Bottlehead Crack Headphone Amplifier Kit Review

[Pugsly]

Where is it? Include a link, please.

And I wonder, do you also challenge the "objectivist" engineers that design the planes that you fly in? I am guessing that your "Challenge" would have to include them if your approach to epistemology were consistent.

I'm pretty sure that the analogy with a plane does not hold water, and thus I can be epistemologically consistent After all, both a poorly measuring and well-measuring amplifier will produce music, while no amount of suggestion or salesmanship will convince anyone that their flight from Chicago to Heathrow was faster etc. due to their wearing a crystal necklace or specially placed wooden pucks - audio and auditory memory, as well as selective attention and our ability to genuinely 'hear new things' due to this, are real issues and effects that many people are not properly aware of (a fact which salespeople consistently take advantage of.)

In truth, note, I am approaching this question from the standpoint of an education and communication, not science. You can of course insist that the science is in, and that the only people who buy the subjectivist tweaker nonsense are deluded chumps. The reality from a communications standpoint, however, is that
(a) discerning the truth from lies in the field of audio, especially given the inherent problems of the echo-chambers of online audio forums, is difficult precisely for those who do not know the science, etc.so that it is easy for them to suffer from fear of missing out, become convinced that some of these magical effects are real, get pulled down the rabbit hole.
(b) objectivists such as Aczel and NwAvguy, for example, have both claimed that the same effects of tube amplifiers could be produced using dsp, and this has been repeated here and elsewhere without evidence, along with the claim that the same effect could be created using an eq - only to have interested parties who are curious about being able to try out the mythical 'tube sound' shrugged off, then given conflicting claims, including claims that this is not possible, etc. so there is a problem of disinformation here, as well
(c) the claim of some objectivists, at least, is that thorough enough measurements tell us all that there is to know (and by contrast, the claim of some subjectivists is that there are still some things that we currently cannot measure and that they are certain that they hear real differences between equally excellently measuring equipment.)
Now you can, of course, dismiss the subjectivists as deluded and just repeat 'abx' - but this ignores the fact that most people are not capable of properly implementing such a test - level matching and all - and at any rate will have a good deal of trouble attempting to get an audio boutique to allow them to make such a test, even if people were not stuck in quarantine!
I would hope that if this last year has taught us anything, it is that being right about the science is of limited value if one fails to communicate the message in a way that connects with the target audience...

 

[Strumbringer]

Bumping with a question:

I've had my BHC Speedball for several months and I'm using 300 Ohm headphones (ZMF) and I'm noting that while the bass extension is quite nice, the high end is lacking clarity, separation, and detail, compared to listening with the ADI-2 DAC. I read elsewhere this is because of the 100 uf output caps.

If I wanted more clarity, definition, and separation in the high frequencies and less "blurry" presentation, I believe I can upgrade to film caps of different values? I saw in post #30 of this thread that @milosz may have done this with good results. I also read elsewhere that film caps of higher value (from brands like Jantzen or Claritycap) are too large to fit in the traditional BHC housing and may need to be outside the chassis. My "hard rock" BHC is pictured below.

If anybody has upgraded their output caps (mine are blue 100 uf) to some other value and have noted improved clarity, detail, and separation in the high-end frequencies, please let me know what you've chosen. The more I listen, the more I'm preferring the RME ADI-2 DAC, however it does not have the same bass extension as the BHC.

 

[Killingbeans]

The more I listen, the more I'm preferring the RME ADI-2 DAC, however it does not have the same bass extension as the BHC.

Use the PEQ in the ADI-2?

 

[Strumbringer]

Use the PEQ in the ADI-2?

Oh yes, I'm absolutely using it. Despite that, when I do the quick A/B between the ADI-2 to the BHC, the latter still has a blurry presentation of the high frequencies. The separation and detail are less on the BHC vs. the ADI-2. I had read that the clarity and separation could improve with changing the output caps to film and different values. I can certainly tweak the bass on the ADI-2 a bit more and see what I come up with.

