Yes, but when I do something myself, I like it to look good too! And personnaly I do it as much for the function of the object than for the objet himself. Here we are talking about homemade audio, not consumer audio. Anyway, I am quite sur most of the people buying high end won't even have a look inside the case so only the outside cosmetic value counts there. So no, obviously an object does not sound as it looks, but I feel better when it looks adequate (or instead of these nice brushed aluminium radiators I would put some random piece of junk metal I found in a landfill and it would do the trick).
I don't get your idea Aandy, if it's homemade, it's homemade, period. And I like it to look good because good workmanship is appealing to me, but maybe not to you? Moreover, this is not a very interesting way to take for this conversation. I thought the thermal distortion point in my post was the most interesting stuff... Any comment about it?
Hello again,
Lumba Ogir, I wouldn't say heat is detrimental. I would say variable heat is detrimental. So larger components temperature doesn't vary as fast as SMD, it is better because more stable. Of course, this is more important for transistors than other components. Large bias has a point : if full signal modulation requires 1mA, a 5mA bias will have 20% of variation wether a 10mA bias will only have 10% of variation. So I am not sure heat is detrimental if you see it from that point of view. You just have to compose with the specs at the expected temperature. Tome, the real problem with heat is accelerated aging of the components with accelerated migration of impurities through the substrate. But anyway who will keep his equipement that long to see it happen?
Regards
Lumba Ogir, I wouldn't say heat is detrimental. I would say variable heat is detrimental. So larger components temperature doesn't vary as fast as SMD, it is better because more stable. Of course, this is more important for transistors than other components. Large bias has a point : if full signal modulation requires 1mA, a 5mA bias will have 20% of variation wether a 10mA bias will only have 10% of variation. So I am not sure heat is detrimental if you see it from that point of view. You just have to compose with the specs at the expected temperature. Tome, the real problem with heat is accelerated aging of the components with accelerated migration of impurities through the substrate. But anyway who will keep his equipement that long to see it happen?
Regards
You can build a layout with lower stray capacitance with SMT, and that usually improves stability and signal integrity. Obviously the parts have to be large enough to keep the thermal effects within whatever boundaries you think are important, but much of this involves copper areas and layout. A lot of thru-hole designs handle thermal issues quite poorly, so I don't think a blanket statement can be made. You need a good designer in either case. The only place where SMT may be more limited is capacitor choice, but I think people get too wound up about capacitors. I just don't use very many in my designs. If you like to swap components and experiment with different semiconductors, thru-hole is the way to go. I have a lot of thru-hole parts on the shelf, so I design with thru-hole. If I were building commercial preamps and low level stuff, I'd go with SMT and almost certainly get better performance. For power amps, OTOH, I really prefer thru-hole for robustness and ease of repair.
Exactely what I said, low level/low-power is perfect for SMT but power stuff, go TH. A big dye will always have more stable thermal stability even if the adjacent copper areas count in it. What counts is the temperature at the junction and this is very hard to control because dissipators connect to it only poorly, through a physical low-pass temperature filter that you can't win against. Once again, probably the VAS stage is the most vulnerable on that point.
Bigger is better?
I have been telling the wife since day one that this is not true. All bigger physical size caps get you is more inductance and distortion. The teflon caps could be made smaller. Most are large due to voltage rating. A thinner dielectric will allow them to be downsized to PP, or PE size.
I feel the same about resistors. A lower Temerature Coefficient will lower the distortion as much as oversized wattage. The RN55E or even better, T9,13, and T16 TC resistors will work as well as any T1 TC resistor in a 2 watt package if power level is kept low. The issue with high wattage resistors is lead diameter. And physical size.
Back to sound, great results are available from both. I prefer TH, but am changing as assembly skills get better with SM. there are PP caps available in SM, I have used them. There are also equilivent S102 bulk metal foil resistors available in SM too.
Course have not seen either yet in commercial designs. The reliability of the PP caps scared me, but never melted one using an iron. Hot air and solder paste would be better.
George
I have been telling the wife since day one that this is not true. All bigger physical size caps get you is more inductance and distortion. The teflon caps could be made smaller. Most are large due to voltage rating. A thinner dielectric will allow them to be downsized to PP, or PE size.
I feel the same about resistors. A lower Temerature Coefficient will lower the distortion as much as oversized wattage. The RN55E or even better, T9,13, and T16 TC resistors will work as well as any T1 TC resistor in a 2 watt package if power level is kept low. The issue with high wattage resistors is lead diameter. And physical size.
