Ensoniq EPS distorted sound


I recently picked up a near mint Ensoniq EPS classic, yet it has one issue. It outputs a varying level of distorted sound. Sometimes not that bad, but sometimes it just kicks in and sounds like raw voltage ran through an amp! I bought the service manual, checked the fuses, power supply reseated all connections and ribbon cables, removed the memory expander trying to narrow everything down as the service manual states, yet I can not find anything wrong. Every thing I checked had the correct voltage. The EPS works flawlessly, I can play any sound, sample anything, sequence, load any sound, etc., it’s just the output that is killing me! Even sampling in, it still outputs distorted sound. Even at it’s best, its almost useable, yet you can clearly hear what almost sounds like faint interference distorting every note.
If anyone has had this and has any advice I’d love to hear it! I’m pulling my hair out over here with this, as I can not for the life of me find anything wrong.


If the distortion comes and goes randomly, that is very odd. Surely it happens in a consistent way - and whatever you can do to narrow down the circumstances under which it occurs will be helpful.

Does it happen with only sounds that you are sampling, or do the factory disks that you know are clean samples distort also?

Do both outputs (Left and Right) distort and sound the same? Same in headphones as speakers?

Does the distortion occur even when the EPS Volume slider is low?


Yes it comes and goes, yet it is always present in the sound even in the slightest. I’ve tried everything the service manual mentioned, checked all voltages with a multi meter, removed the memory expander, tried to narrow it down with no results.

It happens when I use factory disks and when I sample. essentially all sound the unit outputs is oddly distorted. I checked both outputs, headphones and speaker and both are the same distorted sound. When the distortion is occurring badly, yes moving the volume fader makes no difference, but sometimes it is quiet and only distorts the sound when i play the keys, it’s very odd. The frustrating thing is other than the distorted sound, the EPS works flawlessly, and I can do anything on it, it’s maddening. I’m recording a video with my phone, I will try to upload that in a minute


Here is a video I quickly took (turn your speaker down…sorry the noise is loud)

You can see the sound comes and goes to varying degrees.


Here’s one more video, this one shows the oddness of the entire thing, as the distortion starts after a while then quiets down, yet you can hear what I was talking about on each note played, listen for the clicks and static distortion sound in each sound played


This is going to be a very difficult thing to track down. The fact that it makes the noise when a key is not being played says that it is a processor chip failing or something like that. Could be a weak solder joint somewhere also. I think you would spend a LOT of time to pinpoint the cause of this, and if you were paying a tech to do it, the cost would easily exceed the value of the EPS.

Replacing the main board should fix the problem; we don’t have that board available right now, and never know when we will get another. You might just consider buying another EPS and selling that one for parts, or even upgrading to an EPS-16 Plus (which will load all of your EPS sounds and sequences).


Thanks for the input! I was afraid of that…I’ll probably just check here and there for a main board periodically, and most likely invest in an EPS 16+. This EPS was very cheap, under $100, so if I can ever find a main board it would be worth fixing. Thanks again!