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Vintage threads from the first ten years

What is the output imp of boss stomp boxes?

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3/1/2000 5:24 AM
John	What is the output imp of boss stomp boxes? ?

3/1/2000 11:29 AM
Jim	well, depends on the box, but generally speaking an opamp output is low - less than 100 ohms, plus the series resistance of a jfet switching element (if they use that) of less than 100 ohms. So i'd estimate about 100 - 150 ohms. J2k

3/1/2000 11:49 AM
paul perry	Suppose you put a resistor across the output of an effect.If the resistance is equal to the output impedance, then the output voltage will halve. Providing, of course, that loading the effect this heavily doesn't affect its operation. **dont try this with a power amp**

3/2/2000 2:14 AM
Ed Rembold	output Z? more like 10K Ed R.... output Z? more like 10K Ed R.

3/2/2000 5:24 PM

Re: no subject

quote:
"output Z? more like 10K"

What makes you think that? I would speculate that the Boss boxes are op-amp based. There's not much chance they are over a few hundred ohms output Z.

If they have some form of transistor output stage then possibly, but since the poster did not specify what effect he was asking about we don't know.

As paul said, you can measure the output, and then without changing the settings, load the output down with a pot and adjust it until the output is one-half of what it was previously. Measure the pot resistance setting and that is the output Z.

J2K

3/2/2000 5:35 PM
Gus	Go to R.G.'s site almost all fet switching effects use the buffer fet switch set up of the TS in the TS write up. The out z is about 10k with the standard emitter follower out buffer.

3/2/2000 7:46 PM

quote:
"almost all fet switching effects use the buffer fet switch set up of the TS in the TS write up. The out z is about 10k with the standard emitter follower out buffer."

That would be a transistor output as I mentioned, but the output z of that stage still isn't 10k. It is some very low amount for positive swing and 5k for negative (because of the 10k resistors in parallel).

Again, we do not know which effect - the Boss flanger has an out z of about 500 ohms because it is an opamp output followed by a series resistor. Other devices may be different yet.

J2k

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