No unfortunately my only method of measuring anything is line in of integrated sound card, which I wouldn't trust with any kind of THD measurements 
I used to have some nice pro audio interfaces but not anymore as I don't do any audio recording. We'll see what I can do and will post if anything useful comes up
I used to have some nice pro audio interfaces but not anymore as I don't do any audio recording. We'll see what I can do and will post if anything useful comes up
No unfortunately my only method of measuring anything is line in of integrated sound card, which I wouldn't trust with any kind of THD measurements
I used to have some nice pro audio interfaces but not anymore as I don't do any audio recording. We'll see what I can do and will post if anything useful comes up
hi wxn
ok
my proposal is to keep 1 board as its is. the second make mod step 1 then compare. after this mod board 2 with mod 1 +mod 2...then compare....etc...
first i would change the opamp. then 4 input caps 10µF before TPAchip(origin have huge ESR)... change the input caps near the rca before buffer... then.....change the caps around the regulator and the opamps...the cap directly at the power terminals = chnage it(origin has 0,2 ESR) .....the output filter coils and caps could be the last step....
chris
[first i would change the opamp.
Good idea, better OP-AMPs exist.
then 4 input caps 10µF before TPAchip(origin have huge ESR)...
A valid idea to improve linearity and noise. ESR is less an issue because the impedance they look into is in the order of 20KOhm where the ESR seems unimportant.
change the input caps near the rca before buffer...
Yes, for linearity and noise. Don't bother with ESR.
then.....change the caps around the regulator and the opamps...
Yes, for ESR and current ripple durability. Linearity is unimportant.
the cap directly at the power terminals = chnage it(origin has 0,2 ESR) .....
Yes, because the TPA3255 chip pulls current with a large ripple content. So does the Buck step-down converter.
the output filter coils and caps could be the last step....
You know best as you have tested the potential improvement with better filter components.
In conclusion, give a quick consideration to the working conditions of the components, in particular the capacitors.
OP-amps have varying THD, slew-rate and noise performance that influence the sound.
Capacitors in the signal path rarely have an issue with ESR whereas linearity and noise are relevant qualities.
Decoupling capacitors, typically for supply lines, need to keep the voltage stable even with important current ripple. ESR and current ripple rating are important factors while linearity and noise are in many cases of little relevance.
The output filter capacitors are a bit special in that they act as decoupling capacitors (for the carrier signal) but in the signal path. Thus, they are exposed to a high level of current ripple but must at the same time have good linearity (for the audio signal). This is why high-quality foil capacitors should be used.
The output filter chokes must mandatory be able to carry the maximum (peak) current in the speakers without any saturation. Next, the choke cores must be chosen for the carrier frequency of the class D chip, else the inductance is simply lower than assumed. Last, the core losses must not be huge in order not to heat the chokes too much. The influence on the sound from moderate core losses is more difficult to predict as such moderate core losses just add a bit more damping to the LC-resonance. Suitable chokes need to be tested and compared by persons with "golden ears" and a solid audio budget, such as Chris.
Good idea, better OP-AMPs exist.
then 4 input caps 10µF before TPAchip(origin have huge ESR)...
A valid idea to improve linearity and noise. ESR is less an issue because the impedance they look into is in the order of 20KOhm where the ESR seems unimportant.
change the input caps near the rca before buffer...
Yes, for linearity and noise. Don't bother with ESR.
then.....change the caps around the regulator and the opamps...
Yes, for ESR and current ripple durability. Linearity is unimportant.
the cap directly at the power terminals = chnage it(origin has 0,2 ESR) .....
Yes, because the TPA3255 chip pulls current with a large ripple content. So does the Buck step-down converter.
the output filter coils and caps could be the last step....
You know best as you have tested the potential improvement with better filter components.
In conclusion, give a quick consideration to the working conditions of the components, in particular the capacitors.
OP-amps have varying THD, slew-rate and noise performance that influence the sound.
Capacitors in the signal path rarely have an issue with ESR whereas linearity and noise are relevant qualities.
Decoupling capacitors, typically for supply lines, need to keep the voltage stable even with important current ripple. ESR and current ripple rating are important factors while linearity and noise are in many cases of little relevance.
