Be fast and effective with Distrelec, because they do not seem to save shopping-carts, as other vendors do, so you can add things and come back later with more.
Or these if you find a "single" DIP style opamp you want to try. http://www.ebay.ca/itm/180749610268?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
Semiconductor Opamp adapters from Parts Connexion if you are ordering from them anyway...
Hum problem.
I'm having some issues with my DAC passing mains hum to it's output. I'm feeding it to a Pre-amp board I bought from Ebay (to buffer, and provide a Volume control), and then into an ICEPower 125ASX2 module. With the DAC disconnected from the Pre-Amp, I have silence, even at full volume (ok, the slightest bit of hiss if I listen really close to the tweeter). But with the DAC connected, I get mains hum - not terrible - but definitely audible with no music playing at listening volumes.
I'm feeding the DAC with the recommended R-Core transformer, and have kept signal paths short, screened, and paid attention to layout. If I ground one output channel of the op amp on the DAC board, the hum reduces marginally, and if I ground the other, it stops almost completely. I wondered if I had a faulty regulator smoothing capacitor - I had replaced the originals with 100uf Electrolytics, per the BOM. (and the regs were also replaced per the BOM). I tried putting in some different 220uF capacitors, but still to no avail. I've checked component values in the LPF (modified per the BOM) and all ok, and checked and resoldered connections.
Unfortunately I don't have an oscilloscope which is hampering my diagnostics. I've tried running a ground wire to the AC centre tap to bring the circuit to chassis earth and am running out of ideas. I still suspect either a problem with the board (why would grounding one signal channel completely kill the hum, vs the other one?). I've tried changing the Op-AMP too in case it was faulty.
I'm about to try putting 10uF caps directly at the Op Amp supply rails, but I'm not sure what else to try! Anyone else experiencing hum from this board? Any other ideas?
I'm having some issues with my DAC passing mains hum to it's output. I'm feeding it to a Pre-amp board I bought from Ebay (to buffer, and provide a Volume control), and then into an ICEPower 125ASX2 module. With the DAC disconnected from the Pre-Amp, I have silence, even at full volume (ok, the slightest bit of hiss if I listen really close to the tweeter). But with the DAC connected, I get mains hum - not terrible - but definitely audible with no music playing at listening volumes.
I'm feeding the DAC with the recommended R-Core transformer, and have kept signal paths short, screened, and paid attention to layout. If I ground one output channel of the op amp on the DAC board, the hum reduces marginally, and if I ground the other, it stops almost completely. I wondered if I had a faulty regulator smoothing capacitor - I had replaced the originals with 100uf Electrolytics, per the BOM. (and the regs were also replaced per the BOM). I tried putting in some different 220uF capacitors, but still to no avail. I've checked component values in the LPF (modified per the BOM) and all ok, and checked and resoldered connections.
Unfortunately I don't have an oscilloscope which is hampering my diagnostics. I've tried running a ground wire to the AC centre tap to bring the circuit to chassis earth and am running out of ideas. I still suspect either a problem with the board (why would grounding one signal channel completely kill the hum, vs the other one?). I've tried changing the Op-AMP too in case it was faulty.
I'm about to try putting 10uF caps directly at the Op Amp supply rails, but I'm not sure what else to try! Anyone else experiencing hum from this board? Any other ideas?
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No - with the digital cable connected it is the same. If I remove the digital cable, I get white noise superimposed on the same hum. I've tried adding the 10uf caps to the Op Amp supply rails, and that made no difference. I have just reduced the gain of the following pre-amp buffer from 2, to 1.2 as I realised that I was achieving almost full volume too early on the volume control - that obviously improves matters in that the hum appears at a higher apparent volume setting, but the problem is still there. When I prototyped it outside the case, I'm fairly sure I didn't have the hum (but not 100% - I might have dismissed it or not noticed it - it's fairly low level, albeit noticeable). So it *could* be a ground loop. I think I'll try moving everything out of the case and recreate my prototype scenario to see if anything changes.
OK, making good progress; it was an inadequate ground from the centre tap of the R-core supply to the DAC and the chassis. That's got it to around 97% of perfect.
