need help on choosing voltage regulators for PGA2311.

jm150 · 6th June 2007, 08:16 AM

Hi all,
I consider myself a newbie in DIY audio,
and hope someone can help me out here :-)

I'm building a preamp with the PGA2311, and I have run into a problem. Ca. 1 sec. after power off, I get a -1VDC spike on the line out, this flattens out to 0, in 2-3 sec.

I think my problem is the +5/-5 VDC regulators, which power the analog section of the PGA 2311. I have used some old 7805/7905 (1,5A), which I had laying around.
The DC rails feeding the regulators, are +/- 11VDC.
To exclude the PSU as the failure source, I tried replacing it with batteries (+/-9VDC) + I removed all components, except for the regulators, and the PGA 2311, but still the same problem.

When doing some measurements on the regulators, during power off, I can see that they behave very differently.
On power off, the + rail drop much faster than the - rail,
and the 7805(+) output drops faster, than the 7905(-).

I'm thinking this might be the reason for the -1VDC spike,
does this sound reasonable ?

If so, any recomendations on which regulators I might use ?
I've read the datasheet for the PGA2311, bit can't figure out how much current it uses.

Thanks for any help,

Morten.

jaycee · 7th June 2007, 08:40 AM

The 7805/7905 should be adequate here.

I'd perhaps suggest using the MUTE pin to mute the output when power disappears. It should be pretty easy to make a Loss of AC detector to do that.

Just out of interest, why not PGA2310 instead?

jm150 · 7th June 2007, 09:43 AM

Hi, and thanks for the reply.

I've allready tried to lover the volume all the way down, untill the display
shows "Mute", and still get the spike, at power off.
I should think this is the same "Mute" function I get by using the Mute pin ?

Reason I use the PGA2311, instead of PGA2310:
It's not my construction, it's from an article in "Elektor",
and I have just followed the partlists from the article.

Regards,
Morten.

Keruskerfuerst · 7th June 2007, 10:12 AM

I would use LM317/337 or even a voltage reference (TL431) and a transistor.

jackinnj · 7th June 2007, 04:17 PM

the LM317/LM337 -- much better than the fixed value 78xx/79xx regulators -- make sure to bypass the adjust pin on the regulator.

6th June 2007, 08:16 AM	#1
jm150 diyAudio Member Join Date: Jun 2004 Location: Norway	need help on choosing voltage regulators for PGA2311. Hi all, I consider myself a newbie in DIY audio, and hope someone can help me out here :-) I'm building a preamp with the PGA2311, and I have run into a problem. Ca. 1 sec. after power off, I get a -1VDC spike on the line out, this flattens out to 0, in 2-3 sec. I think my problem is the +5/-5 VDC regulators, which power the analog section of the PGA 2311. I have used some old 7805/7905 (1,5A), which I had laying around. The DC rails feeding the regulators, are +/- 11VDC. To exclude the PSU as the failure source, I tried replacing it with batteries (+/-9VDC) + I removed all components, except for the regulators, and the PGA 2311, but still the same problem. When doing some measurements on the regulators, during power off, I can see that they behave very differently. On power off, the + rail drop much faster than the - rail, and the 7805(+) output drops faster, than the 7905(-). I'm thinking this might be the reason for the -1VDC spike, does this sound reasonable ? If so, any recomendations on which regulators I might use ? I've read the datasheet for the PGA2311, bit can't figure out how much current it uses. Thanks for any help, Morten.

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7th June 2007, 08:40 AM	#2
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	The 7805/7905 should be adequate here. I'd perhaps suggest using the MUTE pin to mute the output when power disappears. It should be pretty easy to make a Loss of AC detector to do that. Just out of interest, why not PGA2310 instead?

7th June 2007, 09:43 AM	#3
jm150 diyAudio Member Join Date: Jun 2004 Location: Norway	Hi, and thanks for the reply. I've allready tried to lover the volume all the way down, untill the display shows "Mute", and still get the spike, at power off. I should think this is the same "Mute" function I get by using the Mute pin ? Reason I use the PGA2311, instead of PGA2310: It's not my construction, it's from an article in "Elektor", and I have just followed the partlists from the article. Regards, Morten.

7th June 2007, 10:12 AM	#4
Keruskerfuerst diyAudio Member Join Date: May 2007	I would use LM317/337 or even a voltage reference (TL431) and a transistor.

7th June 2007, 04:17 PM	#5
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	the LM317/LM337 -- much better than the fixed value 78xx/79xx regulators -- make sure to bypass the adjust pin on the regulator.

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