There is the problem - blue won't work. It has to be red. Each LED color has a different forward voltage:
Light-emitting diode - Wikipedia, the free encyclopedia (go down to "colors and materials")
From that chart red LEDs have a forward voltage in the 1.6Vdc - 2.0Vdc range, but blue is 2.48Vdc - 3.7Vdc. Normally, when a LED is just being used as a light, it doesn't matter. But in this circuit NwAvGuy is also using the voltage across the LED as a voltage reference for U2, so it pretty exactly needs to be around 1.78Vdc.
Lol - I should have guessed that was a blue LED when I calculated the 2.64Vdc forward voltage.
But I have actually seen at least one LED fail with a (much) higher forward voltage over the years, so that actually does happen occasionally.He isn't drving that red LED very hard though to save on battery power. What you could do is cut the value of R6 in half, from 40.2K to 20K. An easy way to do that is just solder another 40.2K resistor (a standard value like 39K from Radio Shack works fine too for this) across the existing R6 (parallel resistors) on the bottom of the PC board. That should make the red led roughly twice as bright while still keeping the forward voltage in the vicinity of 1.8Vdc. If you try that put a meter across the LED and see what forward voltage it is running at, after you reduce R6.
I like that case!
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Hmm! jumpbluesdude? The name itself is a dead giveaway that he was using blue LED all the time
Elementary my dear agdr, haha
My O2 started to make a LOUD turn on transient noise and the following test was failed:
"To verify the MOSFETs were not damaged by static electricity (ESD), and the entire power management circuit is working correctly, with nothing connected to the amp and running only from battery, pull one battery out and check for DC at the output jack as above. It should be less than 0.7 volts (700 mV)"
With the O2 turned ON:
With only bt1 battery connected I get 8.2volts (not mili) DC for the right and left channels respectively.
With only Bt2 battery connected I get 1.2volts (not mili) DC for the right and left channels respectively.
So I sent the amp to the manufacturer and it fixed the amp and said that it replaced the R4,R5,R8,R24 to a "components with quieter transient beheviour".
(I still need to test the turn off transient as it seems loud....)
The resistors were changed from the recommended by NWAVGUY 270KOHMS to 276KOHMS (color codes: red, violet,blue, orange, brown).
SO my questions:
1) Does the "mosfet test" that I made indicate for sure a damaged mosfets?
2) Does the O2's performance degrade as result of the manufacturer stray of the recommended 270KOHMS to R4,R5,R8,R24 (the manufacturer chose 276KOHMS)?
3) Do I need to change back the R4,R5,R8,R24 resistors back to the recomended 270KOHMS ones?
I"m really worried about the manufacturer not following strictly NWAVGUY's design...should I be? Is there a chance in degradation in THD, phase performance, FR, etc???
"To verify the MOSFETs were not damaged by static electricity (ESD), and the entire power management circuit is working correctly, with nothing connected to the amp and running only from battery, pull one battery out and check for DC at the output jack as above. It should be less than 0.7 volts (700 mV)"
With the O2 turned ON:
With only bt1 battery connected I get 8.2volts (not mili) DC for the right and left channels respectively.
With only Bt2 battery connected I get 1.2volts (not mili) DC for the right and left channels respectively.
So I sent the amp to the manufacturer and it fixed the amp and said that it replaced the R4,R5,R8,R24 to a "components with quieter transient beheviour".
(I still need to test the turn off transient as it seems loud....)
The resistors were changed from the recommended by NWAVGUY 270KOHMS to 276KOHMS (color codes: red, violet,blue, orange, brown).
SO my questions:
1) Does the "mosfet test" that I made indicate for sure a damaged mosfets?
2) Does the O2's performance degrade as result of the manufacturer stray of the recommended 270KOHMS to R4,R5,R8,R24 (the manufacturer chose 276KOHMS)?
3) Do I need to change back the R4,R5,R8,R24 resistors back to the recomended 270KOHMS ones?
I"m really worried about the manufacturer not following strictly NWAVGUY's design...should I be? Is there a chance in degradation in THD, phase performance, FR, etc???
