IMHO don't use it!
I just don't like the way it works for me. The ease of use and the surety of making good joints far outweigh the "benefits" of lead free. The small amount a hobbyist would use will not have an impact compared to industrial use.
That being said I would not use leaded my water pipes!!
I just don't like the way it works for me. The ease of use and the surety of making good joints far outweigh the "benefits" of lead free. The small amount a hobbyist would use will not have an impact compared to industrial use.
That being said I would not use leaded my water pipes!!
Alexium, another suggestion is to get some emery cloth, fine sandpaper or steel wool and use it to pinch each component lead between your fingers and pull/rotate it through. This will remove a lot of oxides that form on the leads during storage. Then insert the component into the PCB and solder it.
I used the recommended solder and a crappy 25W iron with a heavily oxidised tip. I suppose the above probably doesn't exactly help, but as you as you tin the tip properly and clean it between joints you should be fine. I suspect that the solder you were using was not ideal for this application.
On a different note, I just clipped my gain resistors to drop the amplifier to unity gain on the high-gain setting (Intuitive no?). I have found that unity gain is plenty loud with the K702s and a 2.1VRMS source - I end up listening at just under 9 o'clock: a little more for reasonably mastered music and a little lower for brickwalled stuff.
Do I listen bizarrely quietly, or does everyone else listen loudly? I have read recommendations telling people that 3* or even 5* gain is perfect with normal sources and the K701/2 - with even 3* gain I was listening at a level so low that there was huge channel imbalance.
On a different note, I just clipped my gain resistors to drop the amplifier to unity gain on the high-gain setting (Intuitive no?). I have found that unity gain is plenty loud with the K702s and a 2.1VRMS source - I end up listening at just under 9 o'clock: a little more for reasonably mastered music and a little lower for brickwalled stuff.
Do I listen bizarrely quietly, or does everyone else listen loudly? I have read recommendations telling people that 3* or even 5* gain is perfect with normal sources and the K701/2 - with even 3* gain I was listening at a level so low that there was huge channel imbalance.
I actually have a tool for that. I've scratchedeach pin to shine like a mirror, and there was no effect in soldering vs unprocessed pins.
Thank you all for the advices! I got 60/40 solder, will try it in a few minutes. They also have 62/36/2(silver) for twice the price. I'll try that if 60/40 doesn't help.
Also, I got the wall transformer. Seller claimed it to give exactly 20V idle, but actually it's 22.4V. Will O2 survive this voltage? Can I tune it to accomodate it?
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Do you think the O2 would still be too loud at 2X gain with a K701 ? (the source being a computer)
Just finished my build. Very nice, smooth process, the board was a joy to work on. Took about 3.5 hours, would have been done sooner but somehow I forgot to order R4,5,8 & 24; man was I mad at myself! Well, digging through my bins I came across 20 or so 5% carbon film, so I metered them and used the 4 closest to spec and each other. Thank goodness for "the bin". I always order a few extras, it pays!
Sounds good right off, I'll let it run for a while and listen some more. When I get home I'll check it out again with my good cans, HD600s and compare to my other head amps. I have a few... Mini^3, carrie (essentially a mini ^3 with a grub DAC attached), CK2III, Diamante, and my everyday listening amp, a moderately modded Crack with the speedball upgrade. My source is an AMB Gamma 2 fed from SPDIF out of my "music-PC"
I'll let you know...
Sounds good right off, I'll let it run for a while and listen some more. When I get home I'll check it out again with my good cans, HD600s and compare to my other head amps. I have a few... Mini^3, carrie (essentially a mini ^3 with a grub DAC attached), CK2III, Diamante, and my everyday listening amp, a moderately modded Crack with the speedball upgrade. My source is an AMB Gamma 2 fed from SPDIF out of my "music-PC"
I'll let you know...
