NAD performs well on test bench...

[crashguy]

Check out the link to test bench results for output power for the NAD T753 AV receiver. Its rated at 70w X 5, and puts out 105w X 5, all channels driven simultaneously. Pretty impressive, and more than enough truth in advertising.

If they have got those quality control issues worked out, this is a great product for those who look down their noses at whiz bang surround modes and DSP.

http://hometheatermag.com/receivers/105nad/index2.html

 

[mtrycrafts]

Check out the link to test bench results for output power for the NAD T753 AV receiver. Its rated at 70w X 5, and puts out 105w X 5, all channels driven simultaneously. Pretty impressive, and more than enough truth in advertising.

If they have got those quality control issues worked out, this is a great product for those who look down their noses at whiz bang surround modes and DSP.

http://hometheatermag.com/receivers/105nad/index2.html

Well, you need to look at the distortion that they are using to achieve that power output, if what is written is accurate. If you like 1%, then it is impressive.

 

[sjdgpt]

Of course it would outperform its power ratings, after all it is an NAD

 

[armaraas]

I thought most anything below 2% is indistinguishable to the human ear?
Anyways, 90+ watts at .1% is too shabby either.
Beats the the Yamaha 2400 they rated at 44 watts at 1%.

 

[gene]

Beats the the Yamaha 2400 they rated at 44 watts at 1%.

If you are referring to the power measurements HT Magazine did, there is a very valid reason why that happened and you need to check out our article on "The All Channels Driven Test" to discover why. You may wish to check out my measurements that pegs the RX-V2500 (very similar amp section) at over 140wpc into 8 ohms and almost 200wpc into 4 ohms all unclipped with less than .5% THD. Distortion figures below 1% are usually inaudible, though testing distortion into a resistive load doesn't tell the whole story.

You should also check out Product Managing Receiver Platforms for additional reading.

 

[HookedOnSound]

The issues about rated receiver/amplifier output and distortion is probably the topic that I find the most confusing when doing comparative shopping.

I am just starting to get into home theatre and been doing alot of research (thanks Audioholics for demystifying HT!) and my next purchase is upgrading my AV Receiver and I can honestly say that after looking at receiver specs I cannot rely on them solely in deciding what to buy (aside from listening to them).

I wish they would all talk the same language, but oh no! Every vendor markets their goodies slightly different...

I understand that alot of variables come into play about amplifier designs and how to report them (performance) must be challenging but IMHO there must stricter tolerances on reporting specs and accepted practices. I like the concept of THX certification as a buying tool when shopping for equip. but from what I understand that certification is quite expensive to achieve for vendors and not practical and/or economically feasible.

Am I wrong to think that the consumer market has yet to address this problem?

Thanks

 

[sjdgpt]

I like the concept of THX certification as a buying tool when shopping for equip. but from what I understand that certification is quite expensive to achieve for vendors and not practical and/or economically feasible.

Am I wrong to think that the consumer market has yet to address this problem?

Thanks

Totally correct.

In general, certification, be it THX or Steven's (named after me), can be expensive. There are set fees for just having the units tested (whether the unit passes is not important, I just want my fee to consider the unit). There are fees for each unit sold (and larger fees for only selling a small number of units). And there may even be more fees, if I (Steven) just want to add more fees.

For a manufacturer that is actively improving their equipment (not a bad thing), each change in the design, regardless of whether the model number is changed, could result in additional certification fees.

Thus I would suspect you will find THX on mid line equipment that does not undergo significant design changes and will have moderate to high volume sales, OR high end equipment that seldom has (or needs) design changes.

 

[mtrycrafts]

I thought most anything below 2% is indistinguishable to the human ear?
Anyways, 90+ watts at .1% is too shabby either.
Beats the the Yamaha 2400 they rated at 44 watts at 1%.

Perhaps but one needs to compare amps at the same rated THD.

 

[crashguy]

Well, you need to look at the distortion that they are using to achieve that power output, if what is written is accurate. If you like 1%, then it is impressive.

If you can hear 1%, I'd be impressed.... we could call you Lt. Commander Data...

 

[armaraas]

Hm, okay then, so it's better to compare 2 channels driven at the same THD as a more practical comparison between receivers?

