JJ ECC99?

[levlhed]

I've come across the JJ ECC99 which is touted to be a viable replacement for a 12BH7 in "most" circuits.
link to manuf. spec sheet http://www.jj-electronic.sk/pdf/ECC99.pdf
I don't really know what any of that means.  Info I've dug up in searches doesn't mean much to me either.  All I've gathered is it needs more heater current to work right.

Will this tube work in a Crack Speedball?

Any guesses as to how well it should work?

Thank you

[Grainger49]

Recently PJ posted some of the paramaters that need to be the same, essentially the same, for tubes to be equivalents.

I would like to see that put into a Sticky in the Technical Topics area.  It is a FAQ.

If you go to PJ's profile you can click on recent posts and find this post.  He starts by saying that a tube asked about is not an equivalent for one that BH uses.

[levlhed]

I think I found the post, but I'm afraid it doesn't really help me figure out the answer to my question.  I don't understand what the abbreviations are for the values he speaks of.  Also my question isn't really about the ECC99 compared to a 12BH7, my question is will the ECC99 work in the Crack Speedball circuit?  Comparing the values between the two tubes doesn't really tell me that.

If I understand correctly, a 12BH7 is a stretch in the first place but works with the speedball upgrade.  Is an ECC99 a further stretch that steps out of spec? 

[Grainger49]

Unless the Speedball changes the driver needs you need a 12AU7 equivalent.  This is a thread of equivalents that I put in the Legacy products area:

http://www.bottlehead.com/smf/index.php/topic,1027.0.html

The ECC99 is not on the list.  That doesn't mean it shouldn't be, but it isn't.

Looking at the specs on the tube store the ECC99 draws a lot more heater current, looking further on they are not the same tube at all.  But I still can't say the Speedball won't run it.

[levlhed]

Yes, more heater current!  Too much?

[Grainger49]

They are not the same tube at all.  The heater current is not the only big difference.

[levlhed]

yah I know

[levlhed]

Can anyone provide me with a definitive answer on this?

[Paul Joppa]

The heater should be OK, the PT-3 can handle 3.5A rms. The heater voltage might be a bit low.

A definitive answer should come form PB, a.k.a. Caucasian Blackplate - it's his design. I don't even have a manual or schematic. He's tied up at RMAF right now, so it may be a few days before he can get to the forum posts.

But meanwhile, looking at the curves on the spec sheet, assuming 3.8mA plate current with the speedball, and assuming LED bias, the plate voltage would be about 50v, 2/3 of the normal 75v. Being a direct coupled cathode follower, the output tube should work just fine; it will have a bit more voltage plate to cathode but it's run very conservatively so that should be no problem.

[levlhed]

Thanks
I would have to guess (if I understood correctly) that since the ECC99 wouldn't be running at full voltage that it won't really be working up to it's best in this circuit.

[Paul Joppa]

"...since the ECC99 wouldn't be running at full voltage that it won't really be working up to it's best in this circuit."

That's certainly my opinion - a tube capable of 4 watts running at 0.2 watts dissipation?! Actually, the 6AS7 as a cathode follower is incredibly easy to drive, almost any tube can do the job. So it's down to questions of cathode material purity (which may affect noises), linearity, and mechanical resonances/microphonics when looking for causes of a different sound with a different tubes. Plus of course all the parameters that we don't yet know to be important! ...  Anyhow, I just mean to agree with your statement while also noting that working a tube to it's technical potential is not the only criterion. If it sounds good, it IS good, after all.  :^)