This audio cable business is getting out of hand...

[Julf]

Nice read. I have a question and it maybe a little silly but are these numbers still correct meaning the article was written a long time ago and now we have digital amps so do the newer style amps behave the same way the amps used in this article? I am assuming they are like class ab or something.

Are you talking about class D amps? They are actually not digital, but analog pulse width/pulse density modulation.

Anyway, they behave the same with regards to cables.

 

[xr100]

now we have digital amps so do the newer style amps behave the same way the amps used in this article? I am assuming they are like class ab or something.

The reason they are called Class "D" is because it was the next letter in the alphabet after A, B, and C.

Note that Class D amplifiers can have greater interactions with the speaker load due to large value series inductors before the output.

 

[Not Insane]

Nice read. I have a question and it maybe a little silly but are these numbers still correct meaning the article was written a long time ago and now we have digital amps so do the newer style amps behave the same way the amps used in this article? I am assuming they are like class ab or something.

Thanks

I happened on that article about a year ago. The most fascinating thing I found about it is that you can't post it on a certain other audio site without the thread getting deleted. I don't know if it is the article or the arguments it creates.

It is one of those rare instances where the political "thought process" is deeply apparent in the audio industry. Sometimes all you can do is lead a horse to water.

 

[Julf]

The reason they are called Class "D" is because it was the next letter in the alphabet after A, B, and C.

Indeed.

Note that Class D amplifiers can have greater interactions with the speaker load due to large value series inductors before the output.

Depends on if the output choke/inductor is part of the feedback loop or not.

 

[Krusty09]

Yes I guess I meant class d . I wasn't sure if the interaction of amp and speaker load acted same way but it sounds like it does.

Thanks for the info.

 

[DonH56]

Nice read. I have a question and it maybe a little silly but are these numbers still correct meaning the article was written a long time ago and now we have digital amps so do the newer style amps behave the same way the amps used in this article? I am assuming they are like class ab or something.

Thanks

As noted the D is class D is not for "digital". Their output is an analog PWM (or PFM, or mix) signal similar to the output of a DSD DAC. Class D has been around a long time and was next after A, B, C amplifier classes were annotated. See e.g. https://www.audiosciencereview.com/forum/index.php?threads/class-d-amplifiers-101.7355/ for an intro into how they work.

Output impedance can vary but is not really relevant to what sort of speaker cables you use. Some exotic cables with very high capacitance or inductance may cause issues with some amplifiers and/or amp/speaker pairings but for normal cables and the vast majority of systems it is not worth thinking about. I don't.

The issues with cables, unless miles long, are loss and higher impedance (resistance) impacting frequency response due to interaction among power amplifier output impedance, speaker wiring, and the crossovers and drivers inside the speakers. For those parameters, and in fact most parameters, nothing is different among audio amplifier topologies (A, B, AB, D, G, H, I, T -- at least those are the only ones I have seen! C, E, and F are used mainly for RF amps, never audio, IME).

So, yes.

HTH - Don

 

[Not Insane]

The reason they are called Class "D" is because it was the next letter in the alphabet after A, B, and C.

My Hitachi HMA8500 is class H. I think the H stands for something, though.

 

[DonH56]

My Hitachi HMA8500 is class H. I think the H stands for something, though.

Class G and H add varying power supply rails to (usually) class A or AB designs. As the signal increases, power supply voltages (rails) are raised to provide extra power on demand. When signals are low, the amp runs cooler, as the extra (higher) voltage is only applied when needed.

Class G switches between two (or sometimes more) voltages, like a normal lower rail and higher-voltage rail on demand.

Class H continuously varies the supply rails with the signal, sort of a tracking power supply, instead of using discrete steps.

HTH - Don

 

[xr100]

Output impedance can vary but is not really relevant to what sort of speaker cables you use.

Indeed. However, as you say the primary purpose of using "suitable" speaker cables is to avoid inadvertent changes to speaker frequency response, I thought it worth mentioning in the context of this query that not all Class D amplifiers are well behaved in this respect. (In which case, the problem of unwanted amplifer output/cable/crossover/driver interaction is not necessarily obviated.)

