Compatible Power Tube

[Duke]

I found this listing on fleabay. http://cgi.ebay.com/EL822-sim-to-EL84-M ... 18Q2el1247
the guy has 300 of them for sale. Does anybody have an opinion on how this might work with an 18 watt trem?
Thanks

[Wicksy]

Other than needing to rewire the tube socket a bit it should work assuming all the voltage handling characteristics are similar to the EL84. Might be worth trying out for **** and giggles.

[Phil_S]

It's a video output tube. Who knows if it's really suited for a guitar amp? In addition, the seller isn't matching them, so you'd need to build an amp that allows you to bias each tube separately or buy a boatload so you can cull a few pairs. Me, I'd pass and this "deal". Just 'cause it says "Mullard" doesn't mean you should jump at the chance to own it.

IMO, if you want a decent and inexpensive sub for an EL84, get a 6GK6. This tube is, in nearly every respect except pinout, the same tube.

[Duke]

Just 'cause it says "Mullard" doesn't mean you should jump at the chance to own it.

That's not at all why I'm asking. I just wanted to know if they were compatible. I currently run some old Brimar el84s and use JJs as backups. I figured at the price I'd try them if they were compatible. It's not sounding like that's the case. Just trying new things.

[kleuck]

These : http://cgi.ebay.fr/6P14P-EV-6BQ5-EL84M- ... dZViewItem
are perfectly compatible, great sounding, reliable...and cheap.

[dotfret]

I was looking for something else today and found a thread on a hifi forum where many of the "locals" are real cheapskates, and knowledgable to boot.

The general concensus was that, of all those old TV pentodes, the EL822 has the best potential for audio use, and the low prices might make using them worthwhile. I wouldn't consider them as an immediate substitute for EL84, but it might be worthwhile to build an amp using them ...

[Dark1]

In addition, the seller isn't matching them, so you'd need to build an amp that allows you to bias each tube separately or buy a boatload so you can cull a few pairs.

I didnt think there was any need to match output tubes in guitar amps delivering distortion. Especially if the tubes are already NOS.
2 100k PI plate resistors are often used to create mismatch - no ?

Shame the pinout is different though..

[Phil_S]

I didnt think there was any need to match output tubes in guitar amps delivering distortion. Especially if the tubes are already NOS.
2 100k PI plate resistors are often used to create mismatch - no ?

Opinions differ on this.

First, the 82K/100K on the PI is an attempt to balance the signal. Wiser people than me came up with this, and I believe it works reasonably well.

In using random pairs, you might get a pair that is extreme in the mismatch. Your 130 ohm shared cathode resistor simply won't do it's job properly and the distortion you get won't be pleasing. You also run the risk of excessive current draw on one or the other of the pair, and that can lead to damage, turning your cheap tubes into the most expensive tubes you ever bought.

It is probably true that a minor order mismatch isn't much to be concerned about. Like I said, opinions vary. I don't claim to be an expert. I stick with matched pairs. I build the amp to do the "work" of creating the tone.

[guitarmike2107]

you have to wonder how long it will be before you see tubes for sale deliberately “slightly” mismatched at an additional cost
for extra harmonic content. Probably cryogenically, magnetically and mechanically treated, with a ribbon on it.. packed in
rose petals and vine leaves for more fragrant fruity tone.