True Bypass question
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westondc
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True Bypass question
So I've got an understanding as to what a true bypass is about but does it effect battery life in a pedal when turned off? I've noticed that many of my other (non TB) pedals eatup bats like crazy if I leave a patch cord plugged in. Wondering what causes this and if the same happends to pedals with a true bypass switch?
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s2
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True bypass has nothing to do with battery life. True bypass means you switch the input directly to the output with no other parts in the signal path when the effect is off.
Battery switching is determined my a switch on the input jack. If something is plugged in, the switch is shorted and the battery is active. If not, the swith is open and the battery is inactive.
Battery switching is determined my a switch on the input jack. If something is plugged in, the switch is shorted and the battery is active. If not, the swith is open and the battery is inactive.
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servant
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I hadn't thought about this before, but now you've got me wondering.
Can the True Bypass switch be wired such that it not only switches the circuit in and out of the signal chain (normal operation), but also activates the battery ONLY when you engage the effect? That would enhance battery life; would there be a delay in activating the effect while it powers up?
Can the True Bypass switch be wired such that it not only switches the circuit in and out of the signal chain (normal operation), but also activates the battery ONLY when you engage the effect? That would enhance battery life; would there be a delay in activating the effect while it powers up?
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Francis_Vaughan
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The answer is yes, yes, and no, with a big but.
What you risk in powering the effect up each time you want to switch it into circuit is a big thump as the effect stabilises - especially as it charges various capacitors and the bias networks reach operating points etc etc. Power-up is a pretty ill defined operation for most circuits, and thus there is good reason to have the circuit constantly powered.
A way to avoid the power up transient problem is to have relay based switching and a small time delay, but this gets you back to the issue of a delay - plus the additional power drain of relays.
I will admit I don't have the discipline to always disconnect the input plug, and have killed more than my share of batteries. But the general system does have its advantages.
What you risk in powering the effect up each time you want to switch it into circuit is a big thump as the effect stabilises - especially as it charges various capacitors and the bias networks reach operating points etc etc. Power-up is a pretty ill defined operation for most circuits, and thus there is good reason to have the circuit constantly powered.
A way to avoid the power up transient problem is to have relay based switching and a small time delay, but this gets you back to the issue of a delay - plus the additional power drain of relays.
I will admit I don't have the discipline to always disconnect the input plug, and have killed more than my share of batteries. But the general system does have its advantages.
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s2
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Very true!
Another thing to think about is true bypass has its problems. I don't know if you have noticed, but almost all TB effects have problems with popping. This is due to those same charging/discharging effects just described. There are ways to remedy the popping, but they have their problems as well. A common solution is to use pull-down resistors to alleviate the popping. But what you find upon careful examination of the schematic is effects using this method are no longer TB, because the remedies to the popping sound cause drag on the circuit. Because of this, I have found Clinton bypass (almost true) to be a good compromise. In this case you leave a 1M pull-down resistor on the input jack, which will discharge caps in the signal path when you switch. The disadvantage is the signal loss will be almost zero in some setups and fairly large in others. It just depends on what effects and stuff you have in your signal path.
These problems lead us to why Boss and some other companies have used Solid State buffers for years now. They don't use true bypass. They just slightly boost the signal with transistors (or opamps or whatever) to make up for the difference.
Another thing to think about is true bypass has its problems. I don't know if you have noticed, but almost all TB effects have problems with popping. This is due to those same charging/discharging effects just described. There are ways to remedy the popping, but they have their problems as well. A common solution is to use pull-down resistors to alleviate the popping. But what you find upon careful examination of the schematic is effects using this method are no longer TB, because the remedies to the popping sound cause drag on the circuit. Because of this, I have found Clinton bypass (almost true) to be a good compromise. In this case you leave a 1M pull-down resistor on the input jack, which will discharge caps in the signal path when you switch. The disadvantage is the signal loss will be almost zero in some setups and fairly large in others. It just depends on what effects and stuff you have in your signal path.
These problems lead us to why Boss and some other companies have used Solid State buffers for years now. They don't use true bypass. They just slightly boost the signal with transistors (or opamps or whatever) to make up for the difference.
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Stephen
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