Amplifier hiss that varies with volume

[Denis29]

I noted a peculiar artifact in my Yamaha DSP-E492 as I was playing around with its different settings.

A little background. The E492 can be used in an "internal" or an "external" mode. When switched to "external", it's simply a power amp powering center and surround channels, and you have no volume control or sound processing from this unit. When switched to "internal", you have full access to the unit's sound processor and an active volume control.

In the "external" mode, the unit is very quiet, and you can only hear a faint hum if your ear is right into the speaker. In the "internal" mode, there's quite a bit of hiss, and it gets louder if you turn up the volume. The unit makes the hiss without anything connected to it in the "internal" mode. The hiss is quite obvious within a foot or 2 from the speaker when playing music quietly. About 5 ft from the speaker, you won't hear it with the music on. All this with the volume dial on the Yamaha set at roughly 10 o'clock. With the dial at 12 o'clock, you can definitely hear the hiss 5 ft from the speaker with the music off.

Something in the preamp circuit for this unit? Like a resistor or a capacitor?

 

[markw]

Yep, it's emanating from somewhere in the preamp. It may have always been there, it could be a recent development, or it could have gradually developed over time.

Pinpointing it to one (or several) particular component(s) is nigh on impossible without some pretty sophisticated equipment and technical experience.

I will say that some residual noise is fairly common in all powered circuits.

 

[BoredSysAdmin]

Is this case of ground loop hiss?

 

[highfigh]

Is this case of ground loop hiss?

Ground loops don't cause hiss.

 

[highfigh]

I noted a peculiar artifact in my Yamaha DSP-E492 as I was playing around with its different settings.

A little background. The E492 can be used in an "internal" or an "external" mode. When switched to "external", it's simply a power amp powering center and surround channels, and you have no volume control or sound processing from this unit. When switched to "internal", you have full access to the unit's sound processor and an active volume control.

In the "external" mode, the unit is very quiet, and you can only hear a faint hum if your ear is right into the speaker. In the "internal" mode, there's quite a bit of hiss, and it gets louder if you turn up the volume. The unit makes the hiss without anything connected to it in the "internal" mode. The hiss is quite obvious within a foot or 2 from the speaker when playing music quietly. About 5 ft from the speaker, you won't hear it with the music on. All this with the volume dial on the Yamaha set at roughly 10 o'clock. With the dial at 12 o'clock, you can definitely hear the hiss 5 ft from the speaker with the music off.

Something in the preamp circuit for this unit? Like a resistor or a capacitor?

Caps are used for filtering and don't cause hiss. If they're in the power supply, they cause hum when they break down.

Are you equalizing manually, as opposed to YPAO or some other automatic version? If you're doing it manually, make sure you're not boosting the high end and mid-range too much. It's better to lower the high bands a bit so you can boost the others less.

 

[Denis29]

Thank you all for the replies

I am not using any external equalizers. In my main unit (an Onkyo DVD receiver), which provides 6 channels of pre-amped signal to my separates, I set both bass and treble to +0db, so I am running flat. I am extremely happy with that, and the sound is amazing.

I played around with the settings some more and noticed that by internally boosting the signal to center and surround channels in two stages, the noise level from the Yamaha considerably decreases.

In my main Onkyo receiver, I can choose the db levels for channel equalization. I can do the same in the Yamaha. So, I boosted center +5 db and surrounds +8 db in the Onkyo. In turn, I boosted center +10 db and surrounds +10 db in the Yamaha as well. This lets me dial down the Yamaha volume knob considerably, and the music sounds much richer and clearer, with hiss as good as dead from a listening position (unless you stick your ear into the speaker).

Can someone please explain how the channel db equalization works and why boosting in my case results in less noise from the Yammy? Does this say that the volume pot on the Yammy is causing something bad to happen?

 

[highfigh]

Thank you all for the replies

I am not using any external equalizers. In my main unit (an Onkyo DVD receiver), which provides 6 channels of pre-amped signal to my separates, I set both bass and treble to +0db, so I am running flat. I am extremely happy with that, and the sound is amazing.

I played around with the settings some more and noticed that by internally boosting the signal to center and surround channels in two stages, the noise level from the Yamaha considerably decreases.

In my main Onkyo receiver, I can choose the db levels for channel equalization. I can do the same in the Yamaha. So, I boosted center +5 db and surrounds +8 db in the Onkyo. In turn, I boosted center +10 db and surrounds +10 db in the Yamaha as well. This lets me dial down the Yamaha volume knob considerably, and the music sounds much richer and clearer, with hiss as good as dead from a listening position (unless you stick your ear into the speaker).

Can someone please explain how the channel db equalization works and why boosting in my case results in less noise from the Yammy? Does this say that the volume pot on the Yammy is causing something bad to happen?

As I posted, it's best to boost as little as possible- along with the signal comes the noise. The reason the hiss goes away is due to the Yamaha being set for less sensitivity, but when you add 5dB-10dB of signal, you run the risk of the Onkyo distorting. Take everything down so the one(s) you boosted the least aren't boosted at all and drop the rest by the same amount. You'll need to increase the Yamaha's sensitivity but you should still hear no hiss.

