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Topic: First watt (Read 6743 times) previous topic - next topic
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First watt

I took a look at soundandvison website and I noticed that some expensive power amps had higher distortion at 1W than some AVRs.

Take for example the Marantz 7008 :



And the Cary Audio power amp 7.125 :



According to the testing the Marantz has THD+N from the CD input to the speaker output lower than 0.008 percent at 1 kHz when driving 2.83 volts into an 8-ohm load. The Cary power amp has THD+N less than 0.010 percent at 1 kHz when driving 2.83 volts into an 8-ohm load using the RCA input. Now the difference is probably inaudible, but does this mean that the Marantz is a technically better performing amp with lower distortion?

The Cary power amp is around $5000. The Marantz is $1990, plus it has loads of features and extra channels. Seems strange that an AVR can outperform a very expensive dedicated power amp.

First watt

Reply #1 –
How do you know it's distortion and not noise?

First watt

Reply #2 –
Quote from: Yahzi on
Seems strange that an AVR can outperform a very expensive dedicated power amp.


I don't know about the cost of those two devices, but its quite reasonable that a lower power device will have better performance running at lower power levels than one designed for higher power.  Generally in amplifier circuits, gain and power directly tradeoff against noise.

First watt

Reply #3 –
I can't answer why...  But it's a percentage and at very low levels where you can barely hear the music, the distortion is even quieter and you aren't going to hear it.   

Quote
Now the difference is probably inaudible...
No "probably" about it.  I'm not sure where the threshold of audible harmonic distortion is at 1kHz, but I'm pretty sure it's above 1%.  In fact, I've NEVER heard ANY distortion from an amplifier that wasn't broken or being overdriven.


Quote
...but does this mean that the Marantz is a technically better performing amp with lower distortion?
I don't know...  Is an audio amplifier that goes to 1MHz or higher "technically better" than an audio amp that "only" goes to 20kHz?  Since the amplifier is for audio purposes, I'd say no.

Quote
The Cary power amp is around $5000. The Marantz is $1990, plus it has loads of features and extra channels. Seems strange that an AVR can outperform a very expensive dedicated power amp.
Obviously an "audiophile" product.  Higher prices tend to make the product more attractive, especially to audiophiles.    Plus, producing and distributing in small quantities is MUCH more expensive than mass manufacturing, and you need a higher per-unit profit when you sell in smaller quantities.. 

You should be able to get a power amp for less than 50 cents per watt.  The bigger amp you buy, the more power watts-per-dollar.  Here's a Crown Amplifier that has 1200 Watts per channel at 8 Ohms or 2100 Watts at 4 Ohms, and it's $2000 USD.  I don't know what the distortion specs are but Crown is well respected company and I'm sure there is no audible distortion as long as you don't drive the amplifier into clipping.

First watt

Reply #4 –
Quote from: Yahzi on
If the THD+N is lower, I assume the noise and distortion is lower. If the Marantz has a lower THD+N, isn't that what it means?

Your interpretation of THD+N as noise and distortion is flawed. This should be read as noise plus distortion. These are two separate and independent flaws in the output of an amplifier, and while distortion is strongly influenced by the signal level, noise is not. It is only because it is more difficult to measure each separately than to combine them that THD+N is the usual spec.

If you look at your curves you will see THD+N rising at either end. Distortion increases rapidly at high signal levels, causing the rise toward the right.

In a well designed amplifier distortion is negligible at low signal levels and noise is constant. However, since the THD+N is ratioed to a smaller and smaller signal level, The curve rises rapidly toward the left as well, and is infinite at zero signal.

First watt

Reply #5 –
Quote from: pdq on
Quote from: Yahzi on
If the THD+N is lower, I assume the noise and distortion is lower. If the Marantz has a lower THD+N, isn't that what it means?

Your interpretation of THD+N as noise and distortion is flawed. This should be read as noise plus distortion. These are two separate and independent flaws in the output of an amplifier, and while distortion is strongly influenced by the signal level, noise is not. It is only because it is more difficult to measure each separately than to combine them that THD+N is the usual spec.

If you look at your curves you will see THD+N rising at either end. Distortion increases rapidly at high signal levels, causing the rise toward the right.

In a well designed amplifier distortion is negligible at low signal levels and noise is constant. However, since the THD+N is ratioed to a smaller and smaller signal level, The curve rises rapidly toward the left as well, and is infinite at zero signal.


But can you agree that the noise + distortion is lower on the Marantz than the Cary power amp based on the bench test results?

First watt

Reply #6 –
Quote from: Yahzi on
Quote from: pdq on
Quote from: Yahzi on
If the THD+N is lower, I assume the noise and distortion is lower. If the Marantz has a lower THD+N, isn't that what it means?

Your interpretation of THD+N as noise and distortion is flawed. This should be read as noise plus distortion. These are two separate and independent flaws in the output of an amplifier, and while distortion is strongly influenced by the signal level, noise is not. It is only because it is more difficult to measure each separately than to combine them that THD+N is the usual spec.

If you look at your curves you will see THD+N rising at either end. Distortion increases rapidly at high signal levels, causing the rise toward the right.

