What I do not fully understand

[Jack Hammer]

magnusga, Here's an example of older amp ratings vs more modern pumped up numbers to better help you understand. I had a buddies older amp rated at 30w/ch that was way more powerful than my modern 2ch amp rated at 100w/ch. I played with some speakers in the other room (zone3) that have ~75' of wire between them and the amp (not ideal but I was experimenting:wink. Mine would only put sound to the speakers if the volume was played extremely loud then the speakers would cut out if the volume dropped below obnoxious. His amp would send a whisper to them and do it cleaner.

The quality between the two brands makes it a somewhat unfair comparison but that doesn't change the fact that my "higher" powered amp puts out far less usable power than his "lower" power rated amp. Many times power "ratings" are heavily skewed by marketing to show the maximum peak output they are capable of sending to a single channel, not the amount of power they are able to output to all channels for sustained periods. This is why many people say the ratings are BS.

 

[M Code]

The task of measuring an amplifier for its output power is straight-forward, the disconnect is when they don't follow certain industry standards and/or conveniently forget to make a complete disclosure.

The basic points are:
1. Output power per channel
2. THD %
3. Power bandwidth
4. Load impedance
5. # of channels being driven while doing the measurements
6. Disclose pre-conditioning if any

If the brand will disclose the above points honestly, then making unbiased comparisons between brands, products and different catgeories would be greatly simplified. And the consumer could make a more objective, purchase decision.

Just my $0.01..

 

[PENG]

The task of measuring an amplifier for its output power is straight-forward, the disconnect is when they don't follow certain industry standards and/or conveniently forget to make a complete disclosure.

The basic points are:
1. Output power per channel
2. THD %
3. Power bandwidth
4. Load impedance
5. # of channels being driven while doing the measurements
6. Disclose pre-conditioning if any

If the brand will disclose the above points honestly, then making unbiased comparisons between brands, products and different catgeories would be greatly simplified. And the consumer could make a more objective, purchase decision.

Just my $0.01..

I would add:

7. PF
8. IMD %

PF and impedance together give a better indication of how credible the manufacturer's claim of 'high current' is. Regarding the ACD (all channel driven) thing, it is a controversy previously debated so I am not going repeat the arguments from either side. I would, however, like to remind people to read up on this topic before going blindly with amps that provide the so called 'honest' ratings that are in fact just a different form of marketing hype. Depending on your application, you may be better off with an amp that gives you more 1,2,3 channel driven power but less 5,7 channel driven power.

 

[magnusga]

Thanks for all the replies. To look closer at the two Onkyo's, following the specs M Code and PENG mentioned, we should be able to analyze the difference.

I am simply looking for an argument that states for these and these technical reasons (proven through the specs on the webpage) the integrated amp, priced on the same level as the A/V receiver, will give you higher sound quality.

A-9555
=======
Power Output 85 W/Ch (8 ohms, 0.5 %, FTC)
Dynamic Power
3 ohms, Front 230 W/Ch
4 ohms, Front 200 W/Ch
8 ohms, Front 120 W/Ch
Total Harmonic Distortion 0.08 %


TX-SR707
=========
Power Output
Front L/R 100 W + 100 W (8 ohms, 20 Hz–20 kHz, 0.08%, 2 channels driven, FTC)
Center 100 W (8 ohms, 20 Hz–20 kHz, 0.08%, 2 channels driven, FTC)
Surround L/R 100 W + 100 W (8 ohms, 20 Hz–20 kHz, 0.08%, 2 channels driven, FTC)
Surround Back L/R 100 W + 100 W (8 ohms, 20 Hz–20 kHz, 0.08%, 2 channels driven, FTC)
Dynamic Power 240 W (3 ohms, 1 ch)
210 W (4 ohms, 1 ch)
120 W (8 ohms, 1 ch)
THD (Total Harmonic Distortion) 0.08% (Rated power)


1. Output power per channel: Integrated amp is lower by 15
2. THD %: Same THD
3. Power bandwidth: Not listed on the int. amp, but likely the same
4. Load impedance: Not sure, some of the impedance measures look similar
5. # of channels being driven while doing the measurements: both show with 2 channels driven. (I am assuming you use both the receiver and the integrated amp in the same environment for comparison purposes (i.e. in a 2-channel setup)
6. Disclose pre-conditioning if any: Not shown

Any spec rooted arguments for why the integrated amp should yield better audio than the receiver?

