Elumguy
New Head-Fier
- Joined
- Mar 10, 2005
- Posts
- 7
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The reason I'm posting this in DIY is because I'm hoping to be able to fix this myself. I don't (wouldn't) use this enough to make it worth the money and hassle required to send it in to M-audio. I'm also considering this a learning experience, since this is one of the first and only electronics I've ever attempted to understand, so any information or tips I could use in future troubleshooting such as this would be much appreciated.
My long-winded description of the problem:
Unit powers on fine- or at least that's what the LED indicates. Outside of that, it doesn't do much of anything (that was my original conclusion). After testing multiple inputs (low-z- guitar/CD player/computer mic & high-z- guitar/condenser mic) in both channels, I have yet to see any of the clip or signal LEDs light up- dispite any combination of pading and gains. Headphones at any volume likewise have no signal. The high-z condenser mic requires phantom power, yet when the switch for phantom power is pressed, the corresponding LED does not light up, nor does the phantom power indicator on the mic itself.
I pretty much had given up hope after trying all that, but decided to hook it up to my computer just in case. Nothing seemed to be giving any signal, until I adjusted the volume on my guitar (low-z). The levels jumped! After seeing this I decided to record something. In the program the recording looked like a flat line, but after raising the volume about 80db, a distinguishable guitar sound was present (along with an absurd amount of static). After running several more tests with the various inputs, I discovered that any combination of hardware settings yielded the exact same result (i.e. having all pads and 0 gain sounded exactly the same as full gain and no pads). Even on stand-alone mode, raising the volume 80db produced the same result. The exception was in the high-z inputs, which were much less clean. The phantom-powered mic produced nothing but digital static.
A scan of the insides:
Bigger w/o numbers
Descriptions of the ICs:
1= 5532 1153B JRC; I assumed they were OPAMPs
2= INA163UA; Burr-Brown/TI low-noise Instrumentation Amplifier
3= 24LC64 17P949 0108; Microchip 64k I2C CMOS Serial EEPROM
4= TAS1020A 21T A52L; TI USB Streaming Controller
5= NE555 04M ACNY; TI Precision Timer (oscillator)
6= AK4103VF 1N124N; AKM 24bit 192kHz Digital Audio Trasmitter
7= AK4528VF 025B0148N; AKM 24bit 96kHz Audio Codec
8= L7915CV WCC0Q0141;SGS-Thomson Negative Voltage Regulator
9= L7815CV W990A9819; SGS-Thomson Positive Voltage Regulator
10= L7805CV WCC1A0148; SGS-Thomson Positive Voltage Regulator
11= PJ1117CW; Promax-Johnon 3.3V 1 AMP Low Dropout Positive Voltage Regulator
12= D4101DA 0137; M-TEK, don't think it's an IC
If anyone has any insight as to what is wrong with this Maudio Duo or steps I should take next, I'd appreciate the help. I've enjoyed figuring out as much as I have, but am not sure where to go next.
In a semi-related topic, I'm looking to start work on my first headphone amp. I know this has been asked in a million different ways, but is there anything I should know that isn't in The Audio Bible? Most likely this amp will be used with my iRiver H320 to drive Senn HD497s- would one type of amp be better and are there specific tweaks that I should consider?
Thanks again,
-E
My long-winded description of the problem:
Unit powers on fine- or at least that's what the LED indicates. Outside of that, it doesn't do much of anything (that was my original conclusion). After testing multiple inputs (low-z- guitar/CD player/computer mic & high-z- guitar/condenser mic) in both channels, I have yet to see any of the clip or signal LEDs light up- dispite any combination of pading and gains. Headphones at any volume likewise have no signal. The high-z condenser mic requires phantom power, yet when the switch for phantom power is pressed, the corresponding LED does not light up, nor does the phantom power indicator on the mic itself.
I pretty much had given up hope after trying all that, but decided to hook it up to my computer just in case. Nothing seemed to be giving any signal, until I adjusted the volume on my guitar (low-z). The levels jumped! After seeing this I decided to record something. In the program the recording looked like a flat line, but after raising the volume about 80db, a distinguishable guitar sound was present (along with an absurd amount of static). After running several more tests with the various inputs, I discovered that any combination of hardware settings yielded the exact same result (i.e. having all pads and 0 gain sounded exactly the same as full gain and no pads). Even on stand-alone mode, raising the volume 80db produced the same result. The exception was in the high-z inputs, which were much less clean. The phantom-powered mic produced nothing but digital static.
A scan of the insides:
Bigger w/o numbers
Descriptions of the ICs:
1= 5532 1153B JRC; I assumed they were OPAMPs
2= INA163UA; Burr-Brown/TI low-noise Instrumentation Amplifier
3= 24LC64 17P949 0108; Microchip 64k I2C CMOS Serial EEPROM
4= TAS1020A 21T A52L; TI USB Streaming Controller
5= NE555 04M ACNY; TI Precision Timer (oscillator)
6= AK4103VF 1N124N; AKM 24bit 192kHz Digital Audio Trasmitter
7= AK4528VF 025B0148N; AKM 24bit 96kHz Audio Codec
8= L7915CV WCC0Q0141;SGS-Thomson Negative Voltage Regulator
9= L7815CV W990A9819; SGS-Thomson Positive Voltage Regulator
10= L7805CV WCC1A0148; SGS-Thomson Positive Voltage Regulator
11= PJ1117CW; Promax-Johnon 3.3V 1 AMP Low Dropout Positive Voltage Regulator
12= D4101DA 0137; M-TEK, don't think it's an IC
If anyone has any insight as to what is wrong with this Maudio Duo or steps I should take next, I'd appreciate the help. I've enjoyed figuring out as much as I have, but am not sure where to go next.
In a semi-related topic, I'm looking to start work on my first headphone amp. I know this has been asked in a million different ways, but is there anything I should know that isn't in The Audio Bible? Most likely this amp will be used with my iRiver H320 to drive Senn HD497s- would one type of amp be better and are there specific tweaks that I should consider?
Thanks again,
-E
