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"The Wire" Ultra-High Performance Headphone Amplifier - PCB's
"The Wire" Ultra-High Performance Headphone Amplifier - PCB's
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Old 14th March 2018, 06:17 AM   #2671
FritzS is offline FritzS  Austria
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Quote:
Originally Posted by ammel68 View Post
Having tried MANY op-amps over the years from all the major manufactures, I've never cared for the "sterile" and "lifeless" sound of many of their op-amps(LM4562, LME49610/20) and buffers(LME49600), but hopefully you will!
The LF356N and BUF-03 were two of National's better sounding offerings unlike any of their "LME" offerings.

Glad to see most of these "sterile" sounding National "LME" offerings being discontinued by T.I..
I used LM4562, LME49610/20 too, but I am not convinced about and use OPA627 in my HA now.

What did you think about the old BUF634 - with or without wide bandwidth mode?
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Old 14th March 2018, 03:01 PM   #2672
opc is offline opc  Canada
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"The Wire" Ultra-High Performance Headphone Amplifier - PCB's
Quote:
Originally Posted by N Brock View Post
After 7 years of great listening, The Wire that I built gave up the ghost. I threw the switch and heard loud intermittent static on the output.

I initially thought it was the power supply (failed regs?) since the supply voltage was way down and intermittent. I disconnected the amp board and the PSU recovered to a nice clean +/- 15, so it wasn't that.

I measured the resistance of each rail on the amp board: 3.8Ω V+ to gnd, 6.5Ω V- to gnd. Not good. Maybe one of the buffers?

Since desoldering the buffers was going to be a pain I wanted to be sure of the problem part. I hooked the amp board up to a bench supply and started poking around the board with my finger. All chips were cold but the supply caps were getting hot! I removed the caps and they measured about the same as the rail resistances I mentioned above. I guess they died from the age and being run at 1V below rating?

I powered the amp board without caps, seems like there was no damage. Now I'm just waiting on fresh caps, 25V this time.
Hi N Brock,

Good troubleshooting! Glad you found the source of the problem.

That is quite surprising about those caps... polymer caps were kind of in their infancy when I specified them for this project, but I would have expected better than that. Even if you had it plugged in and running 24 hours a day for the past 7 years, that's still only 60,000 hours, and that seems premature for a modern capacitor to be calling it quits.

That failure mode also seems particularly crummy, as it would gradually overload the regulators and cause large amounts of self-heating which I'm sure further hastened the demise of the caps.

Can you comment on heat inside your enclosure? Was it particularly hot in there when the amp was running? In this application, with essentially no ripple current, and what should have been minimal heat, these caps should have lasted essentially forever, even if operated close to their voltage rating.

All that being said, you made the right call on the 25V replacement parts, and hopefully those will last for at least another 10 years.

Happy listening!

Regards,
Owen
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Old 14th March 2018, 04:25 PM   #2673
Detectit1 is offline Detectit1
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Never mind...

Last edited by Detectit1; 14th March 2018 at 04:29 PM.
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Old 16th March 2018, 06:50 AM   #2674
N Brock is offline N Brock  United States
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Quote:
Originally Posted by opc View Post
Can you comment on heat inside your enclosure? Was it particularly hot in there when the amp was running? In this application, with essentially no ripple current, and what should have been minimal heat, these caps should have lasted essentially forever, even if operated close to their voltage rating.
I never noticed excessive heat. After listening for a few hours I could feel a small amount of warmth coming through the top cover. Actual temps were never measured, maybe they should be this time around. I agree that the caps ought to have lasted longer unless something unintentional was happening.

On the bright side, this has got me thinking about this amp again and I'm tempted to build up one of my rework boards so I can listen to something nice at work.
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Old 19th March 2018, 11:42 PM   #2675
TypodCrow is offline TypodCrow
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A quick update for all those following my perils; I found the problem on my amp.

One of the capacitors on the PSU board was only soldered on one side - I noticed becasue I meant to reheat and touchup what looked like a solder joint, but this lead to the capacitor just falling off the board.

I resoldered all the caps on the power board and everything runs perfectly quietly now as long as my signal ground is connected to AC ground. If I leave signal ground floating, I still get a hum but it's much MUCH quieter than before.

Just trying to find a smaller chassis now; I want to make me The Wire build the size of an O2 (convenience), or have it sit inside a shared chassis with my SRM-252s. Should be a cute little build.

Thanks for all your help @opc and @multisync
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Old 20th March 2018, 11:05 AM   #2676
multisync is offline multisync  Canada
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Yea, fixed!
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Old 20th March 2018, 02:53 PM   #2677
mictester is offline mictester  United Kingdom
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Quote:
Originally Posted by ammel68 View Post
LOL...

I've also built and listened to Mr. Marsh's HA, but only as preamp since I don't give a big ole' damn about headphones.
I have to admit it sounds a little better than this so called "Wire" nonsense, but still sucks moose balls compared to the Schiit Magni 3.
Sorry guys... but sometimes DIY just can NOT compete with affordable commercial designs like the Magni 3.
The "Schiit" amplifier lives up to its unfortunate name. The DC spikes from them at switch on and off are dreadful, and the harmonic distortion and slew-rate distortion are appalling. It wasn't "designed", it was thrown together by someone with little real understanding of electronics.
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