A capital letter would help if you consider it that important. I’m not sure whether you wish to lecture me on my grammar, amplifier design or what Julian Vereker did (or in this part of the amplifier, the 0R22, what John Linsley Hood did first).
I don’t know what your 2nd sentence is trying to say but the story is this:- The capacitance of the dominant pole shows up as an inductive output impedance and, as such, is at risk of resonating with capacitances showing up in the load. The risk is highest in the stopband region where the capacitances of the devices dominate the transfer function and especially where they can change value substantially depending on conditions. The usual inductor is there to keep the load looking inductive and therefore circumvent this issue. One of the alternatives (and they are not always required) is to introduce a zero in the form of a series resistor to extend the “normal” behaviour of the amplifier to a higher frequency and have the available loop gain fall below unity before the problem conditions take hold and to meet stability criteria. Either will work, though I’m dying to hear why “the inductive element deteriorates the overall sound quality” if it doesn’t kick in until perhaps 70 or 100kHz.
But the absence of a Zobel network hasn’t been the case since the chrome bumper days. You can use any cable with DR amps and New Classic and nearly any with Olive and pre DR Classic.
Don’t take my word for it. Take the words of Steve Sells at Naim. There’s more from Naim on this topic in that thread but at 6500 posts long, this it what I could find easily.
@Richard.Dane I was sure there was mention by you of reviewing the FAQ to make the topic on cables less absolutist and more in line with current information from Naim.
FZ, it’s my understanding that there are Zobel networks but it’s the added inductance that is left out with Naim power amps.
As for the latest amps being able to use any speaker cable, while it may be true that they are even more robust these days and won’t blow up with any speaker cable, it does not mean that they will perform optimally and sound at their best with any cable; so Naim’s recommendations still stand.
Yes, updating the FAQ is on the to do list, but I wanted some more feedback from Naim first.
When naim has open up on cables from the NC, and with full balanced to 350s, I have use All nordost cables from power cords all the way to speaker cables , it’s just sound so much openness , depth , huge soundstage, clarity , micro details, punch , synergy , decays are beautiful , precise placing of all instruments, rich music output ,vocal are very very bodied and layered , and many more added values that makes the whole presentation of music to another level that naim has wanted the NC to be .
This is what I did with the cable works to my 332 and 350s and rest of my components . Fully utilised all balanced connections that naim has brought in to the NC
Haha! You may be using the term Zobel Network correctly. Too many people refer to the Boucherot cell as the “zobel”, which has made the description very imprecise.
Yes, I think the whole question is completely outdated and actually, even pre 1980, I doubt Naim fared any worse than any other amp manufacturer. Certainly I’ve seen more blown up Musical Fidelity amps than I have Naims; by some margin, too.
A while back I did some modelling of the core NAP250 circuit (ie. without the response shaping filters around it) and was surprised by quite how nicely behaved it was in that rolloff at the top end. There are a LOT of limitations to this sort of modelling, and it’s much more sensitive to the choice of components IRL than it is on the screen, (and I don’t have a model for their output transistors) but the first impression was quite how textbook it looked. Nice smooth rolloff with no discontinuities all the way down. This region can be something of a mountain range in some amps and you generally don’t get a nice looking result at the first try! That’s with the circuit that does the rounds on the internet, which is as old as the hills. I don’t believe that much has changed since but the point is that it never was a dog.
Yes, the inductor is left out, as is a resistor of usually 2R2 to 12R that most manufacturers put in parallel with that inductor. That combination is replaced by a single resistor of approximately the value of what the resistance of an “ordinary” cable might have been.
Really not much difference if you a driving 8ohms speakers, but Naim amplifiers are capable of going down to 2ohms speaker loads, now if you look at the effect of 0,01mH inductive load at 2Ohms speaker load you will see a phase shift of 21 degrees at 15kH (that i can still hear). In addition the amplifier damping factor is negatively influenced too at higher frequencies and the inductor’s impedance increases, in our case goes to 0.94Ohms at 15kHz so perhaps you can figure out the change in the damping factor yourself. Both these effects start kicking off above 1kHz.
Fortunately few, if any, tweeters present a load of 2 Ohms at 15k. Also, they usually have an inductance in about the same region; do you hear that as well? You also assume that linear phase is better - something for which there is no proof. Moreover, even if that were to be the case, you don’t just look at the phase shift of a single component but of the system as a whole! So, if one assumes that the transfer function of a whole amplifier is a 3rd Order Bessel LP then you are going to NEED that inductor to provide its phase shift so as to keep the whole phase response straight.
Damping factor is a terrible way to model how speakers and amplifiers work together, for numerous reasons. It should be excised from everyone’s usage, as should the image of the amplifier somehow having a vice-like grip over the drivers. It is completely meaningless in the setting you have chosen and I have no clue what you have in mind here.
Thanks for the tip that these things start happening above 1kHz because I wouldn’t have got there by myself. How does less than a tenth of an ohm of impedance impose itself on the loudspeaker at 1kHz?
Amp output stage oscillation caused by capacitive reactance is something that becomes a problem at frequencies higher than 40kHz (depending on load variables)
Naim have been rolling off upper frequency at audio band limits in the preamp stage for a number of years. So the risk of poweramp output stage instability is no longer an issue
I would try out any cables from any makes since naim has open up accepting any cable makes , so I am making use of this concepts to explore other makes , and I landed with Nordost, exploring other cable makes is interesting and let’s you get to listen to more sound DNA, while keeping the DNA of naim
Nearly 1.5dB down at 20kHz and -3dB at 25kHz? I don’t believe it. I know John Atkinson has some limitations in technique when it comes to measuring speakers but I didn’t know it extended to amplifiers. (Dreadful choice of scale, too!) I know these circuits pretty well, and I know what the shape and bandwidth of the “time-aligned” filter is, from the horse’s mouth, and it shouldn’t look like this. This cannot be the control amp alone. The rolloff should be some long way to the right of where it currently is.
The system looks fantastic. I have to say that I’m hugely surprised that Nordost cables work well as that’s really very last place I would look. But I’m delighted for you that they do.
I think it would be fair to say I am biased against them as I have a pretty much lifelong aversion to Litz cables. I don’t listen to them that often and perhaps hear a set once every 10 years or so, but that’s enough for me to ignore them for the subsequent decade. I just don’t hear this additional clarity and, if anything, the high frequencies to me are less precise and seem to me to be in a sea of hiss or tizz. But, as we say, each to his own and whatever floats your boat.
Actually I am super curious to know what your system sounds like. A fully Nordosted Naim system might actually point out some of the merits of Nordost that I have hitherto been unable to find.
That’s with the circuit that does the rounds on the internet, which is as old as the hills. I don’t believe that much has changed since but the point is that it never was a dog.
