Problems with soundcard reducing signal level

[Osse]

Hello ppl, I've got problems with my soundcards(E-mu 1820m) outputs and almost everyone of them(5 of 8) has to some degree lost signal level of some for me unexplainable reason.

I've got passive monitors with a unbalanced amplifier that connects with RCA connectors, and it's when I'm re-patching that the damage seem to happen, not every time, but of some reason it happens sometimes.

This is extremely disturbing, as my soundcard is ******* BROKEN!!! I've got external effects that I can't use nowdays becouse of this.

Anyone with any ideas/suggestions of what it could be? I've also tried with another amplifier and it did the same, and I've also moved to different environments and it's still happening...

Could it be the soundcard that's messed up, or is there some kind of "backfire" currents that ruins the signal of the outputs?

Thanks... This drives me insane as I don't dare to buy a new soundcard as this problem continues

 

[Mike Cleaver]

Sounds like the amp(s)  on the sound card driving the outputs have been damaged.
When you switch amps, are you "hot plugging" the rca's, ie, with the speaker amp powered up?
IC's are pretty fussy about random static bursts and back-fed voltages.
There are no transformers on the sound card to protect the circuits before the jacks.
Personally, I'm not fond of non pro and semi pro sound cards that don't have balanced outputs.
It really pays off both in quality and reliability if you step up to a pro card.
I've been running a Lynx 2 for years, problem free.

 

[abechap024]

Hey sorry to hear about your sound card that really sucks. I had a E-mu and I remember the DSP software mixer that always had to be runnning was always a PITA to use, mybe its that? I don't know but that would be any easy fix...
goodluck
AC

 

[Osse]

Sounds like the amp(s)  on the sound card driving the outputs have been damaged.
When you switch amps, are you "hot plugging" the rca's, ie, with the speaker amp powered up?
IC's are pretty fussy about random static bursts and back-fed voltages.
There are no transformers on the sound card to protect the circuits before the jacks.
Personally, I'm not fond of non pro and semi pro sound cards that don't have balanced outputs.
It really pays off both in quality and reliability if you step up to a pro card.
I've been running a Lynx 2 for years, problem free.

Hello, thanks for your answer.

It is balanced outputs on the card.

That might be the case, I'm not turning the amp off when swapping outputs so it might be back-fireing current into the IC's of the soundcard.

But how many soundcards has got transformers to protect the IC's on the outputs? And IF this is the case, will I eliminate the risk by turning of the amp before swapping outputs and the turning it on again?

I've got to buy a new one but it would be really boring if it went the same way with that one... Otherwise it sounds great.

 

[Osse]

Hey sorry to hear about your sound card that really sucks. I had a E-mu and I remember the DSP software mixer that always had to be runnning was always a PITA to use, mybe its that? I don't know but that would be any easy fix...
goodluck
AC

Thanks, but that's not the problem. THe problem is in the hardware of the breakout box somewhere!

 

[mhelin]

Hi, was that problem ever solved? I've got similar one on one channel only. I haven't been using other than 1L and 1R balanced outputs ever, now the 1L channel and it's positive phase output is about 6 dB quieter than the negative output. Is it possible that just the cap on output goes bad? If not then it must be the opamp, any ideas?

Btw. the output level is switchable between -10 dBV and  +4 dBu, would it be possible that the level converter has gone bad? Got to try swithcing the levels...

E:  No change in fault of output level, regardless of setting the pos is -6 db down. Must be some bad component.

 

[mhelin]

Opened my 1820m box and started measuring the circuit. The outputs have a lots of 6K SMD MOSFET's, and when I measured their Rds in circuit just for comparison with each other, and it measured 54 kohms for almost all of them (there are 24 pieces of them used to switch output voltage and/or mute the outputs) except for on in the 1L output (with three 6K's) which only measured 13 kohms so I suppose that MOSFET is the faulty one (and there was another on some other channel). Guess they are quite sensitive components so it may be better to be careful when plugging or unplugging the cables.

I don't really know which MOSFET is correct replacement for "6K" one but I suppose TP0610K will do and Farnell stocks them so I will try them first, or maybe just borrow one from a neighbor channel.

 

[mhelin]

Ok, I just unsoldered the faulty MOSFET and tested the levels again. Now the output level for both pos and neg phases are the same so it seems the problem is solved. E-Mu 1820m was and is a really nice audio inteface, too bad the electronic devices and the industry these days implement the principles of the Planned Obsolescence (http://en.wikipedia.org/wiki/Planned_obsolescence) which the designers of Fender Stratocaster fortunately didn't know anything about.