 

[SIY]

I had read that the clarity and separation could improve with changing the output caps to film and different values.

Yeah, there's all kinds of absolutely wrong stuff that has attained legend status, and the film coupling cap thing is a big one. They will have no effect on "clarity and separation" except imaginary ones. Now value may have an effect if the originals caps were too small. But 100uF means that for a typical 10k load, the corner frequency is about 0.16 Hz, which is two decades below the lowest audio frequency, so making it bigger gets you only more noise.

 

[Strumbringer]

Yeah, there's all kinds of absolutely wrong stuff that has attained legend status, and the film coupling cap thing is a big one. They will have no effect on "clarity and separation" except imaginary ones. Now value may have an effect if the originals caps were too small. But 100uF means that for a typical 10k load, the corner frequency is about 0.16 Hz, which is two decades below the lowest audio frequency, so making it bigger gets you only more noise.

OK- very good to know. In other words, leave my BHC as-is. I suppose that the somewhat blurry presentation of the high frequencies is just a natural artifact of this design and may be part of the "charm" with tube amps.

 

[Veri]

Bumping with a question:

I've had my BHC Speedball for several months and I'm using 300 Ohm headphones (ZMF) and I'm noting that while the bass extension is quite nice, the high end is lacking clarity, separation, and detail, compared to listening with the ADI-2 DAC. I read elsewhere this is because of the 100 uf output caps.

If I wanted more clarity, definition, and separation in the high frequencies and less "blurry" presentation, I believe I can upgrade to film caps of different values? I saw in post #30 of this thread that @milosz may have done this with good results. I also read elsewhere that film caps of higher value (from brands like Jantzen or Claritycap) are too large to fit in the traditional BHC housing and may need to be outside the chassis. My "hard rock" BHC is pictured below.

If anybody has upgraded their output caps (mine are blue 100 uf) to some other value and have noted improved clarity, detail, and separation in the high-end frequencies, please let me know what you've chosen. The more I listen, the more I'm preferring the RME ADI-2 DAC, however it does not have the same bass extension as the BHC.

That marble look is very pretty. Did you build this crack yourself or was it built to order?

 

[SIY]

OK- very good to know. In other words, leave my BHC as-is. I suppose that the somewhat blurry presentation of the high frequencies is just a natural artifact of this design and may be part of the "charm" with tube amps.

Highly possible. I don't have much experience with their gear, I'll take a look and see if a schematic is available and dig into it a bit.

 

[Strumbringer]

That marble look is very pretty. Did you build this crack yourself or was it built to order?

Thanks- I bought the BHC pre-built and it came with the standard wood housing. I took the housing to the granite counter shop near me and they made me the granite housing. I love the way it looks and functionally, it really dampens vibration, which is nice as the very old tubes are quite sensitive to vibration. With kids running around, this was important!

 

[Strumbringer]

Highly possible. I don't have much experience with their gear, I'll take a look and see if a schematic is available and dig into it a bit.

I believe the schemata was posted by Amir in post #7 of this very thread:

Bottlehead Crack Headphone Amplifier Kit Review

This is a review and detailed measurements of a (built) Bottlehead Crack Tube headphone amplifier. It was sold from one member to another and kindly sent to me in between for testing. The version I have has the "speed ball" current source which brings its cost up to US $430. The original...

www.audiosciencereview.com

 

[SIY]

I believe the schemata was posted by Amir in post #7 of this very thread:

Bottlehead Crack Headphone Amplifier Kit Review

This is a review and detailed measurements of a (built) Bottlehead Crack Tube headphone amplifier. It was sold from one member to another and kindly sent to me in between for testing. The version I have has the "speed ball" current source which brings its cost up to US $430. The original...

www.audiosciencereview.com

OK, I need to correct an error on my part: the load won't be 10k, that's my brain fart. So the corner frequency will be higher, and depending on the impedance of your phones, a larger value electrolytic cap might be beneficial.

