The Objective2 (O2) Headphone Amp DIY Project

[FloridaBear]

I used rs's recommended solder (60/40) for my two O2 builds, but would like to switch to lead-free solder for future products. I know a hotter iron is needed, but are there any other tips for using lead-free solder?

[billyk]

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!!

[sofaspud]

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.

[MrSlim]

I like 63/37 or 62/36/2(silver) from Radio Shack (not lead free).. works very well for me.

[Willakan]

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.

[Alexium]

Originally Posted by sofaspud

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.

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?

[Shamharoth]

Originally Posted by Willakan

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.

Do you think the O2 would still be too loud at 2X gain with a K701 ? (the source being a computer)

[billyk]

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...

[Alexium]

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!

[RocketScientist]

@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.