Someone might measure the input impedance of the operational U9 (in circuit, not unsoldered) and also the values of the potentiometer.
I think the problem that caused the damage was the TRS output to connect XLR input with phantom power turned on. I never had the precaution to disconnect, and nothing ever happened, because he had always used before TRS to TRS.
Another question, how you make the checks and measures in tension. I have no access when I assembled the top plate.
thanks in advanced!
I think the problem that caused the damage was the TRS output to connect XLR input with phantom power turned on. I never had the precaution to disconnect, and nothing ever happened, because he had always used before TRS to TRS.
Another question, how you make the checks and measures in tension. I have no access when I assembled the top plate.
thanks in advanced!
Last edited:
It is normal to haven't any damage when there is a TRS<->TRS cable connection, with power phantom on.
You must have in mind this situation, only when you attach in input an xlr plug. Then the phantom power will cause damage at the next stage.
To apply a good inspection and find the damaged, you need some things:
- pin to pin DuPont cables (females to males) at the joined parts of the two plates.
- an oscilloscope to check
- and of course you have the ability to done smd soldering-desoldering with easy.
With the sidiy schematics, you measure from input end to back to the appropriate points for a good signal and change the problematics parts.
You must have in mind this situation, only when you attach in input an xlr plug. Then the phantom power will cause damage at the next stage.
To apply a good inspection and find the damaged, you need some things:
- pin to pin DuPont cables (females to males) at the joined parts of the two plates.
- an oscilloscope to check
- and of course you have the ability to done smd soldering-desoldering with easy.
With the sidiy schematics, you measure from input end to back to the appropriate points for a good signal and change the problematics parts.
Lemon Thanks for the suggestions. Certainly this is the proper procedure. But I do not have the appropriate means. Just a friend and appropriate tool to reballing SMD desoldering tools.
I'll try to change U9. I have more options now. Everything tells me that may be the problem.
Even so I'd appreciate it if you can measure impedance in your U9.
I have 10ohm between pin 2-3 and 7k aprox between 5-6.
By the way where and parts for the JRC 2068 6040B.
This could be?
http://www.ebay.es/itm/5-PCS-NJM2068MD-JRC2068D-SOP-8-/251372824063?hash=item3a86fce5ff
That package is? DMP8 or SSOP8
NJM2068M DMP8
NJM2068V SSOP8
Here in Spain it is difficult to get these things.
Thanks!
I'll try to change U9. I have more options now. Everything tells me that may be the problem.
Even so I'd appreciate it if you can measure impedance in your U9.
I have 10ohm between pin 2-3 and 7k aprox between 5-6.
By the way where and parts for the JRC 2068 6040B.
This could be?
http://www.ebay.es/itm/5-PCS-NJM2068MD-JRC2068D-SOP-8-/251372824063?hash=item3a86fce5ff
That package is? DMP8 or SSOP8
NJM2068M DMP8
NJM2068V SSOP8
Here in Spain it is difficult to get these things.
Thanks!
Last edited:
Digikey sells similar to JRCs , many substitutes possible !
dmp8 for opamps of outputs and inputs, other opamps in the circuit are sometimes the SSOP8
Here is a picture of a tube output mod, parallel 6n6p with massive power suppl.. note the stock emu0404 transformer is upgraded to a quality one. (sounds better with solid state discrete regulated output stage now), big output caps are for headphone output, small copper ones for amp feed.
dmp8 for opamps of outputs and inputs, other opamps in the circuit are sometimes the SSOP8
Here is a picture of a tube output mod, parallel 6n6p with massive power suppl.. note the stock emu0404 transformer is upgraded to a quality one. (sounds better with solid state discrete regulated output stage now), big output caps are for headphone output, small copper ones for amp feed.
An externally hosted image should be here but it was not working when we last tested it.
I agree 100% with the member misterzu.
@isabito = I can't to measure btw the points that you need, I have different opamps, that maybe have different resistance.
@isabito = I can't to measure btw the points that you need, I have different opamps, that maybe have different resistance.
Pin 2 and 3 corresponds to bases of internal differential cascade transistors. Measuring resistance between them will very depend on the tester being used and comparing results done by different testers will not provide any sane result. Anyway 10 ohm is too low there. Mine tester shows infinity between these pins of unsoldered njm2068.
I changed the U9 and everything works properly. The impedance of NJM between 2-3 and 5-6 pin out of circuit. It is infinite.
Thanks to all for the help.
