Tube Rolling w/Crack

[Paul Birkeland]

I misread some of the comments here and plugged my VT-231 into the output socket and listened away. I actually had a few hours on it before I figured it out. Nothing exploded and it sounded OK to me except a very slight flange effect sound in the mids, but I figured it's old, actually a really old sample. Anyway, I'm wondering what's the harm in continuing to use it as the output from time to time? I've since rolled my 6as7's in and out and the amp's fine.

Someone else did this a while ago and tried to argue that there was no problem.  I went through the laundry list of problems that you'll run into if you do this, but the post is proving to be a little elusive to find.

It's not surprising that nothing happened that immediately.  What you're doing would be like going out and starting your car, then putting a cinder block on the gas pedal and walking away.  Will your car still run for a while?  Probably so, but you can expect imminent destruction in a far shorter time period compared to normal use.

The amp also isn't designed for the 6SN7 to plug into that socket.  The 6SN7 would be a poor choice overall for this position, so it's not like a moderate amount of tweaking would make the 6SN7 work in place of the 6080.  They are very, very different tubes made for completely different purposes. 

[gregr]

Someone else did this a while ago and tried to argue that there was no problem.  I went through the laundry list of problems that you'll run into if you do this, but the post is proving to be a little elusive to find.

It's not surprising that nothing happened that immediately.  What you're doing would be like going out and starting your car, then putting a cinder block on the gas pedal and walking away.  Will your car still run for a while?  Probably so, but you can expect imminent destruction in a far shorter time period compared to normal use.

The amp also isn't designed for the 6SN7 to plug into that socket.  The 6SN7 would be a poor choice overall for this position, so it's not like a moderate amount of tweaking would make the 6SN7 work in place of the 6080.  They are very, very different tubes made for completely different purposes.

OK. Thank's Paul. That's good to know. Maybe I'll get an adapter for the driver socket.
Thank you for the quick reply.
-Greg

[Tom-s]

Another good site i used to learn and draw loadlines for tubes: https://robrobinette.com/Drawing_Tube_Load_Lines.htm

[larmader]

I just wanted to post about my experience with the JJ ECC802s gold pin tube in the basic Crack build (I don't have the Speedball upgrade yet).  I'm finding this tube to be excellent, and I definitely prefer it to the tube that came with the kit (in my case the stock tube is marked as CONN Ltd 12AU7).  The stock tube felt a touch rolled off in the treble and thus lacking a little in sizzle and sparkle.  The JJ tube seems to improve on that considerably.  It has a wonderfully rich mid-range and timbre with orchestral instruments.  At least to my ears, in my crack build, ymmv, i could be deaf, caveat emptor.  Any others try out this tube?

[Deke609]

Another good site i used to learn and draw loadlines for tubes: https://robrobinette.com/Drawing_Tube_Load_Lines.htm

Thanks for posting this. Very helpful.  The more I learn (still only at the beginning of the learning curve), the more I am equally baffled by and drawn to the arcana of tube audio.  Perhaps in every vacuum tube sits an acoustic version of Maxwell's Demon, and tube audio adepts like those at BH have figured out how to coax the demon to separate beautiful sound from noise. 

[tvr2500m]

I just finished a Crack. I love it already. I'm thrilled with it. Simple, well-conceived and executed, elegant, and sounds great. Just doin' the old Sennheiser thing with it; Massdrop x Sennheiser HD-6XXs. Best I've heard the 6XXs sound.

I lived a long time with a Conrad-Johnson preamp that used the 12AU7. It's a comfortable tube family for me and I have a cosmologically large selection of them. The 6080 is new for me.

I have the Speedball upgrade, have it prepared for installation, but haven't installed it, yet. I'm acclimating myself and shaking down the stock Crack. Sounds just fine as-is, though can't resist some fettling.

My Crack was supplied with a '50s vintage Sylvania black plate 12AU7 and a '67-dated GE 6080 wearing RCA livery. They are doing a fine job is sounding very fine. Nice, quiet, good-sounding vintage tubes.

