My Crack destruction/build log

[ramicio]

I bought a Crack off ebay some time ago, pre-built.  It came with AΞON output capacitors.  I've since replaced the RCAs with Neutrik ones and the headphone jack with a Neutrik latching jawn.  The octal tube socket just plain sucks and the signal started becoming intermittent, so I took the amp out of commission and I am going to do a whole slew of things to it.

• I ordered new tube sockets.  They are the teflon composite type from Parts Connexion.  They have a silver-plated crown springs inside the contacts made of beryllium copper.
• The capacitors came dangling.  I just used packing tape to keep them held up.  It works and can't easily be seen because it's clear.  It's not ideal so I designed some brackets in SketchUp and are having them made at shapeways for $3.96 apiece.  They made specifically for my capacitors, and you can see the slots for the zip tie.  Click this sentence to visit the site and maybe purchase them.  I don't get anything for it.  I designed them and put them up for everybody.
• The headphone jack is crooked and could use some mounting work.  I am going to look for a machinist to just nip into the top plate a tiny bit to the shape of the jack's flange so it absolutely will not move.
• I am replacing all hardware with torx hardware.  I haven't found a place where I can get all the same alloy for all of the sizes I need and inexpensive.  McMaster-Carr has them all for cheap, but in different alloys.  Aaron's has any size you can imagine and in whatever alloy you want, but small quantities are expensive.  I would maybe go for larger quantities if people would go in on a buy (hint hint).  Fastenal doesn't really have anything, anymore.
• I am going to have the top plate and transformer end bell powder coated.
• I am looking to add in an audio spectrum analyzer circuit I bought some time ago.  I would like it to be after the volume control.  Will there be any impedance problems?
• I am looking to add a timed relay circuit that won't connect the headphone output at power on until a set amount of time.
• The Speedball upgrade will be done.  What hardware does that kit use?  If I have excess quantities from the bulk I order for the Crack itself it would be nice to have these used for mounting the Speedball.
• I am thinking about solid silver wire with cloth insulation, and not with PVC or teflon innards.  Does anyone know of a place that sells a decent selection of sizes and colors (red, white, and black)?  I found a place in the UK, but I would prefer somewhere in North America.

So far I'm impressed with the amp.  I didn't think the sound would change that much from the on-board amp on my STX card.  Naysayers obviously don't understand that impedance is only measured at one frequency point and high-impedance headphones like my HD-650s are quite demanding of power for bass.  You need a healthy reserve of power to drive low frequencies.

When I got it:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Ftimramich.com%2Fheadphone_amp%2F2012-05-01_18-13_thumb.jpg&hash=86b4b337d0d8bb992e37596cafb5cfbf050c21f3)

After I fiddled with it:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Ftimramich.com%2Fheadphone_amp%2F2012-05-07_19-25_thumb.jpg&hash=2f7818c81d42b31998cb503528ec935ee626f8ac)

More updates to come.

[Grainger49]

No, I just remember the picture post that was made.  The knob is distinct.

[coca]

I love those capacitor brackets. Can you tell me exactly how I can purchase them.

Thanks in advance.

Bernie.

[Grainger49]

That fixed it.

[Grainger49]

I'm a big fan of bending the tube pins out in that way.  Some of them get so crowded it opens up the opportunity that they might short together.  Worse yet, you could bridge two pins when taking voltage measurements.

[jimiclow]

Forgive my ignorance but what are you trying to accomplish with this circuit? A switch?

[jimiclow]

Thanks.
That sounds interesting!
Keep us updated...

[Laudanum]

End mill hell ... that's a free hand with a Roto Zip job  ... starting with a prayer that you dont f-up   

[Doc B.]

I think it's cool that Tim is doing this in such a precise way, having parts CNC'd and 3D printed. It's inspiring me to put our little CNC mill in the lab to work on some projects beyond engraving tape reel flanges. Today I'm updating the wood fired Pentium III we have been using to run it for the past few years to something a little more reliable.

[Laudanum]

I don't understand.

It was a joke about doing it the cheap way.  Exactly like the way I'd do it if I were so inclined   

[Paul Birkeland]

You're pretty brave to use stranded wire, it's pretty tough to build with (Be sure to trim off any little wire fingers/hairs that aren't soldered down).

[Laudanum]

I initially wired FPIII with a teflon insulated, stranded STP.  Tinned every wire before wrapping and soldering to terminals.   It wasnt fancy wire, I just had a hair to try it.  It was a PITA but not as much as it just plain sounded like sh*t.   I ended up tearing it out and using the Belden.   Count your blessings, it could have been much worse ... I know.  

PS ... Looking Good!  Very cool.

[Paul Birkeland]

Ouch, rewiring a Foreplay III is a huge task!

[Paul Joppa]

Double ouch; I was just thinking teflon STP might be an improvement! If you don't mind my asking, what did you use and how long did it burn in before you threw in the towel?

[Laudanum]

If memory serves it was some inexpensive West Penn wire, cant recall the #.   Tinned, stranded.    I dont recall how long but I didnt leave it alone for very long. Certainly not long enough based on most recommendations for teflon burn in but the high end was a mess and I wasnt waiting on it.   I have some teflon insulated wire in the main system that sounded quite good from the start.   I can tell you that the stock Belden STP was a welcome change, immediately so I never looked back.   I never have been able to find a small diameter STP with teflon insulated solid core wire.  Im sure someone makes some but Ive never found any.