Links to full spec:
http://www.us.onkyo.com/model.cfm?m=TX-SR707&class=Receiver&p=s
http://www.us.onkyo.com/model.cfm?m=A-9555&class=Amplifier&p=s


Thanks a lot for sharing your thoughts,

M

 

[PENG]

There isn't enough information to get you the answer but my guess is that the 707 will likely offer more power, in a two channel set up, using 4 to 8 ohm speakers. Unless that integrated amp is one of those high efficient class D and G. Even then, its 120W power consumption, a little more than 1/5 that of the 707, is just way too low. No matter how efficient that integrated amp is, it cannot output more than it consumes. Now, we also do not know whether the specified 120W consumption is for 1 channel or 2 channel, and at full or less than full rated output. However, it is reasonable to assume it is for at least one channel and at rated output. I am not sure if that helps, but given the limited information from their spec sheets and manuals there is nothing further for me to add.

 

[M Code]

In reviewing the Onkyo amplifier's (A-9555/A-9755) Operation Guide it indicates that it incorporates a Digital Amplifier. Whereas the TX-SR707utilizes a traditional, analog Class A/B amplifier (x 7), since these (2) designs are uniquely different one cannot a direct specification comparison.

Regarding Digital Amplifiers, over the last 4 years there has been some very significant design/performance enhancements. Also since these models were developed in 2005, their digital amplifier topology is very dated.

IMHO..
I would pass for any further considerations of the A-9555/A-9755. Unless one is able to do extensive listening tests as to evaluate its sonic performance capabilities.

Just my $0.01..

 

[M Code]

I would add:

7. PF
8. IMD %

PF and impedance together give a better indication of how credible the manufacturer's claim of 'high current' is. Regarding the ACD (all channel driven) thing, it is a controversy previously debated so I am not going repeat the arguments from either side. I would, however, like to remind people to read up on this topic before going blindly with amps that provide the so called 'honest' ratings that are in fact just a different form of marketing hype. Depending on your application, you may be better off with an amp that gives you more 1,2,3 channel driven power but less 5,7 channel driven power.

Yes..
Certainly more specifications will provide more insight into the amplifier's performance capabilities. However in our AVR world less specifications are the norm rather than more..

Regarding the # of channels driven, the crucial point is to know How many? are being driven for that respective power disclosure specification. For example, if the power output is rated as 100W per channel with 2 channels driven. Then 100% of the power supply is driving 2 channels, if one increases the # of channels driven to 4 then simply decrease the power output rating by 50% (50W per channel) as the power supply now must supply twice the # channels. If the # of channels driven is increased to 7 channels, then the power rating is decreased once again by 75% or 37.5W per channel..

Now you can understand how an amplifier rated @ 100W per channel may actually only output 37.5W per channel if all channels are driven. But then again all channels driven specification is more crucial for music source material than movie sound tracks..

Post back if any more questions..

Just my $0.01..

 

[zhimbo]

A-9555
=======
Power Output 85 W/Ch (8 ohms, 0.5 %, FTC)

TX-SR707
=========
Power Output
Front L/R 100 W + 100 W (8 ohms, 20 Hz–20 kHz, 0.08%, 2 channels driven, FTC)


1. Output power per channel: Integrated amp is lower by 15
2. THD %: Same THD
M

Actually, the rated output per channel is not rated at the same THD. But now that I see them next to each other, I realize the 707 is rated at a more stringent threshold. (0.08% vs. 0.5%). I had them switched in my mind.