 

[Strumbringer]

OK, I need to correct an error on my part: the load won't be 10k, that's my brain fart. So the corner frequency will be higher, and depending on the impedance of your phones, a larger value electrolytic cap might be beneficial.

OK, good to know! I'm running 300 Ohm ZMF headphones. I'll absolutely look forward to your thoughts (and anyone else in the know) about what value caps may be beneficial over the stock ones. Thanks in advance!

 

[SIY]

OK, good to know! I'm running 300 Ohm ZMF headphones. I'll absolutely look forward to your thoughts (and anyone else in the know) about what value caps may be beneficial over the stock ones. Thanks in advance!

Let's do a quick calculation:
For a 300 ohm load, the current 100u cap gives an f3 of about 5Hz. So double capacitance would get your f3 a decade below the lowest audio frequency. 330u and 470u are standard values and would likely work just fine.

But still, the limitation is likely to be that 6080 trying to drive a really low load. The input stage isn't great from a transparency POV, but the output stage is almost surely the limiting factor.

(edited to change load)

 

[Strumbringer]

Let's do a quick calculation:
For a 300 ohm load, the current 100u cap gives an f3 of about 5Hz. So double capacitance would get your f3 a decade below the lowest audio frequency. 330u and 470u are standard values and would likely work just fine.

But still, the limitation is likely to be that 6080 trying to drive a really low load. The input stage isn't great from a transparency POV, but the output stage is almost surely the limiting factor.

(edited to change load)

Thank you- So it sounds like like I could try a 330uf or 470uf film cap and try to hear any difference. However, perhaps the input stage (12au7) is a limitation. Others have suggested an adapter and trying a 6SN7 in its place. Perhaps that would have more of an impact on the clarity of treble frequencies more so than the changing of the output caps?

 

[Veri]

Thank you- So it sounds like like I could try a 330uf or 470uf film cap and try to hear any difference. However, perhaps the input stage (12au7) is a limitation. Others have suggested an adapter and trying a 6SN7 in its place. Perhaps that would have more of an impact on the clarity of treble frequencies more so than the changing of the output caps?

From my brief time with a BH Crack, using a 6SN7 adapter brings *more* haze and fuckery, the default tube family was more linear IIRC..

 

[Strumbringer]

OK, I'll stick with the 12au7!

 

[SIY]

90V on the plate of a 6SN7 is a disaster. Bad enough on a 12AU7.

Your limitation is using a 6080 cathode follower (and one with minimal feedback, that's a low mu tube) to drive a low load.

 

[Strumbringer]

Curious if this is a weakness in the design? I can use a 6as7g, but I believe that is a nearly identical spec tube.

 

[SIY]

Curious if this is a weakness in the design? I can use a 6as7g, but I believe that is a nearly identical spec tube.

The 6AS7 will be about the same. The issue is using a cathode follower there- the nearly vertical load line plus low mu (thus low feedback) sets a hard limit on performance. You can do a bit better with something like a White cathode follower, but just a bit, and that will be a massive enough rebuild that you might as well start from scratch.

The right way is, of course, expensive if you want a tube output, and that's an output transformer. A cheater way is to replace the cathode follower with a MOSFET source follower.

 

[milosz]

Yeah, there's all kinds of absolutely wrong stuff that has attained legend status, and the film coupling cap thing is a big one. They will have no effect on "clarity and separation" except imaginary ones. Now value may have an effect if the originals caps were too small. But 100uF means that for a typical 10k load, the corner frequency is about 0.16 Hz, which is two decades below the lowest audio frequency, so making it bigger gets you only more noise.

I did a blind A/B/X of Panasonic polarized electrolytics vs Dayton film caps as output coupling / DC blocking caps in my Crack/Speedball and all the listeners showed a statistically greater than chance ability to hear the difference. And the "preference" was 100% for the film caps. Just throwin' this out there.