So for the 2400 (HTMag)
2 channel 8 ohm .1% THD 102W
2 channel 8 ohm 1% THD 130W
2 channel 4 ohm .1% THD 158W
2 channel 4 ohm 1% THD 195W

2500 (per Gene's comment/review)
2 channel 8 ohm <.5% THD 140W
2 channel 4 ohm <.5% THD 200W
Which makes sense since the 2500 is rated at 10w more than the 2400, right?

The NAD 753
2 channel 8 ohm .1% THD 110W
2 channel 8 ohm 1% THD 136W
2 channel 4 ohm .1% THD 122W
2 channel 4 ohm 1% THD 146W

And 5 channels or all channels driven is more or less irrelevant since it will rarely if ever be realized in a normal, everyday application? If I missed anything I should have picked up in those articles let me know, I went through them but get easily distracted while reading.... Does the all channels driven number tell us anything useful, even if it may never be needed?

The NAD still seems to peform quite well compared to its advertised specs, even if you don't like your 1% distortion levels.

One question I have is why do the Yamahas have such a jump when going from 8 ohm to 4 ohm versus the NAD?

 

[PENG]

One question I have is why do the Yamahas have such a jump when going from 8 ohm to 4 ohm versus the NAD?

You will find the same kind of jump in Denon, Pioneer Elite, and Sony ES models. You will not find the same (that is, much smaller) jump in NAD and HK models, except for their flag ships such as the HKAVR7X00 and the NADT773.

I don't know why neither, but I can only suspect that some manufacturers may focus on producing "honest" all channel driven power. In doing so, their cost increases due to the larger power supply (transformer, capacitors, rectifiers etc.). To offset the increase and remain price competitive, they may have to lower the cost of their amplifiers and heat sinks. Of couse I am only guessing. If you take HK for example, they apparently run hotter, and generally use a fan to help keep things cool. Equivalent (price wise) Denon and Yamaha models do not need fans, indicating they probably have relatively more powerful amplifiers, and better heat sinks. NAD and HK models are usually heavier, has very high instantaneous current rating, evidence of having larger power supplies.

Given that there is only so much to spend on building a receiver, I believe tipping the balance (of course only to a point) towards the amplifier sections is correct, as most audio source including 5.1 channel, do not require all channels to be driven to the same level. If it does, it would likely be for a short duration. Any decent quality power supplies have very generous overload capacity anyway. So it is better to spend more on maximizing the amp section so that each amp has the highest possible unclipped power output.

 

[crashguy]

You will find the same kind of jump in Denon, Pioneer Elite, and Sony ES models. You will not find the same (that is, much smaller) jump in NAD and HK models, except for their flag ships such as the HKAVR7X00 and the NADT773.

I don't know why neither, but I can only suspect that some manufacturers may focus on producing "honest" all channel driven power. In doing so, their cost increases due to the larger power supply (transformer, capacitors, rectifiers etc.). To offset the increase and remain price competitive, they may have to lower the cost of their amplifiers and heat sinks. Of couse I am only guessing. If you take HK for example, they apparently run hotter, and generally use a fan to help keep things cool. Equivalent (price wise) Denon and Yamaha models do not need fans, indicating they probably have relatively more powerful amplifiers, and better heat sinks. NAD and HK models are usually heavier, has very high instantaneous current rating, evidence of having larger power supplies.

Given that there is only so much to spend on building a receiver, I believe tipping the balance (of course only to a point) towards the amplifier sections is correct, as most audio source including 5.1 channel, do not require all channels to be driven to the same level. If it does, it would likely be for a short duration. Any decent quality power supplies have very generous overload capacity anyway. So it is better to spend more on maximizing the amp section so that each amp has the highest possible unclipped power output.

I don't think relating average running temp to quality is fair or accuate. Its based more on class of operation than design quality.

I think NAD doesn't "jump" as much when impedence drops due to the impedence sensing circuitry they equip their receivers with (wahtever that is). They do advertise them as having this feature, or at least they did a year or so ago.

 

[gene]

The NAD still seems to peform quite well compared to its advertised specs, even if you don't like your 1% distortion levels.

One question I have is why do the Yamahas have such a jump when going from 8 ohm to 4 ohm versus the NAD?

