Because as I said it adds parasitic inductance, long leads etc. Use RS, Farnell, mouser etc and you will find quality caps, that are used throughout the electronics industry for far more sensitive designs than this. I don't subscribe to bespoke audio caps, plenty of quality components that would fit and do the job properly, and the caps will be better quality than bespoke audiophile caps.
Its a DAC so there is likely to be high frequency noise about, adding long leads is NOT a good idea, they can and will act as dipoles probably making the noise worse....
Marce,
Some introspective thoughts on design complexity and "tweakers". From an engineer.
DACs and ADCs are indeed particularly nasty with regards to noise issues, particularly delta sigma DAC/ADCs, where you get masses of very high frequency noise to deal with.
I had an interesting experience designing a digitiser for a distortion test set, where I initially treated one of the caps filtering the input to the ADC (on a CS5381) rather too casually. The issue was the CS5381 presents a horrible load to the analogue signal, and without very low Z filtering at MHz ranges on the input, the ADC THD increases by 20-30dB!
A thorough understanding of the design you are undertaking, and how to design the electronics to meet those needs, is essential. The right components usually look very unassuming and need not cost a lot. That does not change the fact that selecting the right bit is utterly essential. In the above example, the right component was a 2n2 NPO 0805 ceramic capacitor. Costs cents, looks boring, but if you swapped this for any other commonly available device (I actually tried this to see the effect after I discovered my stuff up) you can turn a 0.0001% THD ADC into a 0.005% ADC.
The problem hobbyists face is that they want to be involved in what they love. This leads to many wanting to customise things to take some form of ownership. Unfortunately the actual electronics and software is so complex that you have to be an engineer or spend an awful lot of time training yourself to be an engineer to get inside the design. This is beyond most hobbyists.
So with things like DACs, you don't generally see people redesigning the DAC or redesigning the filter. You do see people taking the whole filter out - as this is easy, and is not actually design.
Similarly you see people swapping op amps in and out, but not redesigning the electronics around them. Yet the electronics around an op amp defines almost the entirety of it's behaviour! Same deal - swapping an op amp is easy and does not depend on the person understanding the more detailed electronics involved.
Changing an output coupling cap in my mind is in the same camp. The characteristics of the DAC are really defined by the DAC itself and the filtering applied at its output. I havent looked at what the DAC is, but I would expect to see a low pass filter of some sort and possibly an I/V or differential to single ended convertor. If the OP was modifying these parts, I would agree that real changes to the DAC are expected. I would also be wondering at how much work was involved!
The tweaker part of DIY is real. I do get frustrated at (a) people taking advantage of them and selling them ridiculous stuff with all manner of semi science claims as to the benefits of the product, and (b) the amount of energy some seem to put into modifying something that is probably best left well alone.
30-40 years ago when I was doing electronics as a hobby I quickly settled on speakers as an area that I COULD design stuff that made a HUGE difference to sound. I moved into amplifiers which I could build and understand what I was playing with. For my money these are greatly fruitful areas for any hobbyist or professional alike. Moving into the digital domain and the guts of analogue takes a lot more effort, but has equal rewards if you put it in.
Some introspective thoughts on design complexity and "tweakers". From an engineer.
DACs and ADCs are indeed particularly nasty with regards to noise issues, particularly delta sigma DAC/ADCs, where you get masses of very high frequency noise to deal with.
I had an interesting experience designing a digitiser for a distortion test set, where I initially treated one of the caps filtering the input to the ADC (on a CS5381) rather too casually. The issue was the CS5381 presents a horrible load to the analogue signal, and without very low Z filtering at MHz ranges on the input, the ADC THD increases by 20-30dB!
A thorough understanding of the design you are undertaking, and how to design the electronics to meet those needs, is essential. The right components usually look very unassuming and need not cost a lot. That does not change the fact that selecting the right bit is utterly essential. In the above example, the right component was a 2n2 NPO 0805 ceramic capacitor. Costs cents, looks boring, but if you swapped this for any other commonly available device (I actually tried this to see the effect after I discovered my stuff up) you can turn a 0.0001% THD ADC into a 0.005% ADC.
