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

[Marco]

Aye!

Marco.

[Marco]

Ok, as I said a very interesting session at Duncs... First we listened to the bog-standard metal-film series resistors, which cost pennies from Farnell, and that I had been listening to over the last few days [the little blue things beside the wires on the R/H side, for those that don't know]:





I had been quite enjoying these, especially since they had burned in, and Duncan agreed that they sounded pretty good, detailed and expressive with (seemingly) no overt sonic signature. However, we were keen to hear what the first proper 'audiophile' resistors would bring to the party, so first in went the Caddock MK132V Precision Thick Film resistors, at a value of 20K:





WOW - what a difference!

Dunc and I immediately loved these, commenting that they created a 'blacker' background, compared with the super-cheap Farnell resistors, allowing more harmonic detail in the music to be heard, together with a tuneful, beautifully layered and textured bass, which succeeded to underpin music with a muscular authority. It was considered subjectively easier to 'follow the tune', with the Caddocks in place, and pace, rhythm and timing were in the first rank. These also seemed to do the trick of '3D imaging' rather well.

I remarked that it reminded me in some ways of what Naim equipment does well, but without its tonally rather 'grey and grainy' sonic signature and tendency to 'bleach out' music's natural warmth and colour. Music was subjectively 'fast' and fun to listen to with these resistors in place, which was a good result, with them being one of the cheaper types on test, at £3.07 each. A cultured sound that would also appeal to 'flat earthers'!

Pros: 'Fast and punchy' presentation, but also not without finesse.
Cons: Compared with the best here, lacking in midrange lucidity. Good 'bang for buck'.

Verdict: 7/10.

Next up was PRP PR9372 metal-films, at a value of 22K (as unfortunately 20K was unavailable), costing only 54p each. I got these because this is what Duncan had fitted in his own passive preamp, so I wanted to try them in the Goldpoint:





These were considered to have a very detailed, clear and expansive sound, but also one that was 'harder', somewhat 'matter of fact' and not as '3D', as the Caddocks. We felt that the overall presentation was balanced more towards the high-frequencies, creating a 'crisp' sound, but ultimately one that was low on musical involvement. They had the effect, as we put them through their paces, of us gradually becoming disinterested in the music.

Ultimately, these were a little bland in comparison with the others we tried. Not a great success then, and as such it has now prompted Duncan to upgrade the resistors in his own passive preamp, with the winners of the test. Read on for details.

Pros: Detailed and clear sound. Inexpensive.
Cons: Not the last word in subtlety or finesse.

Verdict: 5/10.

Next up was the Amrans AMRG Carbon-Films, at a value of 22K (again as 20K was unavailable), costing a not inconsiderable £4.40 each:





We were both looking forward to hearing these, being the only carbon-films in the test. After listening to the somewhat poor PRPs, these initially sounded quite impressive, with much better bass, reminiscent of that of the Caddocks, but not as 'fast', rhythmic or tuneful. The sound was also better balanced overall, than with the PRPs, but came with an added warmth and slight 'bloom' in the mid and low frequencies that wasn't welcomed and considered as unnatural.

The Amrans were a fairly musical listen, but definitely had a 'darker', 'creamier', and ultimately more restrained sonic presentation than that of any of the metal-film resistors we had listened to before, so much so that we felt that they were acting a little as tone controls, which was not an effect we wanted. I remarked that the sound was reminiscent of Alps Black potentiometers (also carbon based) - certainly those I used to have fitted to my Croft. The Amrans were good, but not what we were looking for in this application.

Pros: A musical listen with good bass and a warm, yet detailed presentation, which may help ameliorate sterility in clinical sounding systems.
Cons: For our tastes, they acted too much like tone controls.

Verdict: 6/10.

Now things started to get really interesting with the introduction of the 'big guns', the first of which was the AudioNote Tantalum Non-Magnetics, again at a value of 22k, costing £12.50 each. These are also 2W, so rather bigger than the other resistors we had been using up until then:





As soon as these went in, Duncan and I looked at each other and said 'WTF!' These were clearly a considerable step-up in quality from the other resistors we had tried up until this point, producing a huge, bold and vigorous sound, full of drive and energy, and palpable weight and authority, but also one that conveyed significant levels of subtlety and finesse.

Subjectively, they appeared to make the music louder, but that was likely because the noise-floor was lower, allowing the midrange more freedom of expression and natural projection. The midrange presentation of the AudioNotes is really rather special, making female voices in particular seemingly 'float in mid air' and hang somewhat spookily between the speakers.

