Anthem MRX-740 or Denon 6700h for main channels power amp with 2.71 Vrms input sensitivity?

lovinthehd

lovinthehd

Audioholic Jedi
Thank you for bring this up, unfortunately no matter how many times we post on this topic, similar questions due to people's misconception or confusing about the related specs keep popping up and people end up worry for nothng.

I'll just do a quick recap as follow:

1) Denon+Marantz AVRs do not turn off the internal amps.
2) D+M AVRs, from the AVR-X3700H and up, newer models included, have a preamp mode.
2a) In preamp mode, D+M AVRs will enable ECO mode automatically (not in the specs, but reported by some reliable sources, including Gene iirc..) so the unit will in fact runner cooler as the bias current for the power amp will be much reduced in preamp mode.
3) In preamp mode, the AVR will disconnect the pre amp output (so called pre-outs) to the power amp inputs.
4) With the internal power amp inputs disconnected from the pre outs, the power amps are still powered, but since there are no signal for them to amplify, they will never clip.
5) Because the power amps will never clip in preamp mode, there will be no distortions due to clipping fed back to the preamp side, as a result the pre outs will have lower distortions at higher output voltage, right up to its clipping point, that according to Gene (Audioholics) and Amir (ASR)'s measurements. That would be in the range of 3 to a little over 4 Volts.
6) The AVR-X3600H, AVR-X4400H, 4500H (not sure about the 4300), SR6011, SR7010 through 7013 do not have preamp mode, but you can use the amp assign function to have the pre outs disconnect from the power amp inputs, just like the preamp mode, but you can only do it to the front left and front right channels. Gene was the first only discovered this and shared with Audioholics, in his review of the AVR-X3600H:
Denon AVR-X3600H 9.2CH IMAX Enhanced AV Receiver Offers Best In Class Features | Audioholics
In that review (actually preview) Gene also commented that:



7) So basically, in 6) above you can only disconnect the FL and FR internal power amp channels whereas in 2) you can do that, or if you use preamp mode, all internal power amp channels will be disconnected from the pre outs.
8) It is important to understand that even if the internal power amps are not disconnected from the pre outs, it is not true that the pre outs will be clipping at 1.2, 1.4 or even 2, 3 volts, the pre outs can still go up to 3.5 to 4.0 V or a little higher. It just mean that from about 1.4 to 1.45 V, it will generally start being affected by the clipped power amp output distortions fed back to the preamp section, thereby causing the pre out distortions to rise rather quickly. That is shown in ASR's measurements, at 2 V, the preout distortion would be about -75 dB, that is 0.018%THD+N, still not below the threshold of audibility. At voltages higher than 2 V, say at 3 to 3.5 V, THD+N will have increased further but not by much, because the distortion from the power amp clipping will not affect the pre outs proportionally, at some point it would taper off.

I have spend a lot of time posting some or all of the above on AH, I wish there is a quick way for people to find the answers either from my, or others including Gene posts.
I think you should have a sticky thread for this subject....it does come up a lot. That distinction between turning the amp input off vs turning amp off can be tough, tho!

NNear the end there you say " the preout distortion would be about -75 dB, that is 0.018%THD+N, still not below the threshold of audibility" what circumstances/where are you putting the threshold of audibility particularly? Or is that still below the threshold of audibility?
 
P

PENG

Audioholic Slumlord
I was thinking on some of the x7xx series that Amir tested it was closer to 2V or was that just the optimal point? It's been a while.
Amir standardized on testing pre outs at w V RCA, and 4 V XLR. He did test up to 4/8 V occasionally.

Example:

1662071695589.png
 
lovinthehd

lovinthehd

Audioholic Jedi
Amir standardized on testing pre outs at w V RCA, and 4 V XLR. He did test up to 4/8 V occasionally.

Example:

View attachment 57612
Is there an equivalent with the amps enabled? Also wonder what happens in multich.
 
P

PENG

Audioholic Slumlord
I think you should have a sticky thread for this subject....it does come up a lot. That distinction between turning the amp input off vs turning amp off can be tough, tho!

