Does SMT components effect the sound of pedal

[kldguitar]

Many pedal effect like use SMT components. But some one think SMT components would effect the sound of pedal and make sound bad. which one is right?

[Robert M. Martinelli]

Hi,
one of the main problems is not related to the nature of components, but rather to the increased "density" of PCBs, and the consequent increase of stray ( parasitic ) capacitance. Stray capacitance can shunt some of the higher frequencies to ground, or cause self-oscillation in a high gain stage. In the first case the loss is caused by the stray capacitance itself, in the second case losses are due to the need to add NFB loops to prevent self-oscillation.

All in all, I prefer "old fashioned" stompboxes, except when the effect's complexity forces me to move towards SMD-based devices.

Hope this helps

Best regards

Bob

[Steve Conner]

A good designer can take the layout parasitics into account, or make them negligible, and so get any sound he wants with either through-hole or SMT. However, bear in mind the following:

Some parts are not available in SMT (germanium transistors and tubes for instance )
Some parts are ONLY available in SMT
Pedal modders hate SMT because it's harder to mod
Joe Public believes that SMT sounds worse even if there's no evidence for it (so maybe you want to use through hole purely for marketing reasons)

[Mark Hammer]

Do not confuse SMT components, and the production techniques which use them. SMT assembly techniques can reduce production costs, so you tend to find SMT parts in many (but not only) low cost pedals like Behringer. The fact that they use such parts is separate from the decisions they make about which parts to use. For example, I bought a Behringer AC-2 clone. It is almost identical to the Boss pedal except that Behringer uses TL064 opamps, which are not the lowest noise available. For a pedal that boosts the treble to produce an acoustic simulation, this is a bad move.

As well, the "heart" of any IC is many times smaller than the actual plastic package. So, while an SMT device may seem more fragile, the actual amount of silicon involved may be about the same. This is, of course, why a company can offer the same chip in DIP and SMT format with the same specs.

[Robert M. Martinelli]

the "heart" of any IC is many times smaller than the actual plastic package. So, while an SMT device may seem more fragile, the actual amount of silicon involved may be about the same. This is, of course, why a company can offer the same chip in DIP and SMT format with the same specs.

That's why I was talking about the SMT components not being the "real" problem ( if a problem exists ), as the silicon chip inside is often the same of their bigger brothers.

Unfortunately, we live in an era dominated by cost-cutting and marketing considerations, and I agree with Steve that probably most of the "mojo factor" is in the people's ( "Joe Public's" ) mind, but, if this is the case, we're guilty too, because we keep on building hand-wired-point-to-point tube amps instead of using PCBs

Call me romantic, but all this "modern stuff" around don't even come close to my 1964 AC30TB, my 1966 UL4120 or my '59 Bassman.

Cheers

Bob

[kldguitar]

YES, i MAINLY CAUSE STRAY capacitance

Hi,
one of the main problems is not related to the nature of components, but rather to the increased "density" of PCBs, and the consequent increase of stray ( parasitic ) capacitance. Stray capacitance can shunt some of the higher frequencies to ground, or cause self-oscillation in a high gain stage. In the first case the loss is caused by the stray capacitance itself, in the second case losses are due to the need to add NFB loops to prevent self-oscillation.

All in all, I prefer "old fashioned" stompboxes, except when the effect's complexity forces me to move towards SMD-based devices.

Hope this helps

Best regards

Bob

I agree with you SMD components size is samller, so the PCB is compact, the stray capacitance is larger. it make sound not good.
about hand-wire tube and PCB Tube amp, maybe different.