That's great that you might have found a new interest 
Discharging the caps... for anything over a 100uf or so, and you should use a resistor really. The value can be anything within reason, as low as 100 ohm or as high as 10k, all will discharge the caps safely and with no sparks. The higher the resistor and the longer it takes though. If you are unsure then just measure the voltage across the cap. Anything below a volt or so is "safe" for the components around it... if you shorted it to something for example.
In the O2, once the regulators are fitted and working then removing the power will see the caps discharge very quickly because the regs draw current. Without the regs fitted (so just D3, D4 and the caps) and they would stay charged up nearly indefinitely, the charge leaking away due to internal leakage in the caps. So you need to be sure they are discharged before fitting the regs.
When using the braid, don't be afraid to have some solder on the iron. You'll soon get the hang of it and the joints will clean up well. Use a cotton bud and iso or meths and clean any flux of the PCB for neatness. It should all look like new then.
Discharging the caps... for anything over a 100uf or so, and you should use a resistor really. The value can be anything within reason, as low as 100 ohm or as high as 10k, all will discharge the caps safely and with no sparks. The higher the resistor and the longer it takes though. If you are unsure then just measure the voltage across the cap. Anything below a volt or so is "safe" for the components around it... if you shorted it to something for example.
In the O2, once the regulators are fitted and working then removing the power will see the caps discharge very quickly because the regs draw current. Without the regs fitted (so just D3, D4 and the caps) and they would stay charged up nearly indefinitely, the charge leaking away due to internal leakage in the caps. So you need to be sure they are discharged before fitting the regs.
When using the braid, don't be afraid to have some solder on the iron. You'll soon get the hang of it and the joints will clean up well. Use a cotton bud and iso or meths and clean any flux of the PCB for neatness. It should all look like new then.
Are there any infos on which connection on the PCB is for example ground, headphone L/R etc?
I want to install RCA-Connectors for Input/Output, a 6,5mm Headphone-Jack and have the powersupply on the back of the Amp.
I could measure the resistance of each pin of course, but there has to be a better way I think. Also there are 5 pins on each Jack. Do they all need to be connected?
And the original AC-connector has 3 pins and the one provided for the back has only 2. Same question here.
Thx
I want to install RCA-Connectors for Input/Output, a 6,5mm Headphone-Jack and have the powersupply on the back of the Amp.
I could measure the resistance of each pin of course, but there has to be a better way I think. Also there are 5 pins on each Jack. Do they all need to be connected?
And the original AC-connector has 3 pins and the one provided for the back has only 2. Same question here.
Thx
I've never seen the PCB for this amp but the circuit shows an "off board input" at P1 which gives you the correct input points to wire the RCA sockets too. As each channel is identical, it doesn't matter which you designate as right or left. The "tip" of the 3.5mm plug and headphone plug is left, the middle ring right, and the main body is the common.
There is an "off board" output point too for correctly wiring your 6.5mm socket.
For the AC input you just wire the adapter to the centre point of C2 and C3 and the common point of D3 and D4. As its AC it doesn't matter which way round the wires are.
There is an "off board" output point too for correctly wiring your 6.5mm socket.
For the AC input you just wire the adapter to the centre point of C2 and C3 and the common point of D3 and D4. As its AC it doesn't matter which way round the wires are.
I am learning new things here every day, that's awesome! 
I have never really noticed the "off board" connectors of P1 and P2.
You say that the channels are identical. And how do you make sure not to confuse the left and right channel? So that "left" stays left, after it's amplified?
And I noticed that when you look on the pins of the 3,5mm jack, the plug facing up the left pin is left and the right one is the right channel. Is that a standard?
And the two pins on each side are connected as long as you don't connect a plug. Is that some kind of "detector" whether a plug is connected? Does it matter for the O2?
I have never really noticed the "off board" connectors of P1 and P2.
You say that the channels are identical. And how do you make sure not to confuse the left and right channel? So that "left" stays left, after it's amplified?
And I noticed that when you look on the pins of the 3,5mm jack, the plug facing up the left pin is left and the right one is the right channel. Is that a standard?
