Tube Rolling w/Crack

[Tom-s]

1. Don't use too much heat.
2. Don't apply any force before the solder joint is 100% melted. (Resin helps to get it flowing)
3. If cutting the resistor makes removal more easy, is usually do in more difficult situations. As a board is way harder to get vs a new 5 cent resistor.
4. Plan ahead, build in some sort of switch, so you never have to abuse the speedball board again and can switch between 12AU7 and E80CC daily .
5. Plan further ahead, you might want 12BH7 some day, make it a 3 way switch. Really 12BH7's are a very interesting sidestep from the standard 12AU7's. More mellow/air/details compared to the average 12AU7. (oh and the 5731A's are needed for that).
6. I don't know, enjoy your turkey this evening? 
Good luck!

[watonwak]

Thanks for the advice!

A switch seem like a good idea but i am not sure how I would go about that...

No turkey for me today, vegetarian and not american!

I hope you enjoy your turkey!

[tim273]

Any other advice of people using combos with telefunken NOS genuine tubes ???

It pairs great with a Western Electric 421A!  But, then again, so does just about any other tube!

[Love Rhino]

Hi all!  I’m currently working on my 2nd crack, my first is +sb with some cap upgrades.  I’m a big fan of tube rolling, and I have several different varients with and without adapters: 12bh7, e80cc, 6sn7, 6f8g, 6c8g, 7193 and cv6, 6j5...the list goes on and on.

I’ve discovered a weird problem with my 6c8g tubes.  The 6f8g works just fine with speedball, but when I use the 6c8g the sound is muted, with distortion happening around the 9pm mark on the volume.  I’ve tested the adapter with 6f8g on the crack, and with the 6c8g on a darkvoice amp, and no problems.  I’ve also tried different 6c8g tubes and had the same issue.

Any ideas why this particular variant is being so fussy?

[Paul Birkeland]

Any ideas why this particular variant is being so fussy?

That is not a compatible tube.  It has twice the amplification factor, higher plate impedance, and lower transconductance.  Other than all of those differences being not ideal for a tube substitute in the Crack, when you plug it in the operating point will be so far out of whack that neither the 6C8 nor the 6080 will be able to pass any signal.

A voltage check will also verify this.  Terminals 1 and 5 are going to be very, very close in DC voltage to terminals 2 and 4.

(This high voltage on terminals 1 and 5 may also destroy the large Speedball PC board over a reasonably short period of time)

[kill_surf_city]

I got a huge box of tubes off the Facebook marketplace for $50 last summer (mostly NOS RCA and GE) and seeing as I just finished my Crack, I thought I'd see if I could roll some tubes. Been unable to find any power tubes that are equivalent. I found an RCA 9AU7 tube. Clear top. The original tube is a 12AU7, but would this still be okay to run? If so, what's the quality difference between this tube and an RCA 12AU7? I'm still digging through this box hoping to find a 12AU7, but no luck yet.

[Paul Birkeland]

The 9AU7 is the same as a 12AU7 except it's expecting either 9V or 4.5V to heat the tube instead of 12.6V or 6.3V for the 12AU7.  If you plug that tube into the Crack, it will glow very brightly and live a very short life.

[kill_surf_city]

The 9AU7 is the same as a 12AU7 except it's expecting either 9V or 4.5V to heat the tube instead of 12.6V or 6.3V for the 12AU7.  If you plug that tube into the Crack, it will glow very brightly and live a very short life.

Damn. Well I decided to try it out. Huge step up from the Sylvania tube that the crack came with. Almost no tube noise at all. Also much more balanced. With the stock tube it felt like the image wasn’t as centered as it should be - slightly right channel dominant. Def gonna look into the 12Au7 RCA now.

[kill_surf_city]

Found a Tung-Sol 6A8G tube in my box. Wondering if this is safe to try out? I tried comparing data sheets online, but it's a bit confusing.

[Paul Birkeland]

You can put it in the amp and turn it on, but it will blow the fuse immediately.  That is tube is nowhere near compatible.

This post has a reasonably comprehensive list of compatible tubes.

[Thermioniclife]

Hey Kill_Surf
I hate to sound like a dick but you just got your amp up and running reliably, replacing tubes willy nilly will quickly lead you back
into trouble again.
Use the amp for a while and enjoy, while doing so, do some research and get a basic understanding of tube requirements and circuit theory. I would hate to see you get yourself into trouble and have to possibly replace a transformer or other components that could be destroyed.
Just saying.

[kill_surf_city]

Hey Kill_Surf
I hate to sound like a dick but you just got your amp up and running reliably, replacing tubes willy nilly will quickly lead you back
into trouble again.
Use the amp for a while and enjoy, while doing so, do some research and get a basic understanding of tube requirements and circuit theory. I would hate to see you get yourself into trouble and have to possibly replace a transformer or other components that could be destroyed.
Just saying.

I only tried the 9AU7. I've just had this big bin of tubes sitting in my closet and unfortunately didn't find any that would work with the Crack. No offense taken btw.

[legion1capone]

Anyone purchase tubes from tubeworldexpress.com?

[Paul Birkeland]

Tube World has been around a very, very, very long time. 

[legion1capone]

Tube World has been around a very, very, very long time.

Oh good! There website seemed pretty impressive to me as did their selection, advice and measurements posted.
I've ordered from a few others also recently. I just finished my Bottlehead crack. Listened for a few days and rolled a few tubes already. Putting in the speedball now.
I have ordered the following tubes so far:
-5963 RCA Cleartop NOS 1971 (11.2/14.4ma)
-12AU7A Amperex Globe Logo Holland NOS 1970 (11.8/12.8ma)
-ECC82 12AU7A NOS NIB Mazda made in Czech (14.6/14.6ma)
-CV4003 Mullard boxplate wrinkle glass NOS (9.6/9.6ma)

Tubes I own:
Sovtek 6AS7G
Sylvania JAN 6080WB (came with crack kit)
Gold Lion ECC82 12AU7 platinum grade
Sylvania 5963 (came with crack kit)

I started off with the stock tubes mentioned above and was not very thrilled with the sound. Had me wondering what I had just put all that effort towards. So i rolled to the Sovtek 6AS7G and was immediately impressed. It pairs very nicely with the Sylvania 5963. Next I rolled the Gold Lion in, that sounded much different from the Sylvania, but definitely not in a bad way. I can post better impressions later. I'm waiting to find a single GEC 6AS7G or Bendix 6080 but they are so expensive! I'm just going to find my favorite preamp tube with the Sovtek for now. I think I'm most excited to hear the CV4003 mullard and the Mazda 12au7.