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Just wanted to say I got my 1st amp finished. Here are some pics, I do have one question, I would like the LED's to be roughly the same brightness on both. If I'm using a 15k resistor for the Odac (~5v), what should I use for the O2 (~12v). Is there a formula I can use to calculate the same voltage from different sources? This is the led I got if it makes a difference in the formula. In the picture below I'm using a 2200 ohm resistor and you can see how bright it is, lol.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Thanks,
Erik
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Erik - try a 10K resistor instead of the 2.2k. I'm just guessing, but that will cut the current by 1/5. The eye isn't linear and sometimes the LED intensity curves aren't either, so it is all kind of an experimental thing to get the brightness right. If 10k isn't dim enough try a 20k. If 10k is too dim try a 4.7k instead, etc.
Nice case work!
BTW to anyone else interested in this - Erik isn't using this LED directly in the O2 circuit to replace the red LED, as per the issue in the posts above with the blue LED. He has replaced the O2 LED with a certain 1.8V zener, 1N4614 - see post #3346, to act as the O2's voltage reference, then he has this new LED just wired across the 12V power rail. That lets him use a different type of LED. I was thinking of suggesting this to jumpbluesdude above as a way to get a blue LED working, but decided not to pile any more on the troubleshooting effort.
It looks like Mouser no longer has stock on the 1N4614 though. The 2.0V 1N4615 could be used if the O2's power management resistors are changed to work with a 2.0V reference. Mouser has 2700 of them in stock right now.
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Erik - try a 10K resistor instead of the 2.2k. I'm just guessing, but that will cut the current by 1/5. The eye isn't linear and sometimes the LED intensity curves aren't either, so it is all kind of an experimental thing to get the brightness right. If 10k isn't dim enough try a 20k. If 10k is too dim try a 4.7k instead, etc.
Nice case work!
BTW to anyone else interested in this - Erik isn't using this LED directly in the O2 circuit to replace the red LED, as per the issue in the posts above with the blue LED. He has replaced the O2 LED with a certain 1.8V zener, 1N4614 - see post #3346, to act as the O2's voltage reference, then he has this new LED just wired across the 12V power rail. That lets him use a different type of LED. I was thinking of suggesting this to jumpbluesdude above as a way to get a blue LED working, but decided not to pile any more on the troubleshooting effort.
jumpbluesdude - if you should read this, it has to be *exactly* that specific 1N4614 zener, and the polarity goes in opposite the LED polarity in the O2. Then you would just put your blue LED in series with an appropriate resistor across the power rails after the on/off switch. Once the O2's red LED is removed you could probably solder the zener underneath the PC board (again, be sure to flip the polarity vs. the normal LED), which would leave the front panel LED hole exposed enough to stuff the new LED in there, then run wires and a series resistor back to whereever you solder it onto the power rails after the on/off switch. Or just leave the normal LED hole empty and drill a new hole somewhere in the front panel for the new LED.
Thanks for the compliment on the case work. It isn't the prettiest, but it works. I'm going to be more careful, and center the volume knob a little better next time. I'm using a 15k resistor on the 5v from the odac and I think it is about right, lol. I'm assuming multiply that by 12/5 and I should be close? Or am I thinking this all wrong?
-Erik
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@XXTheMatrixXX
Run all tests as per NwAvGuy guide
No- Tolerance around 2% is OK. An expert like agdr might have a better answer to that.
Not necessary IMHO, if you do- you might void manufacturer warranty terms.
No need to worry as the changes are in PM ckt. only, but loud transients may / can damage sensitive h/p resulting permanent damage to sound qualitity. To be very specific the coil may get deformed. Use el-cheapos h/p for any transient chks till all the issues are sorted out.
Run all tests as per NwAvGuy guide
Yes- in majority of cases
No- Tolerance around 2% is OK. An expert like agdr might have a better answer to that.
Not necessary IMHO, if you do- you might void manufacturer warranty terms.
I"m really worried about the manufacturer not following strictly NWAVGUY's design...should I be? Is there a chance in degradation in THD, phase performance, FR, etc???
No need to worry as the changes are in PM ckt. only, but loud transients may / can damage sensitive h/p resulting permanent damage to sound qualitity. To be very specific the coil may get deformed. Use el-cheapos h/p for any transient chks till all the issues are sorted out.
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@availlyrics
When the loud turn on transient happened it unfortunately happened with my Shure SRH840 headphones.
How can I verify that the SRH840 drivers didn't damage from the LOUD transient?
I don't have any HATS measurment head or anything....
