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Speaker sensitivity and noise floor


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Hi all,

 

My horns are very efficient so I can hear a small amount of noise from the associated drive electronics. My question is, I could put an L Pad to reduce the sensitivity a little so I don’t hear the noise floor but will this just mask the noise as its still technically there? Sure I’ll have to up the amp volume a bit to compensate but I’ve got plenty in reserve.  

 

Thanks, appreciate your thoughts.

 

 

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If the noise is before your preamp/power amp combo as you raise the volume the noise will increase also. I have a very low hum from my power amp i can only hear with music off on my hands and knees and my eat against the woofer. Cant be heard a meter away and i sit five meters away so no problem. In my case raising the volume doesnt raise the noise, it stays the one level. 
 

If it is coming only from you power amp only dropping the sensitivity of your speakers will reduce that noise but not if it is coming from further up the line. 
 

As a tip try different signal earthing and mains earthing combos. You maybe able to reduce the noise more. 

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Yes. You could do that ... but the real problem almost certainly lies further back in the chain.

 

Eg. one, or all, of the electronics has too much gain.

 

Tell us more about your amp, source, etc.

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1 minute ago, davewantsmoore said:

Yes. You could do that ... but the real problem almost certainly lies further back in the chain.

 

Eg. one, or all, of the electronics has too much gain.

 

Tell us more about your amp, source, etc.

Im with this guy. 

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2 minutes ago, mwhouston said:

Im with this guy. 

 

You could be right too.... ie. if the noise is bigger than "normal" ... then fixing that, could be the solution.

 

... but when the symptom is "I have heaps of volume dial in reserve" .... then it sounds like (the age old problem of) too much gain somewhere (or everywhere).

 

 

 

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Klien DAC feeding Wayne's BA 2018 linestage from the DIY Audio site to a Weston Topaz amp. 

Pretty sure the noise is from the Topaz as its there even with the volume right down.

 

Thanks

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Posted (edited)
22 minutes ago, Half deaf said:

Klien DAC feeding Wayne's BA 2018 linestage from the DIY Audio site to a Weston Topaz amp. 

Pretty sure the noise is from the Topaz as its there even with the volume right down.

 

Thanks

Best way to check, only turn on the power amp. Then listen. Then turn on preamp and see if there is a difference. How efficient are your speakers. 

Edited by mwhouston
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Yea its there just with the power amp. Speakers are probably around 114db. Azura horn with Yamaha CD.

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Posted (edited)
34 minutes ago, Half deaf said:

Yea its there just with the power amp. Speakers are probably around 114db. Azura horn with Yamaha CD.

What are you using for bass?

 

I'm assuming you have a less efficient bass driver. Level matching with bass is more important than padding the mid down to lessen noise imo. If the issue is with the amp then fix that

 

Im also using Azura horn with a Yamamoto amp and the only noise is a bit of valve noise if I'm up close to the horn.

Edited by Gryffles
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1 hour ago, Half deaf said:

Yea its there just with the power amp. Speakers are probably around 114db. Azura horn with Yamaha CD.

 

Is the Topaz amplifier an "integrated" amp?  (ie. has a volume control?) .... sounds like no.

 

 

If no...  and assuming that your power amp with nothing else connected except the speakers, makes noise ..... then you need to fix the fault with the power amp, or get one with less noise.

 

Check tubes, etc.   Looking at the published specs, they're not the last word in noise, but also should be acceptable  (ie. not hear, without head in horn)

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Put some -10dB attenuators on your power amp inputs.  Not only will they lower your noise floor, they will also give you greater flexibility in your volume control.  Decibel Hi Fi sell Rothwell attenuators.

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Thanks guys

46 minutes ago, Gryffles said:

Im also using Azura horn with a Yamamoto amp and the only noise is a bit of valve noise if I'm up close to the horn.

Thats the noise I'm talking about, not mains hum but general noise.... Really only heard when you get close to the horn. Was just thinking this could be raising the noise floor of what I hear when listening.

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As said above, check you gain structure. That's the likely culprit. 

 

Follow Mark and Dave's advice on finding the source of the noise and you can eliminate a lot of guessing 

 

Also I am a big believer in a good quality power supply. I use a thor b8f. 

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43 minutes ago, Half deaf said:

Thanks guys

Thats the noise I'm talking about, not mains hum but general noise.... Really only heard when you get close to the horn. Was just thinking this could be raising the noise floor of what I hear when listening.

No matter what you will have some noise as all valves have it..........thermal noise. It's just how much is acceptable.

 

I also have a First Watt F6 clone and that is dead quiet however I prefer the single ended Yamamoto with the horns. 

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2 hours ago, Bronal said:

Put some -10dB attenuators on your power amp inputs.  Not only will they lower your noise floor, they will also give you greater flexibility in your volume control.  Decibel Hi Fi sell Rothwell attenuators.

 

Not going to help if the noise is there when nothing is connected to the amplifier  (ie. noise comes from within amplifier).

 

1 hour ago, Half deaf said:

Really only heard when you get close to the horn.

 

Then if it's that quiet, it's nothing to worry about.

 

You might consider an amplifier with less gain.... ~40watts is a lot for a ~110dB/w system

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15 hours ago, davewantsmoore said:

You might consider an amplifier with less gain.... ~40watts is a lot for a ~110dB/w system

Would be the plan but finding something low powered that sounds better than the Topaz is not easy. (Without spending lots of cash....)

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On 18/05/2021 at 8:43 AM, Half deaf said:

Hi all,

 

My horns are very efficient so I can hear a small amount of noise from the associated drive electronics. My question is, I could put an L Pad to reduce the sensitivity a little so I don’t hear the noise floor but will this just mask the noise as its still technically there? Sure I’ll have to up the amp volume a bit to compensate but I’ve got plenty in reserve.  

 

Thanks, appreciate your thoughts.

 

 

The answer for this is to use light dependent resistors, nothing I know of,  will work so well.  You will then have a entirely silent noise floor.  The requirements technically are to have a L pad formed by 4 such devices, and power the anodes with at least 8 volts @3ma of current , and arrange a 2N7000 mosfet in common drain form rather than directly grounding the cathodes.    

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2 minutes ago, stereo coffee said:

The answer for this is to use light dependent resistors, nothing I know of,  will work so well.  You will then have a entirely silent noise floor.  The requirements technically are to have a L pad formed by 4 such devices, and power the anodes with at least 8 volts @3ma of current , and arrange a 2N7000 mosfet in common drain form rather than directly grounding the cathodes.    

Make the LDR's  matched NSL32SR3 , as they are the best specified for audio purpose.

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When it comes to noise i apply the 1m rule. If at one meter from a driver, with your ear in line with that driver and volume at levels you would normally listen to, you cant hear any noise, then there is none. 
 

Normally I’m about 5m back from speakers. Thanks to the inverse square rule for sound, if i cant here it as the test above, then it definitely doesn’t  exist five times the distance away. 

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  • 3 weeks later...
On 18/05/2021 at 11:26 AM, Half deaf said:

Yea its there just with the power amp. Speakers are probably around 114db. Azura horn with Yamaha CD.

Definitely use an L-Pad.  This will increase your signal to noise ratio. 

At 114db and assuming you are sitting 3 meters from your speakers, very loud listening will see an average output of around 150 milliwatt  and average listening will be around 10 to 20 milliwatt, that is getting pretty close to the noise floor. 

The Topaz will perform best around the 0.5 to 5 watt level.  Basically aim to drop 15db to 18db.
So resistor values of R1 = 6.8 ohm and R2 = 1.8 ohm should be a good starting point.

 

L-Pad.gif

Edited by ehtcom
added info
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