The output filter capacitors are a bit special in that they act as decoupling capacitors (for the carrier signal) but in the signal path. Thus, they are exposed to a high level of current ripple but must at the same time have good linearity (for the audio signal). This is why high-quality foil capacitors should be used.
The output filter chokes must mandatory be able to carry the maximum (peak) current in the speakers without any saturation. Next, the choke cores must be chosen for the carrier frequency of the class D chip, else the inductance is simply lower than assumed. Last, the core losses must not be huge in order not to heat the chokes too much. The influence on the sound from moderate core losses is more difficult to predict as such moderate core losses just add a bit more damping to the LC-resonance. Suitable chokes need to be tested and compared by persons with "golden ears" and a solid audio budget, such as Chris.
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Hi FF my friend
I am happy that you can very good explain technically what i did the last month
wxn please do not forget to try FF input circuit... page 31 #303
and no i do not say i have "golden ears"...i am just compare a lot things the last 30 years... a big step in enjoy music is to care not the power its the phase...= time delay or not of all frequencies......eg. open baffle speakers is for me a big step since 4 years....
actually i am happy with my 1 years journey of DIY
thanks to all here
chris
I am happy that you can very good explain technically what i did the last month
wxn please do not forget to try FF input circuit... page 31 #303
and no i do not say i have "golden ears"...i am just compare a lot things the last 30 years... a big step in enjoy music is to care not the power its the phase...= time delay or not of all frequencies......eg. open baffle speakers is for me a big step since 4 years....
actually i am happy with my 1 years journey of DIY
thanks to all here
chris
Hi FF my friend
I am happy that you can very good explain technically what i did the last month
wxn please do not forget to try FF input circuit... page 31 #303
and no i do not say i have "golden ears"...i am just compare a lot things the last 30 years... a big step in enjoy music is to care not the power its the phase...= time delay or not of all frequencies......eg. open baffle speakers is for me a big step since 4 years....
actually i am happy with my 1 years journey of DIY
thanks to all here
My mail took a starting point in your explanation but was mainly meant for members with less experience than you. My message aimed to be that electronics is sometimes less complicated than you think. Try to consider the working situation of a component and you will quickly find out which of a huge amount of characteristics specified in the datasheet that are actually of importance.
For a power line decoupling capacitor: leakage current - no, noise - not really, voltage rating - yes because of reliability, ESR - absolutely and dependent on class D or AB.
For the drop resistor used to feed a LED: value precision+noise+thermal stability+inductance - no importance, power rating - yes because you quickly run into a Watt or more in losses.
I used to work with some very skilled technicians and they were excellent in understanding what was important and what not - while not all were very proficient in more complicated calculations.
My statement of you having "golden ears" is evidently my perception of your skills from an amazing interest (both you and your brother), from decades of experience, from gear much above average. Most of us can hear the difference between good and really bad sound. To notice subtle differences in sound and remember the differences requires years of experience, which you have. Also ears that have not been abused too much for too long (wifes arguing does not count). I once met a very skilled enolog (wine specialist) who had the particular skill of being exceptional in remembering detailed taste impressions years ahead. There is a similarity between wine and sound though you can still drive your car after having listened to audiophile equipment.
We, the electronics freaks, are good at designing for a certain power level, stabilize loops, reduce noise etc. But, we need being pointed in the right direction by the sound "specialists".
You have indeed passed an impressive journey.
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my test were with 28V (LRS 150-24 set to appr. 28,5V)
since my 8R speakrers i keep the LRS350-36V - set to 36V
chris
Why not? Remember that the frequency range of female (and chilfrens') voices does correspond exactly to the highest sensitivity of our hearing perception
!Best regards!
Why not? Remember that the frequency range of female (and chilfrens') voices does correspond exactly to the highest sensitivity of our hearing perception
Best regards!
My wife insists that it is not due to her my ears start hanging like on a saint-bernard dog.
