Second hand Bottlehead Crack seems too quite

[raymondp1138]

I will try to replicate Raymond's setup and see if I'm in the same ballpark.

I'll also check out those brown dale resistors, and maybe take a better picture of them. Great catch Caucasian Blackplate!

Oh, I forgot to mention something important if you want to compare to my sound level measurement. I did add the volume pot padding described in #3 of the Crack FAQ - https://bottlehead.com/smf/index.php?topic=4295.0 My measurement would be higher without this mod.

-Raymond

 

[Doc B]

How consistent is that meter reading? Does it change a lot if the headphones or meter move a little?

 

[RavenTooth]

Raymond, it was a little awkward because my only sound level meter is on my iPhone, so I had to use it as the source of the pink noise and also to measure the dDs, but I got a pretty consistent reading of about 87 dBs. Moving the phone around a little doesn’t really change the volume registered by a ton. So now I’m feeling more like my Crack is probably fine, or at least close.

The brown resisters say 1451, RN70E, 2202F on them.

 

[Paul Birkeland]

Do you happen to have a meter so you can take some voltage measurements?

 

[raymondp1138]

How consistent is that meter reading? Does it change a lot if the headphones or meter move a little?

So I took measurements again, this time varying the mic's position, but always keeping it within the space between the earcups. I then tried with the headphones and meter off the table surface. The variation I get is around +/- 1db.

-Raymond

 

[Doc B]

Good work. That helps to understand how well the measurement can be reproduced. Headphones are tricky to measure.

 

[RavenTooth]

Do you happen to have a meter so you can take some voltage measurements?

Yes I have a multimeter, altho I am no expert in using it as I didn’t build this kit. But I’m sure I can figure it out. I’ve used it to measure resistance on guitar pickups.

 

[Paul Birkeland]

I would start by measuring the DC voltages, which can be found in the manual.

 

[Deluk]

Having bought his Crack third hand RT may not have a manual. A flit through some previous problem posts should bring up some lists which give the correct voltages. Perhaps someone can point one out. Likely that a manual to fit the Speedball will also be needed at some point, maybe for the MK I 3 board version.

 

[RavenTooth]

FYI, I do have the manuals.

How do I fogure out the value of these non-standard Brown Dale resistors? I listed out the numbers printed on them in a previous post.

Or I guess just measure the voltage and see if it’s the same as what the manual states.

 

[fullheadofnothing]

When you do the resistance checks, you will know if you have wrong resistors...

 

[Paul Birkeland]

They are the correct resistance.  If they weren't, the voltages would be way, way off.