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

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Yup I agree that the 6F8G is definitely more microphonic than my other tubes, however this is much different from the common tube quirks. This is like a really loud 150Hz buzz being played at 80% volume. The first time it happened I thought something had shorted within the amp and was genuinely concerned I had damaged my headphones (and ears) lol. Only happens with the RCA 6F8G with the volume knob is turned down fully, and as soon as I turn it up a little bit the noise is radio silent and music quietly starts to come through.

Will try cleaning the pins again with some isopropyl alcohol, only gave them a quick brushdown when I first got the tube but that could definitely be the problem. FWIW, I did replace the volume pot with a stepped attenuator from eBay, but didn't think it'd be the problem since I don't experience the same thing with the other tubes.

Edit: Very interesting development, cleaning the leads didn't help remove the problem, but now noticed that it only happens with my 1/4" to XLR adapter made from the original HD800 cable. I reterminated both my HD6XX and HD800 by adding XLR males and females to the cables. I get the buzzing sound to play through both headphones using the HD800 1/4" to XLR adapter but not with the one I made from the HD6XX cable. Will double check my soldering job, but really weird that this problem only happens with this tube and adapter.
 
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post-15083744
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cddc

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from what i read one more thing you can check is the grounding problem, which can also lead to static.

if you are using a power cord extension, make sure it is grounded. you can try to plug directly into a power outlet instead of using extension or change to another power outlet which you think would possibly have better grounding, and see if the static would go away.
 
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cddc

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from your new development i would now guess it's the joint problem or grounding problem.

check grounding first, since it's easier.
 
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bagwell359

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I can partially comment here, hopefully others will chime in as well (also, I'm by no means an expert so take with a grain of salt).
Those caps should be relatively easy to swap out, assuming you have some soldering experience.
I would not recommend having the caps suspend there, as it would put mechanical stress on the leads and thats probably a bad thing in the long run.
I used the Auricap XO in mine and put a piece of double-sided tape mount them to the chassis. You could also use a wire routing hook with zip ties.

In terms of size, there is a minimum capacitance needed in a given circuit to avoid frequency roll off. I'm not sure what that is in the Mainline. Personally, I would probably use the stock value or slightly higher.

Regarding the cap type, I'm personally in constant question on this topic. On the one hand, there are alot of boutique ($$$) caps that are highly rated subjectively, but on the other hand most people with actual engineering experience brush it all off and say its snake oil. I also think that the differences people mention between caps is pretty exaggerated.
As long as the materials and technology are the same (i.e, metallized polypropylene, film and foil, paper in oil), the differences are probably going to be subtle.
Resistors don't make any real difference. Transistors and caps do for sure. Transistors for instance in a 25 year old tuner when there have been newer versions brought to market. Caps. Firstly every power input cap should have a high pass filter. In non critical areas of the circuit, if the unit is over 20 years consider replacement to avoid leaking at about 27+, but don't spend big. However in the audio paths, if you can fit something bigger and better do it. If you don't understand the circuit, pause until you do.

In speakers it inductors and caps.
 
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post-15109246
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itsikhefez

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Resistors don't make any real difference. Transistors and caps do for sure. Transistors for instance in a 25 year old tuner when there have been newer versions brought to market. Caps. Firstly every power input cap should have a high pass filter. In non critical areas of the circuit, if the unit is over 20 years consider replacement to avoid leaking at about 27+, but don't spend big. However in the audio paths, if you can fit something bigger and better do it. If you don't understand the circuit, pause until you do.

In speakers it inductors and caps.
I'm not sure why you quoted my post but I didn't write anything about resistors.
 
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bagwell359

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I'm not sure why you quoted my post but I didn't write anything about resistors.
That's the way the site grabbed the text, sorry for any confusion.
 
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bagwell359

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Well, for low-impedance headphones, Mainline is the only option between the two, but for 300 ohm + headphones such as the Sennheisers, I think that Crack just stands on it's own in terms of good interesting OTL sound. Please don't think OTL means inferior sound. I had thought that, and it isn't the case, it's just isn't compatable with lots of headphones due to the high output impedance.

I think Crack was the first tube amp I felt worthwhile being a tube amp as it's so engaging with the Sennheiser HD6 series. Mainline just isn't the same experience.

If you get a chance, give it a listen. There's a reason why Crack is so famous. It's a fast sounding with good imaging for HD6 series Sennheisers.

If you are going for a budget tube, I'd recommend Crack as the best introduction.
I agree with SilverEars - and I had access to both of his BH's. The only advantage of the mainline is that it could drive my HEX v2 (very nice under 500 Hz), but my HD-600 sounded clearly better on the Crack than the mainline.
 
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SilverEars

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I agree with SilverEars - and I had access to both of his BH's. The only advantage of the mainline is that it could drive my HEX v2 (very nice under 500 Hz), but my HD-600 sounded clearly better on the Crack than the mainline.
Yeah, I think the so called 'improved' technicalities are questionable, and the main real improment is compatability with wide range of headphones. But, there is also SEX as well, which sounds closer to Crack which is compatable with other headphones like Mainline, and with much greater output power output, and both Crack and SEX are significantly lower priced.
 
