Neurochrome HP-1: Ultra-High End Headphone Amp
Apr 1, 2017 at 1:35 PM Post #92 of 148

tomchr

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  I'm talking about the huge metal tab on the back of the 47900s. The huge pad you're supposed to attach them to is probably a big ground plane and it just sucks all the heat away from the iron/solder...


Are you talking about the LME49600s? Or the LME49990 (not used in the HP-1)? I'm confused.
 
If you're talking about the LME49600s used in the HP-1 and how to solder their tabs, I suggest using a wide tip and solder them from the top of the board. There's enough room on the footprint that you can place the ICs such that a small sliver of the DAP landing pad is exposed while keeping the pins on their respective pads. I give the DAP landing pad (large exposed metal pad under the IC) and the DAP/tab a coat of flux using a flux pen (see which one by following the link in Amageis' post above). Then solder the li'l pins. Switch to a 1/4" (6.3 mm) wide chisel tip and solder the tabs. The flux makes the solder flow nicely under the tabs.
 
Tom
 
Apr 1, 2017 at 1:44 PM Post #93 of 148

strangecargo

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Are you talking about the LME49600s? Or the LME49990 (not used in the HP-1)? I'm confused.
 
If you're talking about the LME49600s used in the HP-1 and how to solder their tabs, I suggest using a wide tip and solder them from the top of the board. There's enough room on the footprint that you can place the ICs such that a small sliver of the DAP landing pad is exposed while keeping the pins on their respective pads. I give the DAP landing pad (large exposed metal pad under the IC) and the DAP/tab a coat of flux using a flux pen (see which one by following the link in Amageis' post above). Then solder the li'l pins. Switch to a 1/4" (6.3 mm) wide chisel tip and solder the tabs. The flux makes the solder flow nicely under the tabs.
 
Tom

The LME49600s. I got it right in my first post, then I typoed it on my second :/. I wonder if my soldering iron just can't pump out enough heat. I had a really hard time keeping the solder melted on that pad. I have my iron set to 370C.
 
Apr 1, 2017 at 2:09 PM Post #94 of 148

tomchr

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What kind of solder do you use?
 
Both the IC tab and the board suck the heat right out of the soldering iron. That's by design. The board acts as a heat sink for the ICs. Unfortunately, this also complicates soldering. You need an iron that can pump out some heat. The METCAL and Hakko ones with the heater in the tip are usually up to the job, though, the wide chisel does help a lot. I generally find that if I can get the tab on the IC hot, the solder will flow fine.
If you're right on the hairy edge of making it work with 370 C on the soldering iron, raising the temperature to 400 C may work for you. Usually the issue getting a good thermal connection between the tip and the tab, though.
 
I use regular RMA flux core 60/40 leaded solder, 0.5 mm diameter. Unleaded solder melts at a higher temperature, so I don't recommend that for DIY purposes. You can see my thesis on solder selection here: https://www.neurochrome.com/choosing-solder/
 
Tom
 
Apr 1, 2017 at 2:16 PM Post #95 of 148

strangecargo

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  What kind of solder do you use?
 
Both the IC tab and the board suck the heat right out of the soldering iron. That's by design. The board acts as a heat sink for the ICs. Unfortunately, this also complicates soldering. You need an iron that can pump out some heat. The METCAL and Hakko ones with the heater in the tip are usually up to the job, though, the wide chisel does help a lot. I generally find that if I can get the tab on the IC hot, the solder will flow fine.
If you're right on the hairy edge of making it work with 370 C on the soldering iron, raising the temperature to 400 C may work for you. Usually the issue getting a good thermal connection between the tip and the tab, though.
 
I use regular RMA flux core 60/40 leaded solder, 0.5 mm diameter. Unleaded solder melts at a higher temperature, so I don't recommend that for DIY purposes. You can see my thesis on solder selection here: https://www.neurochrome.com/choosing-solder/
 
Tom

I'm using a roll of 62/36/2 tin/lead/silver, 0.5mm for most of the PCB, but I switched to thicker stuff (of similar composition, I think?) for the tabs. I'll try 400 degrees and see if that causes it to flow.
 
Apr 1, 2017 at 2:18 PM Post #96 of 148

tomchr

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I suggest trying the thinner solder before cranking up the heat. Thicker solder sucks out the heat of the solder joint more efficiently than thin solder.
 
