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
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
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.
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.
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.
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.
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
Thanks for the replies everyone!
The output impedance of my DAC is lower than 600 but I have also tried with an input buffer on the PGA.
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.
At -20dB I can hear noise from the speakers when my ear is about 30cm away. Annoying!
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
The output impedance of my DAC is lower than 600 but I have also tried with an input buffer on the PGA.
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.
At -20dB I can hear noise from the speakers when my ear is about 30cm away. Annoying!
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
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.
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.
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.
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.
Attachments
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!
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!
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.
You cannot blame the PGA for your problems.
Looking at your photo, your layout probably has issues. How you arrange your grounding and cable dressing will have a significant effecton EMI susceptibility.
I built a high end pre with this device and I can tell you it is superb. Further, Esoteric s' top of the range line pre uses this same device for the volume and gain element (the core of any preamp) and its gotten superb reviews. In fact one reviewer said 'one of the best preamps I have ever auditioned'
Looking at your photo, your layout probably has issues. How you arrange your grounding and cable dressing will have a significant effecton EMI susceptibility.
I built a high end pre with this device and I can tell you it is superb. Further, Esoteric s' top of the range line pre uses this same device for the volume and gain element (the core of any preamp) and its gotten superb reviews. In fact one reviewer said 'one of the best preamps I have ever auditioned'
does it matter if its the pga chip's fault or the fact that its so hard to work with and get stellar results?
I'm sure that with proper grounding, psu-ing and layout - and with pre and post buffering - it should be able to perform well. but the chip is finicky and you do have to be careful about the scr latchup. have to worry about that with cirrus, too, but to a lesser degree.
btw, how would wiring or any of that affect getting clicks at, say, a binary rollover point like 32db? I do hear a click as the internal resistors change over. now, again, I'm not prebuffered but I do cap-block since dc offset is known to make matters worse for clicks and knob movements. I know I tried the burr brown version and the cirrus pga version of the chip as well as the 5v and 12v versions. every one of mine had transitions clicks.
so far - even though - its early in my testing - I'm not hearing this at all in my 3318 proto and that is all hand wired on perf board, about as bad as it can get, lol. yet I don't hear any of the noise or clicks that all my pgas had.
if its really hard to get the pga to work, and there are other choices, then why even bother? there are other choices, now.
I'm sure that with proper grounding, psu-ing and layout - and with pre and post buffering - it should be able to perform well. but the chip is finicky and you do have to be careful about the scr latchup. have to worry about that with cirrus, too, but to a lesser degree.
btw, how would wiring or any of that affect getting clicks at, say, a binary rollover point like 32db? I do hear a click as the internal resistors change over. now, again, I'm not prebuffered but I do cap-block since dc offset is known to make matters worse for clicks and knob movements. I know I tried the burr brown version and the cirrus pga version of the chip as well as the 5v and 12v versions. every one of mine had transitions clicks.
so far - even though - its early in my testing - I'm not hearing this at all in my 3318 proto and that is all hand wired on perf board, about as bad as it can get, lol. yet I don't hear any of the noise or clicks that all my pgas had.
if its really hard to get the pga to work, and there are other choices, then why even bother? there are other choices, now.
I agree with Linuxworks to a certain extent, I know the PGA can be good and I know it's in some very high end equipment but It's not really working in my situation.
I've done star grounding for the PGA and its chassis as best I can, without the VFD connected, with the cover on and it's better but still not acceptable in my opinion, I still hear slight hiss/noise when connected to the Hypex.
Maybe it's the PCB layout or the fussy Hypex amp but I can't really change either of these right now.
I've done star grounding for the PGA and its chassis as best I can, without the VFD connected, with the cover on and it's better but still not acceptable in my opinion, I still hear slight hiss/noise when connected to the Hypex.
Maybe it's the PCB layout or the fussy Hypex amp but I can't really change either of these right now.
Reading datasheets may not be the lucky way to implement low noise devices but it is a good start to any DIY when you know zip about suitable layout or precautions.
PGA2310 datasheet(2/16 Pages) BURR-BROWN | Stereo Audio Volume Control
PGA2310 datasheet(2/16 Pages) BURR-BROWN | Stereo Audio Volume Control
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