Tube Rolling w/Crack

[Dr. Toobz]

At the suggestion of Grainger49, let's compile a list of tubes that can be rolled in the Crack. I'll update this list periodically as more tubes are tested, and have separated the list into drop-in replacements vs. tubes that might need the heaters rewired or some other modification. Please PM me with any additions or corrections! Maybe we can eventually make this thread a sticky? (Last updated: 05/22/2010).

DROP-IN EQUIVALENTS

Input Tubes (Original: 12AU7)

12AU7(A)(WA)
ECC186
ECC82
ECC802(S)
E8025
E82CC
CV4003
CV4122
CV491
5814(A)
6189(W)(WA)
6680 (WL6680)
6067
7489
7316
5963 (computer version of 12AU7)

Sort-of-Drop-In (but not equivalent - for best results, replace plate resistors with Speedball boards)

E80CC
12BH7

Power/Output (Original: 6080)

6AS7G
6080
6H13C
5998
7236
6N13
NOT THE 6SN7!!!!!


SUBSTITUTIONS (circuit changes required)

n/a

FWIW, tube rolling can indeed make a difference in your Crack. I've had the chance to try out another power tube - a Russian 6H13C (6AS7). The amp sounds a bit warmer now, with a bigger soundstage, plenty of bass, and maybe a hair less vivid treble. A good investment at about $20 - I bought mine online from the TubeStore. This definitely sounds a little sweeter and more "tubey" than the 6080 in there before. YMMV, of course.

[ironbut]

Well, I just couldn't resist any longer.
I replaced the Toshiba 5963 that was included in my kit with a mid 50's CBS Hytron 5814a BP, 2mica with the tilted square getter.  I still have the supplied RCA 6080 installed but I replaced the stock signal wire with Cardas 24awg shielded between the RCA's and the pot and 21awg solid silver (from M Percy) for the rest.
It's just been a couple of hours but I'm lovin' it! Great imaging, deep soundstage, fantastic bass, very nice snap, and the highs aren't nearly as forward as with the Toshiba. Very musical!
I almost don't have the heart to try the rest of my stash,.. I said almost.
I'll live with this set up for a while though,.. of course there's that new TKD pot staring me in the face too.
I just have no self control anymore!

[Jim R.]

Steve,

Is that CBS Hytron the red label version?  If the braille on the tube box is correct, I think I just found one of those in my tube box.  I thought I had got rid of all my 12au7 variants, but I'm stil finding one or two here and there, and so far they have all been pretty nice.  I'll ask my wife to verify that it is indeed the 1955 red label.  Glad to hear it sounds so good in the Crack.

-- Jim

[ironbut]

Yup, that's the one. IIRC, it wasn't too expensive either.

[roger_s]

I've so voided my warranty:  All of the signal path wire is multiple-strand silver-plated Teflon mil-spec, the RCA jacks feed the pot via Canare shielded quad, the pot's from DIY-HiFi (their Alps clone), the headphone jack is a Neutrik locking jack, the caps are those huge Axon films, and I've rolled in a RCA 6AS7.

What an amazing amp!  Dead quiet, the bass has incredible slam and definition.  Brushes against a drumhead are stunning. It does a better job with my HD-650's than my K-702's but not by much. Right now I'm feeding it Apple Lossless via a RWA modified iPod. Blows away my DarkVoice 336 and my Woo Wa3. In fact I just gave the DV to my son-in-law.

Dead simple to build and incredible sound. Doc, you guys rock!

 

Well, I just couldn't resist any longer.
I replaced the Toshiba 5963 that was included in my kit with a mid 50's CBS Hytron 5814a BP, 2mica with the tilted square getter.  I still have the supplied RCA 6080 installed but I replaced the stock signal wire with Cardas 24awg shielded between the RCA's and the pot and 21awg solid silver (from M Percy) for the rest.
It's just been a couple of hours but I'm lovin' it! Great imaging, deep soundstage, fantastic bass, very nice snap, and the highs are nearly as forward as with the Toshiba. Very musical!
I almost don't have the heart to try the rest of my stash,.. I said almost.
I'll live with this set up for a while though,.. of course there's that new TKD pot staring me in the face too.
I just have no self control anymore!

[Dr. Toobz]

.... It does a better job with my HD-650's than my K-702's but not by much.

Just how good is it with the AKGs? A couple of us have been wondering if the impedance is too low on those. How about bass?

[Jim R.]

Roger,

How did you implement the Neutrik locking jack with the 2.49k resistors?  I have a couple of those jacks and they don't apppear to have any switched terminals.

Thanks,

Jim

[roger_s]

Overall they're quite good. Bass doesn't measure up to what the higher impedance Senns provides but the soundstage and imaging are on a par.  Bear in mind I don't have a lot of hours on the Crack and am still in the process of trying different phones--still need to plug in some Grados--expect some different impressions over time. However, I suspect that the Senns won't give up their lead.

.... It does a better job with my HD-650's than my K-702's but not by much.

Just how good is it with the AKGs? A couple of us have been wondering if the impedance is too low on those. How about bass?

[roger_s]

Ran them from tip and ring to sleeve. It's not pretty, the holes are too small for wire+resistors. I ended up soldering the wires in place, placing the resistors on top and soldering them in place. It works but I'll likely re-doing it for a cleaner and more mechanically sound installation. 

Near as I can tell the switch function of the stock jack isn't being used.

Roger,

How did you implement the Neutrik locking jack with the 2.49k resistors?  I have a couple of those jacks and they don't apppear to have any switched terminals.

Thanks,

Jim

[Jim R.]

Roger,

Ok, I'll ring out the jack today as I thought those resistors were switched in when the headphone plug was removed, and for what I guessed to bleed down the coupling caps, but I guess they'd do the same thing and prevent power-up transient suppression if just soldered directly as you did.

-- Jim

[Jim R.]

Ok figured out the TRS jack resistors.  Found the step that says to solder a ground wire between both inboard and outboard sleeve terminals (and which also goes to the volume pot.)  Easy enough.

-- Jim

[roger_s]

The jack should work just fine, Jim.  You might try soldering the resistors to the jack and using the resistor leads to connect the various wires.  Should be a much better installation--things get pretty crowded on the back of the jack.

Roger

[levlhed]

Could someone maybe list the different variants of the two tubes that can be used?
I'm familiar with some of the 12AU7 versions, but I guess I don't know all of them (5963? 5814a?) and I know nothing about the 6080/6AS7's.

Thanks!

And yes, I only just ordered my kit today and I'm already looking for tubes
All I have are 12AT7s in my speaker rig

[Paul Birkeland]

You can use the 6CG7 with the Crack also.  Just separate the jumper between pins 4 and 5, then run a wire from pin 9 to whicheven pin (4 or 5) has no wire running to it.  The E80CC is another decent choice. 

As for the 6080/6AS7 variants, you really need to stay within the heater current limits, that's the key.  Tubes like the 6336 will overtax the power transformer.  I will test the 6BL7 sometime this week with my Speedball Crack and see how it lines up with the stock operating points. 

[ironbut]

PJ did a list the other day regarding the 6080 type tubes in the thread "New Production 6AS7/6080 tubes".

There's a bunch of 12au7 subs that can be used in some gear. Here's a link to a tube sellers site with a good number of the more common subs. Like a lot of online tube shops, sometimes the info's good and sometime it's just self serving. Please don't take my link as being an endorsement of this seller.
But, if I'm heading into unknown territory tube wise, I always surf around to the seller sites that have some good info with their ads. You'll find a gazillion 12au7 threads on the Asylum too.

http://www.vacuumtubes.com/12au7.html