Given that power ratings are largely creative acts of marketing, I would have layed down $10 that it's the same amp section...until I saw the message above that these are digital vs analog amp designs.

In which case, it's really an apples-to-oranges comparison.

 

[PENG]

Yes..
Certainly more specifications will provide more insight into the amplifier's performance capabilities. However in our AVR world less specifications are the norm rather than more..

Regarding the # of channels driven, the crucial point is to know How many? are being driven for that respective power disclosure specification. For example, if the power output is rated as 100W per channel with 2 channels driven. Then 100% of the power supply is driving 2 channels, if one increases the # of channels driven to 4 then simply decrease the power output rating by 50% (50W per channel) as the power supply now must supply twice the # channels. If the # of channels driven is increased to 7 channels, then the power rating is decreased once again by 75% or 37.5W per channel..

Now you can understand how an amplifier rated @ 100W per channel may actually only output 37.5W per channel if all channels are driven. But then again all channels driven specification is more crucial for music source material than movie sound tracks..

Post back if any more questions..

Just my $0.01..

As I said, even if the 9555 is a class D or G amp it cannot output more than it takes in, at least not on continuous basis. Yes if you noted that it is class D or G, it will be an apple to orange comparison but based on their power consumption my money is still on the 707 AVR.

Regarding your talk about dividing the power supply between the number of channels I do not believe it is always the case. Just read some of the lab measurements by HTM, HCC you will see that not all AVR follow that rule, some do and some don't. Many AVR do have P/S large enough (e.g. Onkyo 805,875,905, Denon 3808, 4308 and 5308, all HK and NAD AVRs etc.) to deal with all 7 channel to the point their 7 ch driven output drops off only by a couple of dB as long as the load impedance is closer to 8 ohms than 4 ohms.

 

[M Code]

Regarding your talk about dividing the power supply between the number of channels I do not believe it is always the case. Just read some of the lab measurements by HTM, HCC you will see that not all AVR follow that rule, some do and some don't. Many AVR do have P/S large enough (e.g. Onkyo 805,875,905, Denon 3808, 4308 and 5308, all HK and NAD AVRs etc.) to deal with all 7 channel to the point their 7 ch driven output drops off only by a couple of dB as long as the load impedance is closer to 8 ohms than 4 ohms.

Keep in mind...
Our discussions were centered on the Onkyo 707 which sells for $599 @ Amazon, note that it is an entry-level AVR. AVRs that have an SRP of <$999 are built very differently than AVR models such as the Denon 5308 you mentioned which can sell for 4 to 8 x the 707 price.

The higher priced AVRs have a more costly bill of materials, uses higher current components plus having greater regulation within its power supply so they do better for the all channels driven power output specifications. Higher cost AVRs are built and designed around a more conservative, design criteria.

Just my $0.01..

 

[PENG]

Keep in mind...
Our discussions were centered on the Onkyo 707 which sells for $599 @ Amazon, note that it is an entry-level AVR. AVRs that have an SRP of <$999 are built very differently than AVR models such as the Denon 5308 you mentioned which can sell for 4 to 8 x the 707 price.

The higher priced AVRs have a more costly bill of materials, uses higher current components plus having greater regulation within its power supply so they do better for the all channels driven power output specifications. Higher cost AVRs are built and designed around a more conservative, design criteria.

Just my $0.01..

Yes I agree.

 

[magnusga]

Thanks a lot guys.

It seems I got my answer. Even though people dispute that the AVR is just as good on sound as the integrated stereo amp, at least one person puts his/her bet on the AVR.

Next time I am building a 2-channel system i will be careful with choosing a dedicated stereo int.amp. just because it is made for that purpose. An equally priced AVR might in fact give better sound quality, because the pricing on these is more competitive.

Again, I appreciate all the great input.

M