And the two pins on each side are connected as long as you don't connect a plug. Is that some kind of "detector" whether a plug is connected? Does it matter for the O2?
Electrically the two channels are identical and have no "knowledge" of the signals applied to them. So you make sure they are not mixed up by just deciding arbitrarily which will be left and which will be right.
For example... make pin 1 of P1 (P1 is that off board connector) the right channel. To follow that through correctly you need to wire the right headphone channel to pin 3 of P2
The only time it would matter which way round they were is if you wanted to retain the existing sockets. In that case you would want L and R to match whether using the off board connector or the existing connectors. If you got it wrong its only a matter of swapping two wires, either on the input or the output, one or the other, not both
The connectors on the input socket are a detector of sorts... they have continuity when no plug is inserted which allows the off board input to loop through the socket. When you put a plug in the socket it will disconnect the off board input so that you don't mix the two feeds together. (That's assuming the socket used is actually of that type... but that's how it seems to be drawn)
For example... make pin 1 of P1 (P1 is that off board connector) the right channel. To follow that through correctly you need to wire the right headphone channel to pin 3 of P2
The only time it would matter which way round they were is if you wanted to retain the existing sockets. In that case you would want L and R to match whether using the off board connector or the existing connectors. If you got it wrong its only a matter of swapping two wires, either on the input or the output, one or the other, not both
The connectors on the input socket are a detector of sorts... they have continuity when no plug is inserted which allows the off board input to loop through the socket. When you put a plug in the socket it will disconnect the off board input so that you don't mix the two feeds together. (That's assuming the socket used is actually of that type... but that's how it seems to be drawn)
Hello you guys,
I am new here and I am very happy that this thread is active so that I can ask questions here. Correct me if I'm wrong because I don't really know much about DIY.
I am planning to diymod my ipod. Redwineaudio and many people modded ipod video by desolder something and solder something. I am sorry because I will not go into detail. The final result will be the sound should be better.
Redwineaudio and some people put two capacitors not in the iPod but in the LOD cable, or some place. Others put the caps between the cables in the iPod. The result should be the same: The DC Offset 1~2 volts will be blocked from going through the line out.
Here is my thought: It's hard to put capacitors inside the iPod. If I want to make it fit in the iPod, I have to use small electrolytic capacitors. I found some: Nichicon Muse ES 2uf-50V, Elna CE-BP 2uf 50v... But it's not very optimal for the sound quality. I want to use larger capacitors or film caps like Wima's but it's not possible to put it inside the iPod. There are some modifications allowing this like replacing the iPod's harddrive with CF card, but it's not cheap. My original idea is just improve the sound of the line out. The harddrive is fine for me.
Making a custom LOD with caps inside is a nice idea. The work inside the iPod will be simpler than putting caps inside the iPod. But it still costs.
Then I found that I can use the capless iPod with standard LOD connected to amplifier with DC blocking capacitor. I have known that Fiio amplifiers like E17, E12, E11 block DC offset from the input, but I prefer O2. I want to know if O2 has this ability. If allowing DC offset is not safe, so I will use a custom LOD with caps inside.
On NwAvGuy's blog: "The O2 has a DC blocking capacitor to reduce the O2’s own DC offset and prevent DC offset at the input from being amplified which could potentially harm headphones."
I am new here and I am very happy that this thread is active so that I can ask questions here. Correct me if I'm wrong because I don't really know much about DIY.
I am planning to diymod my ipod. Redwineaudio and many people modded ipod video by desolder something and solder something. I am sorry because I will not go into detail. The final result will be the sound should be better.
Redwineaudio and some people put two capacitors not in the iPod but in the LOD cable, or some place. Others put the caps between the cables in the iPod. The result should be the same: The DC Offset 1~2 volts will be blocked from going through the line out.
Here is my thought: It's hard to put capacitors inside the iPod. If I want to make it fit in the iPod, I have to use small electrolytic capacitors. I found some: Nichicon Muse ES 2uf-50V, Elna CE-BP 2uf 50v... But it's not very optimal for the sound quality. I want to use larger capacitors or film caps like Wima's but it's not possible to put it inside the iPod. There are some modifications allowing this like replacing the iPod's harddrive with CF card, but it's not cheap. My original idea is just improve the sound of the line out. The harddrive is fine for me.
