Tube Rolling w/Crack

[ualcap]

Is there a need to increase the heater voltage on my Crack if I change from a 12AU7 to a E80CC ?

[Grainger49]

ualcap,

They are not interchangeable equivalents.  See this thread:

http://www.bottlehead.com/smf/index.php/topic,1027.0.html

[adamct]

Not sure about that. There is another thread here that says they are OK to use. Based on that, I bought one, and it is what I currently use. No problems at all. Gain is higher, though.

[Doc B.]

Will they plug in and work? Yes. Is the circuit optimized for them? It certainly was not in mind when designed since the designer chose the 12AU7. So perhaps the tube could work even better than it does.

[adamct]

Fair enough. 

Here is the thread I was referring to: http://www.bottlehead.com/smf/index.php/topic,3501.0.html

[Nick Tam]

Higher current draw but the total draw is still within the limits of the CT3 transformer. I'm currently using a 6SN7 and had no problems previously with the 12BH7 and E80CC (with speedball). I'm not an expert on the specifics of the circuit design of the Crack but I have done alot of research on the datasheets and the Bottlehead forums regarding the use of the 12BH7/E80CC/6SN7. The extra current draw is within the design limits on the transformer but whether the stock Crack would yield optimal results with the non 12AU7 family of tubes is something else that I could not confirm.

[adamct]

FWIW, I have a Speedball installed...

[mikek200]

  Newbie Question:

Just got the 5998's today..Using the crack with speedball.
I;m using a pair of HD800's,& I prefer classical,light jazz,acoustic guitar,80's rock

Can anyone give me a few suggestions for a good match withe the 5998
I do have an old Mullard coming in:
Mullard 12AU7-Ecc82,Blackburn,1958--thought this might add some warmth to the 5998??

Any suggestions will be appreciated.
Tnx
Mike

[orri]

Has anyone tried the Tung-Sol Re-Issue 12AU7?

[Laudanum]

Tung-Sol 12AU7/6189 is discussed in this thread ...  http://www.bottlehead.com/smf/index.php/topic,3946.0.html

[orri]

Thank you Laudanum.

I'm a new Crack owner and new to tubes and just looking for some cheap but good ones to try out.

Could someone recommend me a cheap alternative to the stock output tube of the Crack?

[Laudanum]

RCA 6AS7G ...  should be inexpensive ($10 give or take a few), they are still plentiful.   But, some sellers do try and get too much money for them.   

[StivVid]

Hello, all.  Seems like there's a definite preference on this forum for the sound of 6AS7G tubes over the less glamorous looking 6080 tubes.  Granted, I only have an RCA 6AS7G and an Amperex (made by RCA).  Both of those tubes sound very loose on the bottom end and both have a very faint high pitched ringing in the right channel.  Most 6080's I've tried, on the other hand, have much tighter, controlled bass and are dead silent--not a hint of microphonics with most--especially military JAN versions.  I'm listening to the line output of my iPod Classic.  The best combo I've found so far, by a wide margin, is an RCA JAN CRC 6080WA paired with an RCA 5963.  Everything opens up with this combo.  Tight, controlled bass; very present and detailed midrange; a nice airy spaciousness to the treble.  I also have a Sylvania Gold Brand 6080, which is nearly as good but not quite; and a Sylvania JAN 6080WB which sounds slightly lifeless compared to the other two 6080's.

I don't have a 5998 and I know this tube is universally praised.  I'm just curious as to why most people seem to prefer the ST shaped tubes to the good ol' straight 6080?  To my ears, they don't sound better.  Anyone else?

Other 12AU7 tubes I've tried in my rig:

unknown brand 6189
Conn 12AU7A
RCA Cleartop 12AU7A
RCA Command 5814A
GE 5-Star 5814A

[Doc B.]

I think we need to be careful when making judgments about a certain production of a tube based upon one sample. One sample might be microphonic, another might be not, and that could mean that if you heard a microphonic one you haven't heard the best example of that particular tube. Beyond that there is of course that fact that we use different headphones with different characteristics and we all put a little bit different emphasis on various aspects of the sound. So any thread about tube rolling is just a starting point.

We have been tryng different tubes in a new circuit we are working up (not a headphone amp). Based upon a lot of things I read I took a slight turn and we tried a slightly different tube that was reputed in quite a few forums to sound better that what we had started with. I didn't think that the sample we got sounded better, I thought it was worse. So we are getting some other samples of that tube to try as well. And if and when the kit comes out we will probably offer instructions for converting the circuit so one can make the comparison on their own.

[adamct]

FWIW, my two favorite tubes so far are a Bendix 6080 with graphite plates and a GEC 6AS7G. I don't prefer either one because of their sound, but rather because they are very quiet. Other tubes may also be quiet, but of the many tubes I've tried, these are the best.

Adam