Just finished my Crack!

[audioclass]

First amp build, though I'm not quite fresh to soldering and electronics.  I spent a few years in the Army working on Avionics for the UH-60 Blackhawk and CH-47 Chinook.  Received my much anticipated package from Bottlehead yesterday 6/6 at around 1:00pm.  After working on it from around 4-10pm, I had all of the soldering done on the chassis.  I went downstairs and glued the based together and went to bed.  When I woke up this morning I ran through all the resistance and voltage checks without issue.  I'm really amazed at how easily the whole kit went together.

At about 10:00 I hooked up my new Schiit Bifrost DAC to my PC, hooked up the Bifrost to my baby Crack, and my brand new Beyer DT880/600s to the Crack.  Now I know there is supposed to be some burn-in time associated with all the new equipment, but WOWOWOW does it sound amazing already!!  I was seriously curious if the overall investment would pay off, and I'm happy to say that it was worth EVERY penny to get setup with some proper hi-fi.  I can't thank Bottlehead enough for providing such an awesome amp at this price.  Something about assembling your own kit is just SO satisfying as well.

I just can't believe how QUIET the amp is.  No static, no hums, buzzing, just crystal clear music.  Now I can truly listen to everything that was recorded.  I won't rabble on as I'm sure you guys know all of this already, but I wanted to take the time to post that my build came out better than I could have imagined   I have yet to order the speedball kit, but I'm anxious to see what it adds to the equation some time in the future.

From the package to my ears in less than 24 hours!

Thanks Bottlehead!

[Laudanum]

Congrats and welcome.   Stick around, lots of help available should you need it and advice for upgrades and mods and just a friendly, helpful group.

I love the Beyers, and to me,  it's almost as if they were made for tubes.     Senns are probably the most popular phones with Crack, atleast on this board.  But if you are a Beyer fan, Beyers on Crack are fantastic, and I dont even own the Premiums.  Both my 880's and 990's are the Pro versions.     I have a hard time listening to my Beyers through my SS amps any longer.  Granted, my SS amps arent close to world class but Crack has spoiled me in regards to the Beyers, no doubt about it.   I'd love to try the  T-1's  but they are out of my league, price wise.  I'll just have to slum it with what I have   

Enjoy!

[audioclass]

The Senn's were on my wish list as well.  I was nervous after reading many reviews that the DT880s were too bright up top, but I think they sound great through my Bifrost and Crack so far.  Maybe someday I'll grab a set of HD600s or 650s, but not at their current price!!

[Laudanum]

The Beyers are bright up top but Ive never found them to be harsh or to introduce sibilance that isnt present in the recording.   To me, they are smoother and better balanced paired with Crack than any of my SS amps.  The 990's are a little more forward than the 880's but the additional bass balances them out.  Great for thin recordings that are weak in the low end although maybe not entirely accurate.   I love them both.  The Senns are a different animal but you may end up loving them.  Incredibly popular.  But whether you prefer the Senns down the road or not,  as it stands now, knowing the Beyers and Crack, I know things have got to be sounding good for you 

[audioclass]

Sounding good? I haven't shut the amp down since I finished all the voltage checks this morning!   That does lead me to another question though.  Obviously amps generate heat, what sort of temperatures are normal?  The chassis plate is pretty warm to touch, not to the point of burning, but I wouldn't feel comfortable leaving my hand there for any extended period.  Is that considered normal for the Crack's operation?  Should I be giving the amp a break after a certain period of time or am I just fine to listen to my heart's content?  The heat doesn't appear to be causing any issues, but I figured I'd best check anyway.

[BNAL]

Audioclass,

The only opinion that matters is yours, so if you think they sound great you made the right decision. I find this forum to be devoid of audio snobs which is one the great things about it.  

Brad

[BNAL]

Depending on the tube that is used the plate temps vary. The Crack comes with the 6080 which generates a little more heat at the base. If you get the 6AS7G or 5998 tubes the plate is a little cooler, because they do not have a metal base.

[audioclass]

Good to know Brad, thanks for the quick reply!

[dwilli852]

Looks like Doc has another one hooked. Enjoy your Crack it's a lot of fun and great sounding amp.

Next comes the Speedball, upgrades and tube rolling it never ends.

Check out the Tube Rolling Thread lots of good info.

[Paul Joppa]

Much of the chassis plate heat comes from the cathode resistors, which do dissipate a lot of heat. The power transformer gets pretty warm, too. If I get my way and we increase the current, they will get even hotter. The vent hole provides for some airflow - make sure you have the feet installed!

This is the price one must pay for OTL operation. Class B solid state runs much cooler, and Class D (iPods etc.) even cooler. Pays your money and takes your choice!

[Laudanum]

Mine has never gotten what I would call "hot".   Pretty warm but not to the point where I would burn my hand on the top plate if I left it there for a few seconds (or longer).   I havent used the metal base 6080 since I first built Crack, that one gets warmer.  But either way, it's not like a full blown 16 tube per channel OTL amp for loudspeakers that also serves as a coffee warmer, hot plate and room heater   

[audioclass]

No complaint here from me, just wanted to make sure it was operating as designed!   Thanks for the info everyone.

[grufti]

Yes, please, more current and a Speedball update to match.

You have already done the work calculating the whole thing. I will someday try to come up with my own modified operating points and associated modifications, but I would much rather just benefit from your expertise.

Much of the chassis plate heat comes from the cathode resistors, which do dissipate a lot of heat. The power transformer gets pretty warm, too. If I get my way and we increase the current, they will get even hotter. The vent hole provides for some airflow - make sure you have the feet installed!

This is the price one must pay for OTL operation. Class B solid state runs much cooler, and Class D (iPods etc.) even cooler. Pays your money and takes your choice!

[Laudanum]

 If I get my way and we increase the current ...

What would this do in a general sense?   Is it something being considered to improve Cracks performance with lower impedance phones?   Or "just" an overall sonic improvement for the high impedance cans it was designed for?

[Doc B.]

It will lower the output impedance a little. It's not going to be so extreme as to make the Crack work perfectly with 32 ohm headphones, but it may make the mid impedance cans in the 100-200 ohm range work better. And yeah, it will make the higher impedance cans sound a little bit better too. All that said there are people who are happy using the original Crack with 64 ohm cans, so it's partly a taste thing.