Making a custom LOD with caps inside is a nice idea. The work inside the iPod will be simpler than putting caps inside the iPod. But it still costs.
Then I found that I can use the capless iPod with standard LOD connected to amplifier with DC blocking capacitor. I have known that Fiio amplifiers like E17, E12, E11 block DC offset from the input, but I prefer O2. I want to know if O2 has this ability. If allowing DC offset is not safe, so I will use a custom LOD with caps inside.
On NwAvGuy's blog: "The O2 has a DC blocking capacitor to reduce the O2’s own DC offset and prevent DC offset at the input from being amplified which could potentially harm headphones."
DC blocking capacitors are anyways in series so it doesn't matters if they are inside ipod or on h/p amp i/p . There should be at-least one in series per stage. As for "DC Offset 1~2 volts" are you sure you are measuring it right? Worst case I've seen were around 10mV in PMP. As for ipod it should be couple of mV(assuming direct coupled o/p). As for capacitor coupled, it should be 0V for all practical purpose.
Capacitors do tend to degrade sound quality(electrolytics are even worse), but by how much I don't know as fortunately I don't have golden ears
Making a custom LOD with caps inside is a nice idea. The work inside the iPod will be simpler than putting caps inside the iPod. But it still costs.
Yes, O2 has DC blocking cap. between gain stage & buffer stage(not at i/p).
So as per RS if you exceed DC at i/p y couple of volts(7V DC) you might damage the gain stage. But no damage will be done to h/p.
As for me. I've connected ipod & similar PMP devices to CMOYs without any DC blocking caps
I have never measured it, because I have not established the mod.
According to this, I think DC offset is about 2 volts both channel (1 volt each)
The Apple diyMod: My Take on the Famous iMod [56k killer] Featuring 3G, 4G, 5G and nano 1G! - Page 193
Code:
http://www.head-fi.org/t/269604/the-apple-diymod-my-take-on-the-famous-imod-56k-killer-featuring-3g-4g-5g-and-nano-1g/2940#post_10341786I meant improve the sound quality from original line out dock. The diymod for ipod meant to connect directly the sound from the DAC to the amp instead of going to many elements in the DAC. That's why I want to do capless because I think it provides the best sound quality (correct me if I'm wrong)Capacitors do tend to degrade sound quality(electrolytics are even worse), but by how much I don't know as fortunately I don't have golden ears
So I think that it's not safe for capless diymod ipod to use with O2.
No source component should present a significant DC offset, but be aware that some headphone Class D output stages in MP3 type devices can rely on the presence of the phones to form part of the output filter network.
The O2 won't be damaged by any conceivable offset from any source component.
The O2 won't be damaged by any conceivable offset from any source component.
But can O2 block 2 volts DC offset from my ipod from being amped so that my headphone will not be harmed?
And what I said about Fiio amps E17, E12, E11 I'm sorry because I didn't find any proves regarding about the ability to block DC offset, it's just a saying from a member from head-fi. I think I will ask fiio support.
Yes, it will block 2 volts applied to the input but, depending on the gain setting resistors used, that 2 volts could be amplified by the DC coupled first stage opamp and cause other problems (such as asymmetric clipping). The headphones will never see DC due to AC coupling of the final stage input by C13 and C14.
If your source really does have 2 volts offset then that suggests it may be a class D stage with lots of HF hash present, and it could be that that you are reading on a DVM. It would really need a scope to see what was there.
Thanks for your comment. Actually if I do capless mod, there will be DC offset from the Wolfson chip from the iPod. the caps actually used to block the DC offset. I think I should use caps to block the DC offset to be safe.
So I just wanted to get some new parts since i believe that some of them are gone now.
Do you guys know any shop, preferably located in Germany (or at least in the EU) with a wide range of electronic parts?
Especially the regulators are difficult to find. Is a MC7812ACT (Fairchild) the same thing as a MC7812ACTG (On Semi)? Or is it just a 7812 in a TO-220?
