[cats4cans]

Crickey, I have had my Bottlehead Crack since October ‘22 and realise I have not put up a couple of pictures. And reading some recent post's here I think the hd800s goes very well with it. I have a TOTL headphone amp too, and quite surprisingly I often reach for the Sennhieser’s with the Crack!

What are the upgrades? Very good use of space.
I'm too timid to build my own, but I tell myself I'm just in the planning stages.
The thing that surprises me is how few people modify the case. It looks like there would be plenty of room to move the volume control and headphone jack to the front instead of the top. I suppose building a custom case or altering the layout would lessen the initial simplicity, but could really open up upgrade choices with additional room.

 

[JTbbb]

Beautiful build! What kind of wood is your case?

And I completely agree - even though I have "higher end" amps now, the BHC is always an absolute treat to come back to. Mine will forever be a permanent resident on the rack.

It is Zebrano wood. Gorgeous to look at!

 

[JTbbb]

What are the upgrades? Very good use of space.
I'm too timid to build my own, but I tell myself I'm just in the planning stages.
The thing that surprises me is how few people modify the case. It looks like there would be plenty of room to move the volume control and headphone jack to the front instead of the top. I suppose building a custom case or altering the layout would lessen the initial simplicity, but could really open up upgrade choices with additional room.

I did not build this! Here is a breakdown of the parts used.

 

[Cowwe]

Hello everyone. While trying to solve an issue with my kit, I decided to replace the stock potentiometer with an Alps Blue Velvet. I got a pcb with it since I've seen people suggest it, but I'm unsure how to go about wiring it (and placing it in the pcb). If someone here has one or knows how to wire this, could you please help me out?

 

[Galapac]

Start here : https://forum.bottlehead.com/index.php?topic=13357.msg121943#msg121943 and https://forum.bottlehead.com/index.php?topic=10866.msg99440#msg99440
Also, you may have to shave a bit of the board off on the wood side to make it fit, i used a dremel to cut the board with ease.
The Alps knob may extend a bit higher as well so may want to cut it with a hacksaw or pipe cutter if you have one but not too much, maybe 1/4 inch.

 

[Cowwe]

Start here : https://forum.bottlehead.com/index.php?topic=13357.msg121943#msg121943 and https://forum.bottlehead.com/index.php?topic=10866.msg99440#msg99440
Also, you may have to shave a bit of the board off on the wood side to make it fit, i used a dremel to cut the board with ease.
The Alps knob may extend a bit higher as well so may want to cut it with a hacksaw or pipe cutter if you have one but not too much, maybe 1/4 inch.

I had seen that thread before, but to be honest I'm still not sure I understand everything.
From what I understand, the purple dots is where the pot needs to sit (on this side). Is this correct?
When it comes to the output wiring I think I understand it, but the input confuses me. What should I wire to the two ground terminals?
Please let me know if what I wrote in the picture is wrong.

 

[Beefy]

When it comes to the output wiring I think I understand it, but the input confuses me. What should I wire to the two ground terminals?
Please let me know if what I wrote in the picture is wrong.

Well, you wire the input to the input. Signal and ground from the left/white RCA goes to Lin and Gnd. Signal and ground from the right/red RCA goes to Rin and Gnd.

From distant memory, the Crack suggests tying grounds at the RCA...? If so, you could just run a single ground and connect it to either Gnd.

 

[Cowwe]

Well, you wire the input to the input. Signal and ground from the left/white RCA goes to Lin and Gnd. Signal and ground from the right/red RCA goes to Rin and Gnd.

From distant memory, the Crack suggests tying grounds at the RCA...? If so, you could just run a single ground and connect it to either Gnd.

Yeah, for input wires I only have left source, right source and one single ground coming from the RCA's, which confused me. I will just go ahead and connect the ground to one of the two Gnd.
I hope I have placed the grounds on the output side correctly.

 

[Galapac]

Yes there are 2 grounds but they both wire to the same point on the PCB, you only need to use one, your pick.
This board is made for multiple types of pots.

 

[Cowwe]

Thank you for the help. I got the new pot up and running smoothly, even though unfortunately that didn't fix my kit's issue.

 

[Hypops]

Thank you for the help. I got the new pot up and running smoothly, even though unfortunately that didn't fix my kit's issue.

Have you tried the Bottlehead forum? Those folks are super helpful and responsive

 

[Cowwe]

Have you tried the Bottlehead forum? Those folks are super helpful and responsive

Yeah, I have a 5 page long thread open since last October, and I have yet to find a solution. Even though it should be an easy amp to trouble-shoot, I have run out of ideas of things to try, other than replacing every single component in the path...

 

[Cowwe]

In the chance that, hopefully, someone might have an idea of what I could try, I'm going to explain my issue and what I have tried in the past months.
My kit had been working perfectly fine for a couple of months, until suddenly it started having a noise issue on the right channel that with time became worse.
-The issue: it's a crackling/static noise that appears exclusively in the right channel, about 10 seconds after I power on my kit. It varies in intensity seemingly randomly, at times it's louder and at times it's quieter. Here's a recording of it. The noise appears with and without a source connected to the amp (simply plugging it into a wall outlet and plugging in headphones is enough). Changing the volume with the potentiometer does not affect it in any way. RCA's being connected or not doesn't matter.
-What I have tried: I extensively chopstick tested to find any weak connection in my solder joints, and reflowed every single joint in the amplifier. I have switched around many tubes that I know worked perfectly. I have replaced the potentiometer. I have replaced the octagonal tube socket with one that makes better contact. I made sure each tube I try has clin pins and a good contact. I have added the reccommended modification with two diodes at the ground tab (it got rid of noises coming from my noisy pc). I have tried different headphones and cables. Different power cords and wall outlets. I have moved to different places of my house and different houses altogether to get rid of possible radio/wifi signals (I even tried placing my amp inside a microwave).
-The most bizzarre part: I have brought my kit to two different repairman places, on two different occasions. In both cases my amp worked flawlessly at their place (in one of the two occasions I have listened to it with my own ears and there was no noise). Upon taking my amp back home, the noise appears again.
That is when, as I said previously, I tried every wall outlet in my house, made sure there was no signal interference and brought my kit at about 4 different places to test. The noise was always there. I have made sure that my houses grounding works fine, and that I wired my transformer for 245V, which is what I read from my outlets.
As of now I am at a complete loss. I can't for the life of me figure out what could be possibly causing this, and why the issue disappears whenever I bring my kit to a professional.
If you have any thoughts or ideas about what I could do, please tell me. I just want to listen to my amp again

 

[Beefy]

First things first.... You should never have phones connected in the first 10 seconds of powering on the amp. When the output tube starts conducting, there is a big DC offset until the output caps charge, and this is very bad for your phones.

So, stop doing that.

Does this noise continue at any other time? Your post isn't clear on that.

Anyway, I'd say check the output caps. Maybe DC is sneaking through.

 

[Cowwe]

First things first.... You should never have phones connected in the first 10 seconds of powering on the amp. When the output tube starts conducting, there is a big DC offset until the output caps charge, and this is very bad for your phones.

So, stop doing that.

Does this noise show up at any other time?

I had looked into that and found contrasting opinions, but I'll stop doing that. Thanks for the advice.
The noise is constant. The only moment it leaves is when I turn the amp off.