I've tried some other 12AU7s. Just a few. I've come upon one that just bests the supplied Sylvania.

I have purchased some other 6080s to try.

I've really liked the 6CG7 and 6SN7 in previous tube lives. I would like to experiment first with the 6CG7 in the 12AU7 position. Reading through some of the Crack discussions, it seems that this is an easy'ish tube to adapt the Crack to run.

[L0rdGwyn]

Seems this tube hasn't been brought up in a couple years, but man, the Tung Sol 7802, while quite rare, is absolutely top three in the output position in the Crack/Crackatwoa.

I recently came across a few auctions on Ebay for untested 7802's, I bought them all, unsure if they would actually work.  Luckily they did.  From my listening, they outperform the Tung Sol 5998.  They lean more to the high end, upper midrange-treble forward, but non-fatiguing, I find they pair very well with warmer headphones (ZMF Atticus, HD650).

I know the Western Electric 421A is for all intents and purposes considered to be the same tube as a Tung Sol 5998.  I own several of both, and my ears say otherwise.  With that being said, I believe the Tung Sol 7802 is on par with the Western Electric 421A in terms of technical performance, but a brighter sound signature.

Here is how I rank my personal Crack tube collection:

Western Electric 421A = Tung Sol 7802 > Tung Sol 421A > Tung Sol 5998 > various 6080 types

Keep your eyes peeled, I will try to keep myself from continuously hoarding them

[Rossputin]

I'm far from expert in this, but two quick things: One, after building the Crack (w/Speedball) I soon learned that the world of tubes, even if looking at just the two tubes for a Crack, is nearly infinitely large so I'll throw out a suggestion which has helped me limit the time and money that I spend with what could a massive obsession: I will only buy tubes made in the year I was born.

Second, speaking of unusual tubes, I recently got a Burroughs 2399, which is basically a version of a Tung Sol 5998 but has a reputation as a stellar tube. Shockingly rare. I mean, there is usually not one for sale on eBay or online at any price. Not cheap but less than the 421A! It also looks really cool. Anyway, I absolutely love listening to the Crack with that tube. (My 12AU7 is a La Radiotechnique also from the year of my birth.) Anyway, maybe something to keep an eye out for.

[Paul Birkeland]

I recently got a Burroughs 2399, which is basically a version of a Tung Sol 5998

It is a TS 5998 that's been rebranded. 

[gonzoznog]

Hello. I have a Crack w/ Speedball. I am currently using a Tung-Sol 7236 and really enjoy the bass. I was wondering whether it would be safe to substitute the 12au7 for a 7N7 if I used an adapter? I really like the 7N7 in a tube buffer that I currently use. Thanks!

[Tom-s]

You can use 6SN7 type tubes and all variants.
I used 7N7 tubes with my Crack with good results (these sound like the best Sylvania 6SN7's).
6F8G is another commonly used alternative with great sound (6C8G is another).
6J5 pair or 7193 pairs will work aswel (and may sound even better).

[gonzoznog]

Thanks! I tried the 7N7 and think it sounds quite good. Been enjoying my Beyerdynamic T1.2 and Sennheiser HD 6XX with the BHC.

[gonzoznog]

I am assuming you need an adapter? And one would have to use a pair of 7193? Like this? h t t p s://www.ebay.com/itm/1pc-Dual-6C8P-2C22-7193-CV6-CV3601-TO-12AX7-12AU7-tube-converter-adapter-6-3V/191552830664

[Tom-s]

Yes. For 6J5 and 2C22 tubes you need an dual 8 pin to single 9 pin adapter like the on in the link.

Good look with experimenting with Crack. Let us know about the results!

Another "6SN7" i had good results with were ECC32's. These are unobtainable so can't recommend them.

[L0rdGwyn]

Is anyone using 6F8G tubes using a 6F8G to 12AU7 adapter in their Crack or Crackatwoa and not getting a 60Hz buzzing in one channel?  Trying to diagnose if what I am experiencing is a grounding issue or if it just the nature of the tube-amp pairing.