Speaker pop

[Seagull]

Hi!

While switching on power with mute jumper in awake position, I get a big nasty pop i my speakers, is this normal?
My 5V regulator gets very hot, is this cooler (see pic) big enough, what happends if the regulator overheats?

My AMP5:
http://hem.bredband.net/scarl/AMP5/AMP5.htm

[Corax]

Hi Seagull,

as I already mentioned to joeltan (http://www.41hz.com/Forums/topic.asp?TOPIC_ID=417) the power dissipation is 1.5W (total via R150 and U5) at my AMP5 (35Vdc and 51mA idle current). If I look at your nice pictures with that huge heatsink something must be different between our two amplifiers (wrong with yours in my opinion). Mine gets just hand warm with a much smaller heatsink. I must take into account that I increased the value of resistor R150 (was 47 ohm and has now 220 ohm / 1W and therefore a voltage drop of round about 10V).

Now take a multimeter and measure the voltage drop across R150 (unmuted and therefore "switching" and no music signals attached), this way you can measure very comfortable indirectly the current flow of your +5V supply. The current flow is determined as easy as the measured voltage drop divided by the resistor value. I would expect a value of about 2.35V.
As I mentioned above my AMP5 needed only 51mA (with DS1802 in place)!
If this value appears to be OK and the heatsink is still that hot you can't even touch it the regulator might oscillate. In this case I wonder that the TA2022 is still working?!?!?!?! An o-scope might be very handy at this point to observe the output voltage of the regulator.
Nevertheless check all capacitors close to the regulator about polarity, correct value, etc.

Now I took a closer look to the pretty nice (if I haven't mentioned that yet) pictures.
And what must I see!?!
There might be four resistors misplaced?!
Actually R201 to R204 are placed, but not needed (unless you use the DS1802 chip), and where they really belong, but from the bottom side of the PCB, are some unknown components placed. Are those really 1k resistors???

The "pop" by the way is a usual behaviour of almost any kind of power amplifier. There are many reasons for that behaviour and in addition it varies with topologies, etc.
Exactly for this reason was a MUTE input invented
In the datasheet for the TA2022 (page 18 - Mute) you'll find some more information about it. There's also a supervisor chip from Microchip stated (the MCP101-450) which implements clean power up/down operation - to use their words.


with kind regards

Corax

[Seagull]

Hi Corax! Thanks for your great support.

My amp is realy working, I can adjust offset and play music.
But the sound is not as good as expected.
I took your good idea and moved some power from the voltage regulator to R150. I have 55mA in R150, slightly more than you, should be less.
I measured with no source, and no speakers. I also have +/-35VDC.
"but from the bottom side of the PCB", what components do you mean?
In my gallery I have 2 more pics now.
So what I/we need is an timer-circuit that unmutes the amp after a few seconds, maybe a simple RC-circuit?

/BR. SeaGull

[pairair]

quote:Originally posted by Seagull
So what I/we need is an timer-circuit that unmutes the amp after a few seconds, maybe a simple RC-circuit?

/BR. SeaGull

That's one reason why I let a microcontroller take care of the mute-function http://pairair.se/AMP5/images/CRW_2185.jpg

Per

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Pictures of my project: http://www.pairair.se/AMP5/

[pairair]

quote:Originally posted by Seagull
"but from the bottom side of the PCB", what components do you mean?

I may be wrong, but take a look at this picture...
http://pairair.se/AMP5/images/AMP5_4.jpg
(it's one of your images with some comments added)

Per

--------------------------------------------------
Pictures of my project: http://www.pairair.se/AMP5/

[nilsomat]

It looks you just jumpered R371, R411, R311 and R521, but there should be 1K each instead! You put the 1K resistors to the volume control (where you don't need them, btw. i did the same...). Replace with 1Ks and it should be fine...

[Seagull]

You all are right, of course.
After reading assembly instructions I thought I could omit these resistors, but after checking the datasheet I understand I cannot.
Now the R150 current are 51mA.
I have measured on the amp with an oscilloscope, and it seems to be very unstable. I can hardly trig on the input signal with power on.
What about C452, se PCB backside, should this position be empty?

[nilsomat]

No, you should have 0.1uF at that position (C452).
BTW i would be very cautious omitting parts of the kit. They are there for a reason. It is an easy way to get into trouble (as you see).
Good Luck!

[Seagull]

Confusing instructions:

"13. Now mount the Tripath chip. There are two capacitors, C44 and C452, (0.1 uF RM5 /200 mil) which should be mounted from the back of the board into the holes of the rail power supply of the Tripath chip. The two components are marked on the back of the board as a line with circles at the ends. The name of the two capacitors
components are not printed on the PCB."

Name 'C452' is printed on the PCB.

I have tried C452 100nF in line/circle position -> amp unstable.
C452 in both line/circle position and 'C452' position -> amp unstable.

Now project is down for a while, see pic.

http://hem.bredband.net/scarl/AMP5/AMP5.htm

[nilsomat]

Please see the Amp 5 FAQ in this forum:

-snip-
> 6) The position marked C452 on the board is incorrectly labeled. Should the
> 12th 0.1uF, RM2.5 cap populate that position?

The C452 should be a 0.1 uF RM2.5
-snip-

The other 2 0.1uF Caps (the ones with 5 mm) should be underneath the Tripath chip, the positions are marked with two lines, not with numbers.

So you need one 0.1uF in labeled C452 position and one 0.1uF(5mm RM) in each of the "line" positions.