Bottlehead Crack Headphone Amplifier Kit Review

[Jimbob54]

Bottlehead crack is the best crack a man can buy.

Ass crack

 

[Kyle / MrHeeHo]

This imo is definitive proof that there is no point in buying a tube amplifier other than the novelty factor. What people like is the high output impedance causing a few decibels bass boost which can easily be achieved at no extra cost through EQ

 

[PeteL]

This imo is definitive proof that there is no point in buying a tube amplifier other than the novelty factor. What people like is the high output impedance causing a few decibels bass boost which can easily be achieved at no extra cost through EQ

so testing one amplifier out of hundreds of design is a "definitive proof" that there is no point buying a tube amp? Notice the title of this website: audio SCIENCE review. In science, we don't prove characteristics of a population X by making a case study of a test sample of one unit.

 

[Thomas savage]

Ass crack

Iv enough for the both of us ..

 

[Racheski]

This imo is definitive proof that there is no point in buying a tube amplifier other than the novelty factor. What people like is the high output impedance causing a few decibels bass boost which can easily be achieved at no extra cost through EQ

This is a decade old DIY product that is far past its peak popularity. The generalizations that folks are making in this thread about all tube amps is excessive - seems like there is an underlying crusade against tube amps that is biasing people's opinions.

 

[DualTriode]

We are talking Crack and HD650 is it not. Not about (tube) amps in general...

Can you show the huge high-Q resonance (means a very narrow band) peak to exist and can you show, by for instance using CSD that bass becomes very flabby ?
Is 3 octaves really a high-Q resonance peak and 4dB in resistance huge ? Is +1.something dB going to make the bass sound really poor, especially when it is really wide band and only slightly increases 'warmth/body' ?

I did not hear any comments about flabby bass from Amir nor from the hundreds if not thousands of users owning a Crack + HD650 or HD600 or HD800 or Beyerdynamics.

Do note that I prefer to listen to the HD650 with the midbass lowered and do not prefer it increased. I have seen lots of people with great hearing abilities being silly enough to remove the foam behind the HD650 driver thereby lowering damping and increasing midbass even higher than the crack does and claiming the sound has become much better.

Yes the HD650 impedance peak is a big deal.

With the low output impedance of a Geshelli headphone amplifier the impedance peak is not nearly so pronounced in its’ effect.

With a high output impedance tube amplifier the loose bass effect is much more pronounced. It is even very much measurable. Many people may even have a strong preference. That is what I call Confirmation Bias.

We are in the brave new frontier of headphone measurement and standardization. As with loudspeakers the closer we get to a standard measurement curve the more the headphones and amplifiers will sound the same.



Thanks DT

https://www.headphonesty.com/2020/04/harman-target-curves-part-3/

https://en.wikipedia.org/wiki/Confirmation_bias

 

[Mad_Economist]

Cool, so what actual conclusions are we gonna draw from that specific graph that Amir posted re this particular amplifier?

I'll copy & paste it up here again for reference as it was a few pages back now:
View attachment 81019

In practice, not a whole tonne from that plot, beyond "this device is very nonlinear at many frequencies". In general, FFTs of distortion products aren't a terribly great proxy for audibility at the best of times. Various methodologies for attempting to project subjective audibility under real usage exist - from the mathematically elegant GedLee methodology, to Steve Temme's psychoacoustic weighting, and I'm fairly sure that Alex Voishvillo proposed a methodology based on multitone nonlinearities - with reasonable support, but there's a reason that my go-to commentary when it comes to device nonlinearity is that it's more of a pass-fail criteria than anything; amplifiers in clipping and transducers with high-order nonlinearities will pretty much always sound terrible. Outside of that, there's quite a large range of cases where audibility with music will be surprisingly low...but you'd probably rather that the nonlinear products be extra low, just to be safe, you know¹?

¹ : wherein "extra low" is, like, -60dB vs. signal level. I'm a man of simple tastes.

 

[Mad_Economist]

Can you show the huge high-Q resonance (means a very narrow band) peak to exist and can you show, by for instance using CSD that bass becomes very flabby ?
Is 3 octaves really a high-Q resonance peak and 4dB in resistance huge ? Is +1.something dB going to make the bass sound really poor, especially when it is really wide band and only slightly increases 'warmth/body' ?

Although CSDs aren't the most stable paradigm of analysis for headphones - you are really basically measuring noise by hook or by crook, when you see differences, in most cases - a hypothetical CSD of a HD600 fed from high source Z would show a longer decay to a given level at 100hz relative to 1khz vs. a voltage source. This would be because the level at 100hz would be raised. Electrical damping is kind of a meme.

 

[solderdude]

This would be because the level at 100hz would be raised. Electrical damping is kind of a meme.

Exactly.

CSD, just like any other measurements have their worth here and there and you can spot certain issues with it. Ringing from Hi-Q resonances for instance which do not even have to clearly show up in the FR like on the plot below (6kHz in this case).

wherein "extra low" is, like, -60dB vs. signal level. I'm a man of simple tastes.

You are even more lenient than me.. I like to keep it below -70dB to be 'sure'.

 

[Mad_Economist]

Yes the HD650 impedance peak is a big deal.

With the low output impedance of a Geshelli headphone amplifier the impedance peak is not nearly so pronounced in its’ effect.

With a high output impedance tube amplifier the loose bass effect is much more pronounced. It is even very much measurable. Many people may even have a strong preference. That is what I call Confirmation Bias.

We are in the brave new frontier of headphone measurement and standardization. As with loudspeakers the closer we get to a standard measurement curve the more the headphones and amplifiers will sound the same.



