guess you could measure voltage on + and - sub and try to calculate it from there??? like the pano test somewhere here on diyaudio?
REW also does your frequency response, distortion, waterfall, spectrograms, speaker impedance, and Thiele-small param measurement. Pretty much an awesome program. Can't believe it's free. 🙂
for the filmcap/shielded inductors version they soldered a wire from bootstrap because pcbtrace was not connected to most right inductor??? for only 3 yuan more 🙂
i could not use the REW program as I do not have a mic or spl, plus that was not foll volume it got real loud I used some test tones from audio check online.
Ohms law. P=IV
That is 224 watts - I assume current and volts are rms? Peak power is then 1.41x224=316watts. That is a lot of power.
You can also just measure rms volts and use average speaker impedance. Say it is 4 ohm speaker the P=V^2/R or 196 watts.
That is 224 watts - I assume current and volts are rms? Peak power is then 1.41x224=316watts. That is a lot of power.
You can also just measure rms volts and use average speaker impedance. Say it is 4 ohm speaker the P=V^2/R or 196 watts.
Damn,I guess I got it right then that is 4 chips in parallel,thing of is I could have gone more,I am gonna call it 250 watts,man those woofers were stretching hard,but they never distorted
xrk971,thanks man you helped me a lot now I gotta ge a mic so i can use that REW it looks usefull.
I use the Dayton UMM-6 and highly recommend it for ease of use and price/performance. The USB ADC avoids sound card or preamp calibration issues.
Similar mic from miniDSP is UMIK-1.
Budget route is a $2 Panasonic WM61-A mic capsule - you need to wire it to a 3.5mm plug though. Will need to use sound card mic input.
Similar mic from miniDSP is UMIK-1.
Budget route is a $2 Panasonic WM61-A mic capsule - you need to wire it to a 3.5mm plug though. Will need to use sound card mic input.
You don't need a mic to measure distortion using REW, just a voltage divider. A pot will do, connected to the amp output with the wiper of the pot connected into the mic/line in of your soundcard.
Take the output from your amp and bring up the signal until you get a clean level on the REW meters. Keep the pot at minimum to begin with, and bring it up slowly until you get about -6dB off the REW output or until REW says the signal level is fine. Then run a sweep test and take a full set of measurements.
This is actually a better method as speaker measurements do not tell you much about amp distortion because speakers
1. have distortion around 10-100x times amp distortion and will swamp it, and
2. are highly dynamic and every millimeter change in mic position affects the measurements.
Strictly speaking you cannot compare measurements taken at home with each other, let alone for testing distortion far below the level the speaker is producing. For T/S parameters and driver impedance measurement, for example, REW does not need a mic at all. It does not care what the input is, just that there is a signal of some sort.
Take the output from your amp and bring up the signal until you get a clean level on the REW meters. Keep the pot at minimum to begin with, and bring it up slowly until you get about -6dB off the REW output or until REW says the signal level is fine. Then run a sweep test and take a full set of measurements.
This is actually a better method as speaker measurements do not tell you much about amp distortion because speakers
1. have distortion around 10-100x times amp distortion and will swamp it, and
2. are highly dynamic and every millimeter change in mic position affects the measurements.
Strictly speaking you cannot compare measurements taken at home with each other, let alone for testing distortion far below the level the speaker is producing. For T/S parameters and driver impedance measurement, for example, REW does not need a mic at all. It does not care what the input is, just that there is a signal of some sort.
Does the soundcard connect negative to ground??? Can you drive a soundcard through a pot from the output of a bridged (BTL) amp like these tpa31xx amps?
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I agree that to measure amp distortion all by itself you just drive a resistive load. Although a low power pot will not allow you to test the distortion when running 50 watts plus. You need a power resistor and a divider to take that voltage down to level safe for line inputs on sound card - be careful you can fry your sound card this way if not careful. I tested with speakers because I wanted to see if there was a measurable difference in the system. And agreed - speaker distortion will be higher than amp in general and room effects dominate. So maybe this test really says that amp distortion is not that important as long as it is less than speaker distortion (around -50dB). Note that testing with resistive load will not present same impedance as a dynamic driver.
Ok still a mono pot can reduce both + and - the same way??? it is a bridged amp and PC soundcards are differential, not SE input???
I think either the + of the bridged amp gets attenuated or the - gets attenuated, giving free path for 1 of them to PC soundcard. After 1 second I think protection of TPA3116 will trip and save your $15 amp, pot should not survive, PC...well 7 to 8 ampères probably for short period
I think either the + of the bridged amp gets attenuated or the - gets attenuated, giving free path for 1 of them to PC soundcard. After 1 second I think protection of TPA3116 will trip and save your $15 amp, pot should not survive, PC...well 7 to 8 ampères probably for short period
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Load current depends on load impedance. A 22k pot with 30v between terminals, typical for an amp operating at 18v rails and btl, will draw around 1.3mA. Not an issue even at full output.
A Class D amp needs a dummy load or a speaker for a different reason, and that is filter performance. Since the frequency response of a Class D amp has a very strong correlation with the load impedance, testing without a load will cause an erroneous result.
There is a very simple way to wire a pot for btl output amps, two additional resistors are needed and the pot is connected between the outputs with the resistors in series between terminals 1&3, the wiper is connected to either end. One pole is connected to the soundcard input and the ground is common.
A Class D amp needs a dummy load or a speaker for a different reason, and that is filter performance. Since the frequency response of a Class D amp has a very strong correlation with the load impedance, testing without a load will cause an erroneous result.
There is a very simple way to wire a pot for btl output amps, two additional resistors are needed and the pot is connected between the outputs with the resistors in series between terminals 1&3, the wiper is connected to either end. One pole is connected to the soundcard input and the ground is common.
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I was watching Germany vs Ghana yesterday🙂 I guess you only connect wiper to computer? Load is always pot value and something added to either + or - totalling pot value again? + is loaded different then - ? And then like you mentioned how does distortion with a 22.000 ohm load compare to distortion on a 4 ohm load, filter distort more with pot then with loudspeaker?
Still don't see it, can you draw a sketch how you would connect a pot to this amp?
Still don't see it, can you draw a sketch how you would connect a pot to this amp?