Weird audio Amp problem...

[g1]

Is the electret mic preamp designed to be running at the voltage you are running it at?
It sounds like you have added a push-button disconnect for the electret and it temporarily cures your problem? The explanation is a bit confusing.

[Enzo]

Whenever I see a symptom of a repressed output that springs to life at power down, my first thought is an unterminated DC voltage somewhere. For example, a missing/open resistor at a transistor base. Or a tube grid. If your preamp uses op amps, check the output pins for DC offset. For that matter, make sure the power to the IC is right. If you are running single sided off a battery, did you include a good voltage reference at half voltage?

[jjj]

What is the model of the 100watt class D amp and why are your turning it off/on briefly? If the amp exhibits no other problem than this I thing you could be upsetting the SMPS Oscillation pattern. If you turn it off then wait 5 or 10 seconds does it still exhibit said behavior?

nosaj

The model is: "China garbo"/ Chip: TPA3116 D2
Yes, you are right... if I turn it off and wait for about 10 seconds and then turn it on, the volume doesn't jump high and then slowly lowers, but the volume level is fairly modest. So, the the rapid power turn off/on must be "upsetting the SMPS Oscillation pattern" and that explains the momentary volume raise. These things I wouldn't know. The stupid thing is, that I actually like this higher volume level, but don't know how to obtain it.
OK then. The question now is: since this is a 100W Amp any higher voltage should deliver more volume; am I right? I'll try to raise the voltage with this one and see if it's any good:

[nosaj]

The model is: "China garbo"/ Chip: TPA3116 D2
Yes, you are right... if I turn it off and wait for about 10 seconds and then turn it on, the volume doesn't jump high and then slowly lowers, but the volume level is fairly modest. So, the the rapid power turn off/on must be "upsetting the SMPS Oscillation pattern" and that explains the momentary volume raise. These things I wouldn't know. The stupid thing is, that I actually like this higher volume level, but don't know how to obtain it.
OK then. The question now is: since this is a 100W Amp any higher voltage should deliver more volume; am I right? I'll try to raise the voltage with this one and see if it's any good:

Let me start off by saying this, you are doing the same thing I have been guilty of many times here. If you want to fix this follow JM Fahey instructions closely, do not go left unless instructed to or right for that matter. Do only what is asked of you and nothing more than reporting back.

You are bouncing all over the place without really answering any questions or responding with any test. What you will find is if you don't help yourself by helping us help you. You will still have the same problem. This is not like other music forums out there, There are real techs from the benches here, not people who might postulate on unreal possibilities.

So lets get this show on the road, go back to JM Fahey's lasy post and please answer the questions, Then G1, then Enzo.

If there is a language barrier please state so we can work with what we know, there are many multiple language people here that can and do help.

Our main goal and possibly motto should be "We can help you get it fixed and if you want more , Help you understand"
The journey of a thousand miles starts with one step, some people never make that first step out of fear though.

nosaj
You can do it, I have faith

[jjj]

I have no doubt that you are all experts in electronics and that's why I begged you for help. Enzo helped me in the past and I never forgot him, too.
I read all the posts and at the same time made sure that I checked out if any of these suggestions/ possibilities might apply. Your previous post happened to fit my problem and that's why I discarded other possible causes. I also understand that it is almost impossible to guess the problem, unless one has all the detailed Info.

But at least we got near enough to what is causing it and that's what I was looking for and I am truly grateful for this help. - You are also right that I should reply to each question, because it serves to narrow down and diagnose the problem. On the other hand I at least changed the electret Mic PreAmp and the 100W Amp and so, knew where I was heading.
Tomorrow I'm going to open the system box again and increase the 100W Amp's voltage to about 18V and observe if the sound volume increases to the desired level and remains steady. - I'll let you know of the result. I really trust that it might resolve the problem. Of course it then still will suddenly raise the volume level if I turn the system rapidly turn off & on again, because that's the nature of this class D Amps, I learnt and I should avoid it.
Besides, I did the same kind of "labor of love", you good people do, for many years, teaching youngsters philosophical insight while performing in public and they were very grateful. I wrote several philosophical books, titled: "A Guide To Personal Contentment" and "Grandpa's Insight"

