Getting a PGA2310 to be silent - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

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

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 7th October 2012, 02:23 PM   #1
maxw is offline maxw  United Kingdom
diyAudio Member
 
maxw's Avatar
 
Join Date: Jun 2004
Location: London
Default Getting a PGA2310 to be silent

Hi,
I'm using a PGA2310 but having trouble getting it to be silent. There is always some background noise. Not hum or crackle but just noise. Everyone says these chips are silent when implemented correctly but I'm not sure what I'm doing wrong here

Here is my setup:
USB DAC ---> Passive 50K Pot ---> Hypex Amp ---> Speakers = Silent
USB DAC ---> PGA ---> Headphones = Silent
USB DAC ---> PGA ---> Hypex Amp ---> Speakers = Noisey

The PGA is not in a case and the Hypex Amp does not have signal ground connected to the chassis.

A grounding issue?
Or a impedance issue?

Any input appreciated
  Reply With Quote
Old 7th October 2012, 04:41 PM   #2
diyAudio Member
 
Join Date: Jun 2011
I have some experience of the PGA2310 and PGA2320. When implemented correctly they are generally quiet, but you will hear some hiss higher up the gain range in some implementations.

In the simplest general terms, noise is dependent on the impedance that an amplifier sees when looking back out of the input. The higher the (resistive element of the) impedance the greater the Johnson noise, which rises as the squareroot of the resistance.

The PGA series like to see a source impedance < 600 ohms for best performance, so you may need to buffer the DAC. Keep the PGA power supply well up close to the rated +/-15V and well decoupled.
  Reply With Quote
Old 11th October 2012, 03:16 AM   #3
diyAudio Member
 
Join Date: Apr 2010
Location: Coffs Harbour, on the east coast
You haven't described the PGA2310 device as more than just the chip. I presume this is an Ebay kit or a breadboard circuit with an adaptor and separate power supply. Perhaps a few details would help to pin your problem down regarding earthing, shielding and impedance. They likely all have a bearing on your set-up, if this is not a ready-built, self contained commercial assembly.

IME all unshielded/earthed audio circuits are noise-prone and digital grounding must be separately maintained to minimise injection from that source. These are great chips and work very well if all the precautions are in place in the application.
__________________
regards
  Reply With Quote
Old 11th October 2012, 05:33 AM   #4
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Quote:
Originally Posted by maxw View Post
Hi,
I'm using a PGA2310 but having trouble getting it to be silent. There is always some background noise. Not hum or crackle but just noise. Everyone says these chips are silent when implemented correctly but I'm not sure what I'm doing wrong here

Here is my setup:
USB DAC ---> Passive 50K Pot ---> Hypex Amp ---> Speakers = Silent
USB DAC ---> PGA ---> Headphones = Silent
USB DAC ---> PGA ---> Hypex Amp ---> Speakers = Noisey

The PGA is not in a case and the Hypex Amp does not have signal ground connected to the chassis.

A grounding issue?
Or a impedance issue?

Any input appreciated
Well if the PGA is silent with headphones it can't be the PGA itself; headphones are about the most sensitive to background noise.
Also can't be the DAC Zout for the same reason.
How far do you have the to run down the PGA, what's the level setting?

jan
__________________
I won't make the tactical error to try to dislodge with rational arguments a conviction that is beyond reason - Daniel Dennett
Check out Linear Audio Vol 7!
  Reply With Quote
Old 11th October 2012, 11:25 AM   #5
Bonsai is offline Bonsai  Taiwan
diyAudio Member
 
Bonsai's Avatar
 
Join Date: Jul 2003
Location: Taipei, Taiwan
Sounds like radiated or conducted noise from the Hypex unit. Can you post a photo of your set-up. I've built a big high end pre using the PGA device and it is indeed silent - see my website for details. Good luck in any event!
__________________
bonsai
Amplifier Design and Construction for MUSIC! http://hifisonix.com/
  Reply With Quote
Old 11th October 2012, 08:33 PM   #6
maxw is offline maxw  United Kingdom
diyAudio Member
 
maxw's Avatar
 
Join Date: Jun 2004
Location: London
Thanks for the replies everyone!

