Denon avr-x3900h preamp measurements

[DenonMate]

I’m pretty happy with the external amps and all other speakers are very silent. Just a bit low level zizzl at ear to speaker distance 2-3cm. It was a bit louder when using the internal amps. I will keep my external setup. There are many reasons for this (in my view) but one day will exchange the x4700. and it will be no denon or other avr with just rca.

 

[Dougey_Jones]

I think it's kinda funny that the internal amps are obviously shielded/protected from HDMI ground loops but somehow they weren't able to apply the same protection to the pre-amp outs. Kinda wild.

I use two of these for for the front soundstage and internal amps for the rest of the channels:

 

[valerianf]

As an EE I can say that it seems there is a faulty design regarding the RCA pre-output exposing them to an excess of sensitivity to the outside noise.
And reading the answers it as not been corrected since several iterations of AVR families.
Is it affecting only the Denon Avrs and not the Marantz variants?

 

[d3miller]

As an EE I can say that it seems there is a faulty design regarding the RCA pre-output exposing them to an excess of sensitivity to the outside noise.
And reading the answers it as not been corrected since several iterations of AVR families.
Is it affecting only the Denon Avrs and not the Marantz variants?

I’ve only ever used the XLR outputs on my Marantz and never tried the RCAs so not sure. And my Marantz had no integrated amp; it was a preamp only (model AV7706).

 

[popej]

I think it's kinda funny that the internal amps are obviously shielded/protected from HDMI ground loops but somehow they weren't able to apply the same protection to the pre-amp outs. Kinda wild.

Exactly this thread provide measurements: HDMI -> RCA out. It is above 110dB SNR. Which means, RCA can work properly. Problem seems to be more complicated.

 

[peng]

I’ve only ever used the XLR outputs on my Marantz and never tried the RCAs so not sure. And my Marantz had no integrated amp; it was a preamp only (model AV7706).

I would just make sure the RCA cables are good, and then the speaker cables are cleanly layout. If those are not the issue, then immediately request a replacement. I have quite a few Denon AVRs in the past, all of them were quieter than my Marantz AV8801. Based on specs and measurements of the previous 3000 series models, I would say with certainty that using the pre outs, preamp mode or not, should be quieter than the AV7706. Hiss is typically not due to ground loop, but interference picked up by cabling, RCA interconnects, and/or speaker cables.

When using the pre outs, which power amp are you using?

 

[peng]

I think it's kinda funny that the internal amps are obviously shielded/protected from HDMI ground loops but somehow they weren't able to apply the same protection to the pre-amp outs. Kinda wild.

I use two of these for for the front soundstage and internal amps for the rest of the channels:

View attachment 545356

Just cautionary comments, my 2 cents, even my entry level X1800H had no such hiss/buzz issues, and not too many users have reported similar issues either, so if you had it with your high models, something else might be wrong with your (and may be others) specific unit(s), or cabling but not because of the preamp mode related design of those AVRs. There should be no need to use those buzz off kind of gadgets except for specific reasons that not everyone might have.

 

[EWL5]

Something doesn't smell right: we went from AKM -> TI -> CL DACs in a span of 3 generations. Many audiophiles swear by the AKM DACs and I haven't really heard widespread complaints about connecting to external amps. If there were 3 different types of DACs and Denon "caused" the hissing each time, doesn't that sound just a teeny bit suspicious?

 

[d3miller]

Overall this is super annoying and I really prefer to not have to do an exchange. I’m gonna try to narrow it down and basically unplug everything and start with just a single pre-out and go from there. It’s probably not a firmware thing, but there’s an update available that I can install.

I would just make sure the RCA cables are good, and then the speaker cables are cleanly layout. If those are not the issue, then immediately request a replacement. I have quite a few Denon AVRs in the past, all of them were quieter than my Marantz AV8801. Based on specs and measurements of the previous 3000 series models, I would say with certainty that using the pre outs, preamp mode or not, should be quieter than the AV7706. Hiss it typically not due to ground loop, but interference picked up by cabling, RCA interconnects, and/or speaker cables.

When using the pre outs, which power amp are you using?

I’m using an Outlaw 5000x amp. RCA and speaker cables are solid—Blue Jeans Cables. Speaker cable layout is clean, but I can probably clean up the RCAs a bit. I’ll also plug my Marantz back in and try the RCAs to compare. Now just need to find the time …

 

[Marc v E]

Overall this is super annoying and I really prefer to not have to do an exchange. I’m gonna try to narrow it down and basically unplug everything and start with just a single pre-out and go from there. It’s probably not a firmware thing, but there’s an update available that I can install.


I’m using an Outlaw 5000x amp. RCA and speaker cables are solid—Blue Jeans Cables. Speaker cable layout is clean, but I can probably clean up the RCAs a bit. I’ll also plug my Marantz back in and try the RCAs to compare. Now just need to find the time …

I would unplug the source too and use a different one (bluray, dvd player, cd player) to see if it's the culprit.

 

[valerianf]

Is the hiss still there in Pure Direct mode (no DSP processing)?

