Bottlehead Crack / Speedball update?

I brought my crack with the speedball upgrade like a month ago.  Its seem they had a demo from a show.  I have it paired with a Beyer  DT990 600ohm.  With stock tubes its sound like the music its all over the place.  Bass is there but not tight and solid, treble was even worst i was getting better sound from my pc.  This was after a full week of using the crack.  Later came the Sylvania 5963 12AU7A ECC82 and RCA 6AS7G.  Now with better tubes its sounds alot better everything is more define with more body and space.  Bass is tight and mids and highs are clearer.  I can actually hear the instrument location with these.  Latest upgrade is a Tung Sol 6680 that i got today.  Right now is not better than the Sylvania but getting there i think from the few hours of use it has less bass but more treble than the Sylvania.  Time will tell on these.  All i can say if you go with the crack be ready to roll alot of tubes.  This amp is made form the start for use with high impedance cans so 100ohm or less cans may not be good.  I believe Doc from Bottlehead said if using a 5998 tube one can even use 70ohm cans, i wonder cause my next cans in line might be a LCD-2 and will sure try one of the 5998 or even better a WE 421A. 

I don't get what is so surprising here......
 

Quote:

Originally Posted by Ctwombly 

Thanks for taking the time to give me such detailed feedback -- surprising news in light of the info on the Bottlehead website....

 

The Crack will never be a good choice for orthos like the LCD-2. Output impedance is too high, damping factor is too low, current capability insufficient. Stick with the high impedance dynamics.
 

Quote:

Originally Posted by Neogeo333 

I believe Doc from Bottlehead said if using a 5998 tube one can even use 70ohm cans, i wonder cause my next cans in line might be a LCD-2 and will sure try one of the 5998 or even better a WE 421A.