I"ve tried to play loudly low frequancies sine waves and it seems that there is no audible distortion....
The turn ON transient from the SRH840 connected to the O2 before the manufacturer fix was a scary BLAST
(the turn on transient could be easily heard from the other end of my apartment ~4.5meters from the headphones).
Thanks for the answers.
When the loud turn on transient happened it unfortunately happened with my Shure SRH840 headphones.
How can I verify that the SRH840 drivers didn't damage from the LOUD transient?
I don't have any HATS measurment head or anything....
I"ve tried to play loudly low frequancies sine waves and it seems that there is no audible distortion....
The turn ON transient from the SRH840 connected to the O2 before the manufacturer fix was a scary BLAST
(the turn on transient could be easily heard from the other end of my apartment ~4.5meters from the headphones).
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Since there is no audible distortion & 1000mW power handling capacity, I'm "Shure" your h/p have survived the turn ON transient
.
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Testing of the O2 failed?
NwAvGuy: O2 Details article.
And only the following test was failed (other tests up to "Check The Current Consumption" measured correctly):
"Measure Resistances – If you have a DMM, with only U2 in its socket (U1, U3 and U4 sockets should be empty), measure across each of the resistors shown in the diagram to the right (click for larger version). The values marked with a “*” may depend on your DMM. If you get a very different reading, try reversing the leads. If it’s still different, check that resistor carefully. If in doubt, heat one end of the resistor from the top of the board and use a small screw driver to carefully pry that end up from the board so it’s only connected at one end. You can then measure it accurately “out of circuit”. If it measures OK, persuade the lead back into board using needle-nose pliars while you heat the pad and lead.
http://lh4.ggpht.com/-YZ8GUyJYrJ0/T...20resistances%2520no%2520power%255B3%255D.png
The wrong resistance measurements are:
R8 is 231Kohm instead of ~245Kohm.
R25 is 287.1Kohm instead of ~330Kohm.
R5 is 117.1Kohm instead of ~100Kohm.
R16 is 1.5Kohm instead of 1.3Kohm.
R22 is 1.5Kohm instead of 1.3Kohm.
Please help...Are the wrongly measured resistors need to be changed?
*I use the VC97+ DMM which is accurate.
**I did follow the instructions EXACTLY.
So I followed your advice and did all of the "Initial DIY Testing" from the
NwAvGuy: O2 Details article.
And only the following test was failed (other tests up to "Check The Current Consumption" measured correctly):
"Measure Resistances – If you have a DMM, with only U2 in its socket (U1, U3 and U4 sockets should be empty), measure across each of the resistors shown in the diagram to the right (click for larger version). The values marked with a “*” may depend on your DMM. If you get a very different reading, try reversing the leads. If it’s still different, check that resistor carefully. If in doubt, heat one end of the resistor from the top of the board and use a small screw driver to carefully pry that end up from the board so it’s only connected at one end. You can then measure it accurately “out of circuit”. If it measures OK, persuade the lead back into board using needle-nose pliars while you heat the pad and lead.
http://lh4.ggpht.com/-YZ8GUyJYrJ0/T...20resistances%2520no%2520power%255B3%255D.png
The wrong resistance measurements are:
R8 is 231Kohm instead of ~245Kohm.
R25 is 287.1Kohm instead of ~330Kohm.
R5 is 117.1Kohm instead of ~100Kohm.
R16 is 1.5Kohm instead of 1.3Kohm.
R22 is 1.5Kohm instead of 1.3Kohm.
Please help...Are the wrongly measured resistors need to be changed?
*I use the VC97+ DMM which is accurate.
**I did follow the instructions EXACTLY.
You did read that those measurements are supposed to be made with U1, U3 and U4 removed? I know you said you followed the instructions, but that's worth making sure.
Also note how the picture says that the values you mention depend on the DMM and the polarity of the leads. Obviously, wait for agdr to give you a definitive answer to your question, but to me it doesn't seem like those values are anything to worry about.
Also note how the picture says that the values you mention depend on the DMM and the polarity of the leads. Obviously, wait for agdr to give you a definitive answer to your question, but to me it doesn't seem like those values are anything to worry about.
XXXTheMatrixXXX - I would agree with dfy that those small variances are nothing to worry about. However it sounds like you want your O2 built with standard part values from RocketScientist/NwAvGuy's BOM so that it measures the standard way. That is something you need to work out with whoever sold you the kit.