BTW, to quote from Tomlinson Holman (of Lucasfilm/THX at that time) in Speaker Builder magazine (Sept/Oct 1990 issue):

"We designed the cable for frequency response variations. Wire gauge is most important. In theaters where we have very long runs, up to 150 to 250 feet, we have to get down to 12- and 10-gauge cable, respectively. I set our standard as plus/minus one eighth of a dB ripple, due to impedance variations. That's probably inaudible."

 

[GeorgeWalk]

Quote from another audio forum (PSC+ is some sort of AudioQuest magic):

"You don't want to have anything below PSC+ in your system. And it doesn't matter that it's the subs because the cables sound even when they are not connected (and powering) any component. To all of you, guys, here... do the experiment: get a spare power cord, plug it into your distributer/power filter (or even into the wall) next to your amps (or a preamp) and put the other end of this cord on the floor (do not connect it to anything!). Now sit down and listen to some music. Next, unplug this cord. Listen again. See what I'm talking about? Power cords have a distinct sonic signature even when they are not powering anything. Their mere presence makes the difference!"​

WTF???

 

[DonH56]

Indeed. However, as you say the primary purpose of using "suitable" speaker cables is to avoid inadvertent changes to speaker frequency response, I thought it worth mentioning in the context of this query that not all Class D amplifiers are well behaved in this respect. (In which case, the problem of unwanted amplifer output/cable/crossover/driver interaction is not necessarily obviated.)

BTW, to quote from Tomlinson Holman (of Lucasfilm/THX at that time) in Speaker Builder magazine (Sept/Oct 1990 issue):

"We designed the cable for frequency response variations. Wire gauge is most important. In theaters where we have very long runs, up to 150 to 250 feet, we have to get down to 12- and 10-gauge cable, respectively. I set our standard as plus/minus one eighth of a dB ripple, due to impedance variations. That's probably inaudible."

Most class D amplifiers these days are similar to their A/AB brethren, all limited by the loop response, with rising impedance at high frequency. Higher switching rates and improved feedback/feedforward designs that close the loop around the output filter have pretty much closed that gap IME. But, again IME, the problem given a reasonable speaker cable (the OP's question), is more with the speaker/amp interaction and less with the cable since the cable contributes only slightly to the impedance (and often helps by adding resistance to reduce the output circuit Q).

I met Tom a few times, did you know him? He did some really neat things that he never seemed to get the credit for -- a behind the scenes kind of guy. As a "small world" moment I spoke for a while with his son about a job in bioengineering, my original career desire, many years ago. I didn't take the job but we did talk about audio stuff for a while.

 

[Julf]

WTF???

If you think that is bad...

When I think of signal, I first think of what I see on an oscilloscope or spectrum analyzer. I look for known problems and design technologies to reduce measurable distortion. But then I go deeper, as if I had a Hubble Space Telescope. I think of what it is that makes up signal- electrons. Electrons too small to see individually on an oscilloscope, only their combined motion can be represented; just as distant galaxies look solid when viewed through a backyard telescope. And just as distant galaxies are made up of billions of stars with trillions of planets and trillions upon trillions of moons orbiting these planets all having an effect on each other, so too is “signal” made up of trillions of subatomic particles (electrons) traveling through billions of molecules, made up of trillions of atoms, all of which influence the collective state or behavior of the electrons that make up signal. It is the combined effect of perhaps an infinite number of variables at the atomic and sub-atomic level that determine the quality and nature of what we as humans ultimately perceive as music from our audio systems.

 

[mhardy6647]

Since someone mentioned Class D (i.e., PWM/"Switching" amplification) -- Class D for audio amplification traces its (commercial) history back to, at least, Sir Clive Sinclair in the mid 1960s.

http://www.vk6fh.com/vk6fh/sinclair x10.htm

source: https://www.americanradiohistory.co...ronics/60s/1967/Radio-Electronics-1967-09.pdf (page 72 of the magazine)

 

[Julf]

Since someone mentioned Class D (i.e., PWM/"Switching" amplification) -- Class D for audio amplification traces its (commercial) history back to, at least, Sir Clive Sinclair in the mid 1960s.