NNear the end there you say " the preout distortion would be about -75 dB, that is 0.018%THD+N, still not below the threshold of audibility" what circumstances/where are you putting the threshold of audibility particularly? Or is that still below the threshold of audibility?
The "not" was a typo. Thank you for alerting me, fixed now.

For power amp, I think 0.1% or less should be below the threshold and for preamp/dac, I would go with 0.08% just to be on the conservative side, ommv..
 
P

PENG

Audioholic Slumlord
Is there an equivalent with the amps enabled? Also wonder what happens in multich.
Yes, but he did it with the 3700. The preout performance for the 3700, 4700, 6700, 8500 are similar. Note that the "clips at 1.4 V is misleading. At preout 1.4 V, the pinternal amps would reach its clipping point, not the preamp.

I have never seen preout tests in all channel driven but it is highly unlikely the numbers would change much, not for preamps because the output currents are so low.

1662072403829.png
 
lovinthehd

lovinthehd

Audioholic Jedi
Yes, but he did it with the 3700. The preout performance for the 3700, 4700, 6700, 8500 are similar.

I have never seen preout tests in all channel driven but it is highly unlikely the numbers would change much, not for preamps because the output currents are so low.

View attachment 57613
Thanks. I suppose my thoughts on multich are more dependent on various levels involved for each channel, as clipping there has happened with some bass management schemes. More just a desire to see more than 2ch testing of an avr....
 
P

PENG

Audioholic Slumlord
Thanks. I suppose my thoughts on multich are more dependent on various levels involved for each channel, as clipping there has happened with some bass management schemes. More just a desire to see more than 2ch testing of an avr....
Agreed, I have not seen multichannel, that is, from 3.1 up measurements other than just power output.
 
P

PENG

Audioholic Slumlord
Just curious why you say the MRX-740 could be a good option if I'm in Canada?
I meant to say if you were in the GTA, Greater Toronto area. My feeling (no proof, just feeling based on what I read on the internet..) is that Anthem is good with amplifiers and the older model AVRs, but the new featured rich AVRs and AVPs may be too complicated for a company much smaller than D+M, Sony, Yamaha, Onkyo etc..

In case I need support, especially repairs, knowing they are within driving distance does make me feel safer to go with something like the AVM70.
 
MaxInValrico

MaxInValrico

Full Audioholic
I meant to say if you were in the GTA, Greater Toronto area. My feeling (no proof, just feeling based on what I read on the internet..) is that Anthem is good with amplifiers and the older model AVRs, but the new featured rich AVRs and AVPs may be too complicated for a company much smaller than D+M, Sony, Yamaha, Onkyo etc..

In case I need support, especially repairs, knowing they are within driving distance does make me feel safer to go with something like the AVM70.
I'd say you need to re-evaluate your feelings.
 
Pandaman617

Pandaman617

Senior Audioholic
I’ve ran my 6700h in both preamp mode and in preamp FL+FR mode with the AVR running 4, 4ohm Emotiva height channels and haven’t ever heard any audible distortion or artifacts and I routinely watch movies at -10 mV to -12mV
 
M

mtrot

Full Audioholic
So, is Accessories4less a reputable place to buy an AVR? I see they list a "Denon Factory Refurbished" 6700 for $2299.99, with free shipping. This is the best price I've seen yet. And they say it has a 3 year warranty. Thoughts?
 
lovinthehd

lovinthehd

Audioholic Jedi
So, is Accessories4less a reputable place to buy an AVR? I see they list a "Denon Factory Refurbished" 6700 for $2299.99, with free shipping. This is the best price I've seen yet. And they say it has a 3 year warranty. Thoughts?
I've purchased several things from them. Be sure you understand their terms of sale on a refurb unit. Is that a factory warranty or the typical 1 year factory warranty on refurbs with a supplemental policy from a third party? FWIW I did get a few bad refurbs (they don't do the refurbs, they're provided by Denon) and after two of those I went for a new unit thru them at a slightly higher price, but dealing with them they even went a bit beyond their terms on the second bad one....ymmv.
 
