Pre-amp tube recommendations for 18 Watter?

Interesting. Both of my 18 watters lose high end when the volume is turned up. I'm using a Westinghouse branded tube in one and a RCA in the other.

One of mine really opened up after I changed the tone pot from 250k to 1m.

 

Short plate Mullards and Amperex are typically quite bright. I've got a bunch collecting dust, send me email if you're interested.

 

A telefunken 12ax7 will add sparkle and high end. They are hard to find without getting a microphonic one, but a non microphonic one sounds like what you are looking for.

 

an EH 12ax7 is usually brighter than the jj's. Also, the new jj ecc803 is a decent tube IF you can get a non microphonic one.

 

Sovtek are bright although I find them harsh in most amps. Funny, I don't usually think of EH as being bright. They do seem to have more gain though.

 

Microphonic Telefunkens? Nothing is immune from problems, but you've had abnormally bad luck (or you don't have real Telefunkens).

In new tubes, the EHs and Ruby STR 7025s are candidates.

 

I find that the speaker is a BIG change in high end response.What speaker are you using?I have tried everything from a celestion vintage 30 to a randall jaguar(my fav) to a Cannabis rex(very nice too)in my 18 watter. All except the randall has high end sparkle.Maybe you have a bypass cap thet is too high a rating,letting only lows by in the frequency range.What are you using for a cathode bypass cap?

Note: Heyboer transformers are notoriously dark.

 

Another vote here for NOS tubes. I have tried multiple Mullards, Amperex, Valvo, Telefunken, RCA, Sylvania, Tung-Sol, Raytheon etc in all positions and the great thing about the 18 watt format is you can really hear the difference good tubes make. Right now I am using an Amperex in V1 and a Telefunken as the PI with a RCA blackplate for the trem channel. Power tubes are late 50's Sylvania blackplates.