Guys, I've got a problem matching my resistors with BOM. Ihave a package from Jokener. I've got 4 resistors like 38.6kOhm, and 2 resistors like 9.86 kOhm. I'm sure I have already sitted R14 and R20, and those were 10k exactly. The others could be R6, R12, R13, but 38.5 is outside of 1% from 40.2, and why 4?.. Also, what should be R9? 133k? Can't find it
Thanks in advance for the help!
Thanks in advance for the help!
@billyk glad your build went well and sounds good!
@Shamharoth the K701 needs a fair amount of drive so it will come down to what your computer is putting out. I would guess you will want at least 2.5X gain.
@Alexium, be careful with tips. Good tips are plated and that plating is essential to making good solder connections. If you "clean" the tip with something really abrasive (especially something like a file) you will remove the plating and be left with whatever bare metal the tip is made out of. That's when you should throw it away and get a new one as it likely won't solder well. Some really cheap irons have un-plated tips and I don't recommend them for serious electronic work.
R9 was switched from 40K to 33K. Any value in that range is OK. 38.6K is also OK for R6, R12 and R13 (but R12 and R13 should match and be the same). So 38.6K is OK for all 4: R6, R9, R12, R13.
@FloridaBear, +1 on staying away from lead free solder unless it's legally required for a commercial application. It's much harder to work with and, even with automated assembly, has far more problems. It's telling that both military and space applications are exempt from the lead free requirements. Leaded solder is preferred, and still used, for both. Look up "tin whiskers" for just one of many problems.
@Shamharoth the K701 needs a fair amount of drive so it will come down to what your computer is putting out. I would guess you will want at least 2.5X gain.
@Alexium, be careful with tips. Good tips are plated and that plating is essential to making good solder connections. If you "clean" the tip with something really abrasive (especially something like a file) you will remove the plating and be left with whatever bare metal the tip is made out of. That's when you should throw it away and get a new one as it likely won't solder well. Some really cheap irons have un-plated tips and I don't recommend them for serious electronic work.
R9 was switched from 40K to 33K. Any value in that range is OK. 38.6K is also OK for R6, R12 and R13 (but R12 and R13 should match and be the same). So 38.6K is OK for all 4: R6, R9, R12, R13.
@FloridaBear, +1 on staying away from lead free solder unless it's legally required for a commercial application. It's much harder to work with and, even with automated assembly, has far more problems. It's telling that both military and space applications are exempt from the lead free requirements. Leaded solder is preferred, and still used, for both. Look up "tin whiskers" for just one of many problems.
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For AKG's with the DMK45 or XXL drivers (K701, K702, Q701, K141, K142, K171, K172, K240, K242, K271, K272) I recommend Hi = 1.6x (up to 1.8x for the 700's), Lo = 1x gain.
The reason is simple. Even with an iPod output, the 1.6x will get very loud (~110dB if I did the math right) up at max volume but when connected to a 2.1V source it will be just at the cusp of maximum power handling, thus not damaging your phones if there's an accident and the pot gets a full rotation.
Unity gain is good for getting high on the volume pot with strong sources.
The reason is simple. Even with an iPod output, the 1.6x will get very loud (~110dB if I did the math right) up at max volume but when connected to a 2.1V source it will be just at the cusp of maximum power handling, thus not damaging your phones if there's an accident and the pot gets a full rotation.
Unity gain is good for getting high on the volume pot with strong sources.
I don't agree unless you're talking about a 2 volt home source. Tyll at InnerFidelity measured the K701 at 0.32 volts for 90 dB SPL. That's not too far off AKG's specs.
As a side note, several AMB Mini3 owners now have the O2 because the Mini3's 2.4 volts wasn't enough for their K701s.
So that's 3.2 volts for 110 dB. An iPod LOD typically only puts out 0.5 volts. So you have 3.2/0.5 = 6.4X gain to hit 110 dB SPL.
If you use the iPod headphone out, that clips around 1 volt in 10K, so that's a gain of 3.2/1 = 3.2X to hit 110 dB SPL.
