Bottlehead Crack

Check out the first page of this thread. OJ posted links to reviews of tubes.

 

Poking around eBay and I found a decently priced one. It looks used. Is there a guide for buying used tubes? Looks like it has some scuff marks on it but nothing to bad.

Listing here.

 

You also have to worry about microphonics. If it doesn't say, the chance that it was tested for microphonics is slim.

 

So I was checking out some other tubes and I see a lot of them labeled "Strong" or "NOS". Is this an indicator that they are new or used? I also noticed that some are short or long plated and black or gray plated. Is there a real difference between these? Specifically the Telefunken 12AU7, it came in either ribbed or smooth. What are the differences between these?

 

I believe your wife or girlfriend is supposed to enjoy the ribbed version more.

 

Alas, I am a bachelor. Quality joke my friend.

 

NOS = New Old Stock = Old unused things.

Unless the subject is a DAC.
NOS DAC = Non Oversampling

 

So I got me some Chatham 6080 tubes; one 6080 and one 6080WA. All is great now! After reflowing joints, separating wires, caps, and resistors, changing the RCA to pot wires to shielded wire, swapping the stock pot with an Alps blue velvet ($11 from eBay!), and changed tubes, I think my crack finally has a respectable noise floor! Oh, I also got a nice Machined Solid Aluminum volume knob from Amazon.

 

Glad to hear it is working well for you now! JAN Chatham 6080's are nice tubes. I have a pair that I picked up back when they were still $5/ea. and still often use them despite having many of the other highly recommended options (GEC 6as7g, various 5998's and a rare 7802), on hand.

 

I just finished my first BHC build, but it looks like I have some weird resistances popping up.

Any ideas on what to check for first?

Here are some pics: http://imgur.com/a/tpOml
Below are my measurements:
Terminal Target Measure
1 * Starts at 20Mohm and slowly decreases
2 * Starts at 20Mohm and slowly decreases
3 0 0
4 * Starts at 10MOhm and slowly decreases
5 * Starts at 8MOhm and slowly decreases
6 2.4KOhm 2.49KOhm
7 2.9KOhm 37MOhm and slowly climbs
8 0 35MOhm and slowly decreases
9 2.9KOhm 37MOhm and slowly climbs
10 2.4KOhm 2.49 Kohm
12 0 0
13 * climb towards 270KOhm 6MOhm and decreasing
14 0 0
20 0 0
22 0 0
B3 2.9KOhm 35MOhm
B6 2.9KOhm 35MOhm
RCA ground red 0 0
RCA center pin red 90-100KOhm 110.1KOhm
RCA center pin black 90-100KOhm 38MOhm
RCA ground black 0 0


EDIT:
Nevermind, it turned out to be a bad solder joint at terminal 13. Once I fixed that, everything else downstream measured correctly. Voltage checks went well too and it finally works! It sounds awesome

 

I have a pair of 5 star GE 5814A (5 star is the military version). I haven't heard much tube combos but I compared it with a rare 12AU7 telefunken blackshield and the 5 star had more clarity in the treble, while the blackshield had a fuller mid range, it was on par with it in sound quality so it is a good value tube for the price. I can sell you one of my 5 star 5814A if you send me a pm, it has very low hours on them, since I only tested it on my Torpedo III and ended up using a different pair of tubes instead, but it does sound amazing in my crackatwoa.

 

Last year, I was interested in a Bottlehead Crack w/ Speedball to use with my HD650. I was wondering about how I would do building one and how much time I might have to spend. Also reading about all of the mods, tube rolling, tools that I would need and wondering how much money I might end up spending.

I decided to take a look on ebay and saw one that really interested me. This is from the listing:
TKD volume control
Furtech RCA jacks
Cardas Quad Eutectic solder
Built by HiFiBuilder Guy (a small business made up of former Bottlehead employees who work with Bottlehead to build Bottlehead products for customers).
Custom bamboo enclosure by Blumstein Audio
The amplifier comes with the stock tubes from Bottlehead.

It ended up costing about what the parts would have cost. The seller packed the amp in a manner that was really impressive. I think that one could have dropped the box (hard) and not have done any damage. I feel that I really lucked out.









I admire you guys that build and mod these. I always enjoy reading about people doing this and looking at pics of the different builds. (Maybe I will feel inspired to build and mod one myself someday.)

I have been thoroughly enjoying listening to my stock version. (That TKD volume control tracks great, btw.)

 

Man, those Blumenstein bases are so choice. Congrats on the acquisition.

 

Yep.. that Bamboo looks incredible.

 

So I sold my crack and bought the T3, wow the T3 sure does impress. But after a while I started to miss the sound of my old crack, so I went full circle and bought the Crackatwoa from TMoney.

Going to be trying to max out the sound quality from it. Having the T3 as a reference is great, making the Crack2 sound more dynamic and clean like the T3 while preserving the musically of the Crack2 is my goal. I think it's worth while because I think Crackatwoa's mids are magical, amazing and seductive blah blah. I prefer the mids from my Crackatwoa over my T3. Just only if Crackatwoa treble wasn't so veiled and if the bass wasn't so bloomy, transients could be faster. Well hopefully some the mods I have waiting for it below will address some of those issues.

I ordered a 7802 Tung-Sol output tube.
It has High Transconductance, according to my calculations it should drop the output impedance from 120 down to ~42ohms. Making the Crackatwoa more suitable for medium impedance headphones and tightening up the sound for high impedance headphones. Really I have high hopes for this tube because lower output impedance should help with the bloom for the bass and also improving transients and dynamics as well.

Also ordered 2x 47uf Obbligato Premium Gold Caps for output coupling cap replacement.
I hope these caps will bring out the treble more it feels veiled to me. The values are lower than stock 100uf but it shouldn't be a problem with high impedance headphones.

I want the Twoquiet stepped atteunator but it's so damn expensive at $269. It's more expensive than a Crack on sale. Probably going to wait until they do a sale.

 

My 7802 Tung-Sol tube came in today and it sounds very good. I wish I have a 5998 to compare it with. This tube has the lowest output impedance that can be rolled into the crack/atwoa, transconductance is at 20,000 (6080 is at 7,000 and 5998 is at 14,000).

Tight bass and crisp clear treble and the mid's are musical and even better than the 6080. I am liking this tube it sounds much better than the 6080 that I had in it.

 

Well... It only took me 9 hours to build this thing. Going slowly over each step and slowly learning how to correctly solder and attach all these little shits into the little holes. I managed this quite well after the first 10 attempts. I made one mistake crossing a cable into the wrong terminal between capacitors and that made the entire thing not work, who would have thought! After correcting it, everything just worked. I was so ecstatic that I threw together my laptop and Modi 2 and listen to "Money" by Pink Floyd and "Lose Yourself to Dance" by Daft Punk. I fell in love immediately with the tube sound. I can just feel the punchier bass and the smooth almost gooey mids. I can't wait for Home Depot to open in 7 hours to get my finish for the wood and put it together so I can pair it with my Bifrost Multibit and pc. Here are some shoddy pictures of me building it and then my 2 electrical engineering friends going over my work. Having an extra pair of eyes and hands really helped with this project. I think the hardest part was actually screwing the giant power-brick thing in the top center to the actual chassis. Everything else was simply slowly working through it and understanding how it works. All in all, an amazing day and an amazing experience. I plan on using my upgraded tubes and the normal crack for a week or so then I am going to put the Speedball mod together.

Spoiler: Pictures