 

[peng]

Overall this is super annoying and I really prefer to not have to do an exchange. I’m gonna try to narrow it down and basically unplug everything and start with just a single pre-out and go from there. It’s probably not a firmware thing, but there’s an update available that I can install.


I’m using an Outlaw 5000x amp. RCA and speaker cables are solid—Blue Jeans Cables. Speaker cable layout is clean, but I can probably clean up the RCAs a bit. I’ll also plug my Marantz back in and try the RCAs to compare. Now just need to find the time …

The Outlaw 5000 was measured on ASR:

It does not seem to be a very quiet power amp at all, though in most cases should still be near silent at 3 meters or further.

If your ears are near a sensitivity tweeter, such as >93 dB/2.83V/m, with long RCA interconnects, and/or have not the best shielding, long speaker cables that you may feel are layout clean, but might be near/cross path with some noisy stuff such as transformers, cables feeding high power devices etc., then you may hear hiss that can be expected in such scenarios.

 

[Dougey_Jones]

Just cautionary comments, my 2 cents, even my entry level X1800H had no such hiss/buzz issues, and not too many users have reported similar issues either, so if you had it with your high models, something else might be wrong with your (and may be others) specific unit(s), or cabling but not because of the preamp mode related design of those AVRs. There should be no need to use those buzz off kind of gadgets except for specific reasons that not everyone might have.

Do you actually have a noisy HDMI device with poor grounding like an HTPC connected to your AVR, or are you just speaking generally?

 

[peng]

Do you actually have a noisy HDMI device with poor grounding like an HTPC connected to your AVR, or are you just speaking generally?

Did you mean to ask the op? I have had no noise issue with my x1800h.

 

[Dougey_Jones]

Did you mean to ask the op? I have had no noise issue with my x1800h.

No, I was responding to your "cautionary" statement regarding pre-amp outputs on Denon AVR's, which was directed at me. The conditions in which this "noise" enters the signal chain is pretty specific, so it's not at all surprising that most people don't encounter it. I asked a clarifying question because you don't have your system listed in your signature and I have no way of knowing what input sources you're using.

As stated previously, this only becomes an issue if you have a noisy HDMI source like an HTPC with poor grounding, so if you don't have one in your system it's obvious why you never experienced it..

 

[peng]

No, I was responding to your "cautionary" statement regarding pre-amp outputs on Denon AVR's, which was directed at me. The conditions in which this "noise" enters the signal chain is pretty specific, so it's not at all surprising that most people don't encounter it. I asked a clarifying question because you don't have your system listed in your signature and I have no way of knowing what input sources you're using.

As stated previously, this only becomes an issue if you have a noisy HDMI source like an HTPC with poor grounding, so if you don't have one in your system it's obvious why you never experienced it..

Okay, sorry, I do have an HTPC source at the time, that is HDMI output from my low cost Acer Nitro laptop PC. If I understand you right, you are suggesting that the internal amps are not affected by such a noisy source input while the pre out is? I can't see any reason for that either because the internal amps are also fed by the same pre outs (electrically speaking), the difference is, obviously, with pre outs, you have the interconnect between them and your external power amp so maybe somehow noise got picked up. If your interconnects are of good quality and the length isn't too long, then I really don't understand you would have audible noise issues, I hope you will eventually find the root cause and can fix it without using additional devices.

 

[Dougey_Jones]

Okay, sorry, I do have an HTPC source at the time, that is HDMI output from my low cost Acer Nitro laptop PC. If I understand you right, you are suggesting that the internal amps are not affected by such a noisy source input while the pre out is? I can't see any reason for that either because the internal amps are also fed by the same pre outs (electrically speaking), the difference is, obviously, with pre outs, you have the interconnect between them and your external power amp so maybe somehow noise got picked up. If your interconnects are of good quality and the length isn't too long, then I really don't understand you would have audible noise issues, I hope you will eventually find the root cause and can fix it without using additional devices.

I know that you don't see any reason (electrically) why it would be the case, because I came to the same conclusion, and it sounds like OP in this thread did as well. I don't have any explanation for why the internal amps seem to be invulnerable to ground loops introduced via the HDMI inputs but the pre-outs are. I don't have an answer or explanation. The only solution for me was to filter the channels that I use pre-outs for using the device I posted above. For the balanced portion of my system, this obviously doesn't apply.

I do however think that you're making a logical leap in assuming that the signal path is identical in terms of ground loop isolation between the internal amps and the pre-outs. It's convenient to think that that's how it's wired internally, but I doubt it is. The internal amps likely have their own dedicated traces on the PCB from one stage to the other, where the pre-outs have to be routed to the back panel and broken out into 9-11 separate RCA jacks. Denon also probably had to think about optimizing the outputs to be compatible with the largest number of amplifiers, something they wouldn't have to care about if they were just driving the internal amps since it's a closed loop that they are managing.

All of those design considerations are why I don't think the RCA outputs are just (figuratively speaking) alligator clips that splice off of the existing preamp > amp circuit.

