Following your link from the NAP140/Ebay kit thread, Jeff, I admit that I have very little listening experience with present day Naim models. It seems most of us are still looking at and cloning historical models because the only known official schematic was that of NAP250 power amp. boards until recently. I did listen to one quite often at social occasions and on many quiet evenings, enjoying my host's collection of good quality classical and pop recordings that included half-speed masters etc and a fully kitted Linn Sondek.
It was still difficult though, to get comparable coupling to the amplifiers from preamps that were different to Naim models. You had to use their products together for a few reasons and the smoother top end was one I recall clearly but the preamps themselves were quirky and somewhat incompatible with some of their own models too. SNAPS outboard power supplies, when they arrived, added confusion to what did and didn't work well together.
I mostly listened with a NAC 32 preamp coupled normally to and powered by a chrome bumper version of NAP250, alternatively to NAP140 and NAP120 models which were then owned by friends. I think the review linked below nails it for the NAP250 amp. but I have no time for the NAC12. It works fine but it's microphonic in a bad way because it employed reed relay signal switching, or at least the first issue version did: Naim NAC 12/ Snaps/NAP 250 (Vintage) | Hi-Fi News
It was still difficult though, to get comparable coupling to the amplifiers from preamps that were different to Naim models. You had to use their products together for a few reasons and the smoother top end was one I recall clearly but the preamps themselves were quirky and somewhat incompatible with some of their own models too. SNAPS outboard power supplies, when they arrived, added confusion to what did and didn't work well together.
I mostly listened with a NAC 32 preamp coupled normally to and powered by a chrome bumper version of NAP250, alternatively to NAP140 and NAP120 models which were then owned by friends. I think the review linked below nails it for the NAP250 amp. but I have no time for the NAC12. It works fine but it's microphonic in a bad way because it employed reed relay signal switching, or at least the first issue version did: Naim NAC 12/ Snaps/NAP 250 (Vintage) | Hi-Fi News
I believe the old Naims worked with most speaker cables just fine. Certain high capacitance, typically exotic audiophile, cables would squeeze stability margins too much. I think high capacitance cable is relatively hard to find.
You really don’t need fancy cables...from the “marketing hype“ zone...to enjoy audiophile performance. E.g. something akin to QED79 is great. More important is connector quality. Low cost cable + expensive banana plugs, soldered.
Pub quiz: does anyone know why Julian omitted the inductor? Have a guess.
The idea to omit the output inductor was not only based on marketing decisions, as we might think.
JV thought that since we will have to use a loudspeaker cable anyway, which would then provide the necessary inductance - together with the wirewound output resistor, which also linearizes the damping factor of the amp. Therefore the amplifier forms a complete unit together with the cable, the cable gets part of the amplifier. The recommendation was - as far as I remember - min 3m.
This is a completely different approach as the high capacitance cables which are still very common (most high end cables have high capacitance and low inductance, or the in-famous CAT5 cable experiments) and which are somehow used to "tame" some amplifiers. Naim amplifiers definitely never really worked with these cables anyway - this is my experience with several attempts.
And, although this Naim approach might "force" potential buyers into buying Naim cables, it nevertheless is a viable way of solving a never-ending discussion about cables (from obvious to snake-oil). Naim did otherwise never really care about cables anyway, as long as they did fulfill the basic criteria. Remember, that the connection cable from a HiCap to the NAP250 was a simple unshielded mains cable with three wires (0.75mm2, 4pin DIN to 3pin XLR).
I am talking about the good old eighties here, of course, and I have little experience what Naim does nowadays.
JV thought that since we will have to use a loudspeaker cable anyway, which would then provide the necessary inductance - together with the wirewound output resistor, which also linearizes the damping factor of the amp. Therefore the amplifier forms a complete unit together with the cable, the cable gets part of the amplifier. The recommendation was - as far as I remember - min 3m.
This is a completely different approach as the high capacitance cables which are still very common (most high end cables have high capacitance and low inductance, or the in-famous CAT5 cable experiments) and which are somehow used to "tame" some amplifiers. Naim amplifiers definitely never really worked with these cables anyway - this is my experience with several attempts.
And, although this Naim approach might "force" potential buyers into buying Naim cables, it nevertheless is a viable way of solving a never-ending discussion about cables (from obvious to snake-oil). Naim did otherwise never really care about cables anyway, as long as they did fulfill the basic criteria. Remember, that the connection cable from a HiCap to the NAP250 was a simple unshielded mains cable with three wires (0.75mm2, 4pin DIN to 3pin XLR).
