Amplifier hiss with Denon x3700h preout

[BullBuchanan]

Well, then it seems the issue might be the higher-than-spec gain, if we can believe the Stereophile measurements.

So the 10/100k input impedance switch doesn't make a difference?

You might just try to run the amp with XLR input to use the lower gain, just get an RCA to XLR cable (or make a decent one yourself):

D

'RCA to XLR Cable ("pseudo-balanced") to buy ?'

Feb 1, 2023

just a short question here:

I want to buy (not DIY) RCA to XLR (male) cables in the ("pseudo-balanced") fashion that Hypex and others recommend (see picture below).

I want to buy ready made / 'off the shelf' cables (of several different lenght) that are of very good* "mechanical" quality,
*by this I mean good materials and well done workmanship, ("should be pleasing to my fingers and eyes") -> I do not mean any cable-woodoo silver rhodium ultra high resolution blah blah

Any quick recommendations from your experience (a link is sufficient).




drawing from Hypex Datasheet:...

• Dirk_67
• Replies: 52
• Forum: General Audio Discussions

• 

Also: did you configure the x3700h to disconnect the amps for the pre-outs?

Connecting an external power amplifier AVR-X3700H

manuals.denon.com

No perceivable difference in noise in the 10/100k input impedance switch or with the Denon x3700h in pre-amp only mode vs normal mode.

What does the RCA shorting test tell us?

 

[staticV3]

What does the RCA shorting test tell us?

Floating (disconnected) inputs can act as antennae and pick up EMI/RFI.

Shorting the inputs prevents that and shows the DUT's true, inherent noise floor without external interference.

A small technical detail but not relevant here I believe.

 

[sam_adams]

The problem is I'm hearing an audible (from the listening position) hiss coming from the tweeters of my speakers

What position is the input impedance switch in?

 

[BullBuchanan]

What position is the input impedance switch in?

View attachment 467143

10k Currently, but I've tried both.

 

[Chrispy]

So far it sounds more like inherent noise in the amps to me. At least with a variety of Denon avrs as pre-amp and a variety of amps, I haven't had any particular noise issues from the Denons.

FWIW what is the sensitivity rating for the amps? The output of 1.4V on the Denon comes from where? Usually they typically can put out more. How do you run two pairs of speakers with this rig? Any particular setup on output level on the Denon?

 

[Sal1950]

So far it sounds more like inherent noise in the amps to me. At least with a variety of Denon avrs as pre-amp and a variety of amps, I haven't had any particular noise issues from the Denons.

Same here. My Denon X4700H into my 30+ year old Adcom amps is dead quiet with my fairly high sensitivity (90db) speakers.
I can put my ear against the tweeters and not hear any noise.

 

[BullBuchanan]

So far it sounds more like inherent noise in the amps to me. At least with a variety of Denon avrs as pre-amp and a variety of amps, I haven't had any particular noise issues from the Denons.

FWIW what is the sensitivity rating for the amps? The output of 1.4V on the Denon comes from where? Usually they typically can put out more. How do you run two pairs of speakers with this rig? Any particular setup on output level on the Denon?

"So far it sounds more like inherent noise in the amps to me" - I would tend to agree except the noise is equal in both and wasn't mentioned in the review of them where they were compared with $10k amps. So I'm not sure they're both equally defective, and it's loud enough that if it's inherent in design, you'd think someone would mention it. Also, the fact that the noise goes away when the Denon is turned off is interesting.

"what is the sensitivity rating for the amps?" - it's not published to my knowledge. output voltage was 35.7DB on the pair stereophile tested in 2006.

"The output of 1.4V on the Denon comes from where?" This is the tested limit I found here for when amps are enabled. I don't know what it is when amps are disabled.

"How do you run two pairs of speakers with this rig?" - I'm only running one set at a time and switching between them. Noise is the same on both speakers.

"Any particular setup on output level on the Denon?" - Is this configurable? Couldn't find anything int he settings and no mention of it in the manual on my searches.

 

[Sal1950]

Because the noise is consistent now across channels, I see two likely possibilities. Either the noise is inherent to the preout of my AVR or it's inherent to the design of the amplifiers.

With one amp turned off, disconnect the input, make a
Is the noise still there?
Make up an input shorting plug for the amp
Is the noise still there.
If the answer is yes to both, the amp is the problem, it should be dead quiet under these circumstances.

 

[Chrispy]

"So far it sounds more like inherent noise in the amps to me" - I would tend to agree except the noise is equal in both and wasn't mentioned in the review of them where they were compared with $10k amps. So I'm not sure they're both equally defective, and it's loud enough that if it's inherent in design, you'd think someone would mention it. Also, the fact that the noise goes away when the Denon is turned off is interesting.

"what is the sensitivity rating for the amps?" - it's not published to my knowledge. output voltage was 35.7DB on the pair stereophile tested in 2006.

"The output of 1.4V on the Denon comes from where?" This is the tested limit I found here for when amps are enabled. I don't know what it is when amps are disabled.

"How do you run two pairs of speakers with this rig?" - I'm only running one set at a time and switching between them. Noise is the same on both speakers.

"Any particular setup on output level on the Denon?" - Is this configurable? Couldn't find anything int he settings and no mention of it in the manual on my searches.

I'm just suspecting the amps so far, or at least suspect the incompatibility is caused more at their end.