Most receivers aren't designed so the volume control section is boosting anything. In fact, the volume control is an attenuator, which is why the display shows -23dB, -40dB, etc. Boosting (gain) adds noise and adds distortion if the output from one stage exceeds the limits of the next input stage.

 

[TLS Guy]

I noted a peculiar artifact in my Yamaha DSP-E492 as I was playing around with its different settings.

A little background. The E492 can be used in an "internal" or an "external" mode. When switched to "external", it's simply a power amp powering center and surround channels, and you have no volume control or sound processing from this unit. When switched to "internal", you have full access to the unit's sound processor and an active volume control.

In the "external" mode, the unit is very quiet, and you can only hear a faint hum if your ear is right into the speaker. In the "internal" mode, there's quite a bit of hiss, and it gets louder if you turn up the volume. The unit makes the hiss without anything connected to it in the "internal" mode. The hiss is quite obvious within a foot or 2 from the speaker when playing music quietly. About 5 ft from the speaker, you won't hear it with the music on. All this with the volume dial on the Yamaha set at roughly 10 o'clock. With the dial at 12 o'clock, you can definitely hear the hiss 5 ft from the speaker with the music off.

Something in the preamp circuit for this unit? Like a resistor or a capacitor?

If the hiss is equal on left and right front channels, it is either a badly designed preamp, or your speakers have a peak between 4 and 7 kHz which is emphasizing noise.

 

[Boerd]

I noted a peculiar artifact in my Yamaha DSP-E492 as I was playing around with its different settings.

A little background. The E492 can be used in an "internal" or an "external" mode. When switched to "external", it's simply a power amp powering center and surround channels, and you have no volume control or sound processing from this unit. When switched to "internal", you have full access to the unit's sound processor and an active volume control.

In the "external" mode, the unit is very quiet, and you can only hear a faint hum if your ear is right into the speaker. In the "internal" mode, there's quite a bit of hiss, and it gets louder if you turn up the volume. The unit makes the hiss without anything connected to it in the "internal" mode. The hiss is quite obvious within a foot or 2 from the speaker when playing music quietly. About 5 ft from the speaker, you won't hear it with the music on. All this with the volume dial on the Yamaha set at roughly 10 o'clock. With the dial at 12 o'clock, you can definitely hear the hiss 5 ft from the speaker with the music off.

Something in the preamp circuit for this unit? Like a resistor or a capacitor?

I owned a Primare I21 integrated amplifier and at some point I had the same problem. The I21 was still under (extended) warranty and I sent back to be fixed. I was told it was the volume circuit part of the preamp and it was fixed, the hissing stopped.
Then, a few weeks later it literally turned to pop corn - I have never seen or heard something like that - a loud thump and small pieces popping and jumping through the amp. Scary.
I took it back and got a brand new replacement. It turned out the problem was in the preamp but not only in the volume circuit - it was hard to tell since almost everything was fried inside...
Anyway - I don't know how helpful my experience was for you

 

[Denis29]

As I posted, it's best to boost as little as possible- along with the signal comes the noise. The reason the hiss goes away is due to the Yamaha being set for less sensitivity, but when you add 5dB-10dB of signal, you run the risk of the Onkyo distorting. Take everything down so the one(s) you boosted the least aren't boosted at all and drop the rest by the same amount. You'll need to increase the Yamaha's sensitivity but you should still hear no hiss.

I see your point, but the hiss comes through from the Yamaha even with nothing connected and nothing playing, and the intensity of said hiss decreases with attenuation of Yamaha volume. The more you attenuate the vol control, the less hiss comes through the speakers. Boosting individual channel db levels allows me to attenuate Yamaha volume pot to a greater extent, and this does let me control the hiss.

What I'm trying to explain is that the amount of db boost on individual channels does not contribute to the hiss level at all! The only thing that matters is how high the Yamaha volume is set. Funny thing - the Yamaha doesn't distort at all, no matter how high I boost the channels.

I have read of hiss issues with this particular Yamaha before. It's not bad at all now that I'm understanding how to control it, but it does weird me out that when I use the Yamaha in the "external mode" - i.e., straight to power amp without using the volume control or sound processor - there is no such hiss! And yes, the hiss does come through on all channels (center and surround) the same way.

So back to my original question. Channel equalization is handled by the pre-amp, right? So why does THAT not introduce any more noise into the system, while fooling with the volume knob does??

 

[highfigh]

I see your point, but the hiss comes through from the Yamaha even with nothing connected and nothing playing, and the intensity of said hiss decreases with attenuation of Yamaha volume. The more you attenuate the vol control, the less hiss comes through the speakers. Boosting individual channel db levels allows me to attenuate Yamaha volume pot to a greater extent, and this does let me control the hiss.

What I'm trying to explain is that the amount of db boost on individual channels does not contribute to the hiss level at all! The only thing that matters is how high the Yamaha volume is set. Funny thing - the Yamaha doesn't distort at all, no matter how high I boost the channels.