I am talking about the good old eighties here, of course, and I have little experience what Naim does nowadays.
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Who said that the inductor cannot be used?
I remember that the Naim marketing department in the 80ies stated that the Naim amplifier with the inductor sound worse than without. But this may only have been the usual bla-bla from the local wholeseller. Propaganda and tech babble was as ubiquitous and omnipresent in those days as it is now perhaps.
There are plenty of other amplifiers which do not use that part anyway (f.e. most capacitor coupled amplifers like the Nero/Nytechs). In contrast to the absolutely necessary Zobel output parts the coils seem to me more a saftey feature than actually really needed for proper function. I have made many amps with and without these coils with no real problems. But Naim explicitely stated in the manual that only those inductive cables should be used and other (presumably high capacity) cables have to be avoided not to infrige the warranty. Naim, at least in this country, refused to repair the amp if it got damaged by using different cables (like the partly crazy "Nordost-Style" types of DIY cables which then were in fashion).
I remember that the Naim marketing department in the 80ies stated that the Naim amplifier with the inductor sound worse than without. But this may only have been the usual bla-bla from the local wholeseller. Propaganda and tech babble was as ubiquitous and omnipresent in those days as it is now perhaps.
There are plenty of other amplifiers which do not use that part anyway (f.e. most capacitor coupled amplifers like the Nero/Nytechs). In contrast to the absolutely necessary Zobel output parts the coils seem to me more a saftey feature than actually really needed for proper function. I have made many amps with and without these coils with no real problems. But Naim explicitely stated in the manual that only those inductive cables should be used and other (presumably high capacity) cables have to be avoided not to infrige the warranty. Naim, at least in this country, refused to repair the amp if it got damaged by using different cables (like the partly crazy "Nordost-Style" types of DIY cables which then were in fashion).
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Keeping a high NFB circuit stable in to any load is tricky. A series resistor helps. 0.22 ohms is large compared to most. I imagine Naim would have used even larger if they could have got away with it in the press. It’s one of those specmanship things where smaller is deemed better without actually sounding better.
AFAIK Krells did not use output coils either, nor output resistors. Why? Low NFB designs. D’Agostino said he used a capacitor box (a bunch of different caps and a switch) to check his amp was stable into any capacitive load, right at the output terminals.
So why might a coil make a Naim sound worse? Think about what is different between a coil and a cable.
AFAIK Krells did not use output coils either, nor output resistors. Why? Low NFB designs. D’Agostino said he used a capacitor box (a bunch of different caps and a switch) to check his amp was stable into any capacitive load, right at the output terminals.
So why might a coil make a Naim sound worse? Think about what is different between a coil and a cable.
A problem is that the coil current variation is pretty big so a ferrite core would be pretty non-linear and tend to saturate. So a relatively large, air-core coil is used (a resistor is like an air-core, magnetically). This is linear but then the magnetic field it produces spreads far and wide.
In tube amps, which had a power transformer (iron core) and a speaker output transformer (iron core), the magnetic field from the power transformer was often strong enough to induce hum in the speaker transformer and you could hear it. To minimize this coupling, the transfomers would be positioned at right angles to one another.
In tube amps, which had a power transformer (iron core) and a speaker output transformer (iron core), the magnetic field from the power transformer was often strong enough to induce hum in the speaker transformer and you could hear it. To minimize this coupling, the transfomers would be positioned at right angles to one another.
This is also where the Torpedo head-phone amps got their shape (and name): they're long and skinny to keep the output transformers far enough away from the power transformer.
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A toroid is a lot better. How many amps do we see that use toroidal output inductors? I’ve never seen one. Presumably, due to cost. Naim was an early adopter of toroidal mains transformers.
Toroids are not perfect: https://worldradiohistory.com/hd2/I...DX/IDX/80s/Ham-Radio-198505-OCR-Page-0121.pdf
Many thanks for the great work!!!
I can open them in kicad 5.1.6 after manually removing the sections "stackup", "max_error" and "defaults" from the *pcb-files. However the footprint files are missing: please would you be so kind to provide them?
I can open them in kicad 5.1.6 after manually removing the sections "stackup", "max_error" and "defaults" from the *pcb-files. However the footprint files are missing: please would you be so kind to provide them?