Hey that is good news that you got it fixed!
Your ATH-M35 has a rated sensitivity of 100dB SPL (sound pressure level) and the Amperior 120dB, but unfortunately neither manufacturer says if that is per volt or milli-watt. About how high up (like 3/4 of the rotation, etc) do you have to turn your volume control on your iPod, with the phones plugged directly in, for normal listening levels? At a sensitivity of 120dB, either way (V or mW), the Amperior is unlikely to need an amplifier. In other words, the headphone impedance figures into how much current the iPod will have to supply, but with a highly sensitive headphone not much voltage swing is required so current becomes a moot point (no external amplifier required for either more voltage swing or current capability).
It isn't likely you damaged your O2 in any way if you are not hearing any difference. Damage would show up as a missing channel or bad distortion.
The grounding wire goes from the middle (front & center) pin of the O2's input jack to the closest cover screw for the case. The connection just reduces some potential for AC hum from the power supply.
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As i understand it the two resistors restrict the charging current to the batterys, and the two diodes provide a path for the battery voltage to bypass the resistors. See the schematic linked below and note the battery charging section up the top which is optional.
nwavguy%2520o2%2520schematic%252030aug11%255B3%255D.png (image)
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Yes indeed.
D1,2,5,6 are in a standard "steering" diode configuration. In that case whichever supply voltage is the highest will supply power to the load and also isolate the lower voltage source.
When the O2 is unplugged obviously the battery voltage is higher and they will supply the load. When plugged in, the 12 volt regulators are the higher voltage and they will supply the load. The resistors allow charging of the batteries but not overcharging.
Cheers,
Dave.
D1,2,5,6 are in a standard "steering" diode configuration. In that case whichever supply voltage is the highest will supply power to the load and also isolate the lower voltage source.
When the O2 is unplugged obviously the battery voltage is higher and they will supply the load. When plugged in, the 12 volt regulators are the higher voltage and they will supply the load. The resistors allow charging of the batteries but not overcharging.
Cheers,
Dave.
Yes indeed, indeed.
Ignoring the small voltage drops across the Schottky steering diodes, the regulator voltage minus the battery voltage equals the voltage across R1 or R2. Ohm's Law V/R=I then sets the charge current for the batteries.
For AC-only operation, R1 & R2, D2 & D6, and the battery connectors can be omitted; D1 & D5 can be replaced with jumper wires.
Ignoring the small voltage drops across the Schottky steering diodes, the regulator voltage minus the battery voltage equals the voltage across R1 or R2. Ohm's Law V/R=I then sets the charge current for the batteries.
For AC-only operation, R1 & R2, D2 & D6, and the battery connectors can be omitted; D1 & D5 can be replaced with jumper wires.
This has me curious as the datasheet claims a forward voltage drop of .5v, so will that translate into a slightly higher + and - rail voltage?
Would there be any other pros or cons in terms of noise when replacing them with jumper links?
Yes, the rail voltages will be slightly higher.
The .5V is spec'd at some value of forward current (and temperature); the exact amount of rise will likely be closer to .35V per rail.
I can't imagine it making a difference either way. The battery voltage during discharge from use varies more than that diode voltage drop.
Hi there i have had a few pcb's of the o2 amp for like a couple of years now just sat in a drawer never got round to doing anything with them but recently decided to build one of them however having the problem that it powers on but doesnt produce any sound through headphones was wondering what the main cause of this is? just wondering what i should be looking for in troubleshooting this problem.
thanks
thanks
Before I take my O2 apart, I'd like confirmation that it will work perfectly OK without the batteries installed, and there is no need to do any other alterations without batteries installed. I am finding that I am using it 100% with the power adapter. Rather than leave the batteries in and risk leaking or whatever, I'd remove them, but I'd like some reassurance before I go through the bother of taking the thing apart.
Search for FQPF10N20C brings back FQPF19N20C. Ok to use?
For the N Ch MOSFET Q2, a search on Element 14 for this...
FQPF10N20C (as per the BOM)
is hard wired to bring back this:
FQPF19N20
Can I use this part? (In Q1 I have the FQU11P06TU as per the BOM)
Comparing the parameters on the data sheets for each, there are many differences.
Interestingly, removing the "C" and searching for FQPF10N20 returns the following message, suggesting it is a "replacement"
FQPF19N20 (NOTE-Suggested replacement for: FQPF10N20)
Thanks!!!
lhalha
For the N Ch MOSFET Q2, a search on Element 14 for this...
FQPF10N20C (as per the BOM)
is hard wired to bring back this:
FQPF19N20
Can I use this part? (In Q1 I have the FQU11P06TU as per the BOM)
Comparing the parameters on the data sheets for each, there are many differences.
Interestingly, removing the "C" and searching for FQPF10N20 returns the following message, suggesting it is a "replacement"
FQPF19N20 (NOTE-Suggested replacement for: FQPF10N20)
Thanks!!!
lhalha
Well.... from a DC standpoint the answer is yes, but from an AC/step-response standpoint it is probably more like "who knows". You would be best off just trying it and see what happens as per turn-on and turn-off thumps, which is the thing that would be affected.
I see that RS Components has the BOM mosfet in stock. Do you have access to them?
Details:
As for DC parameters, the "on" resistance of the 19N20 is smaller (a good thing). The threshold voltage is a volt higher, but in the O2's particular usage that shouldn't matter. The mosfet is being fed from a fast-switching comparator that pretty much goes from 0V directly to either 16V [on batt] or 24V [on AC]) as far as the mosfet gate is concerned. One biggee is that the maximum gate voltage of the 19N20 is still +/-30V, like the 10N20. I actually talked NwAvGuy into changing that on his final BOM as the other mosfets he lists have +/-25V gates and the rail-to-rail is 24Vdc, cutting it a bit close.
As for AC parameters, NwAvGuy is relying on the mosfets being closely matched enough to switch at more-or-less the same instant to avoid turn-on/turn-off thumps in the headphones. I never really could get that to simulate with any degree of accuracy. He was using the actual ocilloscope captures of the turn-on/turn-off ramps in circuit. I see the gate charge is a bit higher on the replacement part. The turn-on delay time of the 19N20 is 10nS or so slower, but the turn-off delay is around 10nS faster. The turn-on ramp time of the 19N20 is about double the 10N20C. Then there is that threshold voltage difference and the associated shift in the Id vs. Vgs curves during switching. But have no idea if those parameter differences would affect thumps in the actual circuit. NwAvGuy is already "slowing down" the transfer with those gate-to-rail capacitors, acting as a turn-on-delay. So all I could say here is try it, and you either get turn-on and/or turn-off thumps or you don't. That would be the only negative effect if the replacement's switching properties don't match up as well as the original.
Good luck!
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Thanks for all this great info - I had for some reason not checked that one on RS which I was doing for every other part on the shopping list. So I now have both parts and can experiment with each. Will report back with any findings...