Yess, there is a need for a switch. and it goes from pin 11 to V+.
not GND.
If You power on that powersupply, it may for a very short time while powering up exceed 18 volts. if the mute/standby/play pin is tied to V+ (even via cap+resistor) it can happen that You instantly kill the chip. Spikes can happen. And will.
not GND.
If You power on that powersupply, it may for a very short time while powering up exceed 18 volts. if the mute/standby/play pin is tied to V+ (even via cap+resistor) it can happen that You instantly kill the chip. Spikes can happen. And will.
Antonio, I would not be happy running the caps that close to their rating; a much bigger margin is more my style ...
Ok so in one position connected to V+ and open on the other for stand by so I won’t need a power switch which at this moment of development is a plus.
Good advice, thks
Good advice, thks
Though it wasn’t the initial goal I’m doing a separate amp for the satellites since it won’t fit inside the original box which includes transformer electronics plus the woofer even for the smaller pcb I did before was going to be a hazel to have it almost touching the speaker and trafo.
Now we will have a 60 VA EI transformer, diode bridge with 10mF first smoothing a small choke and 2x 2.2mF plus one 270u Oscon at each power feed for decoupling.
Yes Frank, 15V sounds too close, need to continue adjusting the secondary to get around 14V DC at the amp feed point.
Now we will have a 60 VA EI transformer, diode bridge with 10mF first smoothing a small choke and 2x 2.2mF plus one 270u Oscon at each power feed for decoupling.
Yes Frank, 15V sounds too close, need to continue adjusting the secondary to get around 14V DC at the amp feed point.
Yes Arty, that will do but prefer it the hard way. That transformer has been set to different voltages in the past so one more time won’t hurt and it’s easy to do on an EI type with separate primary and secondary windings.
Antonio
Antonio
Quite happy with how everything is coming up with the new build, in fact almost finish, missing da switch for the mute/stand-by. The supply was tested 2 days ago and ready to go at 14.3V with no load, and sagged to 12.8V @ 2.5A with R load.
So we might be hearing some music tomorrow...
So we might be hearing some music tomorrow...
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that seems nice, can't wait to hear Your opinion about the amp it self, once it is finished 🙂
then we can get to some tweeking.
then we can get to some tweeking.
In a few moments I will start testing this small amp but in the meanwhile Arty what’s the deal with pin 12 (V ref)?
On page 4 c. paragraph of the Philips spec sheet says that harmonic distortion on low freq can be decreased if two diodes are connected to gnd from pin 12.
Then on page 7 note 8 says that ripple rejection can be dropped by 7dB, again if the 2 diodes are connected to gnd from same pin.
It’s an easy addition those 2 diodes to gain in HD and RR, my question would be if these diodes are connected in parallel in reverse polarity? The spec sheet doesn’t give a clue as far as I have seen.
Looking forward to tweaking tips! 😎
Antonio
On page 4 c. paragraph of the Philips spec sheet says that harmonic distortion on low freq can be decreased if two diodes are connected to gnd from pin 12.
Then on page 7 note 8 says that ripple rejection can be dropped by 7dB, again if the 2 diodes are connected to gnd from same pin.
It’s an easy addition those 2 diodes to gain in HD and RR, my question would be if these diodes are connected in parallel in reverse polarity? The spec sheet doesn’t give a clue as far as I have seen.
Looking forward to tweaking tips! 😎
Antonio
This time around test went smoothly. One side has less than 1 mV the other has 24 mV which is well within spec, in mute position is near 0 mV but didn’t record the number. Test was done with grounded source (0 Ohms) at the input and open outputs (no load).
Need to add a bleed resistor at the supply, those caps are really good they maintain the voltage for hours.
Next will be some
Antonio
Need to add a bleed resistor at the supply, those caps are really good they maintain the voltage for hours.
Next will be some
Antonio
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No cheers yet, one of the sides has oscillation and no music there and is dependent on vol setting. With vol set to ground side you can hear a slight hum on the speaker.
My suspicion is that the side that showed 24mV on the first test is the one causing the problem, will see.
Need to check what’s going on.
Antonio
My suspicion is that the side that showed 24mV on the first test is the one causing the problem, will see.
Need to check what’s going on.
Antonio
interesting, to be honest.
pics of build along with traffo ?
and schematic that shows every part You made, including psu, and actual wiring of ground ?
something is fishy , and we needs to find out what.
pics of build along with traffo ?
and schematic that shows every part You made, including psu, and actual wiring of ground ?
something is fishy , and we needs to find out what.
Geez ... not having much luck there, Antonio, 😕 - hopefully something falls into place soon ... 🙂
There’s something related at the input most surely since vol works on the level you hear the oscillation and think there is nothing serious, hopefully. The board is hard wired in the underside and all components at the top. Mmmm, should work on a real PCB but I'm lazy at etching.
I will prepare a schematic (may take some time) even there is nothing unusual there. I have some pics that I will upload later.
Antonio
I will prepare a schematic (may take some time) even there is nothing unusual there. I have some pics that I will upload later.
Antonio
that board is just fine.
make sure the 100 nf psu filter cap is as close to the ic leads as possible (v+ and power gnd)
Also, needs to see Your ground schematic, is it a single star ground, or a star ground for power, and a star ground for signal type ?
You should try an 47~ Kohm resistor from input to ground(signal) close to the IC pins.
I draw up a schema in a moment.
The IC is fine it seems, a bit of oscillation will not stop us in making it work properly.
make sure the 100 nf psu filter cap is as close to the ic leads as possible (v+ and power gnd)
Also, needs to see Your ground schematic, is it a single star ground, or a star ground for power, and a star ground for signal type ?
You should try an 47~ Kohm resistor from input to ground(signal) close to the IC pins.
I draw up a schema in a moment.
The IC is fine it seems, a bit of oscillation will not stop us in making it work properly.
There you may have a point, no signal star gnd since the board is hard wired I took shortcuts but that could be rearranged, should I also lift the signal gnd to the power gnd with a small R?
There are no 100nF’s and relied only on the Oscon caps (270u for decoupling) which are as close to the pins as possible. Which type of cap would you suggest for the application?
In the process to rearrange the signal star gnd will add the 47KR’s.
There are no 100nF’s and relied only on the Oscon caps (270u for decoupling) which are as close to the pins as possible. Which type of cap would you suggest for the application?
In the process to rearrange the signal star gnd will add the 47KR’s.
sorry for not posting the schematic, i had some problem to fix.
but i can see You get the point 🙂
Yes, You need a start ground for power.
and You need a star ground for signal.
in between You need a small R.
You need the 47 KOhm ressitors on input to define dc parameters for the amp.
You allso need the 100 nf cap. The oscons are not going to do that job for you.
Any film type cap will do, just be sure to have it as close to the chip as you can.
it goes from chip V+ to power ground.
this should fix up the oscillations.
but i can see You get the point 🙂
Yes, You need a start ground for power.
and You need a star ground for signal.
in between You need a small R.
You need the 47 KOhm ressitors on input to define dc parameters for the amp.
You allso need the 100 nf cap. The oscons are not going to do that job for you.
Any film type cap will do, just be sure to have it as close to the chip as you can.
it goes from chip V+ to power ground.
this should fix up the oscillations.
I would just add, for the moment, if you're going to use a 100nF to decouple there's no point unless there is effectively zero lead length involved - in other words, I would solder it directly to the chip legs at the point where they emerge from the plastic, with only just enough capacitor leg metal there for a solder joint to be possible.
If you want to take tweaking seriously this is the sort of approach that's needed, IME ...
If you want to take tweaking seriously this is the sort of approach that's needed, IME ...
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