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SmashBruh

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I agree with SilverEars - and I had access to both of his BH's. The only advantage of the mainline is that it could drive my HEX v2 (very nice under 500 Hz), but my HD-600 sounded clearly better on the Crack than the mainline.
Are you guys sure it's not the HD600 bottlenecking the mainline? That set definitely has some great synergy with the Crack, but to say that the BHC+S is on the same level as the mainline seems a little silly if you're only using a mid-fi headphone to compare them...
 
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bagwell359

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Are you guys sure it's not the HD600 bottlenecking the mainline? That set definitely has some great synergy with the Crack, but to say that the BHC+S is on the same level as the mainline seems a little silly if you're only using a mid-fi headphone to compare them...
HD-600 might be mid-fi in terms of price but it is remarkable in terms of capturing instrument timbre. In particular it handles piano from top to bottom that I haven't heard any can under $1k do.

Also a number of posters have noted the affinity of the crack with the 600.

I have a Ragnarok 1 that gets less out of the 600 than the crack
 
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SmashBruh

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HD-600 might be mid-fi in terms of price but it is remarkable in terms of capturing instrument timbre. In particular it handles piano from top to bottom that I haven't heard any can under $1k do.

Also a number of posters have noted the affinity of the crack with the 600.

I have a Ragnarok 1 that gets less out of the 600 than the crack
Like I said, the HD600 is a FANTASTIC headphone. It and the HD650 can't be beat in terms of price vs performance however it's technicalities aren't up to snuff when compared with say the ZMF Auteur/Verite or the Focal Clear/Utopia all of which play fantastically on the Mainline. That said; the wonderful synergy between the BHC+S and the HD600/650 really can't be overstated!
 
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ohcrapgorillas

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I put in an order for the Eros 2 while the discount was still going on. Good timing, I got three paychecks this month instead of two. I'll be upgrading from a Hagerman Bugle2 which was no slouch and is very transparent, but I love tubes too much for my endgame phono pre to be solid state and powered by a switcher. Table is a Rega 3 but once Schiit works out the kinks in their Sol table, I'm selling it and upgrading. I've also built a Bottlehead Crack and modded the hell out of the thing, and I love it. Super excited to get the kit and have my second piece of Bottlehead gear. Definitely getting some Teflon caps for the Eros, but will listen to it stock first. Also going to be anodizing the top plate black, if anyone has suggestions on how to do that as cheaply as possible,l me know.
 
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adydula

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The HD 600's are bottlenecking the Crack IMO....

I have a crack and a mainline...and use other high end cans and the 600's with the crack is just great and I think its better with the crack than the mainline!!
:>)

or my brain tells me this is the sound I prefer (at least for today!)..

That said I just got a set of Focal Clears and they are fantasic on the mainline...and just a bit better than the crack with the 600s....

Alex
 
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JamieMcC

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I put in an order for the Eros 2 while the discount was still going on. Good timing, I got three paychecks this month instead of two. I'll be upgrading from a Hagerman Bugle2 which was no slouch and is very transparent, but I love tubes too much for my endgame phono pre to be solid state and powered by a switcher. Table is a Rega 3 but once Schiit works out the kinks in their Sol table, I'm selling it and upgrading. I've also built a Bottlehead Crack and modded the hell out of the thing, and I love it. Super excited to get the kit and have my second piece of Bottlehead gear. Definitely getting some Teflon caps for the Eros, but will listen to it stock first. Also going to be anodizing the top plate black, if anyone has suggestions on how to do that as cheaply as possible,l me know.
Congrats on the Eros its a super bit of kit.

Take your time and enjoy the build.
 
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tvr2500m

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Quick request for comment. Right now Bottlehead is having a sale on just about everything. I made a deep commitment to high impedance headphones by buying and building a Crack. The whole experience has been great fun. I bought another Crack during another sale to play with with selected mods/upgrades. Haven't built this one quite yet. I just finally got all the parts in, so that will likely happen soon.

As a related aside, not being able to set up a proper two-channel audio thing, I've now deep-dived into the headphone world. It's been fun. I still have a perfect pair of Sennheiser HD-580 Precision headphones I bought a long while ago. Never liked them; too treacly. But today probing further the reputation of this headphone family, I picked up a set of Drop x Senn HD-6XX (as has everyone else). Okay, nice enough. Pleasant. This probing took the turn towards pairing them with tubes. Fun! Not perfect (whatever that might even mean), but as a whole the experience has been just nifty. The sound. The approach. The ethos. It all comes together nicely. I'm on board.

Which leads me to...

I would like to explore Bottlehead gear with my other headphones - Focal Elex, Hifiman Edition XX and HE-400i. I'm not keen on the jump all the way to the Mainline. Over the last several years, I've been trying to simplify (getting away from the days of large speakers, monoblock tube amplifiers, multi-part digital rigs, etc.) and de-cost (really good audio today is more affordable than ever). SO, I'm thinking about a SEX as the solution to get some very good tubed amplification that can be used across a broad range of headphones. I've read the reviews. They point to that SEX could a nice solution.

What say you?

Thanks!
 
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