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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

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Old 16th October 2012, 08:10 PM   #41
maxw is offline maxw  United Kingdom
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OK I tried the 120R in series with the output and 10K across the input and it didn't change the noise floor. I don't have any suitable capacitors to use on the input, I only have electrolytic.

Perhaps my layout? Or the relay mounted so close to the PGA?
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Old 16th October 2012, 08:33 PM   #42
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I didn`t folow tis thread from the start... But did you try another power amp with your speakers??
Try an Analog one for a change???
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Old 16th October 2012, 08:35 PM   #43
rsavas is offline rsavas  Canada
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That sucks, wish I could help, noise is always a hard one to figure out and solve.
To review, you have grounded the PGA input and hooked it through a headphone amp and it is quiet. So where is the noise coming from? the $1000?
I have this part breadboarded = wire wrap, on two different assemblies, so that I could write/test my code for it. I have already tried PGA2310 and PGA2311, to verify my code. I have to check I might even have a PGA2320, which is the upgrade to the PGA2310. One proto is running off a +/-5V supply, the -5V is generated from a TC7660 = the worst case supply. I will try and test it out to see how quiet it is, in this worst case situation. The other proto I can use an external PS, LM317/LM337 based. Give me a couple of days and I will report back with my findings. May not help you with your situation but it will be some more information for you to use.

Take care
Rick
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Old 16th October 2012, 08:41 PM   #44
maxw is offline maxw  United Kingdom
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Quote:
Originally Posted by BenY View Post
I didn`t folow tis thread from the start... But did you try another power amp with your speakers??
Try an Analog one for a change???
Unfortunately I don't have another one on hand right now!

Quote:
Originally Posted by rsavas View Post
That sucks, wish I could help, noise is always a hard one to figure out and solve.
To review, you have grounded the PGA input and hooked it through a headphone amp and it is quiet.
Well the headphones are connected directly to the PGA but yeah that is the gist of it!

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Give me a couple of days and I will report back with my findings. May not help you with your situation but it will be some more information for you to use.
I would be grateful
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Old 16th October 2012, 08:46 PM   #45
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What happens if the input to the PGA is shorted to ground? Still noisy?
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Old 16th October 2012, 08:51 PM   #46
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Use another µcontroller pin to drive a relay to stop power up/down pops.
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Old 16th October 2012, 08:59 PM   #47
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Quote:
Originally Posted by maxw View Post
Unfortunately I don't have another one on hand right now!

Do you have any other amplifier, like an integrated or so?
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Old 18th October 2012, 06:56 PM   #48
maxw is offline maxw  United Kingdom
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Quote:
Originally Posted by pinkmouse View Post
What happens if the input to the PGA is shorted to ground? Still noisy?
Yeah.

Quote:
Originally Posted by 5th element View Post
Do you have any other amplifier, like an integrated or so?
No, if I had I would have tried it first

I'll pick up a new amp soon and retest. Perhaps a Gainclone or similar. Thanks for the responses everyone!
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Old 24th November 2012, 08:00 AM   #49
atupi is offline atupi  Romania
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I have built one PGA based preamp from zero (etched my own boards) and is dead quiet until 0 db. When it start to have some gain is has a weak noise.
I've put some pictures here: Yet another Volume controlers and source selections

I have separated power supply including separated tranny's for digital and analog part.
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Old 26th November 2012, 06:08 PM   #50
maxw is offline maxw  United Kingdom
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I have since retested with a gainclone amp which is also noisy. I think I'm going to try a DAC with a volume control like a Matrix mini-i or Yulong D100.
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