[FossilizedArt]

HELP!



The static is droning, and the volume is deafening, but the camera didn't capture the full scope of this. The best example of the static in this video is when I play the theme song. I'm so lost right now. I'm wondering, is it possible that the sounds on my sound kit itself are staticy when amplified?

Specs:
Crix Sound Kit
Speakers: 2 X 3.25" SQUARE PIEZO TWEETER
2 X Scosche 4" HD Set
AMP: 8 Watt Mono Amp
My speakers are wired in Parallel.

[jackdoud]

Piezo speakers are generally crap sound quality anyway. The link you posted to them has no info on their rating but i'm guessing they're too-low impedance.

The Scosche have the same problem, they're 4ohm speakers in parallel giving you a total impedance of 2ohms. The amp is looking for 4ohms, try it with just one speaker.

[FossilizedArt]

Hey there, Jack - thanks for the speedy reply. I tried just one speaker (one of the two Scosches in the Sync Gen) and the static remains. Would you recommend trying to wire all 4 speakers in Series?

Failing that, what other ideas do you (or anyone) have? I am ALL ears.

[jackdoud]

Wireing them in series would compound the impedance, making two speakers be 8ohms. The way mburkit's tutorial has it is two 8ohm speakers in parallel giving a total impedance of 4ohms. According to the tutorial thread RP's chip needs 8ohm speakers and the amp needs 4ohm impedance. Dunno if crix's chip is the same way but I think your next step is to try two 8ohm speakers.

[FossilizedArt]

These look ok?

http://www.speakerworks.com/4_inch_high ... w4028s.htm

If so, it's gonna be a little bit before I can shell out for these; gotta make rent first.

[jackdoud]

These look ok?

Far as I can tell, audio electronics makes no sense to me.

[gEkX]

You want 8 ohms man wire your two 4 ohm speakers in series and then try it. You don't need the tweeters.

[FossilizedArt]

You want 8 ohms man wire your two 4 ohm speakers in series and then try it. You don't need the tweeters.

I've tried that, as mentioned in the video. The static's still there.

[Biber]

Like we were discussing in the chat room. I do believe that you should add a little more battery power to the amp. The batteries need to power the amp and speakers... More is better not too much more though

[Cole Funstuff]

Like we were discussing in the chat room. I do believe that you should add a little more battery power to the amp. The batteries need to power the amp and speakers... More is better not too much more though

I'd agree with this, what type of voltage are you putting on your amplifier?

It sounds like you're hitting the rails in the YouTube video. Try using a 9 or 12V power supply on the amplifier. Do NOT use a single power supply for both the audio chip and amplifier (aka don't put 12V on the audio chip)

Understand that there is always going to be some distortion when using these chips and amplifiers. In effect, you're only amplifying half the signal while passing the other half through to the speaker. It's a problem that requires a lot more to fix than just a single amplifier.

[slimershomie]

I had the same problem when my battery's got low i had one 9 v hooked to my amp, and it would kill it in about 30 mins my fix was to try hooking the max power the amp can take i went all the way to 18 v on my amp and it sounds a lot better it nerve racked me to no extent but it solved my problem though

Also do you have a switch disconnecting your amp power when not in use?

[Biber]

Ya i need one of those, so if anyone has any good ideas for a switch between the power for the amp i would love to hear it. But see Ronnie, looks like alot of ppl think it could be the power too hopefully we helped!

[FossilizedArt]

Try using a 9 or 12V power supply on the amplifier. Do NOT use a single power supply for both the audio chip and amplifier (aka don't put 12V on the audio chip)

I've got 8 AA's (12 v) on the amp, and 2 AA's on the sound chip. After talking to Biber, I have also tried 2 9v batteries (a total of 18v) on the amp, with the same staticy results. Also, since I'm only still testing things, I haven't wired up a switch to kill battery to the amp, though I will be implementing this when I'm happy with the sound.

I had the same problem when my battery's got low i had one 9 v hooked to my amp, and it would kill it in about 30 mins my fix was to try hooking the max power the amp can take i went all the way to 18 v on my amp and it sounds a lot better it nerve racked me to no extent but it solved my problem though

Also do you have a switch disconnecting your amp power when not in use?

See above.

Still stymied... Anyone else?

[slimershomie]

I'd try getting a new pot if mines up too high like that is sounds like that too.

[FossilizedArt]

I'd try getting a new pot if mines up too high like that is sounds like that too.

two bad potentiometers, on two different amps?

Besides, I've got a ton of potentiometers lying around here, and it's not them.

Any other ideas? Anyone?

[KieranWalker]

You're probably stuck just waiting until you can get the right speakers for it. I tried to use 4 ohm speakers on my RP sound chip and couldn't find any way to make it not sound like shit, either.

