Does anyone care to ask an amplifier designer a technical question? My door is open.

What is the role and importance of significantly upgraded power cords in component design? It seems to me that the PC is a fundamental part of the electronic device and that the manufacturer should optimize the cord for the device in building it. What are your thoughts on the matter as someone who actually builds electronics?

There is a voltage drop across any power cord that can influence the output power of the amplifier. What is less well understood is that it can affect distortion too. Much depends on the amplifier design of course, but these effects are measurable and no surprise in some cases that they can be heard too.

Question about the effects of different impedance settings and phono cartridges.

The loading is there for the preamp, not the cartridge! I know this sounds counterintuitive but here's how it works:
The cartridge has an inductance and the tone arm cable has a capacitance (along with the input capacitance at the preamp). Together they form a tuned circuit. With a Low Output Moving Coil cartridge, this resonance can be at several MHz. If the preamp is unhappy about Radio Frequency Interference (RFI) at its input, it will affect the sound- the additional distortion will likely make it bright. The loading resistor detunes the resonant circuit and thus prevents the RFI. Problem solved?
The downside is usually two things: 1st, by loading the cartridge in this manner you are causing it to do more work. The energy has to come from somewhere and that means the cantilever will be more stiff- less able to track higher frequencies! The second problem is that (generally speaking) a preamp that requires loading to sound right probably also has stability issues, usually because the designer hasn't sorted out the facts in the 2nd paragraph below your quote. This instability often results in excess ticks and pops that **actually would not be audible were the preamp actually stable**!

This latter fact comes as a surprise to many people, but when you are exposed to a stable phono circuit, it is very relaxing to not be hearing so many ticks and pops. This has nothing to do with bandwidth BTW. For more on this seehttp://www.hagtech.com/loading.htmlandhttps://www.whatsbestforum.com/threads/cartridge-loading-a-misnomer.15077/

@ramtubes

You wrote the following regarding ARC:

Im sorry, but you asked. I'm sorry to be so negative about ARC, but I was a dealer for them from 1975 to 1980. If you have not heard about the "pink papers" thats a story in itself. ARC treats dealers with a heavy hammer, large opening order and threats if you do not follow the party line. Bill called us up one day because he heard we were doing A/B comparisons for our customers. He said "stop immediately or I will pull the line"

Of course I respect your technical experience and ARC anecdotes, but let me just weigh in on ARC.  Perhaps I have been crazy lucky, but I have owned ARC gear for quite awhile and my anecdotal experiences are quite different than yours.  

In particular, as far as linestages go, I've owned the Ref 3, Ref 5, Ref 5SE and now currently, the Ref 6.  As far as amps go, I've  owned the VS110, the VS 115, the Ref 150 and now the Ref 150SE.  My CDP is the Ref CD-8 and my phone pre is the PH-8.    

To date, I have had only one problem; namely:  blown bias resisters in my older amps.  Other than that, no other problems whatsoever.  In the case of my Ref 150SE, I am running KT-150s. So far, … fingers crossed, ... no problems with arc'ing or blown bias resisters.

As far as bench tests are concerned JA tested the Ref 150 amp, an earlier version of the Ref 150SE.  Here is his report:    https://www.stereophile.com/content/audio-research-reference-150-power-amplifier

Notably, JA reported that "Fig.1 indicates that the Ref150 has a wide bandwidth, particularly into loads higher than the nominal tap value, which correlates with a well-defined 10kHz squarewave (fig.2). While this graph reveals a small but critically damped overshoot on the leading edges of the waveform, presumably due to an ultrasonic transformer resonance, no ringing is visible."  By comparison, the Ref 75 did not test as well.  And you noted the same in your prior post.  

I can't speak to whether the circuits in my ARC gear are elegantly simplistic or labyrinthically complex .  I am not a EE.  But so far, my gear is holding up pretty well.

As far as SQ is concerned, … no comment.  I have not had an opportunity to A/B ARC gear against any other brands.  But to my untrained ears, my gear seems to sound OK.

Perhaps your views about ARC might change if you road tested some of their current models.  I understand that ARC opted to simplify the circuits in its latest offering, the Ref 160 mono blocks.  Haven't heard them, but it doesn't matter.  I am not going to drop $30K on mono blocks.

Btw, I owe you two quads of KT-150s for matching.  The 3rd party vendor from whom I purchase the tubes didn't match the tubes to ARC spec.

Regards,

Bruce

Roger,

This has been a great and informative thread. Thank you for sharing your time, knowledge, and insight. I've learned a lot.

A question for you: any further thoughts on ARC's M300 monoblocks? They're a fairly...unique design and perhaps the best evidence of your view that WZJ's ARC designs were often over-complicated. That said, I enjoy them, and they've only blown up a couple times over the years. Any further comment?

(As to your point about the reliability of ARC products, I also have a pair of Ref 600s and pray every time I switch them on that they don't go up in flames.) 

One other question: for those of us with super-inefficient speakers like Magnepans, what should we be looking for in an amplifier? 

VAC seems to be doing some good work these days. I have worked on one of their big preamps, it was nice but picked up hum from a power amp 2 feet away. We were surprised.

Yes, we were! Hey Roger. Great thread!
Bill

Ralph,
Thanks.
I didn't totally follow all that, but that's due to my level of ignorance.