Bottlehead Amplifier Discussion / Comparison Thread: Crack, SEX & Mainline
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NightFlight

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Mine sounded pretty crappy for the first 40 hours. The first hour really had me, seriously questioning the amp. After about 10 hours I could hear serious progress.   Then at around 80 hours it really opened up and I stopped taking notes.  
 
I don't think that was just the caps, but rather the entire circuit was new. IMHO, everything breaks in because... well.. that's what my ears tell me. My best guess on that point would be the new lattice structure of the "solid" conductors adapt to current flow - like a river bed.  I could be completely out to lunch on that point and I'm only parroting what others have said to me. So take it with a grain of salt.
 
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post-13424396
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Doc B.

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Yup, it's not just the caps. The iron changes too. I haven't found a throughly convicing argument for exactly what happens during the break in period. But, having heard it so many times over the past 20 years, for me it's an indisputable effect. We just experienced it yesterday with some new crossover components installed in our prototype speaker kit.
 
Whatever it is, the not-yet-broken-in sound is similar to the compressed, strained sound that tube gear makes before the tubes warm up and show their full resolution capability. I have not heard a convincing argument of what causes that either. But I try not to listen to a system until 20 minutes after it has been turned on.
 
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deserat

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Thanks for the input @NightFlight  and @Doc B.  I was fortunate enough to have my first listen while plugging the mainline in-place of the Lyr 2,  it definitely sounded better than the Lyr, so I was spared then "this sounds like crap" experience - though I was a bit bummed when initially A/Bing it against the HDVA... It's now at 35+ hours ( I plugged in my beater headphones and let it run with white noise since last night ) and the sound has changed substantially.  Very much looking forward to what comes out the other side of the burn-in.
 
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Hunki Chunki

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1 week to get the wood ready :wink: And a nice long weekend to build and test.
 
Really do take your time to read everything twice before executing each step, troubleshooting is a pain. :)
 
Walnut finish and leather wrapped.
 

 
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Allanmarcus

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1 week to get the wood ready :wink: And a nice long weekend to build and test.

Really do take your time to read everything twice before executing each step, troubleshooting is a pain. :)

Walnut finish and leather wrapped.



Beautiful! How did you prepare the top plate?
 
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Doc B.

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Very nice!
 
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Allanmarcus

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​I glued on a thin piece of leather and trimmed the holes with an exacto knife .

AHHH! The top plate is covered with leather! I see. Aren't you concerned about heat?
 
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Hunki Chunki

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​I figured if we could paint it I could slap a thin piece of leather on it haha, the under side is still metal though so no harm trying :wink:
 
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NightFlight

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Nice but, I would keep an eye on the temps.  Especially if you decide to upgrade the output caps, as they are most susceptible to heat - depending on the type. 
 
Leather makes a fairly good insulator, or poor heat conductor.  http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html
 
It would really be hard to say how much the top plate will hold heat based on insulators applied to the surface. Easier to test than calculate I think. :)
 
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deserat

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Hey all. So I went to roll in the Electro Harmonix 6C45Pi tube I bought. It's the one used in the WooAudio WA 7. Which I was gathering was a direct replacement. Unfortunately once in the voltage mesurements on 25 and 30 were in the negative mili-volt range. The tubes innards look substantially different than the stock tube... so I'm wondering if I bought the wrong EH gold plates or if I missed a mod somewhere else in the amp. I would have gone ahead and attempted a bias but the breg and kreg mesurements were also near 0. Any suggestions or ideas?
 
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Loquah

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Hey all. So I went to roll in the Electro Harmonix 6C45Pi tube I bought. It's the one used in the WooAudio WA 7. Which I was gathering was a direct replacement. Unfortunately once in the voltage mesurements on 25 and 30 were in the negative mili-volt range. The tubes innards look substantially different than the stock tube... so I'm wondering if I bought the wrong EH gold plates or if I missed a mod somewhere else in the amp. I would have gone ahead and attempted a bias but the breg and kreg mesurements were also near 0. Any suggestions or ideas?
Hopefully they're ok because I've been using them for ages now. I do recall the bias needing to be redone (significantly), but everything has worked fine for ages in my setup with the EH tubes. Have you double checked the model numbers? From memory there's a 6S45 or something similar that's easy to confuse with 6C45. I'm on a train and unable to easily double check this right now, but will post more when I get home if I can shed more light...
 
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deserat

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Hopefully they're ok because I've been using them for ages now. I do recall the bias needing to be redone (significantly), but everything has worked fine for ages in my setup with the EH tubes. Have you double checked the model numbers? From memory there's a 6S45 or something similar that's easy to confuse with 6C45. I'm on a train and unable to easily double check this right now, but will post more when I get home if I can shed more light...
Thank you. Both the box and the tube is labeled 6C45Pi the tube has an additional EH but I just assumed that meant Elector-Harmonix. I'll try the other tube and see if adjusting the pots has any impact.
 
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deserat

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Put some Mundorf Supremes in tonight. They've been running for about an hour... not nearly long enough to say anything definitive... but a couple of things stood up pretty obviously after about 30 min of running though my normal test tracks. Dynamics are even better. particularly in the bass and mid bass, image position in the highs is more precise... perhaps tack sharp. Female vocals seem a little more recessed. Anyway from what I've read these caps are a very long way from being what they will become... so I'll shut up now and just enjoy their infancy.

Oh and the HDVA 600 has been sent packing. :)

Couple of hours in, I had to come back and say. The difference is not subtle, not sure I'm going to sleep tonight...
 
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rjb1101

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will be selling my BH Crack/Quickie set up on ebay if anyone is interested

How does the quickie affect/work with the crack? I'm not exactly sure what a preamp will do for me. I have yet to take the dive into this hobby and I don't have a ton of money, but I just bought the crack. I'm wondering if it's worth pairing it with the quickie.
 
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