Output tube observations

[dogears]

I spent many hours since getting my new Maxi-Matcher output tube tester comparing different sets of 6L6 tubes in my Bludo Ojai.

I came up with some important observations.

Brand is not as important in many cases as the plate current and transconductance measurements.

In other words, higher headroom tubes sound and feel better to me. I have several quads of SED Winged Cs. However, these all measure low. PC of 16-17 and TC of 2000-2100. The TC is under spec. 2200 or so is considered the low end. These tubes when installed do not sound as good as my stronger rated quads from TAD (short bottles), Tung Sol reissue shorts, Ruby 6l6GC MSTR, and even Sovtek!

I discovered that a nice tube that biases in at -48v to -50v sound good. TC in the 2400-2800 range is nice. Plate current on a Maxi of 20 to 28. Higher the better.

Currently for new stock, I am back to the Tung Sol short bottles. I have a quad installed measuring 25 on the plate current and 2600 on transconductance.

Be careful with SED. The tubes are coming super weak these days.

Any thoughts?

[M Fowler]

When ordering tubes then we need to go to a dealer that provides a rating system and based on your testing what should I ask for in those octal power tubes? The transconductance measurements?

I'm referring to new production tubes.

Mark

[dogears]

Higher numbers on the GT scale or TAD scale.

For instance, TADs with a rating of 6 or 8.

When ordering tubes then we need to go to a dealer that provides a rating system and based on your testing what should I ask for in those octal power tubes? The transconductance measurements?

I'm referring to new production tubes.

Mark

[M Fowler]

Thanks for the information that really helps me out.

ALso, GT has a totally different number system based on matching.

[FYL]

ALso, GT has a totally different number system based on matching.

Details here: http://www.guitaramplifierblueprinting.com/Rating.html

[Structo]

Thanks, good info there.

Sad to hear that the Winged C tubes are not keeping up the high quality that they had earlier on.

[Max]

Seems to be a matter of personal taste, too:

My own personal taste is the same as the one of Scott (headroom). But I've met first class guitar players, who preferred tubes with lower transconductance values a lot and in the very same Dumble ODS.

Cheers,

Max

[dogears]

Max,

Keep in mind I was referring to the 10% underspec Winged C tubes! When they get that low, I don't think those same guys would prefer them.

There is a kind of point you reach where the weak tubes just are not so good.

Seems to be a matter of personal taste, too:

My own personal taste is the same as the one of Scott (headroom). But I've met first class guitar players, who preferred tubes with lower transconductance values a lot and in the very same Dumble ODS.

Cheers,

Max

[M Fowler]

Good information guys thanks.

Mark

[Structo]

Scott what is it you hear when comparing say, some weak Winged C tubes compared to a quad that tests strong?
In other words what does a quad of weak tubes sound like?

I don't have enough experience to know what to listen for other than if the amp just wasn't very loud anymore.

[M Fowler]

The EL34s I got from one supplier were called seconds poor rating and they had less headroom and more stale sounding without any blum.

[tubedogsmith]

Scott what is it you hear when comparing say, some weak Winged C tubes compared to a quad that tests strong?
In other words what does a quad of weak tubes sound like?

I don't have enough experience to know what to listen for other than if the amp just wasn't very loud anymore.

Not Scott, but they're weaker, softer sounding, squishier and can be a bit ratty and gritty sounding even. That description is in comparison to a strong tube and not as bad as it sounds from my description.

[FYL]

Sad to hear that the Winged C tubes are not keeping up the high quality that they had earlier on.

They are still excellent, but it seems that numerous factory rejects have found their way to distributors worldwide...

[dogears]

Where are you finding the strong ones??

Sad to hear that the Winged C tubes are not keeping up the high quality that they had earlier on.

They are still excellent, but it seems that numerous factory rejects have found their way to distributors worldwide...

[talbany]

For some reason and not sure at the time about the matching system but my JCM 800 always sounded the best using GT 6CA7's #7 Used them for like 5 years stayed pretty consistent sounding and feeling and I always re-biased the fresh set..The JJ-34's in that amp sounded and felt rather bad!!

Tony