m-audio studiopro 3 speaker low volume

[Davebassman]

Hi,

I have a pair of m-audio studio pro 3 monitors, but one of the speakers sound's low than the other one. I opened the speakers, and the wires, vol pot seems ok. So, where do I began? I see a pair of 4558 IC's and TDA2009A power amplifier.

Thanks.

[TomCarlos]

Next step, you remove the speakers and swap them into the other cabinet. Does the low volume follow the speaker or is it the cab?

These are powered monitors.... what about the RCA cables from the mixer to the speakers, have you swapped those to see if you have an issue before the monitors?

[Davebassman]

Yes,

I tried to swap speakers, RCA cables... and the problem persist. The problem is the board. I tried to route the audio path with a audio probe, but without a schematic I'm getting lost.

[TomCarlos]

Ok... it is the board - maybe.



So one unit has the power module and the other unit is a speaker only. Correct? https://www.zzounds.com/item--MDOSP3

Do you see anything obviously wrong? Bad solder joint maybe?

Are the 4558s in a socket or soldered onto the PC board? If sockets, can you pull those out and swap them to see if it makes a different? Maybe that is a quick check. The are plenty of datasheets for the 4558 op amp available. Take a voltage check on each pin and report back. Make sure you keep 4558 #1 separate from 4558 #2.

You can do the same for the TDA 2009A amp. Go find a data sheet and take some voltage measurements. In fact, some datasheets show how to use the IC in an amp circuit. So you might find a complete circuit there!! TDA2009A Datasheet.

[J M Fahey]

Ouch!!!! Only 10W per channel?
Thatīs *weak* in a mini Studio monitor situation, even if desktop.

Show a couple board closeup pictures, we might suggest a couple test points.

From the IC complement you mention, TDA2009 is the stereo power amp, 10+10W

Datasheet: https://www.digikey.com/htmldatashee...1/TDA2009A.pdf

Its input pins are 1 and 5 ; speaker outs are 10 and 8, verify with datasheet inn hand.

I suggest you inject, say, 500mV 1kHz at monitor IN (left and right), check how much reaches Chipamp pins 1 and 5, and how much it puts out on pins 10 and 8

That way you know whether signal is lost between input and TDA _or_ one TDA half is weak, for some reason.

I guess 4558 is used as a preamp, mainly to provide for the Bass Boost function.

Plan B: Absolute worst case, junk that board and replace it with some cheap AliBaba one, which is happy with your current power supply.

Not sure you have 28V single supply (so capacitor coupled outputs) or split +/-14V rails.

As you see, you can do some testing even without official schematic.

PS: also show its crossover.
It might be as simple as a lonely capacitor per tweeter.

[Davebassman]

Hi,

I found a bunch of dry electrolytic capacitors. I changed all the bad capacitors and now are much more better, but one speaker still a bit louder than other. So, I think it's enough.

Thanks!