[Cole Funstuff]

Couple things to try:

1. Does the audio sound good coming directly off the sound chip? Try hooking your speaker up directly to it rather than going through the amplifier.

2. How does your amp sound when trying to amplify something else? If you have a headphone plug you don't mind cutting up, try connecting your iPod or something to amp and see if that works well.

3. If both of those work properly, then the issue is more complicated than you think. I don't suspect it will be the case tough.

You need to work through the individual systems to figure out what is causing the issue. Once you try these things report back.

[FossilizedArt]

You're probably stuck just waiting until you can get the right speakers for it. I tried to use 4 ohm speakers on my RP sound chip and couldn't find any way to make it not sound like shit, either.

Yeah, that's probably the next step, and that's gonna be whenever I have some petty cash to dispose of.

Couple things to try:

1. Does the audio sound good coming directly off the sound chip? Try hooking your speaker up directly to it rather than going through the amplifier.

2. How does your amp sound when trying to amplify something else? If you have a headphone plug you don't mind cutting up, try connecting your iPod or something to amp and see if that works well.

3. If both of those work properly, then the issue is more complicated than you think. I don't suspect it will be the case tough.

You need to work through the individual systems to figure out what is causing the issue. Once you try these things report back.

The audio does indeed sound good coming right off the kit, as mentioned in the video. I will get myself an old headphone jack and cut that up, to see if the amp still sounds scratchy from that..

[Martinus]

It almost sounds like square-wave distortion. I had guessed that the piezo's were not presenting a sufficient load to the amplifier (the impedance changes with input voltage on some of them) but given that the output with a standard speaker is still resulting in distortion I'm wondering if there's too much signal at the input stage of the amplifier.

[Spongeface]

I believe I had the same problem. Sound with the sound chip driving the speaker(s) sounded fine, but the volume was just too low. Hooked up an amp and the sound was badly distorted. The volume control also did not work as I expected - little or no control of the volume. I tried hooking up either sound chip speaker driver output or the sound chip’s “PWM” output and the results were the same (V1.2 sound chip). This was with a common ground between the amp and the sound chip.

It appeared that the problem was related to how the speaker driver in the sound chip works - you are not supposed to ground either side, as the speaker is driven differentially. So there is no simple way to connect the speaker output to many single ended amp inputs. The output of either side to ground is not acceptable. An amp with differential inputs (I don’t have one of those) may work fine.

I did finally "float" the amp by using a separate battery and then connected the floating amp's ground to one of the sound module speaker outputs and the other speaker output to the amp's input. This worked fine and there was little or no distortion. I didn’t want to use separate batteries and it is kind of a kludge and I haven't gone back to verify exactly what the source of the problem is.

Hopefully I will get back to that in a few weeks and check out the signals with my scope and see what is really going on!

[Spongeface]

Since you are using separate batteries for the sound chip and the amp you can try the same thing that worked for me: power the amp with the separate batteries and the only connections between the amp and the sound chip would be with two wires: from the sound chip's two speaker driver connections to the amps input and the amp's ground.

Do NOT connect the amp's ground to the sound chip's ground or any other "ground" or common wire or metal component that may get back to the sound chip. The sound chip will be driving the amp's ground, but that is fine as long as it is floating (not connected to some other ground).

[Spongeface]

I looked at the signals from the sound module and it is a differential PWM output. A differential input on an amp should work OK, but may also need a low pass filter, depending on how good the amp and speakers are.

The sound from the module is just not loud enough outside, so I added an amp this weekend. The amp is a simple fixed gain amp with single ended inputs. The sound was very distorted if it was driven directly from either side of the sound module's speaker driver. I looked through my parts bins and found an LM386 dual differential op amp, so built a small circuit to convert from the sound module's output to a more normal single ended output.

Here is the circuit diagram that converts from the sound chip speaker driver outputs to a single ended usable by most amps output. I am running the sound module at about 4.5V, so needed to reduce the output by a factor of 2 to get the maximum volume out of my amp without too much distortion.

If your amp can take a different range, or the sound is too loud at max or too soft at max, just change R5 and R6 to the desired gain. Gain = R5 / 200K, so in the schematic, the gain is 1/2 (100K / 200K).



I just used a couple of standoffs and mounted it on top of the small amp. The battery (I am using an 9.6V RC battery) connection should be the same as the amp, not the sound module.

[IPv6Freely]

So heres a small tidbit for you. I bought the 7w canakit amp, and detached the pot and put it on a length of cable (was going to make one of the gun knobs a volume control). Tons of static.

Bought a new kit, tried it. Zero static.

Reattached the pot on the first amp to the amp on maybe 2-3" of wire.. zero static.

I'm about to try some shielded, twisted wire for the pot. Otherwise, I'll give up on having it separate. You may wanna give that a try, though.

