[amcananey]

Yes, you can just plug in any compatible tube. If you find yourself using any tube other than a 12AU7, ECC82 or 6SN7 (via adapter) regularly as your input tube, you might want to consider some mods in order to optimize the amp for those tube types (e.g., 12BH7 or E80CC), but frankly I don't think it is worth it unless you are sure you will never want to use a 12AU7, ECC82 or 6SN7 again.

Some people claim there are synergies between certain tube combinations. There may well be, but the added benefit is small and trying to find reliable information on tubes, let alone two specific tubes in combination, is almost impossible. The bottom line is that almost every tube I've tried has sounded good in my Crack.

I'll let other comment on the DAC, as I'm not a big believer in differences between DACs once you get above the $100 price point and provided you account for differences in output signal strength.

As for the HD650s....just....don't. The HD600s are better. I've owned three pairs of HD650s. Each time I keep telling myself they can't be as bad as I remember, and each time I confirm that, yes, they are as bad as I remember. I know the HD650s are newer, have a higher number and cost more, but they are still worse than the HD580s/HD600s. Save your cash for something else. If you want an upgrade from the HD600s, save your pennies and buy a pair of HD800s when you can. They are absolutely amazing, especially out of a Crack. Skip the HD650s and HD700s.

Regards,
Adam

 

[Nowhere]

Yes, you can just plug in any compatible tube. If you find yourself using any tube other than a 12AU7, ECC82 or 6SN7 (via adapter) regularly as your input tube, you might want to consider some mods in order to optimize the amp for those tube types (e.g., 12BH7 or E80CC), but frankly I don't think it is worth it unless you are sure you will never want to use a 12AU7, ECC82 or 6SN7 again.

Some people claim there are synergies between certain tube combinations. There may well be, but the added benefit is small and trying to find reliable information on tubes, let alone two specific tubes in combination, is almost impossible. The bottom line is that almost every tube I've tried has sounded good in my Crack.

I'll let other comment on the DAC, as I'm not a big believer in differences between DACs once you get above the $100 price point and provided you account for differences in output signal strength.

As for the HD650s....just....don't. The HD600s are better. I've owned three pairs of HD650s. Each time I keep telling myself they can't be as bad as I remember, and each time I confirm that, yes, they are as bad as I remember. I know the HD650s are newer, have a higher number and cost more, but they are still worse than the HD580s/HD600s. Save your cash for something else. If you want an upgrade from the HD600s, save your pennies and buy a pair of HD800s when you can. They are absolutely amazing, especially out of a Crack. Skip the HD650s and HD700s.

Regards,
Adam

 
cool... thanks for the input. so the 12AU7, ECC82 are the 2 types of tubes i can choose from? without any modifications.
 
i'm surprised you say that about the 650 as i've heard so much praise of them and they seem to fit a sound that i'm seeking over the hd600.
i might simply buy them used to try them out and then resell them if i don't like them, i've read alot about them and it just seems they would fit a type of sonic signature with a tube that i'm looking for. a bit darker, more romantic with a little more bass over the hd600 from what i've read.
i doubt i'll be able to afford the hd800 anytime soon hehe. just getting the crack + hd600 took alot of saving, i can probably get 1-2 more pair of used cheaper headphones and some tubes here and there and that's it for a long while on the audio front for a long time.

 

[swmtnbiker]

Opinions are like, well, you know...

 
The HD650 is enjoyed by a LOT of people. It's not one of the most talked about headphones here, years of discussion, for no reason. For some it's the perfect combination of performance to price and it scales extremely well. For some it's not their cup of tea. YMMV. The only real way to find out is to listen for yourself. I'll say this - for me the combination of the Crack+Speedball and the HD650 is heaven. They were made for each other.

 

[amcananey]

FWIW, the HD650 does not have more bass than the HD600. It simply has less treble.

I will say that the Crack is the amp that best compensates for the HD650's flaws. But the HD600 is still a better headphone with the Crack than the HD650s.

Are the HD650s bad headphones? Well, that's a matter of perspective. Compared to many, many, MANY headphones out there, they are obviously very good. But you can't compare a headphone in the abstract. You have to evaluate it based on price, and relative to its closest competition. The closest competition for the HD650 is the HD600, a headphone that costs less and performs better. That is the only reason I am so dismissive of the HD650. If the HD600 were slightly cheaper and slightly worse than the HD650, you could debate whether the loss in performance was worth the cost savings. If the HD600 were slightly better and slightly more expensive than the HD650, then you could debate whether it was worth paying extra for the better performance. But given that the HD600 is better AND cheaper, there isn't really a lot to discuss. We are talking about headphones that cost $500. That's 1/2 of a thousand. For that amount of money, we have a right to be picky, especially if Sennheiser is billing it as an "upgrade" over the previous model.

Many people who talk about the HD650s haven't done the same degree of testing and comparison that I've done. I've owned three pairs of HD650s, still own two pairs of HD600s and did own a pair of HD580s. I've also owned two pairs of HD800s (still own one) and a pair of HD700s (now sold), not to mention a ton of other headphones. Does that mean I'm unquestionably right? No. My subjective opinion is still my subjective opinion. But take a look at the Inner Fidelity review of the HD580 vs. HD600 vs. HD650. Tyll provides some objective support for my subjective opinion.

In my view, Sennheiser didn't add anything to the HD600 when creating the HD650. It only took away part of the upper end of the spectrum. In the bass and most of the mids, the HD650 and HD600 sound virtually identical. The missing treble is what makes the HD650 sound darker and slightly lifeless, and it leads people to believe the HD650s offer more bass, when they don't.

