Somewhat confused about the High and Low inputs.

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nebukatnessar
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Somewhat confused about the High and Low inputs.

Post by nebukatnessar »

Hi Forum,

I have been lurking in this forum for a while, because a couple of years back I bought an 18 watt Marshall kit. I had done some electrical projects, but I decided to first make some other stuff, like pedals, small transistor amps. And I succesfully made R.O.G. eighteen.

But now I have started actually making it. (Don't worry do have someone that knows stuff about tube amps and the electrocute thing to help me).

But I have a question about the schematic that I'm using (which found here in the downloads).

On the normal channel in this schematic both the High and the Low input have a 1meg resistor to ground. I do not see how the Low channel is low impedance?

This is the schematic I'm using storage/18w%20Schematic.gif
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nebukatnessar
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Re: Somewhat confused about the High and Low inputs.

Post by nebukatnessar »

I think I get it now. When you plug into the low ouput the input sockets ground also connects to input side of the high input. That makes that r3 & r4 parallel resitors to ground. Effectively giving the low input channel half the input impedance of the high channel?
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wmwelch55
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Re: Somewhat confused about the High and Low inputs.

Post by wmwelch55 »

In the amp schematics I have seen, the High input usually goes through tube stages that have more low frequency filtered out, which makes the High input brighter. The Low input can go through stages that let those lower frequencies through, giving a warmer sound.

Mike
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wmwelch55
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Re: Somewhat confused about the High and Low inputs.

Post by wmwelch55 »

Sorry, I posted before I saw your schematic. What I said really does not apply to your schematic.

I think you are right about what the high and low inputs in your schematic are doing.

Mike
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