I hope this is the right section. It was the closest thing I could see to it.
As the title states, I've got an E-Mu 0404 USB box with dead analog inputs here. I wasn't the one who cooked them, so I don't have any details on that. Basically, there's nothing but a faint, nasty sounding version of whatever's fed to it at the output. Mic level inputs are barely audible. In the low end of the gain controls, there's a range where it's not quite as "clipped" sounding. The distortion bursts in around midpoint. Also, both "Soft Limit" LEDs remain on at all times, even with no input connected. The distorted output appears to be of one polarity somehow. I'll attach a picture of what went in as a 1kHz sine.
The output section seems to be working properly, and I can pass signals from the SPDIF input to the outs with no problems. Headphone and main outs both get the same weak distorted signal from the analog ins. I *think* the opamps in the vicinity of the inputs are getting an OK supply. IIRC, the positive rail was around 6 volts, with the negative a bit higher (6.5v maybe). Most of the recent checks were done with no host machine (direct monitor). I've checked mics (condenser & dynamic), and tried both unbalanced and balanced line level signals.
I saw the mod wiki here and noticed there's a few guys who seem to know parts of the circuitry pretty well considering the lack of schematics. I'm hoping someone's either seen this before, or might be able to point me to some areas to check, as it doesn't seem to be all that uncommon. I ran into some "dead inputs" threads in other forums, as well as a few mentions of it in customer reviews, but never anyone having fixed it.
If you need any more details, just let me know.
-Much Thanks!
As the title states, I've got an E-Mu 0404 USB box with dead analog inputs here. I wasn't the one who cooked them, so I don't have any details on that. Basically, there's nothing but a faint, nasty sounding version of whatever's fed to it at the output. Mic level inputs are barely audible. In the low end of the gain controls, there's a range where it's not quite as "clipped" sounding. The distortion bursts in around midpoint. Also, both "Soft Limit" LEDs remain on at all times, even with no input connected. The distorted output appears to be of one polarity somehow. I'll attach a picture of what went in as a 1kHz sine.
The output section seems to be working properly, and I can pass signals from the SPDIF input to the outs with no problems. Headphone and main outs both get the same weak distorted signal from the analog ins. I *think* the opamps in the vicinity of the inputs are getting an OK supply. IIRC, the positive rail was around 6 volts, with the negative a bit higher (6.5v maybe). Most of the recent checks were done with no host machine (direct monitor). I've checked mics (condenser & dynamic), and tried both unbalanced and balanced line level signals.
I saw the mod wiki here and noticed there's a few guys who seem to know parts of the circuitry pretty well considering the lack of schematics. I'm hoping someone's either seen this before, or might be able to point me to some areas to check, as it doesn't seem to be all that uncommon. I ran into some "dead inputs" threads in other forums, as well as a few mentions of it in customer reviews, but never anyone having fixed it.
If you need any more details, just let me know.
-Much Thanks!
Attachments
Hi,
I have exactly the same problem. Are you fixed it? Could you please help with the solution?
Thank you!
Br,
Gyuri
I have exactly the same problem. Are you fixed it? Could you please help with the solution?
Thank you!
Br,
Gyuri
These EMUs are packed with Dual-OpAamps, normally produced by New Japan Corparation. You should know that all these SOIC-8 opamps share the same pin configuration, as 95% of all 8-pin OpAmps worldwide do. With the pinning plan from a data sheet, first check supply voltage at pin 4 / pin 8 reading more than - / + 5V.
If this is ok, continue measuring output pins of op-Amps. DC-offsets bigger than 100mV are a strong indication of a faulty chip.
If this is ok, continue measuring output pins of op-Amps. DC-offsets bigger than 100mV are a strong indication of a faulty chip.
Thank you!
A have few question: Input VU meters works analog, or works digital after AD conversion? Direct monitoring use AD/DA conversions?
My emu inputs works like gated and fully distorsed. After 1/3 of input knob the state of knob doesnt matter: i can hear and see in VU any signal if i shout to the mic. Same when i connect tls..
In audio daw i can see (with disconnected inputs) in the chanel A 0, but the chanel B exactly 0,5 (-6dB) constant DC signal.
Is that DA or preamp/opamp problem in both chanel?
A have few question: Input VU meters works analog, or works digital after AD conversion? Direct monitoring use AD/DA conversions?
My emu inputs works like gated and fully distorsed. After 1/3 of input knob the state of knob doesnt matter: i can hear and see in VU any signal if i shout to the mic. Same when i connect tls..
In audio daw i can see (with disconnected inputs) in the chanel A 0, but the chanel B exactly 0,5 (-6dB) constant DC signal.
Is that DA or preamp/opamp problem in both chanel?
Member
Joined 2018
FYI: 0404USB Input Section Photo
Hi guys,
I took a photo when I replacing Op-Amps in 0404USB.
Most of part were consists of Op-Amp circuity.
You can check SIOC8 pin1 and pin 7 waveforms, if you have oscilloscope.
I changed all op-amps, most of part were replaced with LME49860. My recommendation is replace to OPA1656.
Signal to noise ratio and distortion performance was greatly improved.
Hi guys,
I took a photo when I replacing Op-Amps in 0404USB.
Most of part were consists of Op-Amp circuity.
You can check SIOC8 pin1 and pin 7 waveforms, if you have oscilloscope.
I changed all op-amps, most of part were replaced with LME49860. My recommendation is replace to OPA1656.
Signal to noise ratio and distortion performance was greatly improved.
Attachments
If I connect the mic only the 4,3V DC offset remains on the opamp output. I see in the scope same as hear in direct monitor. (Hard gate then distorsed signal). So 100% that the error in the opamp stage.
You should know that inputs of EMU are DC-coupled: OPA-output voltage DC-offset follows input DC - if existent.
Short the inputs, if OPS output persists it is probably defective.
Short the inputs, if OPS output persists it is probably defective.
Hi All,
I found the cause of fault: the first opamp is dead after the relay (U9 in 1st ch) on both input chanel.
Thanks and Happy New Year!
I found the cause of fault: the first opamp is dead after the relay (U9 in 1st ch) on both input chanel.
Thanks and Happy New Year!
Strange. I got stuck waiting on parts for the tape deck I'm working on and figured I'd pull this thing out again after all this time, and six years later, someone just so happens to have just brought the thread back up. Good news on the find iGyuri. Did you get the opamps swapped and did it work?
Not sure if mine's the exact same problem. If I feed it a sine wave, I am still seeing the wave at pin 7 of that U9 (as well as a lower level one at U12 and U15).
Not sure if mine's the exact same problem. If I feed it a sine wave, I am still seeing the wave at pin 7 of that U9 (as well as a lower level one at U12 and U15).