Variance in Resistance values (when soldered on PCB) may be different as compared to NwAvGuy's guide due to capacitors/ semiconductors or other passives coming in parallel resulting in bit "off the mark" values, no need to worry here. You can verify the resistor values from colour codes.
Imp. point is - Are you still getting ON/OFF transient thumps post repairs?
As for FET's operational reliability - Did you tested your O2 with one battery disconnected & observing for any DC at o/p?(as per NwAvGuy's guide)
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I would think that the measurements by NwAvGuy were made in-circuit and should account for any parallel passive components.
If XXTheMatrixXX's meter is forward biasing, or partially forward biasing, some pn junctions in semiconductors, which are in turn enabling the multimeter to "see" additional parallel circuit paths and components, that might explain the first two measurements, which are lower than expected. But the last three are HIGHER than expected, whereas additional parallel anything would always result in a LOWER resistance measurement than expected.
Before re-measuring, I would check to see if the resistors' labeled/marked/color-coded values match the expected/specified values.
When re-measuring, I would first make sure that the meter has fresh batteries. Then I would make sure that it reads near zero Ohms (like 0.5 Ohm or lower) with the probes shorted together, before starting and after finishing. When measuring, leave the probes in place for a long time, i.e. until the measurement stops changing. The voltage that the meter applies in order to measure resistance might be charging a capacitor, somewhere, for example, and your measurement won't be correct until it stops changing. Also, for each measurement, do it a second time with the probes swapped. If it was mentioned in the write-up there must be a reason for it.
If XXTheMatrixXX's meter is forward biasing, or partially forward biasing, some pn junctions in semiconductors, which are in turn enabling the multimeter to "see" additional parallel circuit paths and components, that might explain the first two measurements, which are lower than expected. But the last three are HIGHER than expected, whereas additional parallel anything would always result in a LOWER resistance measurement than expected.
Before re-measuring, I would check to see if the resistors' labeled/marked/color-coded values match the expected/specified values.
When re-measuring, I would first make sure that the meter has fresh batteries. Then I would make sure that it reads near zero Ohms (like 0.5 Ohm or lower) with the probes shorted together, before starting and after finishing. When measuring, leave the probes in place for a long time, i.e. until the measurement stops changing. The voltage that the meter applies in order to measure resistance might be charging a capacitor, somewhere, for example, and your measurement won't be correct until it stops changing. Also, for each measurement, do it a second time with the probes swapped. If it was mentioned in the write-up there must be a reason for it.
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THANKS agdr, dfy, availlyrics, gootee and everyone for the explanations.
I"ll redo the "Initial DIY Testing"& "STEP-BY-STEP DC VOLTAGES" (didn't do that one) tests with two different DMM (VC97+ and another one) and FOLLOWING YOUR RECOMMENDATIONS/CORRECTIONS.
(NwAvGuy: O2 Details)
Then I"ll post the FULL detailed results.
I"ll redo the "Initial DIY Testing"& "STEP-BY-STEP DC VOLTAGES" (didn't do that one) tests with two different DMM (VC97+ and another one) and FOLLOWING YOUR RECOMMENDATIONS/CORRECTIONS.
(NwAvGuy: O2 Details)
Then I"ll post the FULL detailed results.
O2 amp distortion
Hi,
I built a couple of months ago an o2 amp kit and bought a Sennheiser Hd600.
I am driving them with a macbook pro, Odac combo.
I now just built a Cmoy portable head-amp and I could compare it to the O2 amp.
I was surprised because I can clearly recognize an audible distortion by the O2 amp, especially audible on music with high power on bass.
The distortion is so clear that I think it is a problem to be addressed to my building or component fault in the O2.
Have you any idea or suggestion?
Thank you
Northernsky
Hi,
I built a couple of months ago an o2 amp kit and bought a Sennheiser Hd600.
I am driving them with a macbook pro, Odac combo.
I now just built a Cmoy portable head-amp and I could compare it to the O2 amp.
I was surprised because I can clearly recognize an audible distortion by the O2 amp, especially audible on music with high power on bass.
The distortion is so clear that I think it is a problem to be addressed to my building or component fault in the O2.
Have you any idea or suggestion?
Thank you
Northernsky