Tom
 
Apr 1, 2017 at 8:52 PM Post #98 of 148

strangecargo

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Hmm. The more of these large pads I try to solder, the more apparent it is that my current chisel-headed tip just can't put out enough heat. I just tried to populate L1/L2 and just couldn't get the solder to flow, despite pre-tinning both sides. Looks like the project is on hold until I get tips with the heater at the end.
 
Apr 1, 2017 at 9:15 PM Post #99 of 148

strangecargo

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Actually, it looks like I would need an entirely different Pace soldering station to use any of their high-power heater-tip cartridges... So I guess I'm on the market for a new iron. @tomchr any suggestions for a digital temperature-controlled soldering station that's capable of soldering things like DAPs and the other big PCB pads? I like the cartridge system, though I don't like how my current Pace cartridges are wholly incompatible with their high-power iron...
 
Apr 1, 2017 at 9:51 PM Post #100 of 148

jh4db536

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http://www.sra-solder.com/aoyue-2930-programmable-digital-soldering-station

I used a station like this to take care of my hp1 build. I used a wide chisel but could've used anything really. Regular Kester 63/37 solder

It's a very good station for the price and new tips are $12

For the inductors I had to build up more solder after I tacked it down. I just positioned it on the board and started flooding at the vertex of the board pad and inductor pad.
 
Apr 1, 2017 at 10:07 PM Post #101 of 148

tomchr

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I don't really care about the temperature readout. As long as you can change the temperature (either by turning a dial or by swapping tips). I love my METCAL MX-500. I was fortunate enough to pick up a barely used one for dimes on the dollar some 9-10 years ago. I hear good things about the Hakko brand irons but have no personal experience with them.
 
Tom
 
Apr 2, 2017 at 2:48 AM Post #102 of 148

Rothor

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Hoping I'm not overstepping too many boundaries by posting this.

As many of you know I'm currently studying psychology and am taking a class in consumer psychology. As part of the coursework we are to conduct a market analysis and design a marketing campaign. For the analysis, we have devised a brief survey. I would greatly appreciate it if you'd take the survey: The survey is completely anonymous. It will be a big help to me, both for my psych degree and quite possibly for my business as well.

Thanks,

Tom


Done
 
Apr 5, 2017 at 1:22 AM Post #104 of 148

strangecargo

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It lives! Worked on the first try too! Sounds just like the one behind it that Tom built:) One step closer to an HP-1 for every room in the house! 
L3000.gif

 
The Metcal was appallingly good at heating those big pads, though I think I ordered too fine a tip for all the little SMD parts. @tomchr do you know the part number for the tip you use for the resistors and such? Also, I built this one with the resistor/pad swap you suggested when I emailed you about lifting the ground, but it seems like lifting the ground on this one still clears up the sound for me.
 
Apr 5, 2017 at 1:35 AM Post #105 of 148

tomchr

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Originally Posted by strangecargo /img/forum/go_quote.gif
It lives! Worked on the first try too! Sounds just like the one behind it that Tom built:) One step closer to an HP-1 for every room in the house! 
L3000.gif

 
The Metcal was appallingly good at heating those big pads, though I think I ordered too fine a tip for all the little SMD parts. @tomchr do you know the part number for the tip you use for the resistors and such? Also, I built this one with the resistor/pad swap you suggested when I emailed you about lifting the ground, but it seems like lifting the ground on this one still clears up the sound for me.

 
Awesome. Here are the tips I use:
STTC-126 (SMD passives and IC pins)
STTC-025 (also handy for SMD passives)
STTC-037 (handy for leaded parts)
STTC-036 (handy for larger leaded bits)
STTC-117 (wide chisel for tabs, DAPs, etc.)
 
I do recognize that they're not all the same temperature. I received about ten different tips with my MX-500 when I bought it. If I was to get a subset of those tips, I'd go with the STTC-026, STTC-037, and STTC-017 (or 117). The first digit denotes the temperature (0 = 357 C; 1 = 417 C AFAIR).
 
I'm puzzled by the ground lifting doing anything. With the resistor tweak I suggested (i.e. plucking R46 and R115 off the board and connecting the "inner" pads of those footprints together with either a 0 Ω resistor or a piece of wire), the ground of the HP-1 is already lifted. The only thing I can think of is that the XLR Pin 1 is grounded to the chassis (as required/strongly encouraged by AES48-2005). Maybe your source isn't so fond of that. That'd be odd, but I suppose weirder things have happened. It's good to hear that a ground lift clears it up, though.
 
Tom
 

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