Tube Rolling w/Crack

[TubeGuy12]

I bought a 6SN7 adapter from Garage 1217 and it's very nice quality. I wanted to guard the exposed solder pads and came up with a simple plastic removable sleeve. It's actually made from just a $1 sink drain pipe from home depot. It fits perfectly and looks like it's part of the tube when placed over it. Anyway, this amplifier is just amazing in performance and simplicity (and superb electrical engineering!)

Nice job on that G1217 adapter cover, Mucker. I've been concerned with the proximity of those solder pins to the volume knob, too. I initially thought of simply putting a couple large diameter nitrile o-rings on the pins. I discovered that the problem with that candidate solution is that some nitrile is made with carbon. And carbon could create a quasi-resistor, which in turn might allow a tiny bit of current to move across the o-ring. Your solution is much better. I'm going to do what you did (1.25" diameter plastic pipe). So, thanks for posting those photos.

[Mucker]

Glad it can help you. I was thinking of going without but this was dead simple, plays the part, and does its' job ....

[Knightstick]

Will a 6AS7G/6520 tube work in the Crack? Just curious as to how the tube rolling works?. I saw the tube equivalents post but not sure how it all works as I saw this tube but there was no mention of a 6520 tube. It mentioned nothing about being a power tube though. Is this the defining word I'm missing?

[Larpy]

A 6AS7 will work just fine.  The 6080 tube (usually shipped as stock) is a ruggedized version of the 6AS7.  Electrically, they are the same.

You can also use a 5998 or 7236 (which is a computer rated 5998), though they are harder to find these days.

I'm not familiar with the 6520 tube, though it's often included in the 6AS7 "family."  Presumably it will work, though I'll defer to those who know more about this tube than I do.

[Knightstick]

Thank you very much sir.

[Paul Joppa]

6520 has better balanced sections, and a few other inprovements to reduce drift of characteristics as it ages. Neither is especially important in Crackbecause of the circuit (cathode follower) and the relatively low dissipation.

[cddc]

Will a 6AS7G/6520 tube work in the Crack? Just curious as to how the tube rolling works?. I saw the tube equivalents post but not sure how it all works as I saw this tube but there was no mention of a 6520 tube. It mentioned nothing about being a power tube though. Is this the defining word I'm missing?

6AS7G is basically the same as 6080, just in a different glass envelope, so definitely works perfectly fine in Crack.

6520 is a "premium 6AS7G", but it is essentially either a Tung Sol/Chatham 6AS7G or a 5998. So definitely works perfectly in Crack as well.

[Colonl_Charisma]

I've been using a 6SN7GT as my input tube (using an adapter in my Crack), and I was wondering if anyone has recommendations for another input tube. I love the 6SN7GT, but I've found that they can be a bit noisy. I've tried a few 12AU7 tubes, but I do not like the way they sound in my Crack. To my ears, they seem to lack in gain and soundstage.

[2wo]

Have you thought about the 6FQ7? I think you need an adapter or rewire the socket...John

[Colonl_Charisma]

I’ve never come across that type of tube, John. I’ll look into it. What kind do you have, and what aspects of it do you enjoy?

[Paul Joppa]

6FQ7 and 6CG7 are 6SN7s in 9-pin mini bottles. For what it's worth.

[Colonl_Charisma]

Thanks Paul! So, could I use my 6SN7 adapter on a 6FQ7 tube if I wanted to try out of one of those?

[Thermioniclife]

The 6fq7 is a nine pin tube so no adaptor needed but I will check the pinouts and get back. Stand by.

[Thermioniclife]

Only one snag, the heater wiring is different but it can be done.
First remove jumper between pin 4 and 5 on the 9 pin socket.
Second remove green wire from pin 9.
lastly solder green wire to pin 4.
Be advised that if want to go back to a 12au and its variants or use a 6sn7 in an adaptor you will need to change this back to the original wiring.

[Paul Birkeland]

If you rewire for 6CG7s, you can use a 7AU7 instead of a 12AU7 without reverting the socket to stock wiring.