[jjj]

My victory celebration came too early...
I just finished to add that (shown) voltage up circuit and adjusted it to 22V. It all looks good, but.. but when switch the system on the full sound volume of the 8 Ohm speaker is still only moderate. Yet, when I then turn the power switch fast off + on the sound volume goes "through the roof" (very loud) and I have to curb the volume with that speaker Pot. This high volume level then takes about 20 seconds to gradually return back to the moderate sound level.
So, the 22V voltage increase results in no significant sound volume increase/ change from the normal 11.1V battery supply. How disappointing!
That make me wanting to go back to the sound volume "kick start" idea of quickly turning off and on the power supply. During whistling I can easily find a spot in the melody where I can for 1 second "kick start" the system. The only problem with that how to silence the switching noise?
In three steps:
1) A press onto a tiny push switch at the Mic disconnects the speaker
2) A push button press then turns off & on the power supply
3) and another press onto the tiny push switch (from 1) reconnects the speaker

There surely are better ways of achieving it with just one press on a push button. In all it would make me already happy.
I don't know why this class D Amp causing me all these problems. Maybe I should rather use a small car Amp? With this unit I tried to build a small unit for room size performance. My big unit busking unit has a 30+30W Sony car Amp and a stereo tube PreAmp (which I build) and there I haven't got this kind of problems with the very same components (i.e. Electret Mic PreAmp, => ETI-486 Howl-round Stabilizer => Pedal Reverb).

[nickb]

I suggest you take the output from each section one at a time to an external known good amplifier in order to isolate where the problem occurs i.e mic preamp, reverb, howl suppressor, power amp input. Is there a preamp with tone/ volume somewhere in this?

[J M Fahey]

Tomorrow I'm going to open the system box again and increase the 100W Amp's voltage to about 18V and observe if the sound volume increases to the desired level and remains steady. - I'll let you know of the result. I really trust that it might resolve the problem.

Who asked for that experiment?

Of course it then still will suddenly raise the volume level if I turn the system rapidly turn off & on again, because that's the nature of this class D Amps, I learnt and I should avoid it.

No, itīs not the nature of Class D amps, there are millions of them around and nobody reports that.
In fact, I donīt even think the problem lies in the Class D amp, go figure.

My victory celebration came too early...

Why that doesnīt that surprise me?

That make me wanting to go back to the sound volume "kick start" idea of quickly turning off and on the power supply.

Please be my guest.

[nosaj]

My victory celebration came too early...
I just finished to add that (shown) voltage up circuit and adjusted it to 22V. It all looks good, but.. but when switch the system on the full sound volume of the 8 Ohm speaker is still only moderate. Yet, when I then turn the power switch fast off + on the sound volume goes "through the roof" (very loud) and I have to curb the volume with that speaker Pot. This high volume level then takes about 20 seconds to gradually return back to the moderate sound level.
So, the 22V voltage increase results in no significant sound volume increase/ change from the normal 11.1V battery supply. How disappointing!
That make me wanting to go back to the sound volume "kick start" idea of quickly turning off and on the power supply. During whistling I can easily find a spot in the melody where I can for 1 second "kick start" the system. The only problem with that how to silence the switching noise?
In three steps:
1) A press onto a tiny push switch at the Mic disconnects the speaker
2) A push button press then turns off & on the power supply
3) and another press onto the tiny push switch (from 1) reconnects the speaker

There surely are better ways of achieving it with just one press on a push button. In all it would make me already happy.
I don't know why this class D Amp causing me all these problems. Maybe I should rather use a small car Amp? With this unit I tried to build a small unit for room size performance. My big unit busking unit has a 30+30W Sony car Amp and a stereo tube PreAmp (which I build) and there I haven't got this kind of problems with the very same components (i.e. Electret Mic PreAmp, => ETI-486 Howl-round Stabilizer => Pedal Reverb).

Something occurs to me that is in analogy form but I'm not sure if this is possible.