Thanks DT

https://www.headphonesty.com/2020/04/harman-target-curves-part-3/

https://en.wikipedia.org/wiki/Confirmation_bias

It's really worth noting here that, while the Harman work generally affirms what we know regarding the relative uniformity of preferred response (I have severe gripes with describing it as a new frontier - if anything, it's a wonderful extension of the body of work on headphone response from Toole 1984 to present), Olive, Welti, & Khonsaripour 2019 specifically found a subset of listeners, consisting of 15% of their test population, who preferred radically higher output at low frequencies, including, particularly, the area between 100 and 200hz, vs. the Harman target.

 

[Mad_Economist]

Exactly.

CSD, just like any other measurements have their worth here and there and you can spot certain issues with it. Ringing from Hi-Q resonances for instance which do not even have to clearly show up in the FR like on the plot below (6kHz in this case).

You are even more lenient than me.. I like to keep it below -70dB to be 'sure'.

I traded my leniency with metrology for an extra helping of leniency on nonlinearities. On that note, while I'm afraid I can't volunteer to do the measurements at the moment, I'll note that I've yet to see a time domain behavior of headphones which was invisible in sufficiently high resolution frequency response plots, and I consider the general reliability of CSDs sufficiently poor in this case to be not overly fond of them as a tool of headphone analyss.

 

[NDRQ]

"I started testing with the Sennheiser HD-650 and the result was unexpected: almost infinite amount of power with warmer/nicer amount of bass "

That 30mW really far from almost infinite. That headphone needs at least 100mW if u want to enjoy music with good dynamic range. And also that distortion level is clearly audible.

What happened to objectivity?

 

[solderdude]

"I started testing with the Sennheiser HD-650 and the result was unexpected: almost infinite amount of power with warmer/nicer amount of bass "

That 30mW really far from almost infinite, what happened to objectivity?

Except it can go much louder than 30mW and can reach just over 200mW, just 4dB short of its continuous power rating, which means impressively loud with the feel of an infinite amount of power (120dB SPL peaks).
The high output impedance adds the warmer/nicer amount of bass.
I think Amir's findings are correct and mirror mine, albeit with other tube amps and somewhat lower output R.

 

[NDRQ]

And also how is good if stg adding extra bass to the already elevated bass?
Maybe next time we will say that Beats are high end headphones because the bass even more boosted?

 

[Mad_Economist]

"I started testing with the Sennheiser HD-650 and the result was unexpected: almost infinite amount of power with warmer/nicer amount of bass "

That 30mW really far from almost infinite. That headphone needs at least 100mW if u want to enjoy music with good dynamic range. And also that distortion level is clearly audible.

What happened to objectivity?

30mW would drive the HD600 to 111dBSPL (at 1khz, but the response is linear enough that you could caveat that as "in the midrange" if you prefer). 100mW would be 117dBSPL...

 

[NDRQ]

With good quality high dynamic range music, sometimes you need more than that 110dB.
Also at 110dB, that level of distortion is clearly audible and louder than the fine, quiet parts, so pretty much useless to use the amp at that level.

In my opinion this is a really bad product.
Maybe good for closet bassheads, but in that case better to face reality and choose a more suitable headphone.

 

[solderdude]

And also how is good if stg adding extra bass to the already elevated bass?
Maybe next time we will say that Beats are high end headphones because the bass even more boosted?

We are talking about a 1dB boost in the mid-lows. This is very, very far removed from thunderous bass, just slightly more warmth.
Grab your equalizer, EQ the difference in and switch between them. You'll hear how small the difference is. Far more educational than anything else.

 

[NDRQ]

We are talking about a 1dB boost in the mid-lows. This is very, very far removed from thunderous bass, just slightly more warmth.
Grab your equalizer, EQ the difference in and switch between them. You'll hear how small the difference is. Far more educational than anything else.

The only problem, that the bass already elevated so really dont need any more boost. Ofc not that much difference compared to the original frequency response, but compared to the neutral response, its much bigger difference. Little boost+little boost stacked together are not small boost anymore.

 

[solderdude]

In my opinion this is a really bad product.

From a technical POV ... yes. I think no one here disagrees with that.

For those that want to DIY and play with tubes a bit and get a feel of changed and 'tubey sound' the product is kind of expensive but educational.
Like the ACA it is surprising to find out how crappy our hearing is with a lot of music.

The only problem, that the bass already elevated so really dont need any more boost. Ofc not that much difference compared to the original frequency response, but compared to the neutral response, its much bigger difference. Little boost+little boost stacked together are not small boost anymore.

Oh I agree, the midbass boost of the HD650 is already about 3dB too much, at least to me. Adding 1 more dB (so +4dB) is just going to make it a little warmer/bassier... just a tad. Some will like that some won't. It won't out someone as a closet basshead.. you need quite a bit of more lower bass for that.

 

[NDRQ]

From a technical POV ... yes. I think no one here disagrees with that.

For those that want to DIY and play with tubes a bit and get a feel of changed and 'tubey sound' the product is kind of expensive but educational.
Like the ACA it is surprising to find out how crappy our hearing is with a lot of music.



Oh I agree, the midbass boost of the HD650 is already about 3dB too much, at least to me. Adding 1 more dB (so +4dB) is just going to make it a little warmer/bassier... just a tad. Some will like that some won't. It won't out someone as a closet basshead.. you need quite a bit of more lower bass for that.

And dont forget the high level of distortion, especially broad in the low frequencies, maybe that also amplifying the bass, masks the mids, highs etc. So in the end, probably much more happening than just a few dB boost on frequency graph.