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

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Originally Posted by lurcher

Yes, resistive passives will be very sensitive to capacitance on the output side.

I thought the goldpoint was made using surface mount resistors on a PCB, how has it been converted to a shunt with a single resistor to ground?

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Duncan rewired the switch and added a series resistor, so it becomes a shunt-type control. The signal now only goes through that one resistor, at any point on the volume knobs.

That's why I'm looking forward to fitting some Z-Foils, and the like, to take the place of that single resistor (in each channel). It sounds stunning at the moment, fitted with just some decent metal-films, costing pennies, so goodness knows how good it will get with some top-notch resistors in there!! :eek:

Marco.

Quote:

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Originally Posted by lurcher

Yes, resistive passives will be very sensitive to capacitance on the output side.

I thought the goldpoint was made using surface mount resistors on a PCB, how has it been converted to a shunt with a single resistor to ground?

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My thoughts exactly. If the switch now selects a shunt resistor to ground for each position, not only has the switch been rewired, but the values of the resistors have to be changed if the attenuation values are to remain the same.

Exactly, and that's what has been done, Barry - to great sonic effect. This (with the Goldpoint modded as outlined) is unquestionably the best my system has ever sounded! :)

Marco.

Nick I'm pretty sure you have the correct mental picture of the way Marco's attenuator is now wired, IMO.

One series resistor followed by a varying number of the string of resistors on the attenuator switch as a shunt to ground.

I'm wondering if the 'sweet spot' referred to is just the position that is high enough above the noise floor but low enough not to compromise the full dynamic range required for the music.
Very much dependent on the overall gain structure of the system/components, as mentioned.

:)

A couple of posts while I was typing. Has every resistor on the Goldpoint been changed Marco?

Precisely, Alan. I concur completely, especially with your last sentence [before your edit] :)

Marco.

Then it's no longer a Goldpoint, as all that remains of the original design is the input selector switch and the box. Perhaps you should rename it "The Duncan" using some Letterset. :D

Lol... :eyebrows:

Well, it still uses the superb quality Goldpoint switches themselves, which I have to say are the finest (and quietest) in operation I've ever used. Also, I'm still getting some sonic benefit from the original thin-film Nichrome resistors fitted, as Alan refers to here:

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Originally Posted by Firebottle

One series resistor followed by a varying number of the string of resistors on the attenuator switch as a shunt to ground.

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...together with the lovely case it's all screwed together in! And as all my other kit has been 'bespoke voiced', as it were, then the Goldpoint has simply joined the party! :D

In all seriousness though, modifying things like this, and customising equipment for optimum performance in your system, is an excellent way to obtain maximum SPPV - and *that* is what my system-building methodology is all about :exactly:

Marco.

Quote:

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Originally Posted by Firebottle

A couple of posts while I was typing. Has every resistor on the Goldpoint been changed Marco?

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Nope. All the original resistors are still present on the stepped attenuators, but are no longer directly in line with the signal path - only the two series ones Duncan has fitted are. The rest go to ground. Do you get what I mean? :)

Marco.

I do certainly, some previous description could be mis-interpreted as only one shunt resistor in play at any time, not the case as Nick also understood.

Not sure that in this case you have got good SPPV - in retrospect it would have been cheaper just to get Duncan - or someone - to knock you up a custom passive from scratch.

Still we live and learn and if you don't try things you never gain any knowledge. I can't talk, if I had back the money I'd spent pointlessly on this hobby over the years I could buy a boat.