Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Jonas on September 14, 2025, 02:01:54 pm

Title: Kagliostro low cut switch
Post by: Jonas on September 14, 2025, 02:01:54 pm

hey kagliostro what are your thoughts on the low cut switch you came up with? How did you you come up with the chosen values?

I would like to build another mic pre with a few more features this time around.

Title: Re: Kagliostro low cut switch
Post by: kagliostro on September 15, 2025, 08:45:07 am

Ciao Jonas

Really don't remember about that low cut

EDIT: Ah, OK, It was in a very old thread

Schematic has my name (because I was asking about a mic preamp) but the project author was Richard

I begin the build (for my son) but as he didn't required anymore the mic preamp the project never arrived to be completed

Sorry

Franco

Title: Re: Kagliostro low cut switch
Post by: stratomaster on September 15, 2025, 12:16:43 pm

That's just a passive high pass filter. The values were chosen by choosing standard values close to the target cutoff frequency.

The equation is:
frequency = 1/(2*π*R*C)

In this case the capacitance is fixed and the switch chooses between 3 different resistor values.

This can be made more versatile by running a pot as a variable resistor in series with a fixed resistor. 

Look up "passive high pass filter" in your search engine of choice for more info.

Title: Re: Kagliostro low cut switch
Post by: Jonas on September 16, 2025, 04:03:09 pm

ok thanks for the info

BTW you guys are my favorite search engine  :laugh: