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Old 3rd March 2005, 04:52 PM   #1
HarryK is offline HarryK  United Kingdom
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Default PGA 2311 Test Circuit

Hello All,

Hope someone can help with a basic problem I'm having.

First of all I am Software engineer, trainee level electronics engineer.

I've just bought a couple of PGA 2311 volume controllers and I kind of assumed programming them would be easy. I've done lots of SPI stuff.

But I have two problems.

1) When I connect the audio from a PC I can hear output on Rout pin. This shouldnt be happening because the Datasheet says the controller sets itself to zero on startup. What have I done wrong.

2) Whats the most basic test circuit for this chip.

3) Does anyone have a simple diagram showing how I should be connecting this to a PC audio source, do I need to change to input level or something.

Any help much appreciated.

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Old 3rd March 2005, 07:58 PM   #2
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HI Harry

It is not quite clear, but are your PC somehow connected to your PGA2311, at the same time as you connect the audio output (from your PC) to the input of the PGA2311 ??

Maybe you could make a schematic of your set-up. That would make it a lot easier for us to help you.


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Old 4th March 2005, 09:20 AM   #3
HarryK is offline HarryK  United Kingdom
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The Setup is as follows:

A) PC Running Windows

B) PIC based board connected to the PC via serial.

C) Audio From PC Audio Connector into PGA2311

D) PC sends instruction to PIC to raise volume.

E) PIC sends SPI type commands to PGA2311 to raise volume.

The Audio input (+ and -) from PC are connected to pin 16(+) and 15(-)

I've connected a +5 digital voltage to pin 4 and also a Digital Ground to 5, I've also connected SDI, SCLK and CS.

I've connected a cable from pin 14 (Vout) to the output amplifier.

I've connected the + and - supply on the breadboard to pins 12 and 13. But the chip gets very hot (I've tried two now).

Do you know how I should be connecting the pins, the datasheet doesnt seem to help me and an internet search doesnt seem to show a schematic of anyones elses setup.

I would have thought that If I just connect the SDI, SCLK, Digital +5 and the Ground I should be able to send commands and see a voltage rise or fall somewhere, or am I wrong.

What am I doing wrong.


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Old 7th March 2005, 06:35 AM   #4
paulmac is offline paulmac  Australia
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G'day Harry.

This chip is next on my list of things to play with. You've beaten me to it. I'm also planning on using a PIC to control this, using inputs from a rotary encoder to change the volume. An LCD display will complete the preamp.

1: The + and - supplies from the breadboard: they *ARE* +/- 5v, aren't they? If it's getting hot, I'd reckon you have 12 or 15 volts there instead. The zero volt rail from the breadboard should also connect to pin 16 and 10, and once only to the digital ground on pin 5.

Figure 5 on page 11 of the datasheet is the most basic layout. It sounds like you have it right.

Essentially you should be unplugging your amp from the PC and putting your circuit in the middle. Does your amp and speakers setup work when plugged straight into the PC? (Hope that's not a silly/rude question).
By the sounds of it, (gee it's hard not to make bad puns in this forum) you have a headphone plug plugged into the PC, and you have connected the other end of the cable by connecting the centre core of one channel to pin 16, and the earth braid of the cable connected to pin 15. Then the amp connects it's signal earth to pin 15 also, and the centre core to pin 14. I know I'm reiterating what you've already said, but....

What did you do with the other channel coming out of the PC?
I haven't tried it myself, so I'm happy to be proven wrong, but perhaps the chip is picking up a signal on the other channel because it's floating? If you ground the other input pin 9 to pin 10, I bet you get nothing from pin 11.
And yes, according to the data sheet, you should have no audio through the chip until you send it a volume setting. I'll have to try this one. The spec says 130dB separation...
Unfortunately, you have to stick with changing an audio level, rather than being able to measure a voltage. You could put a 1v sine wave through it and measure the AC volts on the output, but you have the PC there already.

I'd suggest you set up your system so that the PC is playing music, the signal goes through the breadboard, and then into the amp. Then temporarily jumper pin 16 to pin 14. This takes the circuit out of the loop, so you can set the volume on the amp to something normal, so you don't get the crp scared out of you when you figure it out and it bursts into life!

Hope this helps.

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Old 7th March 2005, 07:59 AM   #5
HarryK is offline HarryK  United Kingdom
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Thats a good suggestion about the other channels ground. I think you could be right.

I'll give it a try.

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Old 9th March 2005, 09:04 AM   #6
SDF is offline SDF  France
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I tried to used a PGA2311 with an Atmel C but I don't know if the PGA2311 needs capacitor to block the output DC offset (I don't know if this componant has a DC offset???).

Anybody could answer to me ? In advance, thanks for your reply.
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Old 9th March 2005, 08:27 PM   #7
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The data sheet says 0.25mV offset typical for 0dB gain. The application diagram shows no DC blocking caps.
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Old 10th March 2005, 02:33 PM   #8
SDF is offline SDF  France
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thanks for your reply!
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Old 11th March 2005, 02:22 PM   #9
murphy is offline murphy  Germany
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Lightbulb PGA 2311 gets very hot

If your chip get very hot , the power supply is not switched in correct. You HAVE to switch all supply voltages & analog and digital) at the same time..
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Old 12th March 2005, 03:43 AM   #10
mcs is offline mcs  Denmark
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Default Re: PGA 2311 gets very hot

Originally posted by murphy
You HAVE to switch all supply voltages & analog and digital) at the same time..
No, the PGA chips will work fine with only the digital supply connected (used for stand-by in my circuit).

Best regards,

Mikkel C. Simonsen
My personal electronics website
Remote control kits website
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