speaker hiss

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ShowMaster
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Re: speaker hiss

Post by ShowMaster »

The ring was interesting. I don't have any to try. I'll have to ask my ham friends. Local electronics surplus should have some.

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Re: speaker hiss

Post by LTMNO »

jhsa wrote:What about the idea someone posted a while ago about using a ferrite ring?

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Re: speaker hiss

Post by LTMNO »

MikeB wrote:When I get a moment I'm going to try adding a 47pF capacitor across the (complimentary) inputs to the amp. This might roll off a bit of high frequency, but also suppress some noise pickup on the tracks between the processor and the amp.

Mike.
It will probably take you as much time to show me (in a diagram where that is) as to just doing it yourself.. but if you do, I will try it today, I have time to test that out... that is how much I want to solve this problem ;-)
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Re: speaker hiss

Post by LTMNO »

Any update?


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Re: speaker hiss

Post by MikeB »

Not had time to look into adding that (yet), maybe tomorrow.

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Re: speaker hiss

Post by MikeB »

I tried a 47pF capacitor and I couldn't detect any improvement. It may not be a large enough value, the cutoff frequency may be as high as 26000 Hz. I'll see if I have something in the range 200 to 300pF to try.

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Re: speaker hiss

Post by LTMNO »

Thanks for the update... out of all my radios.. the original MegaSound sounds the best... but out of the other 2 Xtreme's the 4.7uF Cap does the trick, little quieter.. but very clear and no to less hiss. I hope your solutions works... ;-)
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Re: speaker hiss

Post by LTMNO »

Mike, do you have a picture where you are doing this?
Happy to test a few options for your... really want to help solve this... its really bothering me ;-)
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Re: speaker hiss

Post by 9XTremist »

Showmaster said -
[QUOTE]
In the olden days, before ... we added a parallel cap in series with a pot across the audio amp input ... We didn't boost the lows, but rather turned down the highs ... backache has kept me from bending over the bench work.
[END QUOTE]

Did you get a chance to try that yet?
What about 2 coils with opposing polarity causing the noise to cancel itself out without losing any of the frequencies? Aka, Humbucker Coils.

I think the "olden days" way you did things is still pertinent. All of the Sound Engineers and professionals with Degrees in Acoustics that I've bothered for information over the years trying to get the best out of my PA equipment always had one common piece of advice, anytime you go above flat, you have the capability of introducing noise. Roll-off/decrease other frequencies instead of boosting one.
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Re: speaker hiss

Post by MikeB »

Have a look at this:
CapMod.jpg
CapMod.jpg (5.05 KiB) Viewed 12818 times
I've marked two points in RED very near the bottom right corner, at the ends of two resistors.
I'm testing adding a capacitor between them. Since both signals at ths point coming through 130K resistors, if the capacitor value is large, it will block the audio altogether. That's why I started with 47pF.
I've just found a 560pF capacitor, so that will be my next attempt.

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Re: speaker hiss

Post by bob195558 »

Hi Mike,
The picture is only 6 kb and so not able to see where the marked two points in RED are.
This pic is 546 kb, could you use and make this pic ? :?:
Add Cap Mod Sound_b.jpg
Thanks! :)

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Re: speaker hiss

Post by LTMNO »

I think this is the place... from what I can see.

Image

Thanks for the image... Thanks for the info.

Will test today....
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Re: speaker hiss

Post by MikeB »

Yes, those are the correct two places.

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Re: speaker hiss

Post by LTMNO »

I tried a 220pf, 470pf, 1nf, 2.2nf so far...

It seems to introduce another sound...

The hum is prominent.
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Re: speaker hiss

Post by MikeB »

During a bit of testing of adding a capacitor today, the tiny resistor (right one on the picture) failed so I had no audio output. I've replaced it with one from a prototype board for now and I'm back working again.
The interesting thing is with no resistor, there was no hiss/clicking (I have I2C enabled), even though the amplifier was still powered (class D so still driving the speaker). This, at least, indicates the noise is being introduced BEFORE the amplifier.
I was trying a capacitor from the right resistor to ground (560pF), but again, this is probably too low in value.
I'll see if I can try some other values, but don't want to break another resistor!

