[skeptic]

Quote:

The panel is aluminum. Any decent bit will come out unscathed, particularly if one uses a proper cutting fluid. A spritz of WD-40 will work, as will a bit of candle wax on the tip of the bit.

 
The panel was no problem.  It was the unpunched adhesive backings on my four zip tie mounts that thoroughly gunked up the bit.  Appreciate the advice about working with aluminum in general though!  

 

[Doc B.]

Acetone might be good for cleaning off the sticky pad residue. FWIW the pads we buy have the screw hole in them already. You can easily poke the screw through the adhesive foam under the hole. 

 

[Jasper9395]

I am going to build a crack with speedball soon, I am going to build it in stock configuration first to see how it sounds. Now I will be using it with my HD650s which are 300 ohms. I will eventually be wanting to upgrade the output capacitors. I was thinking of using a Clarity cap SA with a 47uf value and bypassing it with a Mundorf M-cap with 4.7uf. According to Tony Gee who runs humblehomemadehifi this mix works quite well. This would give me a cutoff frequency of 10.3hz with the 650s. Is this a sound plan or am I missing something?

 

[dsound]

I'm in week 2 of Crack ownership and it's been great.  Props to Doc and his team for putting out a great product.
 
I ordered a Chatham 5998

  .  I'm currently using a RCA 6AS7G so I'm pretty excited to hear the differences in my (stock) crack.
 
Pic of completed kit:
 

 

[ben_r_]

Anybody use their Crack to power two headphones at the same time? Say if I wanted to run two HD-650's off it with a parallel Y splitter? Seems to have WAY too much power output for a single set of HD-650's, so Im thinking there should be plenty of power left for a second.

 

[dsound]

@ ben_r_
 
I don't think it should be a problem since most people report that the Crack does fine with 600ohm headphones..
 
Since 2x 650 @ 300 Ohm = 600 Ohms that should be fine.
 
Here's a similar post that corroborates this:
http://www.head-fi.org/t/612316/headphone-splitter
 

 

[Doc B.]

No, two 300 ohm headphones in parallel would make a 150 ohm load. That's still OK for the Crack but perhaps not quite as optimal. As regards power, you can't really have too much as long as you are careful not to blow the headphones with signal (that would blow your ears too). Do you perhaps mean there is too much gain? That is a different issue that has to do with how high the output of the source feeding the Crack is.

 

[dsound]

I stand corrected 

 .  Thanks for the clarification.

 

[ben_r_]

Quote:

No, two 300 ohm headphones in parallel would make a 150 ohm load. That's still OK for the Crack but perhaps not quite as optimal. As regards power, you can't really have too much as long as you are careful not to blow the headphones with signal (that would blow your ears too). Do you perhaps mean there is too much gain? That is a different issue that has to do with how high the output of the source feeding the Crack is.

Gain is what I was referring to sorry Doc B. And yes it is directly proportional to the incoming signal. That being said do you think it would be better to split the headphone out in series for a 600 ohm load?

 

[Doc B.]

I would run two headphones in parallel rather than series, but it wouldn't hurt anything to try it both ways.

 

[ben_r_]

Quote:

I would run two headphones in parallel rather than series, but it wouldn't hurt anything to try it both ways.

Very true. I would think the Crack would perform better with a 600 ohm load rather than a 150 ohm, but Im only basing that on what Ive read around the net with various headphone combinations.
 
Doc B, I had another question, I have them both, but since one is already mounted and installed its easier to just as here: the PT-7 is the exact same size and shape have can use the same mounting hold cutouts as the PT-3 correct?

 

[Mak333]

Quote:

Very true. I would think the Crack would perform better with a 600 ohm load rather than a 150 ohm, but Im only basing that on what Ive read around the net with various headphone combinations.
 
Doc B, I had another question, I have them both, but since one is already mounted and installed its easier to just as here: the PT-7 is the exact same size and shape have can use the same mounting hold cutouts as the PT-3 correct?

I don't believe changing the headphones changes the resistance of the amp.  I'm not knowledgeable when it comes to this stuff, but I do believe that changing what the amp outputs to, doesn't affect the performance of the amp, but only the output device.

 

[BmWr75]

Quote:

I don't believe changing the headphones changes the resistance of the amp.  I'm not knowledgeable when it comes to this stuff, but I do believe that changing what the amp outputs to, doesn't affect the performance of the amp, but only the output device.

 
Just because you don't believe, doesn't mean it isn't true. 

 

[silverhead]

 
 
My 6SN7 to 12AU7 adapter(s) showed up from China finally.   The first one (nice, gold looking one) doesn't work.   The second one that showed up does work, however.
 
Do you run the risk of toasting the transformer by using this setup with no other modifications?
 
My unprofessional opinion is that compared to my RCA clear top 12AU7, the  GE and HP 6SN7 tubes I bought cheaply, both sound nice.   I'm getting more output out of them (louder in the headphones at the same volume setting) than 12AU7 tubes.
 
This is my opinion about how the sound has changed:  Less sibilance out of 'S' words, as if maybe the high end is more compressed.  Boomier bass at the 80ish-150hz range which is somewhat annoying.   But otherwise, stereo separation seems to be slightly wider and the sound is a bit more tight and punchy.  Sort of like taking a little hit of nitrous oxide where the whole world feels a bit more refreshing, rubbery, and springy.  Like being thrown into a padded cell after winning the lottery..   I'm not sure I'm good at describing what I'm hearing, but I think the 6SN7 tube can make the hairs on the back of your neck stand up better with some songs than the 12AU7.  
 
It looks weird having one jammed into the front of the amplifier though.   I haven't yet researched what brands or models of the 6SN7 are desirable.  I paid 5 bucks for this pair.  Both are made by GE (one was made by GE for HP.)  So they look identical and sound identical to my ears.  
 
Does anyone have the pinout so I can figure out why the nicer looking one is broken?
 
By the way, this is the one that doesn't work:
 

 
 
It's got a nice ceramic top with gold plated pins and sockets.
 
Meanwhile, this one works fine
 

 
 
It looks to be of lesser quality, but it works... It also costs less on ebay.     I'm trying to figure out how to take the white one apart, but I think it's expoxied together. 
 
And since I'm bored, I figured out the pinout combos of both adapters.  The 'nicer' looking one has two mixed up connections:
 

 

[BmWr75]

I've got one like the one you have that doesn't work.  Mine works fine.