Alesis DM5 drum module - low output level.

[Zotin Khuma]

A musician friend recently got a second-hand Alesis DM5 drum module
which he said put out a very low sound level when he connected it to
the line input of an amp. I checked the output with a scope and it
gave an output of about mic level even at full volume. Since he needs
it for practice with his band for the next few days, I advised him to
plug it into the mic input of their mixer, and I had time for just a
quick look.

There's an SMD version of the TL084 quad opamp near the output jack
sockets and it looked like the outputs of the opamp go to the volume
control, from where they go to the output jacks (no time for a
thorough trace). If this is correct, the opamp must be the
buffer-amplifier for the output.

Can anyone please confirm this ?

A quick probe with a scope showed that the signal levels at the + and
- inputs of the opamps were much higher than at the outputs. If I
guessed the function of the IC correctly, this would seem to indicate
that the IC is defective. It receives +/-5V at the power supply pins.

- Zotin

 

[Mike]

A musician friend recently got a second-hand Alesis DM5 drum module

A quick probe with a scope showed that the signal levels at the + and
- inputs of the opamps were much higher than at the outputs.

Is it possible the previous owner accidentally connected it to a mixer
or amp that was feeding phantom power (48V) into it at the time?

That would seriously upset the TL084's day.

The DM5 has 4 mono jacks for the outputs. If these were connected using a
mono jack to mono jack lead into a mixer that puts phantom power on it's
*stereo* jack input, then 48v will appear on the DM5 inputs.

That could be why the original owner ditched it.

Check in the manual how to route some of the drum sounds to outputs 3 and 4
(the AUX output), look under the "OUTPUT" button/menu, then see if they
are also damaged. How's the headphone output? Functioning OK?

Also, more obviously, have you made absolutely sure someone hasn't turned
down the volume -- the *soft* volume in the "MIX" menu, and the *soft*
volume for each drum sound? Not the hardware volume control!

Mike.

 

[Marcos]

Hi,

Greetings from Brazil!

Maybe the mute transistors are shorted. Check for small SMD
transistors next to the output plugs.

Good luck.

Marcos