Understanding Seymour Duncan KTG-1 boost switches

Tube or solid-state, this section goes to eleven!
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J-fish
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Post by J-fish »

Hello, I'm opening this thread just to ask you if you can help me understanding a specific section of the schematic of a Duncan KTG-1 ("King Guitar Tone-1" :lol: ) that I have..
I'm mostly a player, and I'm trying to figure out what exactly those "active boosts" (as they are named in the manual) do in the circuit of this guitar preamp.
I have the schematic they sent me some years ago (the preamp isn't new..!)
KTG-1.pdf
(322.53 KiB) Downloaded 258 times
If you look closely at the circuit, there are some switches, parallel to the cathode resistors of the tubes.
These are "switched" with a pull-off function of 3 potentiometers of the preamp, kinda like older Mesa Mark amplifiers.

What do these switches exactly do?
Do they link to ground the 22uF capacitor to achieve an active boost in gain? (I'm taking the first switch as an example, but the same applies for the other 2 switches I guess...)
So, if you DON'T close the switch, the 22uF cap isn't grounded, and not parallel to the cathode resistor, so that you have less gain, isn't it?
What those 0.1uF capacitors are for? Do they shape the frequency response, OR you have to look at those 22uF, 1uF and 1uF only for frequency response?
I'm talking about this useful calculator that shows the frequency response of "cathode bypass capacitors" in the circuit:
https://www.ampbooks.com/mobile/amplifi ... capacitor/


Thank you very, very much to everyone...!!

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OC26
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Post by OC26 »

Hi j-fish

The 0.1uF cap / 1M resistor are part of the silent FET switching. The cap slows down the quick FET action to make it clickless. They don't affect the frecuency response. IMHO

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Post by J-fish »

OC26 wrote:Hi j-fish

The 0.1uF cap / 1M resistor are part of the silent FET switching. The cap slows down the quick FET action to make it clickless. They don't affect the frecuency response. IMHO
Thank you very much for the reply! Much appreciated..!

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