My lower D notes are loud and bassy. All others are fine. Why?

This link might help.

https://www.google.com/search?q=Casio+Privia+px-100%2C+loud+key

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What is your piano brand and type?
Damage to the contact rubber can cause note plays loudly or,
note does not plays at all.
It is caused by:
1. Carbon rubber contacts dirty / dusty (yellow arrow). Clean with a pencil eraser (or cloth). Gently rub it.



2. Contact rubber is torn (your case). If this happen,it can not be repaired or glue. So, you have to replace one octave.
The yellow arrow indicates the side that is often torn.

Rubber side that is torn, usually not seen, unless we move / pressing gently on top (In the rubber contact position is not installed on the board.)
Examples of this picture was yamaha psr.

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Below the keyboard, there is a rubber contact (see figure 1). Damage to the contact rubber can cause:
- Note plays loudly or
- Note does not plays at all.

It is caused by:

1. Carbon rubber contacts dirty / dusty (yellow arrow). Clean with a pencil eraser (or cloth). Gently rub it.

2. Contact shredded rubber. If this happen,it can not be repaired or glue. So, you have to replace one octave as in Figure 1.
The yellow arrow indicates the side that is often torn.

sounds like either a blown amp circuit or you simply blew out the speakers, amp circuit is most likely.

Vera hi
to fix this problem you need open where are the contact board keys and clean or change the rubber contact

The woofer is blown recone or replace it

The one furthest from the switch is volume. The next one is a tone knob. Volume rasises or lowers the resistance and makes the guitar louder. You can also "clean up" a distorted tone by rolling off volume. Tone makes the sound more bassy or more treble.

Try plugging another sound source into the unit. The buzz MAY be pickup of magnetic fields in your guitar pickup that clobber your notes from the strings. Bad guitar cables are another possibility. By putting clean music from say a CD player into the unit you can find where the source is. If the CD player generates the same noises, then likely you have a failure of filter caps in the amp or other component failures. Also make sure your guitar can't "hear" the amp as feedback can do strange things.

You MAY be confusing touch sensitivity with VELOCITY sensing. Touch sensitivity is PRESSURE put on AFTER the note sounds that causes modulation. VELOCITY is what is used for example to control the loudness of pianoo notes depending how fast they are struck. VELOCITY sensing is done by using TWO contacts at every key... one closes first. IF one of these gets dirty, FULL velocity will be sensed and it will be LOUD. The contacts can be cleaned using ONLY 99% isoprophyl alcohol and Qtips after MUCH disassembly of the keyboard. The contacts are conductive rubber pills in silicone rubber domes. Clean boththe contacts and the circuit traces they pres down onto.

Either the first or second closure matrix line for the "A" keys is bad.

This may be a cracked or shorted circuit board.

A bank of diodes is used to prevent sneak electrical path if more than one octave has notes pressed.

First thing is to clean ALL the key contact areas and the conductive rubber pills with 99% isoprophyl alcohol.

This involves dis-assembly of the key area. If you are not competent in electronics, best left to a pro shop.

The keys are scanned in a matrix, two contacts per key and all the individual notes are in common (all the "A;s", "B's"...) And each octave is strobed for the first set of contacts and then for the second set of contacts. an the whole octave is read in parallel.

The reason for two contacts is one closes first and then the other as a key is lowered. The time between these is measured and is the note VELOCITY which for a piano controls the loadness of the note. IF ONE of the two fail, the loudness will vary as yours does.