I have read of hiss issues with this particular Yamaha before. It's not bad at all now that I'm understanding how to control it, but it does weird me out that when I use the Yamaha in the "external mode" - i.e., straight to power amp without using the volume control or sound processor - there is no such hiss! And yes, the hiss does come through on all channels (center and surround) the same way.

So back to my original question. Channel equalization is handled by the pre-amp, right? So why does THAT not introduce any more noise into the system, while fooling with the volume knob does??

If 'External' mode means that the preamp isn't used, in favor of another preamp/processor, the hiss is from the preamp not being designed for low signal to noise ratio.

 

[Denis29]

If 'External' mode means that the preamp isn't used, in favor of another preamp/processor, the hiss is from the preamp not being designed for low signal to noise ratio.

I agree, BUT... I don't think it's bad design necessarily. See specs for this unit on the image attached: I'm using the 6-ch discrete input option, which is detailed separately in the specs.

Can this hissing be localized to that blasted volume pot? As Boerd indicated, he had a faulty volume pot, replacing which fixed the problem (albeit temporarily, probably combined with another problem).

Since I am able to "trick" the problem by boosting the db channel signal electronically within Yamaha while turning down its volume pot, doesn't that kind of point toward the volume pot as being the culprit? I don't know how volume pots work... But maybe I could add a hiss filter across it (some website posted a schematic, involving one resistor and one capacitor)...

 

[markw]

By process of elimination...

... you can be pretty sure that the hiss is generated from somewhere after the volume pot and before the main amp inputs.

Good luck, but honestly, I think you're chasing your tail here. It sounds like a design issue.

 

[highfigh]

I agree, BUT... I don't think it's bad design necessarily. See specs for this unit on the image attached: I'm using the 6-ch discrete input option, which is detailed separately in the specs.

Can this hissing be localized to that blasted volume pot? As Boerd indicated, he had a faulty volume pot, replacing which fixed the problem (albeit temporarily, probably combined with another problem).

Since I am able to "trick" the problem by boosting the db channel signal electronically within Yamaha while turning down its volume pot, doesn't that kind of point toward the volume pot as being the culprit? I don't know how volume pots work... But maybe I could add a hiss filter across it (some website posted a schematic, involving one resistor and one capacitor)...

A volume pot is a passive device and won't add hiss. Newer electronics will often have a volume know but it's only controlling a processor, so it's not even in the audio circuitry in any way.

 

[Denis29]

How do you explain the following:

With the power on but nothing hooked up to it (or, equivalently, with all the other devices off), the Yamaha produces the hiss when switched to "internal" but then if you switch to "external", the hiss immediately disappears. Switch back to "internal", and the hiss comes back.

Obviously, this has nothing to do with signal, but I guess maybe the designers accepted this noise floor. To its credit, the Yamaha amp reproduces music beautifully, but I just wanted to get to the root of the cause - if it's an equipment fault or perhaps less than stellar design.

 

[markw]

One last time. Read carefully.

How do you explain the following:

With the power on but nothing hooked up to it (or, equivalently, with all the other devices off), the Yamaha produces the hiss when switched to "internal" but then if you switch to "external", the hiss immediately disappears. Switch back to "internal", and the hiss comes back.

Two simple sentences. Try your best to comprehend them. I'll type slowly.

1) When the switch is set to INternal, you are using the INternal preamp which generates hiss.

2) When the switch is set to EXternal, you are using the EXternal preamp which DOES NOT generate hiss.

if it's an equipment fault or perhaps less than stellar design.

Ya think? Either replace it or, if you have money to throw away, get it looked at by a knowledgeable tech.

Got it? Good!

Next question...

 

[Denis29]

Two simple sentences. Try your best to comprehend them. I'll type slowly.

.................

Got it? Good!

Haha. Be nice, be nice - I'm sure I'm testing some folks' patience with my n00bness, but we all eventually start somewhere, don't we.

Anyhow, my point was that the hiss from the pre-amp is regardless of signal because it was suggested before that amount of signal coming to it might have something to do with the problem.

Peace out!

 

[markw]

"newbie"??

From the other thread you've just started, that's some pretty sophisticatd gear for a "newbie" and you discuss it's features and use in a manner that seems to contradict you're not being able to grasp the fairly simple and basic concepts being expressed here.

Case in point.

 

[Denis29]

From the other thread you've just started, that's some pretty sophisticatd gear for a "newbie" and you discuss it's features and use in a manner that seems to contradict you're not being able to grasp the fairly simple and basic concepts being expressed here.

Case in point.

Thanks. Well, in this thread, I was kind of trying to understand how such a pre-amp works and see how difficult it would be pinpoint the issue within the pre-amp. That's why I kept repeating the issue.

When I started this thread, I knew that the issue was with the preamp and that internal/external means preamp/no preamp. But the devil is in the details, so I repeated myself a few times to make sure I communicated all the details.

Anyhow - Peace. I'm learning here...