Dumble Preamp tubes

[heisthl]

Pardon my ignorance, but what is a LPS?

Is it long plate?

Yes the LP stands for long plate and Sovtek calls it a 12AX7LP the LPS stands for long plate spiral filament and Sovtek calls it a 12AX7LPS - I only use the 12AX7LPS as a PI tube when I'm out of the non-spiral 12AX7LP tubes.

Last time I was in my D'Lite I had 53v on the PI cathodes and 34 on the grids.
I believe that was with an EH in the PI spot.

I don't write grid voltages on my schematics but now that you mention it my earlier post's value of 12volts sounds low. I'll correct that post when I know the correct voltage.

Henry, I think that is good that you tune your amps to current production tubes.
Because one of these days, there won't be any old tubes left.

AFAIC there are not any old tubes left, at least nothing you could sell in a new production amp.

[thyx]

Currently I have a pair of used 6L6 RCA blackplates in my amp (50 watt).

Yes, the hype is true about these tubes. I couldn't believe it the first time I heard them.

Welcome to the blackplate club.

If you like glassy-clean the STR387 or 7581A (military version of the STR, both by Sylvania) do it better than the blackplate. But for midrange detail in that space between clean and dirty, the RCA wins hands down.

[Structo]

Interesting.

I lucked into a pile of Sylvania pre tubes ( they're used but there are some good ones).
That's where the RCA blackplates were from as well.

Also on another amp I built from a Hammond organ amp, it came with 1959 Sylvanias including two silver topped 6V6GT's.

Those tubes sound fantastic!

But I haven't ever tried Sylvania 6L6's.

[thyx]

But I haven't ever tried Sylvania 6L6's.

The 7581As are usually marked Phillips JAN (in green or blue) as they are really just a ruggedized version of the STR387 (with stronger spacers). They're a big-bottle tube, similar in looks to the Svetlana winged-C 6L6GC that is actually modelled after them. They're great in a Fender Twin for crystal-clear highs, and I won't use any other tube in my Boogie MkII.

The Sylvania pre's are to the tube world what a Celestion V30 is to the speaker world...pronounced upper-mid push, but in a nice way for an overdriven amp. They also come in a military JAN version that I use in my Boogie...but I've never been able to find one quiet enough for V1 in that amp. Too microphonic.

[glasman]

Pardon my ignorance, but what is a LPS?

Is it long plate?

Yes the LP stands for long plate and Sovtek calls it a 12AX7LP the LPS stands for long plate spiral filament and Sovtek calls it a 12AX7LPS - I only use the 12AX7LPS as a PI tube when I'm out of the non-spiral 12AX7LP tubes.

Last time I was in my D'Lite I had 53v on the PI cathodes and 34 on the grids.
I believe that was with an EH in the PI spot.

I don't write grid voltages on my schematics but now that you mention it my earlier post's value of 12volts sounds low. I'll correct that post when I know the correct voltage.

Henry, I think that is good that you tune your amps to current production tubes.
Because one of these days, there won't be any old tubes left.

AFAIC there are not any old tubes left, at least nothing you could sell in a new production amp.

Actually the grid voltage for the PI will be almost the same as the cathode. The reason it measures "funny" is that the typical DMM loads down the circuit causing an incorrect reading.

Gary