Tube Rolling w/Crack

[Chris65]

I recently picked up a NOS Mullard 6080, it has similarities to your photos. The date code on it is 'AJ1 R0F4' which I think dates it to June 1970, Mitchum factory.
Only top 2 mica are 'spiky' & single halo getter with no shield at the top like yours. Likely yours is earlier?

[ffivaz]

I have a RCA 6080, quite "recent", that has the exact same construction, especially with the metal base. I use it in my Crack since the beginning. It's dead silent, non microphonic. It tried a bunch of 6as7g and always came back to the 6080.

[JamieMcC]

I am really liking  the Mullard 6080 and its giving my 5998's a real run for the money at a fraction of the price. I wouldn't like to do a blind test and I nearly didn't even try it!

It was in a box of three mixed 6080 I picked up for a few pounds brought really just as spares in case of problem with the build, 1xrca  1xtung sol  (which I dropped and broke) and the Mullard which was just ignored as at the time as I could not make out the markings which were left on the tube at all.  Then the 5998's and GEC brown base arrived and I never got round to plugging it in. I was having a round up of a few tubes to move on and pulled it out had a look with the magnifying glass identified it plugged it in and suddenly hmm its got me questioning the need and cost of the 5998's.  It even sounds good with some of my cheapie 12au7s.

[serpent68]

Buy a different 12BH7.

I finally received a pair of Philips E80CC and a pair of Tungsram E80CC from Ukraine after 1 month of shipping time.  When I plug the E80CC, the same (very) loud buzzing sound was heard through the headphone.  Similar result with the Sylvania 12BH7 and Tungsram E80CC.

I replaced the TS 5998 with a Bendix 6080WB.  No buzzing sound at start up, and the music is fine.  Swapped in my second (spare) TS5998, and the same loud buzzing sound is back.

Could it be a compatibility issue between the TS 5998 and 12BH7/E80CC?

The TS 5998 works with 12AU7, 7316, and 6SN7 (with adapter).  Extremely loud buzzing sound with 12BH7 and E80CC, even with the volume turned down.

Anyone with similar experience?

[Paul Birkeland]

What're the voltages at terminals 1, 5, 7, and 9 with the BH7 and 5998?

[bdr529]

I get a loud buzzing on my 5998 too, at least for the first minute as the tubes warm up. After that it becomes completely silent. I checked the voltages and everything was within 10-15%, so I don't know.

[Paul Birkeland]

Can you post what they are?

[bdr529]

I can get them Friday when I go back to work after the holiday. I was using the equipment there today to measure it, but I didn't write anything down as I checked it. I remember the high voltages were about 5-10% above the ones in the manual. Is the buzzing a bad sign?

[bdr529]

Okay, new discovery. The buzzing is only present if the volume is at 0. As soon as I move it away from zero the amp goes silent. That is interesting.

Sorry to bring this into the rolling thread, I had already mentioned this in another thread, but i just saw that someone else had a similar problem...

[serpent68]

Thanks for the input.  Unfortunately, I'm not able to verify the voltages right now because I just loaned out the 5998 to a good mate for a couple of weeks to try out in his amp.  Really strange phenomena, I am suspecting if there is something wrong with my pair of 5998.

My initial voltage check was near perfect, but it was done with the stock GE 6080 + 12AU7 tubes.  Would a different type of tube pose a different set of voltage readings?

Running in the Bendix 6080 + Philips E80CC right now.  Sound is very similar to the 5998 + 7316, and I may like this new combo a bit better because it is a shade more dynamic and has better bass slam.

[bdr529]

I wasn't able to measure the voltages Friday, but pretty sure it is just a bad tube. My other tubes work fine.

With the Speedball, the 12BH7 will function in the circuit, but it changes the operating point of the 6080 pretty dramatically.

I'd remove the red LED's on the 9 pin socket and replace them with 1.2K resistors (1/8W is plenty) to bump up the bias a bit, and bring the plate voltage up to ~90V (with the Speedball).

-PB

With this change is the circuit still suitable for 12AU7 tubes?

[Paul Birkeland]

I wasn't able to measure the voltages Friday, but pretty sure it is just a bad tube. My other tubes work fine.

With the Speedball, the 12BH7 will function in the circuit, but it changes the operating point of the 6080 pretty dramatically.

I'd remove the red LED's on the 9 pin socket and replace them with 1.2K resistors (1/8W is plenty) to bump up the bias a bit, and bring the plate voltage up to ~90V (with the Speedball).

-PB

With this change is the circuit still suitable for 12AU7 tubes?

Not particularly, no.

[bdr529]

Is it worse than running a 12BH7 without the mod? Or should I really just pick one or the other and stick with it?

[NightFlight]

I can't seem to beat the stock tubes.
I got an RCA WA6080 and a some USA made white labelled 5814A, but all white silk screen has been mostly rubbed off.

I've tried:

• Tung-Sol 5998 - Wide soundstage, but insufficient "weight" in the bottom end.
• RCA clear top - Too bright
• CV4003 - completely flat response, no fun at all

I'm pretty happy with my stock input tube. I'm fairly certain its a halo getter GE 1960-61 5814A seen here:
(https://www.tubeworld.com/5814ap1.jpg)

In both cases of the input and driver tube I keep going back to the stock tubes for a sublime listening experience.  My original complaint with the RCA 6080WA is that it was too intimate and muddy. The speedball seems to have cleared up the mud - but it remains a hair intimate for my liking. In retrospect I also slightly preferred the stock Crack over the speedball - it seemed slightly more honest.

I'm picky, I know. 

Is there a output cap thread? I'm looking to retrieve a little more detail from the crack. I'm on a budget for the next year or so otherwise I would be building a mainline by now. What mods can I make? I'm thinking the component upgrades. What are the best suggestions - or is this a thread on its own?

[Paul Birkeland]

Or should I really just pick one or the other and stick with it?

Yes