Ah, yes, I have a fair bit of his stuff (even two C5s), but have been spared the X-10...

 

[xr100]

My Hitachi HMA8500 is class H. I think the H stands for something, though.

The specifications for the Yamaha NS-SW300 powered subwoofer (one of which I own) state that its power amplifier is a "High Efficiency Class D" type.

However, looking in the service manual, the block and schematic diagrams label it as a "PS amplifier"--whatever that means?

I can't see that it could possibly be a Class D amplifier, with its conventional topology, including Darlington bipolar output transistors (Sanken STD03N/P.)

There is obvious circuitry to modulate from the supply rails to them, but figuring out its operation is beyond me. I suspect this follows the output level so it's Class H; certainly the rear heatsink is invariably cold to touch.

But it certainly seems that the power amplifier "alphabet soup" can be misleading.

 

[mhardy6647]

FWIW, I am pretty sure Class G was (initially) mostly a Hitachi thing, and Class H was Soundcraftsmen's.
Not sayin' there might not have been Class H Hitachi hardware... but I am skeptical

HitachiSR2004 by Mark Hardy, on Flickr

source: https://www.americanradiohistory.com/Archive-High-Fidelity/70s/High-Fidelity-1977-09.pdf (page 77 of the magazine)

source: https://www.americanradiohistory.com/Archive-Audio/80s/Audio-1986-Equipment-Directory.pdf (multipage ad section)

source: https://www.dynacord.com/technology.php?id=24

 

[xr100]

Since someone mentioned Class D (i.e., PWM/"Switching" amplification) -- Class D for audio amplification traces its (commercial) history back to, at least, Sir Clive Sinclair in the mid 1960s.

Indeed, with the Class "D" nomenclature predating this.

Apparently the Sinclair Class D amplifier performance was appalling, so whether you want to call it an "audio" amplifier...

 

[Not Insane]

The specifications for the Yamaha NS-SW300 powered subwoofer (one of which I own) state that its power amplifier is a "High Efficiency Class D" type.

However, looking in the service manual, the block and schematic diagrams label it as a "PS amplifier"--whatever that means?

View attachment 45294

I can't see that it could possibly be a Class D amplifier, with its conventional topology, including Darlington bipolar output transistors (Sanken STD03N/P.)

There is obvious circuitry to modulate from the supply rails to them, but figuring out its operation is beyond me. I suspect this follows the output level so it's Class H; certainly the rear heatsink is invariably cold to touch.

But it certainly seems that the power amplifier "alphabet soup" can be misleading.

The claim to fame of the "class H" amplifiers, IIRC was that they could give a pretty solid "fairly continuous" power output double that of their RMS power. So mine was "200 WPC", but really "400 WPC."

On a side note, and demonstrating my stupidity at the time, around the turn of the century one channel went out on my HMA8500. I was no longer using it as a bottom to my bi-amped ESS AMT 1B monitors as I lost those speakers in a divorce a couple of years before. I was in a sort of "downsizing" mode at the time. So once I determined that, yes, one channel was dead, I tossed it in the trash. Dead serious.

My problem was exacerbated by the fact that at the time tech was undergoing some major changes and I was slipping into a "It's cheaper to replace than to fix" mindset.

I still have the HMA7500 and the HCA7500 pre-amp though.

 

[xr100]

My Hitachi HMA8500 is class H. I think the H stands for something, though.

According to https://www.kenrockwell.com/audio/hitachi/hma-8500-mk-ii.htm, the HMA-8300 is Class G. It says that the HMA-8500MkII is Class AB. Interesting measurements on that page, too.

To quote from Douglas Self ("Audio Power Amplifier Design Handbook"):

"Class-H is occasionally used to describe Class-G as above; this sort of confusion we can do without."

 

[Not Insane]

According to https://www.kenrockwell.com/audio/hitachi/hma-8500-mk-ii.htm, the HMA-8300 is Class G. It says that the HMA-8500MkII is Class AB. Interesting measurements on that page, too.

Ha! that's what I get for working from memory.

I must have been converting it to "H" for "Hitachi".