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Adding external amp to preout of internally amplified channels?

Flash

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I have a Denon X6500H and looking to improve performance of my front sound stage (NHT C3's + CLCR). Owners point to more power to really help them sing. My uneducated research started with external amps that I can connect to the pre-outs on my X6500H, but all the talk of benefits of turning off internal amplification led me down the AVR upgrade road...and how the DAC's in the 700 and 800 lines of denon have changed for the worst.

I unfortunately have gone down a 2-day rabbit hole learning from @amirm 's reviews about SINAD, @peng 's spreadsheet, replacement DAC degradation, and the merits of external amplification.

My questions are:
1) Is the noise added to the pre-out on the amplified channels audible by human ears, or are we talking about bench measurements only?
2) Is it a forgone conclusion that the pre-outs are going to clip at a certain volume level? I definitely don't want to spend the money on external amps if I am audibly compromising
3) What solution is audibly worst: Using pre-outs on the X6500H or say an X4700H in true pre-amp mode from the fronts with the downgraded DAC?
 

NTK

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Welcome to ASR!
  1. I am using Amir's X3500H (same product generation as X6500H) measurements as my reference. Noise level at the RCA outputs looks decent and shouldn't be a problem.

    index.php


  2. The X4700H pre-out started clipping at 1.4 V, which is 3 dB below max level. So the deterioration only happens at the last 3 dB of the output range. I wouldn't worry about at all since we are talking about THD levels of 0.03% at only at the very loudest levels (from 3 dB below max to max). Your speakers are easily giving >10% THD at those outputs.

    index.php


  3. My guess is that the differences will be inaudible.
 

Chrispy

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Get better speakers if you really want to improve things, not the avr/amp thing....
 
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Flash

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Welcome to ASR!
  1. I am using Amir's X3500H (same product generation as X6500H) measurements as my reference. Noise level at the RCA outputs looks decent and shouldn't be a problem.

    index.php


  2. The X4700H pre-out started clipping at 1.4 V, which is 3 dB below max level. So the deterioration only happens at the last 3 dB of the output range. I wouldn't worry about at all since we are talking about THD levels of 0.03% at only at the very loudest levels (from 3 dB below max to max). Your speakers are easily giving >10% THD at those outputs.

    index.php


  3. My guess is that the differences will be inaudible.
Thank you for this feedback, and #3 is really the most important question to answer...but I wonder about your references:

1) I think in Amir's review, the pre-outs were at ~95db, which I think are not terrible. So there is hope
2) X4700h can turn off the internal amps, which is what you have graphed here. My X6500h cannot, so I don't think I can use this info.

Either way, it is all about audible difference, and the more i read about the science behind sound, the less I think I believe that an external amp is actually going to make the "significant" difference that so many folks claim...especially when I rarely turn the dial past 70. Maybe I take one of these 30-day guarantee amp manufacturers out for a spin to confirm. Would hate to spend thousands of dollars to result in largely the same sound I have today.
 

NTK

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2) X4700h can turn off the internal amps, which is what you have graphed here. My X6500h cannot, so I don't think I can use this info.
I was referring to the X4700H curve with the power amp on (green/turquoise curves). They started clipping at 1.4 V (-3 dB) output, and the SINAD dropped to 70 dB at the 2 V max (0 dB) output, which, assuming the number is distortion dominated, is equivalent to a THD of 0.03%.
 
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Flash

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I was referring to the X4700H curve with the power amp on (green/turquoise curves). They started clipping at 1.4 V (-3 dB) output, and the SINAD dropped to 70 dB at the 2 V max (0 dB) output, which, assuming the number is distortion dominated, is equivalent to a THD of 0.03%.
ahh, gotcha. Sorry I missed that originally. Thank you very much for the additional insight.
 

alex-z

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Owners point to more power to really help them sing.
There is little or no truth to that statement.

Your X6500H already has a decent DAC section, and a reasonable amount of power available. You should be able to comfortably drive them to 90dB at 10ft, without accounting for any room gain.


The real problem with the NHT C3 is the tweeter causing an uneven radiation pattern, and also somewhat high distortion.

If you are trying to chase higher sound quality, I would either opt for different speakers, or doing extensive acoustic treatment to your room.
 
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Flash

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Any suggestions on better speakers with a similar neutrality to C3s?
 

Head_Unit

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(NHT C3's + CLCR). Owners point to more power to really help them sing.
Um. Maybe.
- Unless you are REALLY cranking, it is unlikely you are clipping. And even then, it is likely the speakers are distorting. The only speakers I've heard without horns that could play super loud with hard rock and metal were the Monitor Audio Silver 300s (at Upscale Audio, driven by a PrimaLuna tube integrated. Even Motorhead sounded amazingly clearer than I'd heard before, at levels I wouldn't listen to long without ear plugs).
- "MORE" power than an AVR would mean something like 300+ watts into 4 ohms for a start, given the logarithmic nature of our hearing. That's expensive.
- In which case the money would as @Chrispy and @alex-z noted be better spent upgrading the speakers either moving up in the NHT line (like those guys!) or yes I recommend Monitor Audio.
Ah, what do you mean by "making them sing"? What do you feel is lacking in the current sound?
 
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Flash

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To be honest, not much is missing. But when all owners talk about audible differences with external amplification, I am more wondering how much better they could sound.

Some folks point to the drop in impedance at kick drum frequencies being harder to drive with the denon (when played loud), so figured I could try more power to see if that is in fact the limiting factor. Otherwise, I am hearing perhaps the mechanical limit of the speaker at what I think isn’t deafening loud levels (speaker starts to have a “fart” sound). Only fix so far is raising the crossover.
 

Chrispy

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To be honest, not much is missing. But when all owners talk about audible differences with external amplification, I am more wondering how much better they could sound.

Some folks point to the drop in impedance at kick drum frequencies being harder to drive with the denon (when played loud), so figured I could try more power to see if that is in fact the limiting factor. Otherwise, I am hearing perhaps the mechanical limit of the speaker at what I think isn’t deafening loud levels (speaker starts to have a “fart” sound). Only fix so far is raising the crossover.
Most of the time I see comments like an amp will make them sing I roll my eyes. More likely a speaker limitation in most cases. Having plenty of power isn't a bad thing, tho...and would depend on your actual usage. If you're hearing bad port noises another way to deal with that is to seal the ports.
 
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Flash

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These are acoustic suspension (sealed) speakers. No port
 

Chrispy

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These are acoustic suspension (sealed) speakers. No port
Does NHT do acoustic suspension rather than just sealed? Did think of port noise being more likely. I'd suspect you're just hitting speaker limits, maybe amp, but more likely speaker.
 

Jack B

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When I went to Front & Center channels routed thru a seriously more powerful amplifier than my receiver, I noticed a lessening of compression. Totally subjective response, no science or controls involved. YMMV.
 
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