speaker hiss

[ShowMaster]

Off Topic

It was May/June 2012 when I first got voice working with the Emartee module.

On the 9XTreme, the volume is entirely software controlled, there is no hardware involved.
ersky9x now has an option to use software volume control on all platforms.

Mike.

"ersky9x now has an option to use software volume control on all platforms."

Does this include the Taranis, pro, and my Skyboard builds Mike?

[jhsa]

Skyboard and PRO have it. Not sure about the Taranis..

João

[LTMNO]

Talk about memory lane...
I remember working with Oliver, Hans and you and Mike on this... back then...
The radio was the first thing I ever bought before a quadcopter or plane.
Still have the Emartee in the Wrapper. It never saw the light of day... we went right into the MegaSound.

[MikeB]

"ersky9x now has an option to use software volume control on all platforms."
Does this include the Taranis, pro, and my Skyboard builds Mike?

Yes, on the Hardware menu, second 'page'.

Mike.

[jhsa]

I know it is off topic but, my 9x voice evolution

João

[LTMNO]

Off Topic

Great post Joao,
That should be the opening post/picture on the MegaSound thread... or there should be the museum thread...

I have sold all my other radios... don't have my original boards except for the Emartee Board. I even sold my failed Oliver attempts.
I have lots of design docs, printed charts for SMD placements and a box of parts that can build a whole new MegaSound board.

[tedbmoss]

To be clear (ahem) the hiss level is way down with the latest software. ersky9x9xt_romPbDsm.

[gb21914]

New unit arrived, and installed. Good to go...no more hiss or crackle.

Thanks everyone!

[don9f]

Hey that's good news.....you've been very patient, so well done !

Cheers Don

[LTMNO]

Amen to that!

[LTMNO]

Has anyone tried putting a Cap on the Speaker?
I did on my radio with the MegaSound I can't even hear a thing when its right beside my ear... at full volume of 7.
Just checking?

[jlsalas]

Could you please explain a bit how to put the Cap?.Thanks in advance

Enviado desde mi GT-P5110 mediante Tapatalk

[chris9691]

Hi all heres a fix that may solve the problem. The problem seems to be RF noise from either the transmitter or rf generated by the 9 xtreem board itself. Try getting a small FR choke with a internal diameter big enough to pass the speaker plug through, loop the speaker cable through the RF ckoke once forming a loop in the cable by passing it through the centre of the RF choke twice, this should choke the RF signal which is being picked up on the speaker cable and stop the RF hiss on the speaker.

[LTMNO]

Could you please explain a bit how to put the Cap?.Thanks in advance

Enviado desde mi GT-P5110 mediante Tapatalk

I have put a 4.7uF Cap on my speaker, its a littler quieter than others.. but not a squeak of other noise on the line. Crystal Clear.
I am using MegaSound on this unit.. I am going to try on my Xtreme as well... haven't got there yet.

[MikeB]

With an 8 ohm speaker, a 4.7uF capacitor creates a low pass filter with a cutoff frequency around 4kHz. So what you are really doing is removing higher frequencies, including those in the voice output.

You may also find that the capacitor also fails after a little time as the amplifier output is a bridge circuit, so drives the speaker with both polarity voltage. You need to use a non-polarised capacitor.

Mike.

[LTMNO]

You see, i know enough to be dangerous... not enough to be helpful.
I saw this on another mod, put it into my radio as i had it opened.. it worked.. sounds great.. I will trust you on that and put in a non-polarized one...
Thanks for the information... Truly!

[SkyNorth]

FYI , you can make a Non-polar cap by using 2 of them in series ..attach the two positive leads together , and
use the two minus leads for the connection .... The thing to remember is that capactiors used in series , will half
the capacitance rating ... so to get 4.7uf , you would use two 10ufs in series ....

[LTMNO]

Neat!... thanks for the information... If I could do it all over again, I would goto school for Electrical Engineering.