Their ability to excel at micro-detail and harmonic texture was also extremely beguiling and addictive, rather like the sonic and musical qualities that the best valve amplifiers bring to the party over their solid-state counterparts. In that sense, the ANs acted as the '300Bs' of the resistor world... The level of musical insight offered by the AudioNote Tantalums was quite something to behold, and we just wanted to keep on listening to more and more music - always a good sign. However, we had to get on with completing the test!

Pros: Amazing midrange lucidity, weight and micro-detail.
Cons: Low-end 'heft' and tonal richness could prove too much in some systems.

Verdict: 9/10.

Last up was the Charcroft Z-Foils, at a value of 20K, costing £9.17 each:





These were very well received indeed, possessing beautiful filigree detailing at the top end, with subjectively a little more 'air' and extension than that offered by the AudioNotes, such that leading edges were crisper and had marginally more 'attack'. However, the sound lacked the weight, power and authority of the AudioNotes (although by normal standards certainly was not lacking), or their extremely lucid, communicative, 'out of the box' midrange.

The Z-Foils have a slightly more 'delicate' and precise sonic presentation, and perhaps one that is also a little leaner. In the red wine world, one could say it would be like comparing a good Chianti Classico Riserva (the Z-foils), with a rich and full-bodied Amarone (the AudioNotes). The former providing the greater 'acidity' with which to savour a perfectly cooked char-grilled T-bone steak, and the latter, the structure and depth to accompany a fine roast grouse.

Therefore, simply choose one's 'dish' accordingly, and apply it to musical choices liable to lend themselves best to the respective 'flavour' of either of these highly capable components. In the final analysis, to my ears (and those of Duncan) the AudioNotes edged it overall in the musicality stakes: that magic effect which makes you just want to listen forever and rediscover your music collection.

Pros: Superb high-frequency extension and ability to delineate the musical message.
Cons: Leaner in presentation and a little more 'matter of fact' sounding than the AN Tantalums.

Verdict 8/10.

So there you have it, folks.

However, what I intend to do is live with the AudioNote Tantalums for a week, a) to allow them to burn-in fully, and b) to acclimatise myself to their sound, by chucking all sorts of different music at them. At that point, once I've had them for a week, I'll then swap to the Z-Foils, which of course I must hear in my own system before coming to a proper conclusion, in terms of which resistors are considered best in the context of my system, and thus will take up permanent residence inside the Goldpoint.

Hope you enjoyed reading the resistor comparisons and that they may be of some use in your own equipment experiments!

Marco.

[anubisgrau]

what's actual role of these resistors? to fix the output impedance or something else?

[struth]

Looks like you had fun. Glad your happy with it now.

[walpurgis]

Weird that just a choice of resistor can have such varying effects Marco.

[Marco]

Hi Gordan,

what's actual role of these resistors? to fix the output impedance or something else?

Duncan explained it earlier, in terms of how the Goldpoint passive preamp has now been rewired:

The Goldpoint is a series attenuator not a shunt type, originally.

I've connected the in and outputs to ground and connected the original ground to the output side of the z series resistor.

Creating a shunt type attenuator.

The resistors that were compared in the above test were the series resistors that the signal is now going through, with the original surface-mount ones (used in the stepped attenuators themselves) now acting as shunts, going to ground.

Therefore, what I'm listening to now effectively is the sound of the AudioNote Tantalums - and the sonic improvement is significant!

Marco.

[Marco]

Looks like you had fun. Glad your happy with it now.

Yes, but the Z-Foils might make it there in yet!

Marco.

[Marco]

Weird that just a choice of resistor can have such varying effects Marco.

You better believe it, Geoff. Everything I've reported was genuinely heard by both of us. I didn't realise that different resistors could have such a pronounced effect either, but clearly they do!

Marco.

[User211]

Annoying result as in good resistors cost too much.

This sort of thing makes you realise just how complex getting a decent sound is. This is magnified far more in complex circuits, where the number of component interactions increases by a big factor.

[walpurgis]

You better believe it, Geoff. Everything I've reported was genuinely heard by both of us. I didn't realise that different resistors could have such a pronounced effect either, but clearly they do!

Marco.

Wish I'd been there to hear all that. It may (and may still) have influenced my selection of resistors for a couple of projects.

It makes one realise why some makes appear costly for seemingly the simple designs they manufacture. Audio Note spring to mind. I'm sure they spend a lot of time and money actually listening to the effects of every discrete part of what they make.