Second hand Bottlehead Crack seems too quite

[RavenTooth]

Hello,

This is my first post. I was looking into buying a Bottlehead Crack kit and building it myself but then one came up locally, already built, with some extras such as some tubes and an uninstalled Speedball, so I grabbed it. With my HD600s the amp sounds quite good, but it just seems quiet. I like my music moderate to loud, and I apparently don’t have any hearing loss. I find I have to turn it up to 80 or 100% and still wish there was more. This is my first dedicated headphone preamp, and I don’t have a lot of other high end gear yet.

I’ve tried a few different sources which mostly seem to be the same. iPhone 6 plugged right in playing Spotify or Tidal and volume at max. Also tried Apple TV playing tidal plugged into my tv, optical out into a Gefen D to A, into the Crack. Volume is about the same. Best thing I can find is out of the headphone jack of my UAD Apollo recording interface into the Crack. I pretty much crank the Apollo and then I can get good volume at around 60-70% on the Crack. I don’t have TS-RCA cables or I would use the line-out on the Apollo.

I tried all the different tubes and they’re all close in volume.

When I search for this, most people have the opposite problem and are installing pads and attenuators. I wasn’t told of any mods to this build, except for the volume pot. My first thought was “maybe someone installed a bunch of pads”, but I don’t think so. I’m not exactly sure what to look for, but I don’t see any caps near the RCA inputs.

Anything I should be checking? I want to install the Speedball, and I hear this will add some dBs, but I want to make sure it’s working properly as is first.

I can take pics as needed.

[Alonzo]

Definitely Pics! (and this will probably be moved over to the Crack sub-forum). 

[RavenTooth]

Move me as needed! Here's a basic pic. I can take more angles as needed.

[Paul Birkeland]

I don't see any pads installed on your Crack.

I think you are maybe the second or third person who has said the Crack didn't have enough gain for them.  I think one of the two others just didn't have the volume sliders all the way up on his source, you might want to be sure that the volume is cranked up on anything feeding the Crack.

-PB

[RavenTooth]

That could maybe be it. I wonder if anyone can confirm that the volume straight from an iPhone or this Gefen DAC isn’t very loud. Even the volume from my cheap old Fisher receiver headphone jack is a lot louder.

[Paul Birkeland]

Can you be sure that it is turned up all the way?

[Bonzo]

Maybe to avoid any doubt you should connect a pure "line out" (maybe an old cd player output).

[Kitchener]

I’ve been using my Crack with HD6XX and an iPhone 6S Plus and an iPhone 5 as a source (volume maxed on phones) for months, loud as all hell.
I usually turn the pot halfway for medium (or whatever it’s called) and 3/4-7/9 for too loud.

Maybe we just have different aural tolerances?

Edit:
Have you checked under Music in the settings of your phone?
At least here in Europe there’s a setting to limit max volume to EU regulated safe levels?
But you mention several sources, so it’s ptobably not that.

[RavenTooth]

Great ideas. Looks like my iPhone is set for full volume in the settings. Again, I have it all the way turned up.

As a comparison, using my iPhone with Apple earbuds (the wired ones), I listen to AC/DC Back In Black album on full blast. It’s slightly too loud. But it’s equal to about 3 o’clock on the Crack (full being like 5 o’clock). So I guess the Crack with HD600s is slightly louder than the iPhones with earbuds. Does that seem right? Or should it be WAY loud than the iPhone with earbuds? I mean, I can’t imagine someone needing to attenuate this. Some people say they can hardly turn it up to 9 o’clock.

I could live with this volume probably, and get some more dBs with the speedball, but I still want to make sure the Crack is fully operational.

I’ll see if I can find something line level to try.

Maybe everyone just has really loud DACs?

[Bonzo]

Plese take into consideration that you can further limit the headphone output on iPhone with Settings>Music>Volume limit

When set at full limit I cannot stand listening to it with apple earbuds (and I'm a drummer, so I love loud music!)

Hope this helps!

Ciao

[Paul Joppa]

When you get the questions settled, and if you still want more gain, I think a conversion from 12AU7 to 6922 or 6DJ8 is relatively uncomplicated and should produce about 6dB more gain.

[Tom-s]

ECC81, 12AT7's also work in a crack (with speedball) without further modifications.
These give you a lot more gain; mu=60.

[Paul Birkeland]

ECC81, 12AT7's also work in a crack (with speedball) without further modifications.
These give you a lot more gain; mu=60.

No way Jose.  Plate voltage will rise significantly on the driver stage and leave no operating voltage for the 6080 (and potentially a ton of dissipation on the big C4S).

I still believe the OP doesn't need to mod the amp.  The next step may be doing a voltage check to see that everything is operating properly.  A dead tube would make the amp much quieter than it should be.

[RavenTooth]

Let me just add some more info to alleviate some guessing.

The iPhone is definitely playing at full volume. I checked all the settings and it’s at max. I probably do have a pretty high volume tolerance, as I am a musician and play electric guitar and sometimes drums. But the question remains: is a Crack with HD600s only slightly louder than an iPhone 6 with Apple earbuds?

I have 5 different big tubes and 2 little ones that came with the kit. I’ll go through it again but they don’t seem to be wildly different than each other.

Also, the quality of the sound is good. It’s not quiet, it’s just not loud with tons of extra gain. The thing I’m hung up on is that people are modifying this with pads and attenuators. I would never do that with this.

Could it be my upgraded volume pot?

A speedball was once installed (and came with it uninstalled). Could something related to removing the speedball have caused this?

The amp was apparently built by the previous previous owner, but the speedball was removed by the guy I bought it from.

[Doc B.]

Unfortunately this is subjective. To get a precise answer you would have to compare it with another Crack to determine whether the output is nominal, or send it to us to check it out for you.