Tube Rolling w/Crack

[Paul Birkeland]

The 12BH7 needs some tweaks for the voltages to come out about the same as the stock circuit.  In the stock circuit, the plate voltage would end up being pretty low and I think the 22.1K resistors would burn up.  I don't see a good way to run the 12BH7 in the stock circuit without changing out the LEDs for cathode bias resistors and changing the 22.1K plate loading resistors for something with a different value and a much higher wattage rating.

[Mucker]

Whew, I am getting ready to try a 12BH7A once I get my new transistors for the SB board. I had to go back and read the last reply relieved to hear it was with stock Crack about burning things up.

Can an E80CC be tried in a stock Crack (no SB) without worry or does it take some serious modding? The E80CC is pretty amazing IMO.

[Paul Birkeland]

E80CC in a stock Crack is close enough to try.  Changing the 22K resistors for 33K/1W would be a good idea if you're committed to the E80CC.

[Mucker]

Ah nice, great info.

[mcrushing]

Indeed, thanks for the info Paul. I’ll leave that bh7 in the drawer.

E80cc sounds interesting, though!

[Mucker]

The E80CC is a great tube IMO but they are rare and expensive now. I am actually going to try the 12BH7 route because of the price and availability now. Will be interesting to know how it will stack up against the E80CC. I also want to try the 6CG7 (apparently a 6SN7 equivalent) but socket rewiring is required which doesn't look too difficult. You may not need Speedball for a 6CG7 and socket rewire but PB would have to confirm that.

[Mucker]

My ON MJE5731AG transistors arrived today and I swapped them out on the Speedball boards so that I could use the 12BH7A safely. I have 470 ohm resistors permanently installed on the boards so that I can run my favorite tube, the E80CC. To run the Matsushita 12BH7A, I soldered on 150ohm resistors in parallel to arrive at 113 ohms. T1 and T5 voltages ended up being 74.8/73.0.

The tube sounds outstanding with a Chatham 2399 power tube and my new HD-600. I need to compare it more to E80CC but right now sounds just as good. They are more affordable and available than E80CC so that is a plus.

[Mucker]

E80CC in a stock Crack is close enough to try.  Changing the 22K resistors for 33K/1W would be a good idea if you're committed to the E80CC.

Hi Paul, is this the only required change if i want to run an E800CC long term? TY.

[Paul Birkeland]

Hi Paul, is this the only required change if i want to run an E800CC long term? TY.

How long would you like your amp to last?

[Mucker]

Well, I'm 57 so it's not going too be to long. Hopefully 10 more years if I'm lucky. Ears are still amazingly in good shape for being in the mining industry my whole life.

[Paul Birkeland]

You'll want to change around those resistor values then I think.

[Mucker]

OK, thanks! I want to give a good long listen to my Tung Sol NOS 12AU7's and those Nichicon coupling caps before I get too excited about doing anything. Could be a while but I will definitely use this info going forward. Appreciate it!

[tlite]

Howdy all.  New to Tube rolling with a Bottlehead Crack 1.1 w/SB.

To get a sense of "the extremes", what would be two VERY different sounding input tubes and two very different sounding power tubes I could try in the Crack to help develop my ear for tubes?

I guess I'd like to stay under about $25/tube for this experiment... but can go higher if there's a reasonable resale market for a particular suggestion. 

[larcenasb]

Hi tlite,

For about $25/tube, you'll have to do some searching or be patient on auction sites. People are really overcharging for tubes these days...

I think two very different-sounding input tubes would be: RCA 12AU7 clear top & Brimar CV4003

And two very different-sounding output tubes would be: any generic U.S.-made 6080 (like the ones usually included in the Crack kit) & any generic U.S.-made 6AS7G (RCA is the most common, and Sylvania, G.E., Raytheon are other budget options, these all seem to sound very close to one another.)

I've tried many, many tubes in the Crack+SB and I think what I suggested is a reasonable place to start. Once you're ready for the next step, getting a 6.3V 6SN7-to-12AU7 adapter with any U.S.-made 6SN7GT will tend to have a significant difference in sound to most 12AU7 types, and it's a well-regarded tube type in the audio world. Have fun and be sure to report back differences you hear with whatever tubes you end up buying. Cheers!

[StormNinjaPenguin]

Hi all,

I'm new here, just finished my Crack (no Speedball) that came with GE 6AS7GA and RCA 12AU7 (not clear top).

My tube rolling experience so far:

• Winged "C" 6H13C power tube: I like this much more than the stock GE tube. It has better staging, it sounds more 'open' with better imaging without being hollow or thin. In comparison, the GE tube is more 'congested'.
• Genalex ECC82 Gold Lion preamp tube: all reviews praised this and it has a very clear, nimble, 'decent' sound but the bass amount is significantly lower and the overall warmth is gone. I prefer the stock RCA tube because it has a fuller, warmer, more engaging sound. I still keep the Genalex tube because classical music sounds awesome with it but the majority of the time I listen to the RCA.
  

Does anybody know if there is a difference between the RCA clear top and not-clear top?