Tube Rolling w/Crack

[JamieMcC]

I recently received this tube in the mail. It’s a Chatham 5998, and "650" with the letter J is printed on the base. It has a clear top. The description stated that it has "triple mica, black plates and twin bottom D getters.”

Are bottom or top getters better? Or does it make a difference? It sounds great. Just curious about some details. Also would like to know what year this tube was made in.

There’s so many variations of the Tung Sol and Chatham versions of this tube. I’ve searched through this and other threads to learn about these tubes. I’ve read the 116 pages in this thread.

These early 1950's clear top 5998's are nice sounding tubes, I prefer them to the later 5998 and WE421a variants.

[Tom-s]

After a year without use i got my Crack back in working condition.
And for once i did a count of the tubes and with over 150 12au7's and many others i'm, once again, in for a long journey discovering the sound of different tubes.

But my love for Crack is mostly in the modding options for running all sorts of tubes.
I found a few ECC32's (1950's Mullard brown bases) and i'll try using Crack with those soon.

Any experiences with these? I think it should work in a standard speedball crack with R1 resistance for E80CC and the normal 1.5V bias? I also have the bias for 5687 build in to switch to?

Edit, now enjoying Bendix slotte graphite 6080 with Brimar CV491  red labeled(1950's).

[Paul Birkeland]

The ECC32 is a 6SN7 and should work with the stock Speedball.

[Tom-s]

That's the thing. It's not a 6SN7 equivalent. It might be close. But still different.
Please note the electrical comparison on the following website: https://www.tubeworld.com/ecc32ecc33.htm

Tube data: http://www.r-type.org/exhib/aad0139.htm

But my guess is that it indeed will work!

Might try tonight.
 
i'll measure 1 and 5 to see what the voltage is there (lets hope it comes in around 75V plate voltage).

[Paul Birkeland]

Please note the electrical comparison on the following website: https://www.tubeworld.com/ecc32ecc33.htm

The mu values on that table are way, way off!

The ECC32 does have slightly higher mu, higher Rp, and lower Gm, but the curves are pretty close.

i'll measure 1 and 5 to see what the voltage is there (lets hope it comes in around 75V plate voltage).

It should be pretty close.  You may see more like 85V.

From a comparison standpoint, the Crack is already a bit heavy on the gain, so adding more isn't generally helpful to the amp (though no harm in trying).

[Tom-s]

My typical 6SN7's measure 80-85V +-.

The ECC32 measures in at 115V+-

With R1 switched to double the resistance it's 80-85V.

Oh and the sound is good. It's better than my Brimar 6SN7GT (closest thing i have), 6N8S metal plate Melz, various VT-231's.

I'm a fan of these.

[vafan13]

I have it on good authority that Santa is bringing me a pair of Beyer T1s to go along with my crack w/speedball.  Currently using stock tubes, considering trying something else.  Are there any in particular that work well with the T1?

Took me a while but I ended up with a Mullard CV4003 and IBM-branded 5998 at not-insane prices (relatively-speaking).  The 5998 was a bit of a gamble, but no microphonics or noise issues, and it sounds great.  I got the CV4003 first, so had a decent amount of time with that plus the stock 6080 before the 5998 went in.

[Paul Birkeland]

The ECC32 measures in at 115V+-

I just pasted the curves into paint and you're correct.  Setting the plate current for 2mA should be about right.

[InnerTube]

I have used several 6F8G tubes in the Crack with great success - especially the Tung-Sol.  What a great sounding tube.  In addition to the sound, the 6f8g runs quite cool.  It hardly makes the plate warm while the 6080 makes the plate quite hot.  I recommend adding this tube to the collection although it requires and adapter. 

[Tom-s]

I have the same experience with these tubes.
More lush, spacious than your average 6SN7 tube.
IME they do tend to be a bit microphonic from time to time.
The VT-99 is indeed a great tube. I use them with square plate and round plate versions with the black glass.
Both are great. The round plate is supposed to be a bit better, but i can't hear that.

[InnerTube]

I have 8 or 10 of these tubes and have only had trouble with one of them.  It causes substantial pops and cracks especially in the left channel.  As good as these tubes sound I do not know why I listen to other tubes.  Cool running is also a real plus.  I wonder if this tube will be added to the crack list.  Wishing you good listening, JS

[Kitchener]

I wonder if this perhaps should go in the General Discussions subforum?
I'll risk it here and let the mods move it if I messed up.


I been tried out two types of 6SN7 valves in my Crack recently with an adapter (I'll be vague and say the adapter comes from a Bottlehead competitor, don't want to tread on any toes here).


But I'm so far most displeased with their performance.
They seem to be excellent antennaes for interference from pretty much everything in my office.
I keep my Crack pretty close to my computer and monitors, but the 12AU7 valves hardly pick up any interference.
-some slight high pitched whining if I move it around, but pretty much dead quiet.
Not so with the 6SN7s.
I've tried two USSR brown base 6SN7s and one RCA "smoky" valve, all are unbearably noisy.
-the RCA is busted anyway; loud popping when I wriggle the tube.

I thought maybe it was the adapter since it's kind of exposed, but I tried covering it in Sugru (not sure if that helps in the slightest though) and it made no difference.
Clamping my hands around the valves removes the noise, but I find it a little impractical in the long run.


Anyone else have the same experience?

[Paul Birkeland]

This is pretty typical of many of the adapters sold online.

[Kitchener]

Seems like it from what I’ve read yes.
Bah, I can’t even tell the difference between different 12AU7s or 6080s.
Whatever difference I’ve thought I’d heard, turned out to be my imagination.

Im confident Bottlehead used the 12AU7 for a reason.
I’ll file the 6SN7 experiment under P for Pointless.

[Paul Birkeland]

The driver tube in the Crack ultimately works best when it has the lowest possible gain, as well as being able to operate fairly well without a ton of voltage.  The 12AU7 is just more available than the 6SN7, doesn't take up as much space on the chassis, and can't be plugged into the 6080 by accident. 

The 6CG7 is a 9 pin 6SN7, and a minor change to the 9 pin socket wiring would allow its use (and the 7AU7 would then also work instead of the 12AU7).