gregdubuis wrote on Fri, 22 September 2006 02:20 |
Hi everybody!
What do you think about the Surface Mount components?
We can find this components in SSL AWS900/ Neve summing box/ Dangerous Music
I'm asking this because i' ve "talk" with Chris Muth and he give me is version of the SMC stuff.
At the begin this technology was for portable stuff but right now they are using this into High End equipment... Unfortunately all my friend who buy some of this type of gear have ton of problem (Mic preamp, bus output out of order).
This technology can really replace "normal" discreet components?
Could you please share you're experience into this new way of design.
Best regards
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There is a lot of wrong information floating around in audio, and the through hole vs surface mount discussion is not spared.
Generally, a good way to view components is "one at a time", without any pre conceived notions. The comparisons between parts should be done AFTER you study the parts, and it does depend on a specific use, and on a case by case basis.
There are few "formulas" or words of wisdom that hold a real examination. For example, You will probably no find a surface mount resistor that can handle say 10 watts of power. Power means heat generation, and dissipating 10 watts in a tiny volume will cause huge temperature rise. But how often do you dissipate that much? Each resistor in a circuit dissipates some known amount (it depends on the specific circuit). Say you have a 5V on a 10KOhms, then the current is .0025 watt. Even the tiny surface mount resistors can handle much more then that with no noticeable change in behaviour. Aside from resistor power, there is current handling capabilities, maximum operating conditions (such as temperature) and more.
Similarly, capacitors should be viewed according to their capabilities. From questions about voltage, ripple current, internal impedance to the more subtle issues such as dielectric absorptions, frequency characteristics and more... At the end of the day, you find the same various materials in both through hole and surface mount.
With semiconductors, there is some wide spread but misguided belief that the bigger through whole part will run cooler. It is not always the case. The semiconductor chip itself is "wired to the package pins via very thin(!) wires and the length of the wires does make a difference, the same way that the length of the leads of a transistor does. Often, a surface mount "pin" can be coupled to some copper area (pad, or ground plane or power plane) to conduct heat better then the old through hole...
Surface mount certainly has the advantage in high speed applications, where reducing size amounts to much lower capacitance and inductance (which tend to stand in the way of fast voltage and current changes).
I could go on and on. But to simply state it: I would strongly suggest to avoid making judgements based on the choice of packaging. True, you are unlikely to find a GHz system based on through hole, and unlikely to find a power amp speaker drive based on tiny surface mount transistors, but there is a lot of middle ground in between. The choice of each component in each individual circuit is based on numerous factors, from material to placement, from reliability to environmental conditions, from distortions to price... This is the domain of the designer, and coming at it from the outside with general statements is going to get you into wrong conclusions any day of the week.
Design of gear requires following and forcing "signal flow" in circuits. Doing the job well means that there are no shortcuts to studying and understanding the various factors that impact the signals. That requires knowledge about which factors apply in each and every case. For example, when working with say 15V range, I already know that I do not need to care about 100KOhms resistor heating up. But if I wanted to use 100 Ohms value, then I need to address the issue of heat...
One can not "shortcut" years of study and practice with a simple statement such as "through hole" sounds better. Such statements are NOT scientifically based, and the "data" supporting it is no better then "I hear it" with no real ABX tests to support it, and certainly with no measurement data to support it.
I am not aware of a single case where a proper repetitive ABX was administrated to show that through hole is better or worse then surface mount. Doing such a test is ridicules. Such a test could not be done by just replacing through hole with surface mount parts. The decision to use one type or the other may be based on good rational that applies to that specific design. A house meant to be made out of wood may not stand up when you make it out of rocks...
Regard
Dan Lavry
http://www.lavryengineering.com