normal, as neither of those items phase invert the signal. Essentially, in any scenario where the Croft is the last thing that the signal 'sees', before going to the power amp, you would reverse the polarity of the speaker cables. In all other instances, you would leave things as normal.

Hope that makes sense :)

Marco.

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Originally Posted by 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. :)

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Oh Lord, please don't go there! At least not until we've flogged this subject to death.

Are we nearly there yet, mum?

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Originally Posted by DSJR

I believe the main issue with smd could possibly be in the quality of machine-soldering? Repairing an smd populated board is also tricky without the skills, tools and experience needed.

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Sure, but none of that automatically makes them crap! ;) The quality of the soldering on the Goldpoint Nichrome SMDs, observed under a microscope, appears to be first class.

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Me? I've been a pauper-coward and ordered a ladder type Dale attenuator to see what that does. Constant impedance on every step, the resistors have a good rep for basic types I think and if it's load of rubbish, I can say I've tried!

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Ladders, done well, are arguably the best. Good luck - hope it delivers a significant sonic upgrade for you :)

Marco.

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Originally Posted by awkwardbydesign

Are we nearly there yet, mum?

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Almost. We just need to find a cure for Metaphysical Solipsism, which obviously is rife in certain parts... ;)

Marco.