Anyone put a loudness circuit into a DIY tubed preamp?

[chasaboo]

Just curious if anyone has experience putting a loudness circuit into a DIY tube preamp, particularly if it's defeatable so you have the option of using it or not.

Thanks if you have some info or experience with this. :yes:

[Nikko75]

There is a dozen ways of doing it, depending on the circuit of the preamp/amplifier. It is usually connected with the volume control though some preamps have it buffered and placed with a gain stage. I'd need the amp infront of me to design it but these pictures show what it may consist of. Unbuffered loudness/bass/treble controls upset the impedance that the source sees, but are used anyways.

The simplist and worst way to to do it is shown in the first drawing. Basically find a resistor on your input. It may be 10K to 50K. A switch in parallel with a resistor and capacitor whose values will depend on your preamp will allow higher input of frequencies on the bandwidth extremes. The value of C1 will be very small.

[chasaboo]

Thanks for the info.

I have a friend who is thinking about building a simple 12AU7 preamp from a Rozenblit schematic that was in Glass Audio years ago. He is in love with a loudness button on his receivers and was wondering about implementing one in his preamp.

I had not seen anyone doing this so I was curious about it.