The problem hobbyists face is that they want to be involved in what they love. This leads to many wanting to customise things to take some form of ownership. Unfortunately the actual electronics and software is so complex that you have to be an engineer or spend an awful lot of time training yourself to be an engineer to get inside the design. This is beyond most hobbyists.
So with things like DACs, you don't generally see people redesigning the DAC or redesigning the filter. You do see people taking the whole filter out - as this is easy, and is not actually design.
Similarly you see people swapping op amps in and out, but not redesigning the electronics around them. Yet the electronics around an op amp defines almost the entirety of it's behaviour! Same deal - swapping an op amp is easy and does not depend on the person understanding the more detailed electronics involved.
Changing an output coupling cap in my mind is in the same camp. The characteristics of the DAC are really defined by the DAC itself and the filtering applied at its output. I havent looked at what the DAC is, but I would expect to see a low pass filter of some sort and possibly an I/V or differential to single ended convertor. If the OP was modifying these parts, I would agree that real changes to the DAC are expected. I would also be wondering at how much work was involved!
The tweaker part of DIY is real. I do get frustrated at (a) people taking advantage of them and selling them ridiculous stuff with all manner of semi science claims as to the benefits of the product, and (b) the amount of energy some seem to put into modifying something that is probably best left well alone.
30-40 years ago when I was doing electronics as a hobby I quickly settled on speakers as an area that I COULD design stuff that made a HUGE difference to sound. I moved into amplifiers which I could build and understand what I was playing with. For my money these are greatly fruitful areas for any hobbyist or professional alike. Moving into the digital domain and the guts of analogue takes a lot more effort, but has equal rewards if you put it in.
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Googlyone,
A agree with all you said. Yes electrical engineering is complicated.
But all that aside, just look at he picture in the opening post. Even to a layman, that should look highly unprofessional. I mean with all the technical issues ignored, that just looks bad!
Why would anybody think that is acceptable to do?
A agree with all you said. Yes electrical engineering is complicated.
But all that aside, just look at he picture in the opening post. Even to a layman, that should look highly unprofessional. I mean with all the technical issues ignored, that just looks bad!
Why would anybody think that is acceptable to do?
I put that in as an 'over the top', way out extreme and total exaggeration, it was meant to be a joke!
... that's not the cary DAC B.T.W., nor is it even mine!
I am grateful for your time and trouble and I have taken note of the D.I.Y. advice in this thread and links too! Basically keep it in the allotted space, keep the flying leads short and don't bother with 'boutique' caps. This all makes sense to me and appears to be good solid and sensible advice! However, there are always 2 sides to a discussion and both Nick Lucas of HiFi Collective and Dan Wemmer of Cary have said: "The only degradation may be the extra lead length but the better caps will make up for that, customers who have bought larger caps for the quality have not reported any such issues (parasitic inductance). I have seen a circuit diagram for this DAC but I don't think the caps in question are in a feedback loop or anywhere else that might be susceptible to instability". That's a dilemma and I guess it's up to me to decide which way to go, I have collected the evidence from both camps and will probably try both concepts to establish what I personally prefer.
Funnily after many years in electronic engineering, initially building test gear, the last 30 years doing PCB design I agree with you...
U started this tread with a question would be a bad idea to put large caps with extra leads in your DAC.
We all said that's a bad idea and don't do that!!!
And u don't listen and doing on your own(You rather listen a Sellers who want sell as many product as they can to naives like u ).
And again as it is in so many threads here on diyaudio people asking for advice and the doing on thier own.
I'm asking Moderator to close this thread pls!!!
The parasitic inductance would be evident with a scope that could do high speed signal, you often find your analogue waves are fuzzy with the modulated high frequency noise instead of nice thin lines, This noise can be rectified and add to the overall noise of a system, worse it can be spread further afield as the leads act as dipoles adding further noise or worse to the overall system. Noise added to a analogue signal can result in what is perceived as a fuller sound. Such mods often do change the resultant sound sometimes because of actual circuit improvement and sometimes because the circuit operation has been reduced and system noise or distortion increased. Hense why I am against ears only testing.
🙂
I am unbiased, neutral. I have to give merit and respect to Nick and Dan as well as DIYAudio members, they are entitled to give their opinion as well as you, it's not a one sided argument! Please respect other peoples advice even if its wrong! You do not have a right to demand that this thread should be closed. Stay open minded please.
Yes, thank you marce, I see what you are saying and respect your advice. However, if a listener perceives the distortion as a superior sound (as far as they are concerned anyway) - surely that's all that matters, no matter how that is acheived? (even if someone spoils the party by saying "actually ~ it's just noise"), if the listener prefers it, so what? Can't I just use EMI/RFI Shielding Tape on the flying leads?
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I agree, if you enjoy it then its OK.
Shielding is more problematic than just using shielding tape, in fact its a pain. proper shielding is all down to slots and seams and is a PITA.
Shielding is more problematic than just using shielding tape, in fact its a pain. proper shielding is all down to slots and seams and is a PITA.
???
All this opens another 'can of worms': can shielding tape be used without grounding? (anyone). I've only seen grounding on braided earth wire, not tape?
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...interesting that the best JB JSX caps finish in price is were the Mundorf Mcap MKP starts and goes on to hundreds per cap. Does this show the Mundorf superiority, or are mundorf purely praying on the naive hobbyists?
Shielding is a science on its own, just putting shielding tape round wires can make things worse. Yes it has to be rounded, current will run through the shield...
Henry Ott again buy his book...
Here are some LT notes...
http://www.analog.com/media/en/training-seminars/tutorials/MT-095.pdf
Slots and seems are holes in the shielding that can act as wave guides and make things worse... I do a lot of designs that have to be shielded and it is a pain to do properly. If you look at shielding cans on PCBs (open your phone up) you will see how much attention is paid to ensuring there are no slots or open for the shield, they are usually soldered all round to make sure this is so.
Henry Ott again buy his book...
Here are some LT notes...
http://www.analog.com/media/en/training-seminars/tutorials/MT-095.pdf
Slots and seems are holes in the shielding that can act as wave guides and make things worse... I do a lot of designs that have to be shielded and it is a pain to do properly. If you look at shielding cans on PCBs (open your phone up) you will see how much attention is paid to ensuring there are no slots or open for the shield, they are usually soldered all round to make sure this is so.
Not really "audiograde" means nothing unlike automotive grade or industrial, that are backed up by research and development. Use good quality known brand capacitors, the best quality and temp range you can get. Derate the working voltage by at least 50% and finally use the correct capacitor for the correct job, that is the correct electrical parameters, not some hand rolled paper 'n' oil audiograde cap.
Dunno how great this Cary is...running 6922 at low voltage as a sonically and technically pointless cathode follower...not my choice at all. The silly "buffer" is there just to add the label "tubes" at the least possible cost to the manufacturer. Yes, tubes are great, but not used like that.
Having expressed my mild reservations, the Monacor caps clearly have to go. I did not notice what the original caps have been, if it was even mentioned in this thread, but chances are they were cheap electrolytics which an ex owner upgraded to films.
Going overboard with really nice caps in this half-witted circuit is probably extreme. What would work very well though is one of the Blackgate NX series. A 10/50 maybe?
If you insist on a bulky high voltage film cap, then by all means go for it. I see no problems with longer wires, as it is after all a low impedance circuit.
Having expressed my mild reservations, the Monacor caps clearly have to go. I did not notice what the original caps have been, if it was even mentioned in this thread, but chances are they were cheap electrolytics which an ex owner upgraded to films.
Going overboard with really nice caps in this half-witted circuit is probably extreme. What would work very well though is one of the Blackgate NX series. A 10/50 maybe?
If you insist on a bulky high voltage film cap, then by all means go for it. I see no problems with longer wires, as it is after all a low impedance circuit.
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