Lay the instrument on its back. Magnetically join the Installation Tool with the Modulator, looping around the Modulator.

Holding the ends of the installation tool, lower the Modulator into the instrument through the Left F-hole until the Modulator is entirely inside and has cleared the faceboard.

Position the Modulator under the wood so it is only half visible through the f-hole. Place the Black Outer Magnet on the instrument top at least 3 inches away from f-hole and slowly slide it towards the spot over which the Modulator sits.

Once the outer magnet and the Modulator have magnetically connected, gently remove the installation tool up and out. Holding the outer magnet only, slide the entire Modulator away from f-hole into the tone & wolf control area.

This can be reversed for removal, however the entire Modulator + Black Outer Magnet are pulled out together.


Krentz Modulator Installation Illustration 1

1. Before unpacking the modulator, sit and face cello with endpin extended about 18 inches and firmly planted. LEAN THE CELLO TOWARDS YOU, the bottom of the bass f-hole is still accessible to both of your hands. Hold instrument in place with your knees.

Krentz Modulator Installation Illustration 2

2. Unpack the box, separate the two magnets, and grasp them firmly, one in each hand. First, insert THE FELT END of the piston assembly halfway into the lower hole of the bass f-hole BUT DO NOT RELEASE IT. Then position the black outer magnet about 3 inches directly below the lower hole of the bass f-hole with the felt side touching the top of the cello.

Krentz Modulator Installation Illustration 3

3. Make sure you are still holding the cello tilted towards you. Release the piston assembly. It will jump into the cello and snap into its position inside, right behind the black outer magnet. That’s it!




1.Do you have a modulator for violin, viola, or bass?

Yes! We have modulators for violin, viola, bass, cello, and a slim model for cellos with smaller f-holes. Simply select your instrument from the drop down menu on the product page.

2.How big are the modulators? Will it fit in my instruments f-hole?

The modulators are designed to fit an f-hole with the following size:
Violin 8.3mm | Viola 9mm | Cello 16mm | Cello (slim) 14.1mm | Bass 22mm

3.Will you be developing a “slim” model for the cello?

Yes! The slim model for the cello is here. Just select “Cello (slim)” from the drop down menu on the product page.

4.Will the Krentz Modulator damage my cello?


5.How easy is it to install?

If you follow the instructions exactly, you should have no problem installing your modulator in a matter of minutes. However, if you have reservations, any luthier would be able to install it for you.

6.If the Krentz Modulator doesn’t work for me, can I return it?

Yes! We offer a full refund policy. We are proud to claim “Every cello, every time,” but if for any reason under the sun you would like to return your Krentz Modulator, we will oblige. We highly recommend that you contact us with your concerns first, however, in case a simple conversation can clear up any confusion or concern.