P.S.: Unsoldering a TO-220 is really a pita. Even with desoldering braid... Or is it just me and I am too stupid?
Do you guys know any shop, preferably located in Germany (or at least in the EU) with a wide range of electronic parts?
Especially the regulators are difficult to find. Is a MC7812ACT (Fairchild) the same thing as a MC7812ACTG (On Semi)? Or is it just a 7812 in a TO-220?
P.S.: Unsoldering a TO-220 is really a pita. Even with desoldering braid... Or is it just me and I am too stupid?
The G just means lead free. The ACT bit means T0220 outline which is correct. So yes, all the same, and there are countless variations and manufacturers. If it says 7812 and is the right shape its fine. Same for the 7912. These should be available from any store selling parts.
Desoldering... well I guess it takes practice if your struggling. One technique... but don't damage the board... is to hold and simultaneously lightly pull on the reg while heating all three pins at once. Use plenty of solder to bridge all three pins to get heat to all pins and it will come out in an instant. Then use the braid to clean the excess from the board.
If you use braid to actually unsolder each pin at a time (which is the correct way) then try looping the braid over the iron tip and then pressing that onto the joint. The solder should be wicked up in an instant. If the solder isn't melting then the iron may not be hot enough or have a large enough tip to carry the heat.
If you can get hold of some scrap electronics PCB then practice on that first.
Desoldering... well I guess it takes practice if your struggling. One technique... but don't damage the board... is to hold and simultaneously lightly pull on the reg while heating all three pins at once. Use plenty of solder to bridge all three pins to get heat to all pins and it will come out in an instant. Then use the braid to clean the excess from the board.
If you use braid to actually unsolder each pin at a time (which is the correct way) then try looping the braid over the iron tip and then pressing that onto the joint. The solder should be wicked up in an instant. If the solder isn't melting then the iron may not be hot enough or have a large enough tip to carry the heat.
If you can get hold of some scrap electronics PCB then practice on that first.
...P.S.: Unsoldering a TO-220 is really a pita. Even with desoldering braid... Or is it just me and I am too stupid?
You can use a desoldering pump
BTW I use 2 soldering irons to desolder those TO-220, they just fall off on floor, thanks to Sir Isaac Newton
If you know the part is shot, cut the leads and remove them one at a time. Then remove any remaining solder with either solder wick or a desoldering tool.
I like this one, and have used it or a similar one from OK industries for over 40 years.
DP-200 OK Industries | Mouser
I like this one, and have used it or a similar one from OK industries for over 40 years.
DP-200 OK Industries | Mouser
If you are measuring out of circuit, first thing to do is put a new battery in your DMM. The battery is used for resistance readings and when they start to do dead you will get readings all over the place. Even if it is a brand new DMM out of the package - I've run into a least one over the years that sat on the shelf so long the included battery was flakey. Then make sure your meter test leads are fitting tight in the DMM. I've seen some loose ones over the years that will mess up readings. Highly unlikely the problem is actually your resistors, especially if they are on a cut tape like that (all from the same batch). 236k for a 274k would be 14%, way out of the ballpark.
If you are taking measurements in-circuit, well that doesn't really work reliably as Mooly has noted. In-circuit voltage readings to ground are a much more reliable way to go. At the very least for in-circuit resistance readings you need to make sure the O2 is completely unplugged from the AC, batteries out, and take a small value resistor (like 1 ohm or just a straight wire) and short out every single capacitor on the board for a a few seconds to discharge them all. Charged caps will give you bad in-circuit readings. Even then once you put your ohmeter on something it may start charging up a cap nearby, resulting in a "moving" resistance reading. And resistors in-circuit often have other parts across them, like other resistors and transistor junctions, so that the resistor is unlikely to read what its markings say. If you really want to measure a resistor that is in-circuit already the best thing to do is unsolder and "lift" one leg out of the PC board so you can make an good measurement.
EDIT: I just took a look at the O2 BOM to verify. R4, 5, 8, and 24 are 270K. You probably got that crossed with the line above in the BOM that is 274R. But 236K would still be 12.5% off and 274 is 1.5%, which is unlikely to happen for 1% resistors.
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