Need help Dating and Valueing NOS (or maybe just old) tubes

dmt · Jan 26, 2008

I got some NOS tubes, well old anyway. Just wanted some help dating them and or seeing what their value is. One or two if these I am not if they can be used in the preamp as they may be Tv or Radio tubes.

RCA 12AU7A Clear top w/ square side getter

RCA 12AX7A

RCA (?) 12AX7A Script Logo (Electron)

Mullard ECC82/12AU7

Mullard 12AT7A/ECC81 (Labeled Heath), Wing Shaped, Square Getter

PHILCO 12AU7A

Sylvania 5814WA Blackplate, Square Getter

Unknown, GE? CBS? 12AX7A, "C" on bottom, Square Getter

Unknown, GE? CBS? 12AX7A, "C" on bottom close up of getter, Square Shaped

Are these usable as preamp tubes? I think one is for TV the other for Radio.

RCA 6U8A

Sylvania 6AU8

I got all of these for $100, so its not a bad deal, but if the 6U8A/6AU8 dont work for guitar I can trade em for some other tubes.

Also can I use 6V6's in my Simul-Satellite without modifications? Class A? Simul-Class?I have to help this guy catalog 4 boxes of tubes. 100 lbs or so of em...

Rocky · Jan 26, 2008

the last 2 will NOT work as guitar preamp tubes.

Best way to get a rough value on all of those is for you to spend a little time on E bay searching for current and completed sales

dmt · Jan 27, 2008

I tested all the tubes in my amp, the Mullard 12AT7 turned out to be microphonic,

and the Philco tube is just muddy. The RCA/GE 12AX7's are great with each other or paired with an 12AT7, and the RCA/Mullard 12AU7's are very nice for clean and crunch, but terrible for distortion. These I am saving for when I get a Quad, for the clean channel. The 12AT7's paired are very bright and sound great, while a pair of 12AX7's sound a bit more muddy. The Sylvania 5814WA is very strong for a AU7 and is very balance, a bit more middy. Breaks up nice.

dmt · Jan 28, 2008

I replaced the 6AU8 and 6U8A and PHILCO and Mullard 12AT7 with these:

Sylvania 12AV7, Black Plate, winged

GE 5751, Black Plate, Square Getter

RCA 12AT7, Black Plate, Square Getter

Sylvania 12AX7,

The 12AU7's

The 12AX7's

The 12AT7's

The Collection

edgarallanpoe · Jan 28, 2008

The Sylvania 12ax7 is a monster. IMHO it is the perfect tube for Boogie preamps. It has wicked headroom and a walloping bottom end. What did you use the other tubes for? The AT7s and AU7s are really not all that great in many applications. If the Mullard AT7 didn't work as a preamp tube, it might be fine as a reverb driver. Don't assume that because it didn't work in V1 that it is useless.

dmt · Jan 28, 2008

It worked great as a driver, but it was microphonic and picked up vibrations. I loved how it sounded. The 12AT7s that I've been using were in the phase inverter slot and sounded good there, or also paired in the driver as well. Very bright sounding, clearer than the 12AX7's, it is especially good paired with a 12AX7 in the driver as it cleans up the tone nicely.

SixVeeSix · Jan 31, 2008

Depending on your taste, the GE 5751 can be a great first preamp tube (V1). It has about 70% of the gain and less noise than a 12ax7. It may let you turn your amp up a bit and get a better output grind. Worth a try in any case. Can also smooth out a reverb. It is safe to swap with a 12ax7, no worries.