Quote:
Originally Posted by counter culture View Post
The PGA series like to see a source impedance < 600 ohms for best performance, so you may need to buffer the DAC. Keep the PGA power supply well up close to the rated +/-15V and well decoupled.
The output impedance of my DAC is lower than 600 but I have also tried with an input buffer on the PGA.

Quote:
Originally Posted by Ian Finch View Post
You haven't described the PGA2310 device as more than just the chip. I presume this is an Ebay kit or a breadboard circuit with an adaptor and separate power supply.
Well, I have actually tested it with two different modules, one I built and designed and a standard one from Ebay. Both show the same result.

Quote:
Originally Posted by janneman View Post
Well if the PGA is silent with headphones it can't be the PGA itself; headphones are about the most sensitive to background noise.
Also can't be the DAC Zout for the same reason.
How far do you have the to run down the PGA, what's the level setting?
At -20dB I can hear noise from the speakers when my ear is about 30cm away. Annoying!

Quote:
Originally Posted by Bonsai View Post
Sounds like radiated or conducted noise from the Hypex unit. Can you post a photo of your set-up. I've built a big high end pre using the PGA device and it is indeed silent - see my website for details. Good luck in any event!
Could be. I'll take a photo tomorrow. Nice preamp design by the way!

I've just read this application note from Hypex:
http://www.hypex.nl/docs/appnotes/earth_appnote.pdf
So I might try changing the grounding arrangement of the Hypex and see if it makes any difference
  Reply With Quote
Old 11th October 2012, 10:45 PM   #7
diyAudio Member
 
linuxworks's Avatar
 
Join Date: Jul 2008
Location: santa clara, CA
every one of the pga's that I've built (from ebay junker kits, though) were noisy. in most, one channel was bursty-noise and the other more constant. I suspect that they routed the digital and analog traces too close. the chip does seem sensitive to layout. careful about what you put below its core..

I did not pre-buffer my pga's but I think its wise. a lot of people say its not worth the effort but I think its good design practice. I also think that output buffering is a good idea, as well. sandwich the chip from the real world.

I'm kind of giving up on the pga series now that I'm getting good luck with the cs3318. if you need only 2 channels, its a bit overkill but the chip is SO much quieter and more featureful.
__________________
My Photostream:http://www.flickr.com/photos/linux-works/
  Reply With Quote
Old 13th October 2012, 12:45 PM   #8
maxw is offline maxw  United Kingdom
diyAudio Member
 
maxw's Avatar
 
Join Date: Jun 2004
Location: London
PAH I give up!

I tried all sorts of grounding arrangements including floating, non-earthed chassis, signal GND tied to chassis, different sources like my phone or mp3 player. The noise varied a bit but still not as quiet as my passive pre. I noticed in all the Hypex docs they really discourage the use of unbalanced signals.

I might just give the PGA2310 a miss and take a look at the CS3318.

Linuxworks, do you have any spare? I see they are about 12 here.
Attached Images
File Type: jpg IMG_0623.jpg (568.5 KB, 501 views)
  Reply With Quote
Old 13th October 2012, 02:50 PM   #9
diyAudio Member
 
Join Date: Apr 2010
Location: Coffs Harbour, on the east coast
Default PAH?..nahh

janneman deduced from your statement that the device was quiet with headphones connected, that the problem can't be with the PGA device. You replied that you could hear the noise at -20 dB with speakers, presumably still with the Hypex amplifier which is not exactly changing anything, unless I misunderstand you.

Logically, that still leaves the amplifier as the noisy or rather noise prone device. The connection and grounding between these units is likely one problem, regardless of the fact that your passive control is fine in this connection. The preamp is not in a case which surely makes it prone to CFL and fluorescent light noise (if you use them) or any background hash from SMPSs which likely you are surrounded by.