Thanks to all for the help.
Does anyone know of an external clock? I don't know what frequency it would require. My quick experiments show that the coax can dropout but optical seems to not, so I would prefer optical.
v
v
Well unplugging the Coax cable gives like 2dB lower noise floor. Maybe would be 0 if I had a proper transformer there.
As far as the dropout COAX external clock seems stable coming from my X-Fi. The instability might have been from using my mobo clock.
Hopefully someone can point us to a low jitter solution for external clock.
As far as the dropout COAX external clock seems stable coming from my X-Fi. The instability might have been from using my mobo clock.
Hopefully someone can point us to a low jitter solution for external clock.
So to get all the mods in one place misterzu:
You have "Removed D26-27-28-30-31"
-That is 5 diodes and it seems like there are six (2*D1, 2*D2, 2* D3) is the missing one 29?
Removed softlimiter (desoldered R121, R122, R123) and D5D8.
-Found the Rs but not sure where D5/D8 are on the provided schematics
Changed opamps:
-"postDAC: U22 -> LME49860, U33, U39 - OPA1612'
-preADC: U1 -> OPA1612, U9, U12, U15 - LME49860
-Am I missing any and are those the current recommendations?
Did left channel wire-around fix
Replaced 0 Ohm resistors R147, R159, R134, R380 with FERROCORE DL0805-0.39
-couldn't find ferrocore but will digikey MLF2012DR39M work?
-Are those all or is that just one half?
Removed C257
-Is there a positive side equivalent?
Replaced C61, C63 with 100uF polymer and 10uF ceramic
-Again, is there a positive side equivalent?
You have "Removed D26-27-28-30-31"
-That is 5 diodes and it seems like there are six (2*D1, 2*D2, 2* D3) is the missing one 29?
Removed softlimiter (desoldered R121, R122, R123) and D5D8.
-Found the Rs but not sure where D5/D8 are on the provided schematics
Changed opamps:
-"postDAC: U22 -> LME49860, U33, U39 - OPA1612'
-preADC: U1 -> OPA1612, U9, U12, U15 - LME49860
-Am I missing any and are those the current recommendations?
Did left channel wire-around fix
Replaced 0 Ohm resistors R147, R159, R134, R380 with FERROCORE DL0805-0.39
-couldn't find ferrocore but will digikey MLF2012DR39M work?
-Are those all or is that just one half?
Removed C257
-Is there a positive side equivalent?
Replaced C61, C63 with 100uF polymer and 10uF ceramic
-Again, is there a positive side equivalent?
Not exactly. So here is summary, if didn't forget anything:
Input stage (only left channel mod'ed):
Replaced opamps: U1 -> OPA1612, U9, U12, U15 -> LME49860
Replaced zero-ohm R134, R380 with 0.39uH/200mA-250mA SMD inductors
Replaced two 10uF/16V caps near left level (didn't note how they labeled) with 100uF/16V polymer caps + 1nF NP0 ceramic in parallel
Removed TVS-es: D5, D8
Removed C40
Removed softlimiter: desoldered R121, R122, R123
Re-routed left channel line with a wire (described on wiki)
Output stage:
Replaced opamps: U22, U33, U39 -> all to LME49860.
Replaced two 10uF/16V caps - C103, C109 - with 100uF/16V polymer caps + 1nF NP0 ceramic in parallel
Removed TVSes: D26, D27, D28, D29, D30, D31
General:
Replaced C257 -> 100uF/16V polymer cap + 1nF NP0 ceramic in parallel
Added C259 (on my board it was not soldered at all!) -> 100uF/16V polymer cap. Probably tantalum SMD would fit there better, but I didn't have such one
Also I use custom linear main PSU instead of factory one. While I didn't get rid of that on-board DC converters linear mains PSU still makes sense, at least when did all that things. I attached 3 oscillograms, taken from main output of my modded EMU. First - taken with EMU being powered off, but everything else around on - so there'is some noise coming 'via air' and may be via USB, but most probably its 'ground loop' interference. Second picure - board being powered ON from linear PSU. Same small spikes definately become bit bigger, but not critical. And 3rd pic - is when EMU powered with factory PSU. Small spikes much bigger + added new even bigger spikes reaching 15mV peak-to-peak that didn't present on first two oscillograms. Obviously - they generated by PSU, and they 'visible' much more than own on-board converters. I think again its againg coming to oscilloscope via ground loop, but not through board power modulation - there're lot of filtering stuff.. But anyway it doesnt matter much - this ripple noise can come to amplifier's input by same way.