I probably still have too much gain in the pre-amp buffer - what I would consider full (clean) volume is somewhere just over the mid-point of the volume knob. I've reduced gain of that stage to around 1.2 (56k/47k) but I'm wondering whether I should reduce it to Unity gain (will I risk stability issues?). To reduce it further, I'd have to reduce the input to the pre-amp buffer, and I'd rather avoid that.
I probably still have too much gain in the pre-amp buffer - what I would consider full (clean) volume is somewhere just over the mid-point of the volume knob. I've reduced gain of that stage to around 1.2 (56k/47k) but I'm wondering whether I should reduce it to Unity gain (will I risk stability issues?). To reduce it further, I'd have to reduce the input to the pre-amp buffer, and I'd rather avoid that.
OK, making further progress. Ignoring the gain issue for now. I detect, with preamp volume at Zero, a very low level of hum at the speakers. Have tweaked the layout of cables a little more and am trying to reduce that hum next. Still getting a slight hum from the preamp stage at full volume in addition, but will tackle that in a minute. They might be the same source. My expectations might need adjusting before long!
Have you got a star grounding arrangement of the RCA ground cables on the pre amp?
Heyyas,
@ClaveFremen: i was just trying to replicate your shopping list with as high quality parts as i could with my favorite dealer. Granted, shipping for distrelec and partsconnection aren't that bad, but ... i cannot help it - i'd really like to buy there.
So anyways, they do have the full WiMa product line, so i'd use them where you planned them.
As for the regulators i've read some datasheets and have chosen taiwan-semi TS7809CZ C0, as far as i can see the ripple rejection is about as good, if i understand the on-semi datasheets correctly noise is even a little better (on-semi is 10uV per volt V0, with V0=12V we'd have typical of 120uFV mine has typical of < 100uV), so they should be okay to go?
As for the resistor i've chosen 0,1% 0,6W "MPR".
The biggest problem are probably the electrolytic caps, right? Reichelt.de carries panasonic FC-A (EEAFC1*****). Are these good enough for the various purposes?
Also, my list can be seen on https://secure.reichelt.de/index.html?;ACTION=20;AWKID=520017;PROVID=2084. I'd really like to add my items to your PDF (even if its only for me own reference), but my pdf-editor choked on it. Do you have some kind of original file (openoffice, excel or the like)?
Anyways, thanks for your big help! Regards
- NebuK
@ClaveFremen: i was just trying to replicate your shopping list with as high quality parts as i could with my favorite dealer. Granted, shipping for distrelec and partsconnection aren't that bad, but ... i cannot help it - i'd really like to buy there.
So anyways, they do have the full WiMa product line, so i'd use them where you planned them.
As for the regulators i've read some datasheets and have chosen taiwan-semi TS7809CZ C0, as far as i can see the ripple rejection is about as good, if i understand the on-semi datasheets correctly noise is even a little better (on-semi is 10uV per volt V0, with V0=12V we'd have typical of 120uFV mine has typical of < 100uV), so they should be okay to go?
As for the resistor i've chosen 0,1% 0,6W "MPR".
The biggest problem are probably the electrolytic caps, right? Reichelt.de carries panasonic FC-A (EEAFC1*****). Are these good enough for the various purposes?
Also, my list can be seen on https://secure.reichelt.de/index.html?;ACTION=20;AWKID=520017;PROVID=2084. I'd really like to add my items to your PDF (even if its only for me own reference), but my pdf-editor choked on it. Do you have some kind of original file (openoffice, excel or the like)?
Anyways, thanks for your big help! Regards
- NebuK
I'd advise you to have a look at other specs, which are as or more important than noise rejection, like impedance, which most fixed regulators generally do not exhibit because it's much poorer than on variable regulators like the 3X7 family.
In noise/ripple rejection you also can lower them by bypassing the adjusting resistor with a higher value capacitor up to 22ouF.
Simple Voltage Regulators Part 2: Output Impedance
Have a look at TNT regulator articles.
