Skar audio RP4500 need help!

[Basshead1989]

Ok Perry the rca grounds are intact.

On the op amp that drives the driver board audio I don't see the noise.

The capacitor did make a visible difference it made the noisy signal smaller as you can see in the pics below
SCOPE SETTINGS 1ms / 50mv x10

 

[Perry Babin]

Will the amp ever produce audio?

If so, is the audio cleaner with the cap?

 

[Basshead1989]

Yes that amp produces audio it looks somewhat fuzzy and it does clean up with the cap it takes away the fuzziness of the signal

In the pic below is the signal on the speaker terminal with no audio injected I also noticed if I do twist and pull on the inductors fairly hard it will clean the signal in the pic below up or cause it to get fuzzy again but it does the same when I move around power wire to amp

SCOPE SETTINGS FOR pic below 20mv / 20us x10

 

[Perry Babin]

For the most part, you evaluate the amount of noise on the output of a class D amp with the scope on 2ms and 5v/div (with or without audio).

 

[Basshead1989]

Ok heres what it looks like on 5v / 2ms probe x1 on speaker terminal with no audio just the squealing sound from amp before and after cap added.pics below

 

[Perry Babin]

I should have asked for a more precise definition. How loud is the squealing?

Is it audible when a subwoofer (no mods or tweeters) is connected? Would it be audible with the woofer in the trunk of the vehicle?

 

[Basshead1989]

Yea its audible it's not real loud but it's definitely there and can be heard over the audio at low volume I think you could hear it in a trunk forsure it sounds funky like dial up internet almost but depending on how you move it or what you touch it will stop then start back up again

You can't hear the squealing unless a speaker is connected

 

[Basshead1989]

To be more clear I have only 2 fets for each transformer on power supply side and 1 output fet in for each bank on the output side

 

[Perry Babin]

From the way you described it, I thought it was borderline so loud that it would cause hearing damage.

Does it sound like this?

http://www.bcae1.com/temp/cooleditmixedoscillator01.wav

 

[Basshead1989]

Yea it's sounds just like that basically yea its not gonna hurt your ears but its loud enough threw the subwoofer to hear from 10 feet away

 

[Perry Babin]

That's covered under item 6 on the basic class D page. It may be slightly louder than normal if the low voltage is causing the oscillation frequency to be a bit lower than normal.

It's caused when two oscillators (PS and output) are not synchronized.

 

[Basshead1989]

Oh ok seems i need to re read threw the class d files again.

So what the next step then because other then that it plays well with LV supply

 

[Basshead1989]

Yea ima go threw a read the tutorial again since it's been updated I didn't realize how out-of-date my tutorial was

 

[Perry Babin]

Install all of the outputs and re-check the drive waveforms. Make sure it still produces audio and none of the outputs overheat.

 

[Basshead1989]

All outputs were installed and all drive waveforms looked the same rail-rail was 30vpp @35.7hz and 8v above positive rail on highside gate pads and 10v above on negative rail gate pads.

It still plays audio well and stayed pretty cool actually.

 

[Perry Babin]

Increase the number of turns by 4, 5, 6... It's not critical and see if the oscillating frequency goes up any.

 

[Basshead1989]

Ok i will but right now i don't have enough wire on there to do that many more wraps maybe 1 or 2 I cut it down not thinking id need to wrap more so ill rewrap it tomorrow as soon as I'm home from work.

As always thanks perry.

 

[Perry Babin]

Whenever you do it, you can just add to it. You don't need to completely re-wrap it.

 

[Basshead1989]

Oh I was just thinking could I add a length of wire and heat shrink it. Will that be fine

 

[Basshead1989]

And do to lack of space can I wrap on top of the first wraps or over lap each other alil?