To me this seem like a carborated engine, similar to pumping the gas before starting giving it an inrush of gas an air to make the engine rev.. which it goes back to normal after the excess gas has burned off.

So first off stop turning it off then on real fast. Turn it on feed a sine wave signal into it with a dummy load in place of the speaker and take an AC voltage measurement, if we can get roughly 85 watts out of the amp, you have no problem with it and have created a problem where there was none.

nosaj

[J M Fahey]

Oh, he will never get that amount of power out.

Just 15W into 4 ohms with straight 12V from battery, and maybe 70W RMS from a *stiff* overrated 26V power supply, none of that cheesy booster fed from a puny underrated battery nonsense, simply because thatīs what voltage swing allows.

The test should be to feed whateverīs needed (think 500mV to 1V RMS or so) to Class D amp until it just clips, first check that it holds output steady, then turn it on-off many times to see whether there is a volume surge (I bet none will be found ) and then start checking for the real problem.

[nosaj]

Oh, he will never get that amount of power out.

Just 15W into 4 ohms with straight 12V from battery, and maybe 70W RMS from a *stiff* overrated 26V power supply, none of that cheesy booster fed from a puny underrated battery nonsense, simply because thatīs what voltage swing allows.

The test should be to feed whateverīs needed (think 500mV to 1V RMS or so) to Class D amp until it just clips, first check that it holds output steady, then turn it on-off many times to see whether there is a volume surge (I bet none will be found ) and then start checking for the real problem.

Well I just kinda pulled that number outta my a$$ for a rough estimate I guess I should start doing the math.

nosaj

[jjj]

Test result: If I ran the same setup with my Sony car Amp and I haven't' got this problem. Yet, since I tried to create a small traveler's unit with the same components I ran into 1000 problems. To me the components (i.e. electret Mic PreAmp, ETI-486 Howl-round Stabilizer and the pedal Reverb work fine, only the 100W Amp doesn't' deliver to my expectations. Maybe the pedal Reverb's output is too low?
- I'm about to give up, because my electronics knowledge is limited and thus, unable to locate the problem with this 100W Amp. Yet, at least it works to my satisfaction in that "kick-start" method. I now already returned all as it was before and chose one tiny switch and push button, which I glue to the Mic.
Three fast presses then will "kick-start" the system until one good day on which I meet an electronics expert, willing to have a look at it.
Thus, best is I pack it up and send it to you. How much will cost me your expertise ? I can compensate your efforts with all my inherited musical expertise/ recordings. Albeit my wife calls me "Einstein", I can't possibly be perfect at everything...
For years I tried to miniaturize this setup... now I gotten old and I'm still at it and never will give up hoping for success! - I wished I could buy such a small/ compact, fairly powerful travel unit, but most of them (on AliExpress and eBay) lack proper reverb. are either too big or too expensive.
I'll show you a Pic of the Mic with the 2 "kick-start" switches...

[g1]

Test result: If I ran the same setup with my Sony car Amp and I haven't' got this problem.

And the whole system including the sony amp was running off the LiPo that you are now using?

If so, maybe the new amp requires a different signal level than the sony. Or maybe the new amp is just defective.

If you were not running the system with the sony amp off the same LiPo, you need to test it like that.

[jjj]

Yes, the Sony Amp runs on the same 11.1V LiPo battery as well. It could be that the 100W Class D Amp. needs a stronger signal. In that case I would need to amplify the strengthen the reverb signal. Yesterday I lifted the voltage for the 100W Class D Amp to 22V and the output volume to the 8Ohm remained almost the same. It could be that a weak input signal is causing it?
Today I wired that said "kick-start" idea to the Mic and it works a charm...
Here's the Pic of it:

[J M Fahey]

Well I just kinda pulled that number outta my a$$ for a rough estimate I guess I should start doing the math.

nosaj

Oh, donīt worry with that, I thought you were referring to the published spec for that class D amp, which IS advertised as a "100W amplifier"

Just check the very first post:

4) 100W (class D) Amp running on a 11.1V LiPo.

I was answering to *that*.