Oh, very interesting article. I've understood the general problem and seen the difference (ON: 1.1mOhm, Taiwan: 19mOhm), but ... as far as i understand the 7812 powers one digital 3.3v and one digital 5v and the opamp, the 7809 powers another digital 3.3v (thats it?). So those thingies mainly power other regulators, with buffers in between. Only the 7812 has to power multiple different load situations (opa and regulators). Will all the bad things mentioned in the article occur in this situation too? I could understand that a certain noisefloor backfeeds from the digital supply regulators to the 7812, but as it doesn't directly power logic circuitary (but only its regs) i'd not think that the OPAs supply is affected that much?
Also, please don't get me wrong - i'm not trying to doubt you (way too much of a beginner for that), but rather to understand whats going on!
Thanks Again
- NebuK
Also, please don't get me wrong - i'm not trying to doubt you (way too much of a beginner for that), but rather to understand whats going on!
Thanks Again
- NebuK
Finished. A DAC integrated, ICE Powered Amplifier, using the DAC module in this thread, a pre-amp module, and an ICE Power, 125ASX2 power amplifier module. DAC has had the voltage regs upgraded, the LPF corrected, and I'm using LM4562 Op Amps in the DAC and pre-amp.
Solved the hum problem - I had to run grounds to chassis from the centre tap, and then bond that to signal ground on the DAC board and on the pre-amp board. If I turn it to full volume, and stick my head against the speaker, I can *just* perceive some slight mains hum, but I couldn't eradicate that with any amount of fiddling or changing layout. It's such a low level now I can live with it. I've attached pictures in case anyone is interested in the layout, or the finished product. The case is from a Rotel 10 series DVD player that died a few moons ago. I created a new front panel from Dark Walnut, which turned out to be the trickiest part of the build as it needed some quite complex routing to accommodate the chassis.
Solved the hum problem - I had to run grounds to chassis from the centre tap, and then bond that to signal ground on the DAC board and on the pre-amp board. If I turn it to full volume, and stick my head against the speaker, I can *just* perceive some slight mains hum, but I couldn't eradicate that with any amount of fiddling or changing layout. It's such a low level now I can live with it. I've attached pictures in case anyone is interested in the layout, or the finished product. The case is from a Rotel 10 series DVD player that died a few moons ago. I created a new front panel from Dark Walnut, which turned out to be the trickiest part of the build as it needed some quite complex routing to accommodate the chassis.
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Hi folks, and a VERY Happy New Year to you all
I've decided I am going to use the schematic posted below for the output stage on my DAC - looks simple & elegant which usually bodes well for good sound quality. Would any of those 2sk170s/2sj74s need to be matched, and of certain grades to work optimally? Thank you.
Cheers,
- John
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This dealer is good for Wimas but there you can't find all other components needed...
No problem if you want to use it but in this way you can't populate the board according my BOM, sorry.
No, sorry, but OnSemi regulators are different from all others, Those TaiwanSemi are as like alll ohters.
They're fine if you just want to implement the right outèput stage for AK4396 but quality-wise they're no different from the original ones supplied with the kit...
Sorry, no again, Panasonic FCs, while excellent SMPS caps, are not suitable for audio, IMHO.
They've a nice appealing 'loudness' effect but, to my taste, they're also compressed and definitely harsh.
Sorry but your shopping list is noway similar to mine...
Dario, whilst I applaud the amount of work you've put into your BOM (which I'm, and many others, are greatful for), and helping others, there ARE other parts people can use/substitute instead of your selection which may well give even better results. There's an infinite amount of possibilties with parts selection afterall, plus not everyone has the same taste/ears. I think people should be encouraged to experiment with parts selection, rather than everyone following the same BOM and getting the same results
Dario, whilst I applaud the amount of work you've put into your BOM (which I'm, and many others, are greatful for), and helping others, there ARE other parts people can use/substitute instead of your selection which may well give even better results.
There's an infinite amount of possibilties with parts selection afterall, plus not everyone has the same taste/ears. I think people should be encouraged to experiment with parts selection, rather than everyone following the same BOM and getting the same results
Thanks John
I do agree completely and I encourage experimenting but there are some things that must be taken in account:
- The new BOM it's no longer mine, it can be even better but it's a different one.
- NebuK didn't tried parts included in his shopping list, they're selected only on availability from his preferred supplier.
In my opinion the answer is simply no...