Percussion release click

[geldo79]

Hi,

Is it normal that the key click is much louder when percussion is enabled? I did some rewiring on my m3 (I want to chop it), and now I hear a very loud key click when percussion is enabled. When I slightly press a key, first I hear the percussion sound (wich does not decay). When I continue pressing down the key, I hear a loud click and then the percussion tone decays. I am not shure, but I can not remember that it was there before. Any ideas?

Christian

[David Anderson]

Percussion steals one of the drawbars and busbars to trigger. If you push down a key just slightly, it is possible to get an audio signal without triggering the percussion decay due to the fact that the distance between busbars and key contacts is not exactly the same. You're closing several switches at the same time. You'd never play it that way.

The question is how it behaves in normal playing.

[geldo79]

Ok, but what could be the reason for the loud clicking? It is very much louder than without percussion. The organs key click is pronounced without percussion, but with percussion it is really disconcerting now.

[geldo79]

Do the wires going from the percussion unit to the Amp need to have a certain resistance? One of the two yellow wires is a bit thin.....could that be a reason for the problem?

[geldo79]

I did not find a solution for my problem so far. I still hear a (too loud) click when the percussion decay is triggered. What I have tried is to
install a small capacitor between terminal K and ground. This noticeably removed the highs from that click, but it is still too loud. Does
anyone have an idea what the source of this click could be? On my other M3 I also can hear that click (in the moment when percussion decay is triggered), but very quiet....it doesn't
have any effect to the overall percussion sound.

Did anyone of you have such a problem before? Maybe it has something to do with grounding, but as far as I can tell the ground connections are correct.
What's different on my M3 is that I chopped it, and for that i installed a 32-pin connector which connects the top and bottom part. On one pin I collect all
the ground connections from the top, which then are led to the AO29 chassis. Could that make problems?

Greetings Christian

[enor]

You say you "did some rewiring". What exactly did you change, and how?

[geldo79]

....all wires from the top part going to the bottom part are fed into a 32 pin connector now. But I had to collect the ground from all shielded wires on one pin, and on the other side of the connector, that pin is connected to all wire shieldings again.

[Jaim]

First of all, terminal K is the percussion trigger which is grounded through the tone wheel filter when the key is depressed. The audio signal from DB 3 or 4 goes in Terminal H. What happens when all of the DB's are pushed in?

Jim

[geldo79]

When all drawbars are pushed in, the click can be heard very clear because only the percussion sound is audible. I know that
terminal k is grounded when a key is depressed. Thats why i installed a capacitor between k and ground. In more detail, K is grounded when
the first busbar (1') connects to its key contact.....and thats exactly the moment when i hear the click (and the percussion tone starts
to decay). Thus, the grounding of terminal k produces that click. I think it is normal, as i can hear it on my other m3 as well. But it is
not normal that it is so loud.

[enor]

I'm confused. Why the capacitor?

[geldo79]

It was a test.....I wanted to see if it helps reducing the click. And it did noticeably.....but still not enough.

[Jaim]

If I remember correctly (I don't have an M3 to look at), the ground to the preamp is via the shields on the wires. Try attaching a wire to one of the screws on the terminal cover of the preamp and the other end to the TWG grounds.

Jim

[geldo79]

If I remember correctly (I don't have an M3 to look at), the ground to the preamp is via the shields on the wires. Try attaching a wire to one of the screws on the terminal cover of the preamp and the other end to the TWG grounds.

Jim

I don't understand. What wire? And why? The TWG should already be grounded to the amp I think.

[Admin]

The click is due to the percussion control keying transient being coupled into the audio. This could be through the signal wiring, the power supply wiring, or a problem with percussion circuitry. I'd suspect a grounding problem due to wiring since the problem began after re-wiring. It's important that there be zero resistance between ground points. Adding a heavier wire, as Jaim suggests, might help, although it might make things worse by creating a ground loop. Ground loops occur when multiple paths with different resistances to ground exist. Increasing wire lengths or changing grounding points when you rewired may have created these conditions.

There's really no simple solution to your problem other than process of elimination. You could start by unbundling the percussion wiring and moving it away from the audio cables. If you changed the ground configuration, e.g. by grounding wire shields that weren't grounded at both ends before, using a different grounding point, or eliminating a ground wire that was there previously, restore the wiring to the way it was. Finally, have a look at the percussion circuitry to make sure that it is not the source of problem.

[Jaim]

I've done this to test AO28/29's on the bench. Disconnect terminal H. Jumper a suitable tone from the TWG to terminal H. The tone should be heard continuously. Ground terminal K - you should hear a ping (hard to detect as the ping and tone are the same frequency) and the tone should decay. Cycle ground on K to repeat. Evaluate the key click.

Jim