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Re: speaker hiss

Post by s_mack »

I think 1000 of those resistors costs around a dollar :)
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Re: speaker hiss

Post by jhsa »

you're buying them cheap ;)

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Re: speaker hiss

Post by bob195558 »

Hi,
I just ran across this youtube-video (How to Upgrade Your Taranis Speaker!) and after doing the speaker upgrade for the Taranis-X9D,
the speaker hiss disappeared, and the sound amplification was greatly increased too.
Click here to view this youtube-video: (https://www.youtube.com/watch?v=JB0qbx96BI0).

Could this speaker fix the hiss in the 9Xtreme ? :?:

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Re: speaker hiss

Post by OctavioS »

For that speaker to fit the 9x one will have to cut the power switch board in half, right?

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Re: speaker hiss

Post by bob195558 »

I think it will fit with little trouble as the 9x and Taranis cases are very similar in size.

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Re: speaker hiss

Post by s_mack »

I really doubt it would fit without modification.

When I shopped for speakers... keep in mind there are hundreds of thousands of speakers out there... the field quickly narrowed given the constraints.

8 ohm (ok, that narrows it down to tens of thousands)
40mm or smaller (now we're down to about 5 thousand)
At least half a Watt (still 5 thousand)
No more than 5.5mm thick

Whoops... that last one brings us down to pretty much 4 or 5.

Not many are that thin. And certainly not the one shown in that video, which I would guess is closer to 25mm.
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Re: speaker hiss

Post by bob195558 »

I was thinking more toward, Can a different speaker fix the hiss ? :?:

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Re: speaker hiss

Post by LTMNO »

No fix as of yet on the 9Xtreme Hissing Noise...?
Did anyone try the new speaker yet? Did it do the trick?
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Re: speaker hiss

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I did try a larger 8 ohm speaker like I used for my Taranis upgrade but no change.
The concerned hiss as we're calling it, is still not heard on 2 9xt boards unless in a quiet room. Verified by many at my field and club meetings. Much lower than a buzzy Taranis if you don't move the antenna around.
I'm not saying live with it, just that when outside flying, where I use it the most, it disappears.
I have been laid up and also dealing with the holidays, but have more bench time now.
I did find the using a finger on the audio IC circuitry I could introduce a lot of hum from my CFL overhead bench lights. This tells me that the traces and gain circuits are maybe high enough impedance to pick up adjacent data noise floating around. Like Mike, I don't think this noise is generated in the actual IC amp circuit, but instead it's being picked up and amplified. And eq or degrading of the amp circuit itself is just trying to mask it. This in turn will degrade the audio quality.
The idea of out of phase input coils or hum buckers, or balanced inputs, does work, but usually for lower end frequency hum I'm thinking.
All thinking on my part, so far, I also believe it's not the amp, but the circuitry before it, and that could be more challenging.
I've tried to scope the source but so far haven't found a direct visible cause. My scope probe actually introduces issues.
I'm open to circuit places to look at and the technique to use to actually see the offending hiss over the ambient noise already there but not heard.
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Re: speaker hiss

Post by s_mack »

I personally think that if we could get the amp to shut down when not in use, that would satisfy most people. My understanding is that people are annoyed with it hissing when it is NOT talking, right?
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Re: speaker hiss

Post by jhsa »

Couldn't the amp shutting down and restarting again introduce other noises and also other issues like delay on the sound?
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Re: speaker hiss

Post by s_mack »

Tis possible! Experimentation would be required. The whole speed-of-light thing has me optimistic, but I'm not sure by any means.
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Re: speaker hiss

Post by s_mack »

Hey... that also has me wondering. Is the hiss ONLY there when there's no voice output? I honestly can't hear the hiss unless I'm in a very quiet place (which has me concerned my hearing should be checked)... but even when I can hear it, it seems to "disappear" when a voice is spoken. My assumption was that it was being masked or simply that the louder voice made the hiss less noticeable. But is it possible that it is only hissing when there's no output? I guess what I'm getting at... can we generate an output that is less noticeable than the hiss?

Probably not. Just a thought.
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Re: speaker hiss

Post by ShowMaster »

Thinking? Any gating of the amp input or power, could introduce a pop? Doesn't this audio IC have a standby mode? I can't remember it's device # but I think it has. Wife's away for a week so more bench time tomorrow.[emoji2] I'll miss her, but I'll just have to work on Rc projects 24/7.
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Re: 9Xtreme speaker hiss

Post by s_mack »

s_mack wrote:This is the IC: http://www.issi.com/WW/pdf/31AP2005.pdf
It has shutdown mode. I see it has a 36ms time to wake up. Is that enough to cause problems with audio?

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