And some notes:
Removing TVSes (D5, D8< D26..D31) noticable reduces THD on high frequencies when EMU used with hi-Z load, but almost doesnt change when working on low-Z (for example on EMU's own XLR inputs). However it also makes device much more vulnerable to static electricity, so I do not recommend do this if you want to use your EMU in hard studio environment, with all that long cables and people, running around.
Your inductors should be OK. Any will be ok while they can conduct enough current, and IMHO 200mA is enough. However 0805 inductors bit larger than 0-ohm 'resistors', but its still possible to solder them.
Input stage (only left channel mod'ed):
Replaced opamps: U1 -> OPA1612, U9, U12, U15 -> LME49860
Replaced zero-ohm R134, R380 with 0.39uH/200mA-250mA SMD inductors
Replaced two 10uF/16V caps near left level (didn't note how they labeled) with 100uF/16V polymer caps + 1nF NP0 ceramic in parallel
Removed TVS-es: D5, D8
Removed C40
Removed softlimiter: desoldered R121, R122, R123
Re-routed left channel line with a wire (described on wiki)
Output stage:
Replaced opamps: U22, U33, U39 -> all to LME49860.
Replaced two 10uF/16V caps - C103, C109 - with 100uF/16V polymer caps + 1nF NP0 ceramic in parallel
Removed TVSes: D26, D27, D28, D29, D30, D31
General:
Replaced C257 -> 100uF/16V polymer cap + 1nF NP0 ceramic in parallel
Added C259 (on my board it was not soldered at all!) -> 100uF/16V polymer cap. Probably tantalum SMD would fit there better, but I didn't have such one
Also I use custom linear main PSU instead of factory one. While I didn't get rid of that on-board DC converters linear mains PSU still makes sense, at least when did all that things. I attached 3 oscillograms, taken from main output of my modded EMU. First - taken with EMU being powered off, but everything else around on - so there'is some noise coming 'via air' and may be via USB, but most probably its 'ground loop' interference. Second picure - board being powered ON from linear PSU. Same small spikes definately become bit bigger, but not critical. And 3rd pic - is when EMU powered with factory PSU. Small spikes much bigger + added new even bigger spikes reaching 15mV peak-to-peak that didn't present on first two oscillograms. Obviously - they generated by PSU, and they 'visible' much more than own on-board converters. I think again its againg coming to oscilloscope via ground loop, but not through board power modulation - there're lot of filtering stuff.. But anyway it doesnt matter much - this ripple noise can come to amplifier's input by same way.
And some notes:
Removing TVSes (D5, D8< D26..D31) noticable reduces THD on high frequencies when EMU used with hi-Z load, but almost doesnt change when working on low-Z (for example on EMU's own XLR inputs). However it also makes device much more vulnerable to static electricity, so I do not recommend do this if you want to use your EMU in hard studio environment, with all that long cables and people, running around.
Your inductors should be OK. Any will be ok while they can conduct enough current, and IMHO 200mA is enough. However 0805 inductors bit larger than 0-ohm 'resistors', but its still possible to solder them.
Attachments
Great, thanks.. Anyone care to add?
Also, would you recommend a different inductor package than 0805?
Also, would you recommend a different inductor package than 0805?
Argh. Forgot to add to "Output stage": R149, R157 - also changed to same 0805 inductors. And I can't edit that message anymore.
Not sure about different inductors. Generically speaking, good inductor - big inductor. 0805 is the biggest that can fit there without additional wires🙂
Not sure about different inductors. Generically speaking, good inductor - big inductor. 0805 is the biggest that can fit there without additional wires🙂
I am looking at posts 140 and 144. You mention the negative supply line, pre-adc caps which I think are C61 and C63. Some questions:
-Are c61 and C63 opposites power +/-? And did you end up changing both?
-Are the two that are "Replaced two 10uF/16V caps near left level (didn't note how they labeled) with 100uF/16V polymer caps + 1nF NP0 ceramic in parallel" the ones from the third graphic in Post 144?
-Are c61 and C63 opposites power +/-? And did you end up changing both?
-Are the two that are "Replaced two 10uF/16V caps near left level (didn't note how they labeled) with 100uF/16V polymer caps + 1nF NP0 ceramic in parallel" the ones from the third graphic in Post 144?
- Status
- Not open for further replies.