In a well designed amplifier distortion is negligible at low signal levels and noise is constant. However, since the THD+N is ratioed to a smaller and smaller signal level, The curve rises rapidly toward the left as well, and is infinite at zero signal.


But can you agree that the noise + distortion is lower on the Marantz than the Cary power amp based on the bench test results?

Yes, at low signal levels.

First watt

Reply #7 –
Let me chime in ...

Quote from: Yahzi on
I took a look at soundandvison website and I noticed that some expensive power amps had higher distortion at 1W than some AVRs.

As has been noted before, at the lower end it is noise that dominates.
This is a speculation, but it seems that the Cary amp has an overall lower signal-to-noise ratio. Higher distortion at higher power output as well.


Quote
Now the difference is probably inaudible, but does this mean that the Marantz is a technically better performing amp with lower distortion?

Yes but with lower THD+N.

Now I can read into the future and know that audiophiles will tell you of distortion profiles and euphonic distortion .... which is nonsense:
a) speakers clearly dominate this,
b) distortion sounds awful,
c) less distortion sounds less awful than more distortion,
d) Rod Elliott has shown with valve amps that "supposedly 'nice' even order distortion creates more intermodulation products than the 'nasty' odd-order distortion",
(when manufacturers of amps with lots of even order distortion show graphs they show single tone measurements where conveniently there is no intermod)
e) intermodulation distortion is (audibly) the worst,
f) Keith Howard wrote on Stereophile, based on listening tests:
Quote
Unless and until somebody comes up with a "magic" pattern of nonlinearity that truly enhances sound quality, I will believe euphonic distortion to be a fantasy. The only "good" nonlinear distortion is that of a nature and amplitude such that the human ear cannot detect it.




Quote
The Cary power amp is around $5000. The Marantz is $1990, plus it has loads of features and extra channels. Seems strange that an AVR can outperform a very expensive dedicated power amp.

Quote from: Yahzi on
The parts used in receivers are often of poorer quality. Flimsy power supplies, for example.

Two things:
a) I would be surprised if an expensive product targeted at audiophiles did not perform worse. I could name many super expensive audiophile products that are crap.
b) Using expensive or special parts does not make a good product. In fact many audiophiles products prove this. It is the overall design that matters, not individual parts. Even if you have a 100 great parts, a few "wrong" ones or design fails and all the money spent on the great parts was for nothing. Take 100 cheap parts, use them properly, and you can still achieve better performance for a fraction of the cost..

Big manufacturers have the personnel and very expensive equipment to design and measure the best sounding devices for a given budget. Small manufacturers often do not, their designs are based on what one or two guys are convinced to be the ultimate solution ...
Also, there are even audiophile manufacturers that design "by ear only" and the results are often abysmal in performance, like clipping in a DAC, high distortion and noise floor in power amps, ridiculous gain in headphone amps ...

It is often a warning sign when manufacturers advertise their products by naming some expensive/boutique parts, or "military grade" something, or their ultimate circuits ... instead of providing performance data.
"I hear it when I see it."

First watt

Reply #8 –
You can actually run your signal through a bunch of cascaded op amps or do multiple A-D and D-A conversions, and it won't make one iota of audible difference as long as distortion, crosstalk and noise remain sufficiently low. If it's in the source material, every last bit of "air", all "velvety blackness between notes" and every bit of "front-to-back depth" or rumble beneath Carnegie Hall will be preserved.

But I'm not as persuasive a writer as those high-end pundits who say otherwise  And as a general rule, they won't come anywhere near a proper ABX test.

First watt

Reply #9 –
4season, that's right. If if you have many op-amps that degrade signal quality a bit, the output stage still usually completely dominates noise and distortion ... and speakers completely dominate that.

Also, you can achieve better performance with more parts. The O2 headphone amp is such an example, which splits the gain and output stage into separate stages (as I suggested to NwAvGuy) and therefore requires an extra op-amp (cmoy, mini3 ... use a single stage). The result is lower noise, distortion, DC offset ...


All that audiophiles really should care for is what is coming out of the outputs, or rather out of the speakers, and not marketing material about how fancy the insides of some device are.
"I hear it when I see it."

First watt

Reply #10 –
Quote from: 4season on
You can actually run your signal through a bunch of cascaded op amps or do multiple A-D and D-A conversions, and it won't make one iota of audible difference as long as distortion, crosstalk and noise remain sufficiently low.


To add to this, a typical op amp is actually composed of multiple discrete amplifier stages:



(Taken from wikipedia's page on the 741 op-amp)

Often very good designs require many discrete amplifiers to deliver performance better than any individual amplifier could alone.
 

First watt

Reply #11 –
Yeah, this directly leads to: negative feedback.

Audiophile manufacturers that try to avoid it (for whatever usually invalid reasons) end up with products with subpar performance that even sound different. Different sound must mean the amp is better, right? No, it's usually just the high output impedance causing linear distortion. Or lots of nasty distortion.

For anyone interested: The F-word or, why there is no such thing as too much feedback - Bruno Putzeys
"I hear it when I see it."