...second board makes troubles.....as i wrote...
during testing my boards at the weekend between different power supply i use my nice board which i used for along time for 4R config, new opamp, new caps everything was fine.
the last time i want to use it i get surprisingly a loud pop noise....i use the switch and i never had this before....
any ideas? now i have the switch and during on/off i hear a loud pop! during mute the amp is still queit so its working...but the pop is new
see pic 1+2 for left /right channel output.
at post #679 i wrote about the strange pop noise comming from one day to another..... now it did this modification:
https://www.diyaudio.com/forums/class-d/287470-tpa3255-diy-discussion-design-etc-73.html#post5488402
so the reset/mute switch is still installed. the switch is off (power the amp)
the anti pop circuit is just working for power on- so a silent pop is noteable nothing more
at power off the pop is at 36V psu voltage loud.
the behavior that the switch for mute/reset is doing a pop at power off is still valid....
the board is working...music is playing everything is ok. i need this board for an amp build in a small housing... i want to cancle the rest/mute switch becaue of less space at the back panel. so the anti pop circuit have to work.
any ideas?
thx
chris
chermann, hahah, what kinda ideas could help there if that IC has only one single pin for On/Off? I also have Off click noise with 3251(On click is tiny and acceptable), and I have no idea what to do with it. I never had Off pop or clicks before with lots of class D on my bench, because fast synchronous Off all mosfets guarantee pop/click free power Off process. I.e. Off process is trivial, usually, pop/clicks happen during On process and require some timing for precharge etc. I gonna try to Off IC 12VDC DRV rail instead of RST pin to avoid Off clicks. If that doesn't help I've no idea how to avoid that click, and I won't ask Ti support because in my experience it is useless time spending.
I don't have that Power-Off-Pop feature on my implemenation of TPA32XX, neither 51 nor 55. The Pop comes from a race condition in fall-times of the power rails and can most likely avoided/tuned if the detection level for the voltage-supervisor is set tight to the supply voltage. If the level is to close to "nominal voltage", the amp will mute on high power with a weak supply. The EVMs solution with feed-forward capacitors is more prone to this effect as it kinda boosts dips in supply voltage change.
Using a TPS3802K33DCK, the threshold voltage for the SVS is 2.93V. The resistor divider 27k+3k3 then trips at about 27V.
Trip levels for other voltages:
34.9V: 36k + 3k3
32.2V: 33k + 3k3
30.3V: 30k9 + 3k3
29.6V: 30k + 3k3
27V: 27k + 3k3
24.2V: 24k + 3k3
22.5V: 22k + 3k3
20.7V: 20k + 3k3
So for a 36V system you may try 33k or 36k instead of 27k.
Using a TPS3802K33DCK, the threshold voltage for the SVS is 2.93V. The resistor divider 27k+3k3 then trips at about 27V.
Trip levels for other voltages:
34.9V: 36k + 3k3
32.2V: 33k + 3k3
30.3V: 30k9 + 3k3
29.6V: 30k + 3k3
27V: 27k + 3k3
24.2V: 24k + 3k3
22.5V: 22k + 3k3
20.7V: 20k + 3k3
So for a 36V system you may try 33k or 36k instead of 27k.
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thanks doc
as you know the YJ TPA3255 board has no TPS xxxchip...i will try the 33k-36k and report back
chris
Hi Chris,
I had a quick look at the circuit proposed by "The Doctor" and The Doctor is clearly the best to advise a solution to your problem.
My immediate doubt was to the 4V7 zener that, if used, will result in a voltage in the order of 4.7V on a /RESET input that as "absolute maximum" allows 4.2V (3.3V logic)! I may have overlooked a detail but else, complaining about performance when the operation is above the absolute maximum rating could seem illogical. Perhaps a 3V3 or 3V9 Zener?
I had a quick look at the circuit proposed by "The Doctor" and The Doctor is clearly the best to advise a solution to your problem.
My immediate doubt was to the 4V7 zener that, if used, will result in a voltage in the order of 4.7V on a /RESET input that as "absolute maximum" allows 4.2V (3.3V logic)! I may have overlooked a detail but else, complaining about performance when the operation is above the absolute maximum rating could seem illogical. Perhaps a 3V3 or 3V9 Zener?