New Tungsol tubes, problems?

[Bob-I]

I just bought a bunch of the new Tungsol 12AX7's to test in my Dumbles. I have some pretty tired originals that sound pretty good, I'd hoped that these new ones would be better.

I tried these in all positions except the loop and reverb with the same results. Great tone but crank the drive a bit and they oscillate, in the audible range, in the PI around 400-500Hz but in V1 or V2 up around 5K (esitmated from a really old uncalibrated fuzzy scope).

The dissapointing thing is that they have really nice open harmonics but I can't use them if they're gonna oscillate.

I'm back to EH in V1 and V2 and a Sovtek 12AX7LPS in the PI, JAN Phillips 12AT7 for the loop and still playing with the reverb.

Anyone else have this type of issue?

[Bob-I]

Now that's bazaar.

Since no one else replied, I figured it had to be my amp. I opened her up and figured while I was in there I'd look for lead dress issues, maybe solve the little bit of hum I've been having.

That little bit of hum turned out to only be there when the loop was active. I moved some grounds, no luck. Hooked up my scope to the amp ground and magically the hum was gone. Took the scope ground off, HUM.

Connected a clip lead to the cathode ground bus, no hum, and the other end of the lead wasn't even connected. As I moved the lead around the hum would come and go.

I moved the cathode grounds to the pot grounds. Quiet as a mouse.

Put the Tungsols in, no oscillation, and they sound pretty good. I gotta test more when I get my other cab back from the rehearsal room, but I'd say they sound good. Smooth, complex and a tad more gain than the EH.

[Luthierwnc]

Mine have been fine. You found what I usually do -- chasing down a parasitic is usually a matter of shielding/moving a signal wire. sh

['67_Plexi]

I'm with you Bob, I had 20 reissue Tung-Sols that were all less than average. I had high hopes for them. They sat on the shelf for months and eventually I just threw them away.

[Fischerman]

I only recently bought 2 of them and I like the tone...mine have slightly less gain than the EH I was using.

I really like the tone though...especially everything above the bass frequencies. To me the EH has a little extra bass hump in there somewhere...and I have a love/hate thing going on with it. The word that comes to mind describing the EH is...greasy. Sometimes I like greasy...sometimes not so much. One word for the Tung Sol would be...refined.

But mine were not micro or noisy or prone to oscillation...quite good in those departments I think.

[greiswig]

I had one TS tube where the filament buzzed. You could hear it acoustically with the standby switch off. I swapped it out, and the problem went away, even when I put the same tube back in the same socket. I'm still scratching my head over that one...

[Bob-I]

I only recently bought 2 of them and I like the tone...mine have slightly less gain than the EH I was using.

Interesting, mine has MORE.

I really like the tone though...especially everything above the bass frequencies. To me the EH has a little extra bass hump in there somewhere...and I have a love/hate thing going on with it. The word that comes to mind describing the EH is...greasy. Sometimes I like greasy...sometimes not so much. One word for the Tung Sol would be...refined.

Good description, I agree.

But mine were not micro or noisy or prone to oscillation...quite good in those departments I think.

Interesting that this was a very well behaved amp until I put the Tungsols in. I had to move a ground to a location that's given me nothing but trouble in other Dumble's to solve it, go figure. The amps stable and quiet again.

[tubeswell]

Hi there

First Post on this forum

FWIW I like the New Sensor "Tung-Sol 6V6GT reissue" I put in a SE amp I built recently. Seems to handle about 364VDc on the Plate with 13.7W dissipation. Has a nice phasey swirl when cranked if the guitar vol is wound back to keep it clean. Otherwise its a dirty hounddog.

So I'm going to try a pair of them now in a push-pull amp

[pamaz67]

I've had some tung sol 5881 in one of my amps since 6 months.
They performed well and the tone was amazing, but suddenly one of the tube became very noisy.
Browsing in diffreent forums, I've heard that other guys have the same reliability problem with the 5881.