APEX PA16 chip in Gainclone

[TB]

Hello,
The PA16 chip from APEX was recommended by few members as a excellent choice for Gainclone. As such I got pair of these chips, but I am not sure how to implement them. Datasheet shows only one example for car audio with 3.2 ohms speakers and supply voltage of 12 V; http://www.cirrus.com/en/pubs/proDatasheet/PA16U_J.pdf

I did search the forum for any schematics of Gainclone with PA16 chips with no avail. Can someone who built the amplifier share its details including power supply info?
Thanks for the help

 

[DigitalJunkie]

The datasheet schematic should work well up to it's rated rail voltages/power. You may have to change the value of the current-limiting resistors,but that's no biggie..they should work fine at least for testing.

It says the heatsink tab is isolated,so you don't need to worry about insulators/'live' heatsinks either.

 

[AndrewT]

Hi,
with +-19Vdc as absolute maximum, you could run the chip at a nominal +-16Vdc, leaving a margin for mains overvoltage and the transformer's regulation.

You could just about get 15W into 8r0 (15.5Vpk, 2Apk & 6Apk on fast transients).

 

[TB]

Thanks for answers. The datasheet calls for another document, which specifies how to calculate current-limiting resistors. I will look into it this weekend.
Meantime, I would like to get your input how to use that chip. I thought about basic Gainclone: non-inverted with 1000 uF caps with volume control at the input. I have 12 Volts, 120 VA transformer which would give me 16.92 Volts output.
Output impedance should be 8 ohms. I do not listen to music at really high volume levels and speakers would be single driver ones. Should capacitance at power pins be higher or the 'classic" setup is enough?

 

[AndrewT]

I have 12 Volts, 120 VA transformer which would give me 16.92 Volts output.
Output impedance should be 8 ohms.

12+12Vac transformer should be about right.
12Vac is not suitable.
The load impedance required by the amplifier is ~8ohms.
The amplifier's output impedance is likely to be ~0r1

 

[TB]

In reference to transformer: it has two 12 Volt windings.
In the example of car audio amp in datasheet 100 kOhms resistor is used in the feedback loop. Should that value be changed for my purpose?

 

[TB]

Hello,
Can anyone who used this chip successfully in Gainclone post a schematic of your implementation, please?

Thanks.

 

[TB]

OK, it looks like I have asked stupid question. So, maybe someone will take time to answer this one:
- I will use schematic from the datasheet. Current limiting resistors: what value would be suitable for stated transformer ( I am a newbie. I do not know how to calculate it. The suggested 0.27 ohms is not easy obtainable ).

- can I use gainclone standard 1000 uF capacitors or higher value is recommended

This is a link to datasheet. The one listed in my first post is broken:
http://www.cirrus.com/en/pubs/proDatasheet/PA16U_K.pdf

Thanks

 

[AndrewT]

Four 1r0 in parallel = 0r25

 

[TB]

Thanks AndrewT.
Since no one cooperates here I have contacted Apex tech support directly. This is what I was told:
- for 8 Ohms load with my supply voltage ( +/- 12 Volts ) current limiting resistors should be 0.2 Ohms / 3 W mounted on heatsinks. The higher value would be fine in terms of chip protection, but it would constrain current delivery to the load.

- volume control pot should be between 20K to 50K.

 

[TB]

In this case still one question remains; would this chip well work well with 1000 uF caps or it needs more capacitance.
I have also noticed in the schematic the input cap is small, 0.47 uF. is it enough or it should be increased to 1 uF?

 

[TB]

Man, it looks like a tough crowd here.......

May be this question will prompt the answer..... original amp schematic does not show Zobel. But, Figure 22 in this document:
http://www.cirrus.com/en/pubs/appNote/Apex_AN01U_I.pdf
mentions the use of it. I do not understand why it was not mentioned in orginal schematic. Is it due to use of current limiting resistors ( Rcl ) which might grant stability control?
So, my another question is: should Zobel be always used for this chip or it would depend on speaker impedance/sensitivity?
And of course my other two questions are still unanswered........