Do give the gadget a chance in its properly grounded, metal shield case. I can't imagine you haven't already tried that, but the earthing may not be complete, as I found mine wasn't when leads were bolted to anodised aluminium, for example.

The next feature which I haven't come across in audio DIY yet, is the Vacuum Fluorescent display in what I think I see as the "hi-end PGA2310 kit" on the left side of your nice pic. That uses a high voltage generated by something like a ringing-choke inverter which could cause problems too. I don't see how it logically fits the symptoms and looking at the physical separation, but see if you can disable the display illumuination by disconnecting the ~-70V supply to it. Otherwise, listen if the noise varies as the digits flick over to other readings. This may be interesting.

FWIW, a couple of years ago I bought the cheapest PGA2311 kit and tried it with generally noisy results until I worked out how fussy the assembly was with its case, PSU etc. I improved it but gave up too when a NAC42 clone with cheap pot. proved quieter.

Later I bought a pre-built PGA2311 version because a client was in a hurry for a cheap, working remote preamp. 10 days and voila! Funny; on checking, it was the same chipset and parts with a slightly different layout and display. It was as quiet as a mouse, however, and with whatever I used it. I reluctantly sold it on and bought another for my own use. This newer version was more compact and hum was just evident so I have substituted a shielded, smaller toroid I had on hand and all was well again.

I played it recently in my PC 2.1 setup and can't hear a blind bit of noise at -12dB setting which is unbearably loud at the usual distance.

I tell you this anecdote, not because I have fixed the first kit problem yet either, but because the supplier did it right in his build and I didn't. Had he not cost-cut on the second unit, it would have been a similar result.

Keep at it and better luck!
__________________
regards
  Reply With Quote
Old 13th October 2012, 05:09 PM   #10
diyAudio Member
 
linuxworks's Avatar
 
Join Date: Jul 2008
Location: santa clara, CA
Quote:
Originally Posted by maxw View Post
PAH I give up!

I tried all sorts of grounding arrangements including floating, non-earthed chassis, signal GND tied to chassis, different sources like my phone or mp3 player. The noise varied a bit but still not as quiet as my passive pre. I noticed in all the Hypex docs they really discourage the use of unbalanced signals.

I might just give the PGA2310 a miss and take a look at the CS3318.

Linuxworks, do you have any spare? I see they are about 12 here.
mostly, I tried junker ebay boards. once or twice I built a pga on perf and I don't remember if I heard the same static bursty noise or not.

what I found weird was that the 3chip pga board from ebay and the single smd pga board from ebay (different layouts, entirely) were both noisy in one channel much more than another.

I didn't get around to trying my opto isolator idea (I am using one on the cirrus board I have, though) but there's a good chance that noise from the cpu could be getting thru, either power/gnd or even the logic signals. I am just not sure, and the opto part is a dollar and good cheap insurance. I guess I'd try that before finally giving up.

note, there are suspected fake chips out there. that could be an issue, too. half of mine came from ebay and only a few came from mouser.

I did try the 5v chips and the 12v chips.

could just not get the noise level down to where its competitive with modern dacs, say. the pga was the noisiest thing in my system.

the cirrus is a lot more complex and its more expensive when you blow it (sigh, I already had a chip burn on me) but the SOUND is so, So, SO much better than pga

and you get 8ch which is great for 'active xo guys' like me. I can allocate 3 pairs for my 2-way spkrs+sub, then allow the last pair for headphones use (switching off the other 3 to engage the last pair for phones).

also, I was never able to get a clean click-free value change on pga. even 32db (binary points) would click and you could definitely hear the clicking in the spkr. not every value and not even every binary rollover point, but some of them.
__________________
My Photostream:http://www.flickr.com/photos/linux-works/
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
silent amp jaudio Chip Amps 1 24th January 2005 04:07 PM
silent headphone electro samurai Headphone Systems 0 3rd June 2004 04:07 PM
Silent Fans jteef Parts 8 19th March 2002 06:50 AM


New To Site? Need Help?

All times are GMT. The time now is 10:22 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2