[jhsa]

If I could do it all over again I would go to school

João

[ShowMaster]

I was scratching my head/brain about the cap and how the speaker PC board dual pads were utilized? Did you separate/cut isolate, the pads to allow them as you pix shows, to put the cap in series with the speaker? I'm just getting facts not commenting on the application there. The concept, if cap values were tried vs highest audio freq you want to pass, could cut off unwanted noises as long as they aren't in the same range as wanted sounds. I think MikeB did some tests but I don't recall the results.
Yes to how to make a non polarized cap. It is magic if you know the tricks.

[ShowMaster]

I am curious about the ferrite ring used on the speaker leads? The concept is certainly valid and used a lot. I would like to hear a before and after audio sample to hear what "hiss" it's eliminating to know we're all on the same hiss page. Mine doesn't change and is very faint on mine with or without the XJT module installed. But the idea of the CPU's and data busses radiating RF (data) that the speaker leads pick up is interesting idea.
If you've actually heard a big improvement, it's certainly something to try.

[LTMNO]

I was scratching my head/brain about the cap and how the speaker PC board dual pads were utilized? Did you separate/cut isolate, the pads to allow them as you pix shows, to put the cap in series with the speaker? I'm just getting facts not commenting on the application there. The concept, if cap values were tried vs highest audio freq you want to pass, could cut off unwanted noises as long as they aren't in the same range as wanted sounds. I think MikeB did some tests but I don't recall the results.
Yes to how to make a non polarized cap. It is magic if you know the tricks.

Hello ShowMaster, I wired it exactly like the diagram, with the wire (+) itself and Cap in series to the (+) Pad.
I am going to test tomorrow on Xtreme and fix what Mike suggested on my 9x Solo(non-Xtreme).

Will report back tomorrow.

[ShowMaster]

Ok, the schematic shows your hookup, but looking at the picture from that angle, it's difficult to see the cap wired in series with the speaker. The schematic after you add 2 10 ufd caps + to +, or - to -, in series makes it very clear.
Thanks for testing the idea on your 9XT.

[LTMNO]

Understood, its looks deceiving with the heat shrink on the wire...
Here is the marked up photo.

[LTMNO]

Okay, I have tested the following.
I have placed a polarized CAP as that is what I had in the 4.7uF range and that significantly reduced the noise by 50% I would say from using my ear.
I then found a Ceramic Cap non-polarized at 4.7uF and that worked exactly the same but to the point of the smart ones, its the right way of doing it.
So, I would suggest people trying it out for themselves to see the difference. I would record it but I don't think you will hear the difference...
I am going to solder in my Ceramic Cap on both platforms. I am going to say that my 9x Clean build didn't need the CAP as I have one without it and its just louder and has more bass it seams. The Xtreme, there is a lot of noise but the CAP reduces that by 50% at a minimum I feel. Let me try to record for you all.

[tedbmoss]

I'd go with a .01 or .1 cap across the speaker connections because it's easier. I am trying different sizes and listening to the voice to see what is best for me. This sound level varies but is around 9 dBA above ambient, which is minuscule.

[LTMNO]

I just wanted to report back....
I tried the :

" .01 or .1 cap across the speaker connections "

with no success... Didn't change a thing, the in series method definitely reduces the sound output but always 1/2 the hissing/buzz as well.

[ShowMaster]

In the olden days, before bass and treble controls were added to am bcst radios, we added a parallel cap in series with a pot across the audio amp input. That way we could dial in the amount of audio high roll off. We didn't boost the lows, but rather turned down the highs. I'm wondering what a pot and cap in series to ground on the IC amp input would do?
I'm supposed to be trying this but the Holidays and minor bothersome backache has kept me from bending over the bench work.
My hiss as we're calling it is not heard while flying due to the much higher ambient outside field noise. It's in house I can hear it.
Old news but I'm glad you're giving it a try.
Be careful of shorting out your board.

I'd like to propose a rating scale of 1-10 , 10 being best, of how many can live with what they hear. Especially while actually flying at their favorite spot.
I'd say I'm a 9 -10, right up there with my older Taranis tx's I'm happy with.
Probably a 11 when the EDF or real turbines are flying, or the person that tunes his Nitro engine endlessly in the pit area. Yes, we all have at least one of those that never seem to fly their plane, just like to tune it up.

[MikeB]

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.

[jhsa]

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

João