[GhostGuy]

"I've got 8 AA's (12 v) on the amp,"

It's just a hunch, but your power supply may be inadequate. According to my calculations, to put out 8w at 12v requires 0.66 amps. The AA batteries can supply that, but only for around 1.25 hours, and within only one hour, the voltage they output will have dropped from 12v to 8v which is the minimum the amp needs. (And it will put out less wattage with less voltage.)

Your batteries here may be effectively dead, even though you can hear the sound. They may not be supplying adequate current to the amp.

This site shows you what I'm talking about. Look at the 500mA discharge rate chart:
http://www.powerstream.com/AA-tests.htm

And here's some more charts. From these I can deduce that if you used D cells, they'd last around 8 hours:
http://www.candlepowerforums.com/vb/sho ... -Shoot-Out

NiMh will give you more bang for your buck, but NiMh AA's will still run out after 2 hours (see energizer chart 25% of the way down the page):
http://www.candlepowerforums.com/vb/sho ... -Shoot-Out

Of course none of this is evidence that the batteries are your issue. If they are fully charged then it seems like they should be able to put out enough power.

If you have a multimeter, set it to V and stick it across the battery terminals and see what you get.

[GhostGuy]

"I will get myself an old headphone jack and cut that up, to see if the amp still sounds scratchy from that."

Careful. You don't know what the impedance of those headphones are, or how much wattage they can take. You could end up frying your amp.

Then again it may be perfectly safe. I don't know enough about amps and speakers to say for sure. All I do know is that less resistance = more current, and too much current = fried electronics.

[Cole Funstuff]

"I will get myself an old headphone jack and cut that up, to see if the amp still sounds scratchy from that."

Careful. You don't know what the impedance of those headphones are, or how much wattage they can take. You could end up frying your amp.

Then again it may be perfectly safe. I don't know enough about amps and speakers to say for sure. All I do know is that less resistance = more current, and too much current = fried electronics.

Power amplifiers tend to have high impedance inputs, so current would not be an issue. You just need to make sure the volume is turned down on whatever you're amplifying since the gain is typical an order of magnitude (if not more).

Spongeface is 100% correct with the circuit he posted. Unfortunately though, most people aren't interested in going that detailed. If you're up for making that circuit, then do it. I would bet you most, if not all, audio issues would be resolved with it.

[IPv6Freely]

I looked at the signals from the sound module and it is a differential PWM output. A differential input on an amp should work OK, but may also need a low pass filter, depending on how good the amp and speakers are.

The sound from the module is just not loud enough outside, so I added an amp this weekend. The amp is a simple fixed gain amp with single ended inputs. The sound was very distorted if it was driven directly from either side of the sound module's speaker driver. I looked through my parts bins and found an LM386 dual differential op amp, so built a small circuit to convert from the sound module's output to a more normal single ended output.

Here is the circuit diagram that converts from the sound chip speaker driver outputs to a single ended usable by most amps output. I am running the sound module at about 4.5V, so needed to reduce the output by a factor of 2 to get the maximum volume out of my amp without too much distortion.

If your amp can take a different range, or the sound is too loud at max or too soft at max, just change R5 and R6 to the desired gain. Gain = R5 / 200K, so in the schematic, the gain is 1/2 (100K / 200K).



I just used a couple of standoffs and mounted it on top of the small amp. The battery (I am using an 9.6V RC battery) connection should be the same as the amp, not the sound module.

Pardon my noobness, but I'm just getting into electronics and having some trouble with your schematic. The protoboard circuit in the photo only has one LM386, but your schematic has two... can you clarify?

EDIT: nevermind, just noticed you have pins 1,2,3,4 and 8 on one and 5,6 and 7 on the other. So it *IS* just one LM386, just drawn that way for clarity, yes?

[ChapterMasterTu'Shan]

It's because of the internal circuitry of the LM386.

[melbman]

I too have been having static problems but have been using a 7w+7w stero amp. As soon as both were wired up, problem solved.

I kind of wish I hadn't wasted my time with amp and speakers as I have discovered that my x-mini portable speakers sound super loud and crisp direct off the CRIX board. They are tiny speakers with amp/bass built in, easy to use and rechargeable.

The only downside is that the swithes to turn these on are on the sides so it can be inconvenient to turn them on/off if mounted hidden inside your pack.

http://www.x-mini.com/products-detail.aspx?sid=1

[FossilizedArt]

Back again, folks. Thanks for all the input.

SO I've removed the two 4 inch speakers and am gonna be returning them (or maybe using them for something else down the road, who knows).

Instead, I'll soon be ordering a pair of these:
http://www.speakerworks.com/4_inch_high ... w4028s.htm

8-ohms each, so that SHOULD help out, too. ALSO, I'm gonna be acquiring one of the really handy-looking amp-modules Spongeface designed! Cross your fingers!