With a 2 volt home source, like a home CD player, you have 3.2/2 = 1.6X
RocketScientist, thanks for the help. That puts everything in place, since all 4 resistorrs are exactly the same according to my DMM.
Is my understanding correct that plated tips won't get corroded? I was in the shop today, looked at the tips, but found them a bit too expensive. Those all seemed to be plated with some white metal. All tips I ever saw or had are bare copper and get corroded in no time (those parts not covered in soldering alloy). If those more expensive tips don't get corroded - I definitely want to get one.
Is my understanding correct that plated tips won't get corroded? I was in the shop today, looked at the tips, but found them a bit too expensive. Those all seemed to be plated with some white metal. All tips I ever saw or had are bare copper and get corroded in no time (those parts not covered in soldering alloy). If those more expensive tips don't get corroded - I definitely want to get one.
With a plated tip, and a simple iron (no closed loop temp control) the solder on the tip will still turn black but it's just the solder, not the tip itself. A wipe on a wet sponge while it's hot and it's shiny clean. With an unplated tip, the tip itself corrodes.
A closed loop temperature controlled station can go much longer before even the solder turns black because the tip runs much cooler when it's just sitting in the holder.
A closed loop temperature controlled station can go much longer before even the solder turns black because the tip runs much cooler when it's just sitting in the holder.
@Alexium, the regulators are going to run really hot at that AC voltage--especially if you work the amp hard. I would suggest building it and seeing hot they get with your headphones. If you're worried they're too hot you can either get a different transformer or you could add some 10 - 15 ohm, 3 - 5 watt resistors and put them in series with D3 and D4. Mount D3 and D4 on "end" (standing up) with only one lead in the correct location on the board. Do the same with the resistors in place of the other diode lead. Then solder the free ends together and make sure they don't touch anything--especially the top of the enclosure. Each diode/resistor pair should form "^" shape above the board.
Alexium, if your O2 breaks it will be very likely due to your soldering problems not the regulators. If they get too hot, they just shut off.
You need to be very careful with your soldering, make sure all the parts are in the right way, in the correct locations, etc. before you ever apply power. Follow all the testing steps carefully. When it comes time to plug in headphones make sure they are headphones you do not care about in case they are damaged by some problem you're not aware of. Good luck.
You need to be very careful with your soldering, make sure all the parts are in the right way, in the correct locations, etc. before you ever apply power. Follow all the testing steps carefully. When it comes time to plug in headphones make sure they are headphones you do not care about in case they are damaged by some problem you're not aware of. Good luck.
A wall wart I had in my bin that stated 20VAC and read 23.2 unloaded on my meter ran fine but R1 and U6 get quite hot, cannot hold finger on R1, U6 is almost too hot to hold. This is after 20 minutes. The only problem other than the heat was the turn off/on pops were very loud, I feared for the headphones, this was true at any volume setting. I won't use this traffo again, but thought my findings would be of interest.
@Willakan (and @RS) for the K702's you can't really go lower than 2.26kΩ gain resisters on the O2 for redbook-compliant sources (in case you're wondering, I actually do use the number 2.1V) without risking damage to the headphones if AKG's specs are to be believed. I recognize that the K701 may have been less sensitive than the K702 is, but if something's too loud for a person, then the gain needs to come down... and AKG's max specs back up the claim of lower gain values for the K702 and Q701. These are the currently-produced models as the K701 is discontinued. The good news is that on the K702, you should be pumping 115dB at that point. With an iPod, you are, in fact unable, to go higher than 103dB. That's way too loud for me.
So, my 110dB math was wrong and I can't find where I got it wrong (oops!). So... an iPod can't push a K702 past 103dB with a 2.26kΩ gain resister pair; but neither can a redbook-compliant source damage your cans... just your ears.
So, my 110dB math was wrong and I can't find where I got it wrong (oops!). So... an iPod can't push a K702 past 103dB with a 2.26kΩ gain resister pair; but neither can a redbook-compliant source damage your cans... just your ears.