[JoshK]

I thought in the interest of continual learning, it might be fun to keep a thread going for us to share what we learned this week.  You are never too smart or too old to learn something new.  And it might help others to share it.

I'll go first.  Well the best way to learn something is to f**k something up right?  Well, I was testing out my UcD monoblocks, after having rebuilt them for the, well I lost track, time.  I somehow managed to switch the polarity of my bridges to the cap banks (dual bridges, 4 pole jensens = lots of wires).  This means when you switch the mono's on something is likely to blow up, but I had DIY Cable's softstarts on these amps, so instead the white coffin sand resistor started glowing red and smoke started to seep out of the resistor and I hit the off switch. 

After the smell vanquished and I realized that I was complete daft  , I fixed the problem.  Well it wasn't that expensive of a mistake due to the softstarts.  But I wondered why other things weren't damaged by the stupidity of my brilliant move.  Then I came across a thread when researching something else.  It turns out that white coffin sand resistors are otherwise used as fused resistors or current limiting resistors.  They are intended to blow and fail open when overloaded, thus acting like a fuse. 

The resistors have an open side that is suppose to point away from the PCB so when it blows it doesn't ruin the PCB or components around it.  I never knew this about the white coffins.  But it is a lot less expensive mistake thanks to the DIY Cable softstarts. 

Technically I should have used my variac and brought the amp up slowly...I just didn't know if the softstart would click on without full voltage.

[richidoo]

Good topic Josh! I hope it continues into a mega thread. We can all learn from each other's mistakes and discoveries.

I learned to remove the cable clamp from ribbon connectors before crimping them or the whole thing will disintegrate. I never did it before, so I didn't even know it was a clamp on there. I also learned CA glue and severe patience can put it back together. 

Also not to lick my finger before turning instruction pages while I'm soldering with lead. 

Thanks
Rich

[BobM]

I re-learned the audible benefits of star-grounding the power supply board high current components - cutting away those little hairlike traces to the common ground plane and wiring up direct connections to one common grouond point. Much blacker background due to a noticeable drop in the noise floor on my Zhaolu DAC.

I also learned the audible benefits of bypassing a relay on the analogue output section of the Zhaolu DAC. Clearer, with a decidedly deeper soundstage.

As some of us have found out over the years, component layout and fundamental audiophile "best-practices" can be DIY'ed on inexpensive equipment, with a little extra effort, to impressively good effect. A little beyond swapping out caps and such, but not all that difficult overall.

Enjoy,
Bob

[JoshK]

As some of us have found out over the years, component layout and fundamental audiophile "best-practices" can be DIY'ed on inexpensive equipment, with a little extra effort, to impressively good effect. A little beyond swapping out caps and such, but not all that difficult overall.

That's real DIY imo, the other is parts swapping. 

[Gordy]

A little mundane perhaps but, Friday I built a couple of dc blockers (a 1 diode drop and a 2) and tested them with a stereo bridged chip amp with twin toroids.  I used a space heater to get the transformers buzzing enough to be heard from the listening position and spliced the blockers, in turn, into a PC.  The one diode blocker wasn't all that effective, though it did cut the noise down to where I could only hear it from 2-3 feet away.  The double diode blocker worked quite well, I had to basically put my ear to the chassis to hear the transformers, though removing the lid made them audible again. 

I built two more of the double diode blockers and inserted them prior to the Felix conditions in my monoblock  amps and the original in the preamp.  I'll probably disassemble the single diode and build another double, putting it and a 17a Felix in a "hot box" to feed the entire system.

[SET Man]

I re-learned the audible benefits of star-grounding the power supply board high current components - cutting away those little hairlike traces to the common ground plane and wiring up direct connections to one common grouond point. Much blacker background due to a noticeable drop in the noise floor on my Zhaolu DAC.

Enjoy,
Bob

Hey!

  Bob,  I was thinking about doing that with my Audio Note M1 Phono. But I still don't know where to start.

   As of right now it is not dead quiet but still it doesn't bother me at all. But I might give it a shot someday.

Take care,
Buddy

[BradJudy]

How about something I learned in high school?  When working with a Millikan oil drop experiment (a few hundred volts of DC across plates to float charged droplets) I learned to be careful with DC power supplies even after you've unplugged them.  I unplugged the supply and immediately grabbed both leads (an uninsulated part) to disconnect them and got a nice jolt.  Nothing damaging, but it got my attention and I learned that lesson well. 

[Russtafarian]

This week I'd like to learn what a GGP is.     Right now all I know is it's a modifiable tube preamp... but that's about it.

Russ

[tanchiro58]

I would try to gather infos to build my first open baffle speakers.  Any help would be appreciated. Thanks.

[randytsuch]

How about something I learned in high school?  When working with a Millikan oil drop experiment (a few hundred volts of DC across plates to float charged droplets) I learned to be careful with DC power supplies even after you've unplugged them.  I unplugged the supply and immediately grabbed both leads (an uninsulated part) to disconnect them and got a nice jolt.  Nothing damaging, but it got my attention and I learned that lesson well. 

Something I learned a while ago was to put bleeder resistors on tube gear, if they did not already have any.  If you don't have the tubes in, the big lytics on the power supply stay charged up.  Scared me once, buy luckily did not cause any physical harm.

BTW, cool thread Josh.

Randy

[mgalusha]

I learned that the space heater in my shop can make a Felix buzz like crazy. Thought I'd done something bad even though I checked everything with a meter before powering it up.

Relearned one tonight, that fluorescent lights can make IR remotes flip out.

Russ - a GGP is a Grounded Grid Preamp designed by Bruce Rozenblit (www. transcendentsound.com).

[JoshK]

Something I learned a while ago was to put bleeder resistors on tube gear, if they did not already have any.  If you don't have the tubes in, the big lytics on the power supply stay charged up.  Scared me once, buy luckily did not cause any physical harm.

BTW, cool thread Josh.

Randy

I have a few screwdrivers with suspicious pairs of black marks on them.      I do hope this thread keeps momentum, as these ideas generally help us all.   What may have been a rather insignificant discovery to you might turn the light bulb on for someone else.  All too often on other DIY forums people expect others to understand what they are discussing and it can prove a tough barrier for people just learning.   

[aerius]

I have a few screwdrivers with suspicious pairs of black marks on them.    

This is why I use a cheap $10 multi-meter when testing out my gear right after the build, sometimes I get a bit careless with the probes and BAM!  No more probes or a fried meter.  Surprising how much damage a 75uF motor run cap with ~300V on it will do when accidentally shorted.

One thing I've learned this week, transformer prices are going up surprisingly fast, likely due to the surge metals prices.  I wanted to order in some toroids and found out that they now cost twice as much as they did 2-3 years ago.  That was not a pleasant surprise.