M

mtrot

Full Audioholic
I've purchased several things from them. Be sure you understand their terms of sale on a refurb unit. Is that a factory warranty or the typical 1 year factory warranty on refurbs with a supplemental policy from a third party? FWIW I did get a few bad refurbs (they don't do the refurbs, they're provided by Denon) and after two of those I went for a new unit thru them at a slightly higher price, but dealing with them they even went a bit beyond their terms on the second bad one....ymmv.
Thanks. Yes, it says "1 Year Denon + 2 Year Free Extension". I don't see a listing on their site for a new 6700.
 
lovinthehd

lovinthehd

Audioholic Jedi
Thanks. Yes, it says "1 Year Denon + 2 Year Free Extension". I don't see a listing on their site for a new 6700.
They're mostly about the refurbs, but occasionally have new stuff.
 
lovinthehd

lovinthehd

Audioholic Jedi
Then another consideration is waiting for the newer models later this year?
 
gene

gene

Audioholics Master Chief
Administrator
I'm pretty sure the X8500/A110 models are the only ones currently that you can turn off the individual internal amps with pre-out mode. That gets you closer to 2V before clipping with the Denons IIRC. If the Anthems can output 3V unclipped then that seems a better solution assuming you're keeping the Krell.....
You can't turn amps off any AV receivers AFAIK. You can only do a preamp disconnect which decouples the amp section from the preamp to avoid ingress of noise and distortion from unloaded amps clipping when you exceed the max preamp voltage drive:

I've been measuring this for years and realized this was a real problem for most AVRs that exceed about 1.4 to 1.5Vrms which is the drive level that puts the internal amps into clipping.

When I gave these results to Denon/Marantz, they completely revamped their next generation AVRs to include a buffer circuit to minimize this problem and also a standard preamp disconnect. You can see the improvements in our SR8015 review:

 
gene

gene

Audioholics Master Chief
Administrator
Denon and Marantz AVR preouts don't clip at 2 V, won't likely clip until it reaches 4 V. People get confused with the internal power amp clipping, and the resulting higher distortions would affect the preamp section because of the feed back loop. Such bad effects tend to taper off though so distortions would increase more rapidly after 2 V but tend to rise at a gentler way from there, until about 4 V when it would actually start to clip.

In the X3600H preview, Gene included the follow graph, he said was "output vs distortion plot courtesy of Sound United Engineering", note that the Clipping point shown is 4.25V.

View attachment 57603
Dude you rock. PM me if you want to write articles for us.
 
lovinthehd

lovinthehd

Audioholic Jedi
You can't turn amps off any AV receivers AFAIK. You can only do a preamp disconnect which decouples the amp section from the preamp to avoid ingress of noise and distortion from unloaded amps clipping when you exceed the max preamp voltage drive:

I've been measuring this for years and realized this was a real problem for most AVRs that exceed about 1.4 to 1.5Vrms which is the drive level that puts the internal amps into clipping.

When I gave these results to Denon/Marantz, they completely revamped their next generation AVRs to include a buffer circuit to minimize this problem and also a standard preamp disconnect. You can see the improvements in our SR8015 review:

Yeah @PENG touched up the definitions earlier.
 
gene

gene

Audioholics Master Chief
Administrator
I think you should have a sticky thread for this subject....it does come up a lot. That distinction between turning the amp input off vs turning amp off can be tough, tho!

NNear the end there you say " the preout distortion would be about -75 dB, that is 0.018%THD+N, still not below the threshold of audibility" what circumstances/where are you putting the threshold of audibility particularly? Or is that still below the threshold of audibility?
It's very unlikely anyone could hear 0.018% THD+N with real program material in a room with speakers and NOT headphones. It's why I'm not a fan of the SINAD gospel of people chasing a #. I strongly believe based on my years of testing and designing highly sensitive audio communication systems for Telcom and Government defense that anything below 0.01% (80dB) THD+N is below the threshold of audiblity using test tones and with controlled listening with headphones and noise isolation. Once you play the tones in a room on loudspeakers, I think the threshold can be a bit higher. Of course with program material, all bets are off as the masking effect tends to dominate unless severe clipping is present.
 
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