Tube Comparison

[auburn-grad]

This may be over-simplifying things.....but, what are the tonal differences between 'Long-plate' and 'Short-plate' pre-amp tubes ?

Can you make any generalizations about tone with respect to the plate size ?

If not, then please feel free to let me know...

[Blue Strat]

You really can't. Every brand is somewhat different. You've got to be specific.

All in all, you can discuss tonal differences with words that were never meant to describe sound until the end of time. Until you've heard it for yourself it's mostly meaningless. I know this isn't a popular answer, but after 25,000 tube orders and discussions with customers I've learned a few things.

[DT7]

VERY generally speaking, the longer plate versions tend to have extended highs...but there are exceptions. If you want more definite answers you'll have to come up with a specific make/model.

[Rambergwest]

I would offer that every family of tubes has a somewhat unique mix of qualities. You can read forever about them as folks try to put words to their experience but within a family of tubes the longer plate versions are usually more lively. This at least partially explains the higher degree of microphonics associated with the increase in surface area of the plates. This has some predictable impact on the tonality as the resonant signature is different. I will stop here knowing that this is not a popular opinion but conclude that the differences are to a degree predictable within a given family of tubes. If you sift through all of the comments posted regarding the best 12ax7 as an example I see patterns that support this idea.

[Blue Strat]

Originally Posted by DT7

VERY generally speaking, the longer plate versions tend to have extended highs...but there are exceptions.

A definite exception is the GE long plate.

[Tommy_G]

Any ideas simply based on the physics of electron flow in a tube?

Do shortplates, on average, have lower mu's, earlier onset of distortion, less current handling, different internal capacitances or resistances?

Those have less to do with the fundamental tone than how they react in a circuit. Tonewise, even within shortplates, there's no discernable trend I can pick up on, other than the converse of what the one commenter said that longplates are more lively; I think shortplates sound duller and sterile

[Rambergwest]

You are on the right track and the only real limit to this line of reasoning is the large number of variables that need to be considered. Surface area is one but dimensions inside the plate structure is also going to be impacted by a change in plate size. Most folks would be quick to point out that it is not predictable but it is more accurate to say that the number of variables makes it extremely complex, not impossible. That is the level that the engineers were working at when tubes were at their best.

[riffmeister]

I've always heard that long plates were more prone to microphonics.

[jtaylor996]

Originally Posted by auburn-grad

This may be over-simplifying things.....but, what are the tonal differences between 'Long-plate' and 'Short-plate' pre-amp tubes ?

Can you make any generalizations about tone with respect to the plate size ?

If not, then please feel free to let me know...

Nope, you just can't. There's just too much variation in everything else that has nothing to do with the length of the plate.

You can compare, short plate mullards to long plate mullards (like a '58 to a '67), but the difference is completely different than what you would hear comparing long plate telefunkens to short plate telefunkens. I've done exactly this, and generalizations just don't work.

[Blue Strat]

Originally Posted by jtaylor996

Nope, you just can't. There's just too much variation in everything else that has nothing to do with the length of the plate.

You can compare, short plate mullards to long plate mullards (like a '58 to a '67), but the difference is completely different than what you would hear comparing long plate telefunkens to short plate telefunkens. I've done exactly this, and generalizations just don't work.

I completely agree with the spirit of this comment. There are, however, no short plate Telefunken 12AX7s. There are smooth and ribbed plate versions both of which have the same length plates. (just in case anyone was wondering)

[Kelly]

Originally Posted by Blue Strat

A definite exception is the GE long plate.

Indeed. I tried one in my amp's v3 spot the other day and lost tons of high end. Very clear sounding tube, but I missed the highs too much

[Blue Strat]

Originally Posted by Kelly

Indeed. I tried one in my amp's v3 spot the other day and lost tons of high end. Very clear sounding tube, but I missed the highs too much

What amp? Also note that worn out tubes will cut highs in not such a good way.

If the amp, pickups or speakers were overly bright a less bright tube could help.

[Kelly]

Originally Posted by Blue Strat

What amp? Also note that worn out tubes will cut highs in not such a good way.

If the amp, pickups or speakers were overly bright a less bright tube could help.

Fryette Deliverance. I was just switching out the stock Chinese with any old tubes I had lying around. I don't mind bright, but the Chinese i have are a little frizzy.

[Timbre Wolf]

So I'll take a shot at this. But Blue Strat's caveat still remains - you've really got to get to specific makes/eras to have more meaningful discussions. Think of the generalizations as if you're asking someone with severe myopia to describe a landscape...

We're talking 12AX7, right? I've listened critically to quite a few (over 50 vintage variants), in amps I know intimately, so here goes:

Long-plate: more openness, clarity, sometimes earlier breakup

Short-plate: more compressed, less clear, usually later breakup


All things are not equal, and cannot be (like a long vs. short plate Telefunky, mentioned). I'm read to discuss exceptions, if anyone needs to.

- Thom