 

[peng]

I know that you don't see any reason (electrically) why it would be the case, because I came to the same conclusion, and it sounds like OP in this thread did as well. I don't have any explanation for why the internal amps seem to be invulnerable to ground loops introduced via the HDMI inputs but the pre-outs are. I don't have an answer or explanation. The only solution for me was to filter the channels that I use pre-outs for using the device I posted above. For the balanced portion of my system, this obviously doesn't apply.

I do however think that you're making a logical leap in assuming that the signal path is identical in terms of ground loop isolation between the internal amps and the pre-outs. It's convenient to think that that's how it's wired internally, but I doubt it is.

That is not really even an assumption on my part, in fact, it is 100% logical because:
- there is only one physical original connection point, that is at the volume control IC, the NJU72343, from there it would go through some switch ICs (NJU72750), opamps, HDAMs (Marantz only) and would eventually branches off to the power amp inputs, P/H output, and pre outs. I would agree that the connections to the power amp inputs would most likely involve no cabling, just pcb traces, while the pre out branch would likely involve short, but really short wires to the RCA connectors.

- You mentioned:

The conditions in which this "noise" enters the signal chain is pretty specific, so it's not at all surprising that most people don't encounter it. I asked a clarifying question because you don't have your system listed in your signature and I have no way of knowing what input sources you're using

If you believe this is the issue, then the internal power amps should be affected too, logically right? Unless the power amp section has some ways to cancel/filter out the noise, as you alluded to, in another earlier post:

I think it's kinda funny that the internal amps are obviously shielded/protected from HDMI ground loops but somehow they weren't able to apply the same protection to the pre-amp outs. Kinda wild.

but wasn't that your assumption or you got it from some reliable source? I have seen a few schematic and did not see such circuitry/components to cover HDMI ground loops. Granted, the X3900H was newly launched so there's no available service manual for me to access, but historically, the signal path being discussed are very similar if not virtually identical for the Denon 3000/4000/6000 series, hard to imagine the X3900H would do worse, but anything is possible.

Based on the above, I still think, as you mentioned already, that we really don't the explanation...., though I am of the opinion, just opinion, that if you are getting the noise issue with a specific input, or specific media source output device such as the HTPC you mentioned, or something like one of those Nvidia device someone might have mentioned, then there would likely be some issues/defects of the specific X3900H units, but not some inherent design related issues with the preamp/DAC section as such.

So first question remain, in you case, is it specific to a particular input, or source input/output device, sorry I have to ask I thought the answer to this question is yes but I am not sure.

The internal amps likely have their own dedicated traces on the PCB from one stage to the other, where the pre-outs have to be routed to the back panel and broken out into 9-11 separate RCA jacks. Denon also probably had to think about optimizing the outputs to be compatible with the largest number of amplifiers, something they wouldn't have to care about if they were just driving the internal amps since it's a closed loop that they are managing.

All of those design considerations are why I don't think the RCA outputs are just (figuratively speaking) alligator clips that splice off of the existing preamp > amp circuit.

We are basically saying the same, that using pre outs will invariably involve the use of interconnects, but that's all external, so can blame the preamp circuitry. The internal connections between the preamp output, at the volume IC are likely very short pieces of wires that wouldn't pick up much noise at all. If anything, the internal power amp will for sure inherent additional noise because of the NJU72750 multiplex IC switches ahead of it, there are not present/needed for the pre outs path.

 

[Dougey_Jones]

- You mentioned:

If you believe this is the issue, then the internal power amps should be affected too, logically right? Unless the power amp section has some ways to cancel/filter out the noise, as you alluded to, in another earlier post:

Like I said, I don't actually know why this is the case, just that it is. Perhaps the PCB that houses the signal path from preamp > amp is well grounded and isolated from the HDMI input board and whatever additional circuitry is required for the RCA outputs is not, I really don't know.

So first question remain, in you case, is it specific to a particular input, or source input/output device, sorry I have to ask I thought the answer to this question is yes but I am not sure.

It's not specific to a specific HDMI input, my HTPC is a typical "MiniPC" (think NUC) and I've ran through many of them over the years. I actually had to return one from "MinisForum" that was AMD Ryzen based because the noise that it put out over HDMI was so bad that my in-line filters couldn't wrangle it. This is obviously switching PSU noise as these PC's are made at the lowest cost possible and that noise infects the HDMI ground. I'm now using an i5 based NUC style PC that only injects minimal noise, which I then clean up with the Rolls before it hits my Apollon Hypex amps.

To answer the question though, it doesn't matter which HDMI input I choose, it affects that input. I know that it doesn't affect internal amps because I use a mix of internal amps and external amps in my HT setup, you can verify by putting your ear to the tweeter, simple as that.

 

[jonfitch]

I think it's kinda funny that the internal amps are obviously shielded/protected from HDMI ground loops but somehow they weren't able to apply the same protection to the pre-amp outs. Kinda wild.

I use two of these for for the front soundstage and internal amps for the rest of the channels:

View attachment 545356

Don't these affect the frequency and phase response somewhat? I usually address HDMI ground loop hum by simply using fully isolated optical HDMI cables since it will have no effect on the sound output while eliminating the hum.