Back to sound, great results are available from both. I prefer TH, but am changing as assembly skills get better with SM. there are PP caps available in SM, I have used them. There are also equilivent S102 bulk metal foil resistors available in SM too.
Course have not seen either yet in commercial designs. The reliability of the PP caps scared me, but never melted one using an iron. Hot air and solder paste would be better.
George
In the 'middle of the pack' of audio quality, SMD and TH are all over the place, one can be better than the other. For the reasons of execution, design, etc. As usual no two pieces are the same, so direct comparisons are difficult.
In my experience...at the highest of the highest end, with regards to 'maximum that is humanly possible' audio quality, TH wins out.
There have been some designers who have gone through the process of designing an item after looking at availability of components..and then building one that is all SMD..and another than is all TH. It is possible, with a thorough look at a catalog, to find enough components from a group of companies to commit to this exercise. What I mean is find some different series of transistors capacitors and resistors and diodes that are available in BOTH packages,and then look at the execution of the different packages as well, so that the ancillary parts are identical as possible, ie legs vs termination on the SMD. Are they both of the same type of metals and coatings? Things like that.
When the apples are of a close enough type to one another, to control the variables as much as is possible..then the test is done and the result is the same. TH sounds better than SMD to the few designers I've seen that have publicly commented their experiments in this area.
In my experience...at the highest of the highest end, with regards to 'maximum that is humanly possible' audio quality, TH wins out.
There have been some designers who have gone through the process of designing an item after looking at availability of components..and then building one that is all SMD..and another than is all TH. It is possible, with a thorough look at a catalog, to find enough components from a group of companies to commit to this exercise. What I mean is find some different series of transistors capacitors and resistors and diodes that are available in BOTH packages,and then look at the execution of the different packages as well, so that the ancillary parts are identical as possible, ie legs vs termination on the SMD. Are they both of the same type of metals and coatings? Things like that.
When the apples are of a close enough type to one another, to control the variables as much as is possible..then the test is done and the result is the same. TH sounds better than SMD to the few designers I've seen that have publicly commented their experiments in this area.
the only thing wrong with smt is in the minds of the people that
do not like it,
do not like change,
do not like to develop better things,
and in most cases afraid of it,
and can not see it.
to use it.
It is the best thing I have used and i only wish i had put TH in the trash bin sooner
Progress
do not like it,
do not like change,
do not like to develop better things,
and in most cases afraid of it,
and can not see it.
to use it.
It is the best thing I have used and i only wish i had put TH in the trash bin sooner
Progress
I don't see why you can't just recognize the fact that a SOT23 transistor has generaly twice the junction to ambient thermal resitance than a TO92. And this resistance is part of the physical thermal low-pass filter I evocated previously. So the dye of a smt will ALWAYS be more prone to high frequency temperature change and the resulting modulation in a given dissipative environnement. For power audio applications, it's not the best, for the rest it's fine. And there is no question that smt's are better at high frequencies applications like DAC because of limited parasitic effects. But in this thread we are more prone to talk about power applications right?
I think it's not only a matter of dissipation via the tracks. For example take the temperature of power transistors bounded to a big radiator. You take a temperature probe and put it on the radiator, it's quite constant and you could calculate the junction temperature from it and assume it's constant. Put your probe on the case of the transistor and this will be the expected temperature but with more fluctuation. Now imagine the junction itself and the big fluctuations occuring there. So the dissipator may dissipate, but as said before there is a physical thermal low-pas filter in between because the energy distribution in from the junction to its surrounding is not instant. So a bigger dye will not suffer as much from it. I mean, it's physical, there is nothing to argue about. It's not only a static equation and dissipative values. You have to see it in the time domain too. Put a piece of metal on a quickly fluctuating stove, a little nail would follow the temperature fluctuation but a big chunk of metal would barely reflect it because the transmission of energy is not instant. The bigger dye is more temperature stable because of that effect. It's not a belief, it's just physic. But I also agree that thermal distortion reality is not totally accepted.
Regards
Regards
The temperature of that little piece of silicon is rapidly changing, both for thru-hole and SMT, and there's nothing you can do about it save keep the signal swing very small and/or the impedance high. It's might be less for an SMT part vs a TO-92 part because the lead frame may be more robust. Or not, depending on who made the parts. Fortunately I don't think negative feedback is evil, so those internal considerations don't show up in any way I can hear or measure. In a low feedback design you might see all manner of mysterious few-cycle performance changes.
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