The Yamahas are typically designed to be very dynamic and can deliver good instantaneous power. For example the RXZ9 uses 80V caps. An amp delivering 170wpc doesnt need caps rated above 60V to do this, but they design in a lot of overhead so the amp can deliver more than speced power for brief periods. This is also something that THX tests for. You want an amp that has good dynamic headroom.

It appears NAD's rate their amps at lower power so they can pass the alleged all channels driven test (again an unrealistic test load and test condition) to appease consumers and market that they conservatively rate their receivers. This isn't a bad thing by any means but realize everyone is playing the power game. They just each do it differently.

If you look closer at the rated measurements in the mags for all these receivers, you will notice that the Denons and Yamahas and Onkyo/Integra consistantly have at least a 10dB lower noise floor and better channel to channel cross talk isolation than their counterparts for example. I have also found this to be the case in many installations which is why we have found the Yammie/Denon/Integra products to be such a great value. Depending on your application, speaker sensitivity, etc, this may never present a problem.

NAD makes some very nice sounding, easy to use equipment. Our best advice is to play with these units first hand when making a purchasing decision.

 

[PENG]

It appears NAD's rate their amps at lower power so they can pass the alleged all channels driven test (again an unrealistic test load and test condition) to appease consumers and market that they conservatively rate their receivers. This isn't a bad thing by any means but realize everyone is playing the power game. They just each do it differently.

Okay, that makes sense, but Gene, as Armaraas had asked, why would their (NAD) power output into 4 ohms not jumped as much as say a Yamaha did? Armaraas already quoted the Yamaha numbers, so I am going to do the same for the Denon.

H.T. mag lab measurements:

"This graph shows that the AVR-3805's left channel, from CD input to speaker output with two channels driving 8-ohm loads, reaches 0.1% distortion at 132.2 watts and 1% distortion at 162.3 watts. Into 4 ohms, the amplifier reaches 0.1% distortion at 218.4 watts and 1% distortion at 243.0 watts."

Any chance you can shed some light on this, or at least an educated guess?

Thanks!

 

[PENG]

2500 (per Gene's comment/review)
2 channel 8 ohm <.5% THD 140W
2 channel 4 ohm <.5% THD 200W
Which makes sense since the 2500 is rated at 10w more than the 2400, right?

I thought Gene's numbers show 1 channel 4 ohms 200W, 2 channel was just under 120W.

 

[gene]

Okay, that makes sense, but Gene, as Armaraas had asked, why would their (NAD) power output into 4 ohms not jumped as much as say a Yamaha did? Armaraas already quoted the Yamaha numbers, so I am going to do the same for the Denon.

Without having a unit here to test, or schematics at my disposal, I can't say for sure. But it sounds like the NAD has a current limiting circuit to protect the amp /power supply from being over taxed. This is not uncommon in a budget priced multi channel receiver.

I thought Gene's numbers show 1 channel 4 ohms 200W, 2 channel was just under 120W.

Keep in mind that unlike most of the A/V magazines that hold the line voltage constant without telling you, I don't do this in my tests. This makes a world of difference, especially when testing multiple channels. But in reality, not holding the line voltage constant is more real world since most people don't have this capability. In this case, the Yamaha was current limiting since the line voltage wasn't sagging too much.

 

[PENG]

Gene, thank you for responding to my question about the NAD's test results, and I do understand we are only speculating.

Regarding the Yamaha, did you mean the line voltage "was" (you wrote "wasn't") sagging too much. If it wasn't sagging too much, then why would it be current limiting, did you mean limiting by design? If it was sagging too much, what would be the reason? A 15A circuit at 110V should be able to deliver 1650 VA, or at least 700 to 800W total at the outputs of the amps (multi-channels)., before you will see any significant voltage drop, right? Thanks again.

 

[SVI2004A]

Power Jumping / impadance

The amplifier that returns similar figures in 4 and 8 ohm usually have a dual tap secondaries for the amplifier stages - in 8 ohms it shall recieve a higher rail voltage and the lesser in 4 ohms... some units have the infamous impedance selector switch on the back whilst others have impedance comparator circuits that utilise a relay to select high or low tap