That doesn't mean that there aren't people who will prefer the HD650 sound signature over the HD600 sound signature, and that is certainly up to them. But the HD650 is not an objectively better headphone than the HD600 in terms of reproducing the audible frequency spectrum, it is worse. Far too many people here buy into the model numbering and cost-status hype of the HD650 and believe it must be better, just because it is "50" more and costs more...

Feel free to dismiss and/or ignore this post. If anyone wants to buy the HD650s, or has HD650s and likes them, that's perfectly fine by me. I'm just trying to give people additional information so they can make an informed decision on their next purchase/upgrade.

And to bring the discussion back on topic: the Bottlehead Crack is, in my experience, unquestionably the best amp for either the HD600 or the HD650!

Best regards,
Adam

 

[Nowhere]

great, convincing points. .
although if buying used they're around the same price usually, i see both the hd600 and 650 around 320-400 used.. and i have read that article you mentioned about the comparison.
 
it might be that i'm easily swayed but you might have convinced me lol. 
perhaps i will look to another headphone away from sennheiser sound instead of the 650.
 
okay, i agree back on topic to the crack.

 

[Jd007]

In general less treble does mean more bass/mid-bass though. Frequency response shows the relative loudness of the frequencies, normalized at a certain point (eg 0dB at 1khz). If the treble region is lower you can think of it as the bass and mid regions being higher. Think of bass strength as the dB difference between bass region and other regions. Raising the bass response or lowering the treble response both increase that frequency response delta (in dB), as a result increases perceived bass.

 

[skeptic]

The same hd650/hd600 debate pops up from time to time if you skim back through the thread, and there's no right answer.
 
Compare the FR graphs below and pick your poison.  hd650's have a little bit of mid-bass bloat (which makes them sound fuller but can also obscure details), hd600's have a mild treble peak around 2.5khz which *can* make them sound more clear.  On the downside, there are a lot of instruments (e.g. violin, piano, trumpet, etc.) that play fundamental frequencies > 2.5khz - so the hd600's will actually make some treble notes (not just overtones) sound louder than they are on the recording.  For me, that's a big strike against them, and I prefer hd650's to 600's (when I'm not listening to my hd800's). 
 
Edit: oh and the paint job on the hd600's is ugly 

 

As for tubes, you can also use 12bh7's in the front socket without any mods (assuming you have a speedball).  1950's Tung Sol 12bh7's can be had for under $30 and are my favorite input tube to date.  In the rear, you can run 6as7, 6as7g, 6080, 7236, and 5998.  The last two have higher gain and also higher transconductance than 6as7's/6080's.  They actually lower the output impedance of the amp and provide a slightly different flavor.

 

[amcananey]

The paint job on the HD600s is beyond ugly. No questions there. I actually like the HD580s in terms of looks...

You can certainly use 12BH7s without any mods. It won't harm the amp and will sound fine. But as indicated here: http://www.bottlehead.com/smf/index.php/topic,663.msg45199.html#msg45199, the Bottlehead team recommends removing the red LED's on the 9 pin socket and replacing them with 1/8 Watt 1.2K resistors when using the 12BH7, since it otherwise changes the operating point of the output tube.

 

[Nowhere]

thanks for the tube info, any tips on a reputable seller i can start with... (ebay and store)
i don't plan to buy tons and tons of tubes, i'd prefer to buy a couple here and there  and then spend time with it and not switch tubes out all of the time.. more of a quality rather than quantity approach.
 
i was looking at this place but they're not the cheapest ever, i like in some of them they have the option for "cryogenically treated".  haha that's awesome.
https://www.upscaleaudio.com/12AU7/
 
there's a Tung-Sol 12AU7W / 6189 platinum grade for $25... but of course the more expensive ones interest me more as usually the case hah.

 

[skeptic]

The paint job on the HD600s is beyond ugly. No questions there. I actually like the HD580s in terms of looks...

You can certainly use 12BH7s without any mods. It won't harm the amp and will sound fine. But as indicated here: http://www.bottlehead.com/smf/index.php/topic,663.msg45199.html#msg45199, the Bottlehead team recommends removing the red LED's on the 9 pin socket and replacing them with 1/8 Watt 1.2K resistors when using the 12BH7, since it otherwise changes the operating point of the output tube.

 
Thanks for the heads-up!  I've been running various 12bh7s for quite a while now (based on much earlier posts in the tube rolling thread), and had thought they were a drop in replacement.  You've certainly piqued my interest as to the potential for further improvement.  On the downside, pulling the speedball boards to gain clean access to the a-socket is a bit of a hassle.  Going to have to think on this one.

 

[amcananey]

Also: remember how small and delicate those LEDs are. Once you pull those, there is no going back. They aren't expensive to replace, but I'm just saying...

 

[skeptic]

I hear you. I damaged one of those suckers inadvertently during my speedball install. Removing the speedball and then the broken led, and installing the new one, was definitely the most complicated maneuver I've attempted with a bh amp.

Maybe instead, I should take this as an opportunity to try some new 12au7s

 

[Zashoomin]

Hey guys was looking for an upgrade to the stock pot and came across this: http://www.ebay.com/itm/281158933289?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649.
 
It looks like it would be a lot easier to solder than with those small pins.  Anyone know if this is really an alps pot or not?  Its from hong kong.  

 

[whatthedac]

Still haven't built the Crack yet.  What's the point of the LEDs?  They get installed underneath the tubes, right?  Is it just to let you know they are on?  To give it extra glow?

 

[Loquah]

  Still haven't built the Crack yet.  What's the point of the LEDs?  They get installed underneath the tubes, right?  Is it just to let you know they are on?  To give it extra glow?

 
They're used as a resistor.