Just looked at the review a bit, they tested the amps with a fairly high voltage from the pre-amp it seems.

That's just a distortion level, the voltage is typically higher, albeit at a higher distortion (but still quite useable).

Both are fairly sensitive speakers, yes?

Speaker trim level would be one way.....assume you're just at default 0 level? No subs so you didn't run Audyssey or other setup?

 

[BullBuchanan]

With one amp turned off, disconnect the input, make a
Is the noise still there?
Make up an input shorting plug for the amp
Is the noise still there.
If the answer is yes to both, the amp is the problem, it should be dead quiet under these circumstances.

I already shorted the input to the amp via the RCA cable and posted results on the previous page. When shorting the RCA, it's silent.

 

[BullBuchanan]

I'm just suspecting the amps so far, or at least suspect the incompatibility is caused more at their end.

Just looked at the review a bit, they tested the amps with a fairly high voltage from the pre-amp it seems.

That's just a distortion level, the voltage is typically higher, albeit at a higher distortion (but still quite useable).

Both are fairly sensitive speakers, yes?

Speaker trim level would be one way.....assume you're just at default 0 level? No subs so you didn't run Audyssey or other setup?

I have subs, but just testing these in direct mode for now. I haven't run audyssey on this setup. Just went to preset 2, as I have an audyssey config on 1.

Not sure about the trim mode.

 

[Chrispy]

I have subs, but just testing these in direct mode for now. I haven't run audyssey on this setup. Just went to preset 2, as I have an audyssey config on 1.

Not sure about the trim mode.

The Audyssey config was for the avr alone with one set of speakers/sub? To incorporate the external amp for a particular setup of speaker/sub, I'd re-run Audyssey, it will set trim levels as appropriate for the combo (may not be a significant difference, more curious what it would do). Direct mode is setup to use a sub for 2ch content? If you use the Audyssey Editor App you can save more than two setups....

 

[BullBuchanan]

The Audyssey config was for the avr alone with one set of speakers/sub? To incorporate the external amp for a particular setup of speaker/sub, I'd re-run Audyssey, it will set trim levels as appropriate for the combo (may not be a significant difference, more curious what it would do). Direct mode is setup to use a sub for 2ch content? If you use the Audyssey Editor App you can save more than two setups....

"The Audyssey config was for the avr alone with one set of speakers/sub?" Correct. It's for the Large charcoal speakers (Tekton Double Impacts) that I've been using as my primary. I just got the von schwiekerts and have been auditioning them against the Tekton.

"Direct mode is setup to use a sub for 2ch content?" ive mostly just been testing with music so far. Direct bypasses bass management so the sub would be out of the equation. However it doesn't matter which mode I use, the noise floor stays consistent.

 

[BullBuchanan]

Update

The issue does seem to be related to The Denon x3700h somehow, either via noise on the pre-oits or the comparability issue others mentioned regarding output voltage.

I plugged in an EL DAC from JDS Labs in place of the Denon and the noise was far quieter. It still isn't silent like the Denon internal amps are, but it's a fraction of the noise I get when using the pre-oits, and it's not audible from the listening position.

Comparison:

Denon x3700h pre-outs: https://photos.app.goo.gl/4FsQ9KZk5skWj4uQ7
JDS Labs EL DAC: https://photos.app.goo.gl/xDoydVc7454iwHu97

I guess the next step is to find a different amp and see if the Denon puts noise through that as well or if it's exclusive to this combo

 

[BullBuchanan]

Update 2 - I bought some cheap XLR to RCA cables. This significantly lowered the noise floor when no content is playing. Not sure if this is primarily because of the lower output gain on the amp when powering by XLR or a design flaw/performance degredation in the RCA input of the amps.

Other things I noticed:

• With The RCA cables, the speakers would make a pop sound when turning on the amp. When turning on with the XLR's they now make more of an "energizing" sound, like an old CRT TV.
• With The RCA cables, the noise coming from the tweeter was a loud hiss, audible from the listening position when the receiver was on. With the XLR, noise is only audible from the tweeter with my ear 6-8" from the tweeter. Instead of a hiss, it's more of a fast ticking sound, like a watch. I'm guessing this is from the amps, as it's the same in both and was consistent across different power outlets.

At this point, I'd like to try a different preamp if I can source one cheap to see if the sound goes away completely with a different configuration and a different amp to see if I get better results with the Denon.

I have the amps listed for sale right now, but not sure whether to consider them as faulty or not. I have basically no experience with amp separates, so not sure if this sort of thing is within normal parameters. Hopefully I'll be able to confirm with other equipment soon.

 

[Sal1950]

At this point, I'd like to try a different preamp if I can source one cheap to see if the sound goes away completely with a different configuration and a different amp to see if I get better results with the Denon.

Do you have a local dealer? Maybe you can get a loaner for your test. Pretend your maybe a buyer.
Or many online dealers have fantastic return policies.
Crutchfield pays return shipping for 60 days, great people to do business with.

 

[PJR918BMW]

Hi. I had/have similar issue with same Denon. See
www.audiosciencereview.com/forum/index.php?search/47476759/&c[users]=PJR918BMW&o=date
I have put it down to the Denon. That is the faint hiss - not the ticking thing. If you do some digging this sort of thing has come up before. Maybe asking too much of a relatively budget receiver stuffed full of electronics!