Tube Rolling w/Crack

My 5998 Tung-sol Chatham came in the mail today. I'm listening to the Scorpions at the moment.  Its sounds quite good.  I've never heard my HD600 sound this good.  

I also have a CBS 6AS7G.  It sounds almost as good as the 5998.  It has a little bit more bass.

IMG_0271.JPG
 
Mr. Davis said:
My 5998 Tung-sol Chatham came in the mail today. I'm listening to the Scorpions at the moment.  Its sounds quite good.  I've never heard my HD600 sound this good.  

I also have a CBS 6AS7G.  It sounds almost as good as the 5998.  It has a little bit more bass.
Click to expand...

Nice. I just received a pair of RCA 6AS7G yesterday. Not a whole lot of difference in sound over the Tung-Sol 6080 that came with it, but it sure looks cool. Makes the Crack look like a beast.
 
Mr. Davis said:
My 5998 Tung-sol Chatham came in the mail today. I'm listening to the Scorpions at the moment.  Its sounds quite good.  I've never heard my HD600 sound this good.  

I also have a CBS 6AS7G.  It sounds almost as good as the 5998.  It has a little bit more bass.
Click to expand...

I initially thought that the 6AS7 had a bit more bass than the 5998 as well (and it may).  But I wasnt so sure after listening for a while.  I heard subtleties in bass lines, for example, a little bit clearer with the 5998, skin attack on drums seems a little crisper and more defined.  Upper mids and treble seems a bit cleaner with a little more detail and treble maybe slightly more extended but smooth.  These were pretty subtle differences but noticeable.  With these differences in both the lower and upper ends of the frequency range I wasnt so sure that I was really hearing less bass but that it was a bit tighter. The 5998 has higher gain which is the most noticeable difference right off the bat.   But I did not play a wide range of music to compare and I didnt spend a huge amount of time analyzing the differences which isnt something Im good at anyway.  I'd rather just listen to the music and stick with a tube based on how the music "feels" rather than my actually thinking about how it sounds ... if that makes sense.
I was/am quite happy with the RCA 6AS7 and really wanted to try the 5998 more for my AKG K601's.  But the 601's reportedly have a long burn in and they really have changed from out of the box.  I put the 5998 aside to revisit after the 601's have had some good hours on them.  It will, in all probability, end up being the tube I use in Crack.  To me, it has a certain rightness to it's sound beyond the descriptions that I dont have the vocabulary to describe, assuming it's actually someting that could be put into words.  
 
Just a quick question from a newbie, I have built the Crack with Speedball, was wondering if by swapping out to different tubes, would that alter my voltage check numbers?  Thanks.
 
Yes, different tubes can change the voltages on pins A1, A6, B1, B3, B4 and B6 somewhat.
 
HI all! Regarding soviet era tubes...I was wondering what, if any difference is between the 6H13 and 6N13. I just got a 6H5 ... not a great tube in this application imho.
 
Nothing more than a translation issue -- h and n being alternate western designations for the same cyrillic letter.  Likewise b and v.  Source is a good friend with a Ph.D. in Russian Literature who works mostly as a translator.

In other words, it should bwe the same tube.

-- Jim
 
Sure that makes sense but funny that they would use both within slavic countries. Извини, пожалуйста!
 
When looking at suitable alternative tubes, what are the main points that I should look for in the datasheet. For instance I have a 12AV7 (5965) tube. Could this work in place of the 12AU7?
 
For a good match, you must match gain (mu), plate resistance (rp), and transconductance (gm). They are related, and a match of any two means the third will match as well. However, rp and gm are strong functions of plate current, so make sure the parameters are quoted at similar currents. Here is an example:

12AU7  at 10.5mA  mu=17, rp=7700, gm=2200
6CG7    at  9.0mA  mu=20, rp=7700, gm=2600

These are within less than 20%, indicating a close enough match for most purposes. Note that the 6CG7 needs twice as much heater current, fortunately Crack has enough current available to handle this requirement. You should always check this too, though!
 
While wandering through an electronics junk store while visiting my daughter for Thanksgiving I couldn't stop myself from buying a couple of tubes from their piles (literally) of tubes. I got an RCA 6ca7g that was just sitting in the bin (no box) that could be new (or not), and what appears to be a new in box GE 6ca7ga. The place (see below for those of you in the silicon valley area) had a simple pricing scheme: all tubes of a given type cost the same, independent of condition, with no testing and no guarantee!

So here's my real question: I now have two tubes that could be perfect or could have been sitting in that bin since somebody determined they didn't work 40 years ago and never got around to throwing them out.  Having experienced some rather interesting tube failures over the years, I'm a little nervous to just plug them into my shiny new crack and fire it up.  So nothing to worry about, just slam them in and look for fireworks in case I need to pull the plug? Or just write off this small impulse buy and get some tubes from somebody that has actually tested them before I put them in?



*http://www.yelp.com/biz/hsc-electronic-supply-santa-clara-2
 
Well, the 6CA7 is a power pentode (el34 equivalent), so there's no place to use it in the Crack.  Both tubes in the Crack are dual triodes -- one small signal, one power.

HTH,

Jim
 
Okay, violated my "don't ever send email after midnight because bad things happen" rule.

The two tubes are, of course, really a 6AS7G and 6AS7GA. I guess I have 6CA7 seared into my brain after too many years of nursing a Dynaco Stereo 70 in my youth (showing my age!).
 
Ah, well I'm sure we've all been there :-).

If it were me I'd probably start with the one in the factory box, do a visual inspection to make sure everyting looks ok internally, then make sure the filament is a low resistance and the other pins are very high -- ruling out any shorts between elements) and then give it a try.

This is assuming that you know the amp is working to begin with.

HTH,

Jim
 
Thanks Jim, that sounds like good advice. It's been 25 years since I had tube technology in my system, and I've forgotten even the basics. I'll be home in a couple of days and give the tubes a try.  The recently finished crack is working just fine, but all of the discussion of tube rolling made me feel like I needed to play around as well. Besides, the crack will look a lot cooler if the ST bottle tube works ;-)
 
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