SED C WINGED EL 34'S as replacements

[gatom21greyhound]

I purchased SED C-winged EL'34s for my Dual Rectifier as well as my Stiletto Ace Combo. Do I need to take these amps to the shop to have them re-biased or are these tubes compatible to Mesa's standards? Thanks

 

[domct203]

Did you ask the Tube Vendor to sell you tubes that were compatible with your amp?? I have no idea what rating tubes you have, or how your vendor chose to rate them.

Mesa's are non-adjustable fixed bias. That means that you need to change a part on the PCB to adjust the bias. That is why you buy tubes selected to run at Mesa's bias spec's.

I would take it to a tech to verify the idle current draw, you may be fine as-is. Others may tell you that if the tubes don't glow red you are OK. The choice is yours.

Just remember that blowing a tube could result in damage to the amp.

Dom

 

[espboogie123]

The sed winged c el34s work great. No biasing needed due to fixed bias. As long as they were a matched quad they be just fine. EL34 mode runs warm so the winged c's will run great. It is the 6L6 mode is where a person should tell the tube vendor what amp it's for. The 6L6 side runs cooler and some too cool. The tube vendor can find a quad that will rate higher to get a warmer bias. I currently have SED 6L6 winged c's and have SED el34 winged c's as backup for my roadster. Both tube sets sound great. Just flip the 6L6/EL34 switch to correct tube type and your ready to go.

 

[domct203]

The sed winged c el34s work great. No biasing needed due to fixed bias.

Fixed bias DOES NOT mean you do not worry about idle current draw (bias). Fixed bias simply means that the output stage runs at a constant (fixed) bias point (voltage) during operation. Some amps have adjustable fixed bias (bias pot), some amps like Mesa have non-adjustable fixed bias (bias resistor).

EL34 mode runs warm so the winged c's will run great.

This is even more reason to be concerned with your idle current. Yes, EL34 mode runs a little warmer, but with this your tubes are also closer to MPD (red-plating). Depending on how the tube eventually fails it could put alot of stress on other components in the amp, maybe to the point of their failure as well. I've had a tube that was at only 50%MPD short out and take a screen grid resistor with it. Guess what, the fuse never even blew.

Just flip the 6L6/EL34 switch to correct tube type and your ready to go.

Not true, unless the tubes have already been screened and selected to run at your particular amps bias setting. Even then you should double check the idle current draw. I took some JJ E34L's that run at about 70% MPD in my Roadster and through them in my MKV. The inside pair ended up at 105% MPD, and would have red-plated immediately if I tried to play the amp that way. This is the reason why I own a bias probe. Even when I ask a vendor for tubes rated to run in a Mesa (as these E34L's were), I always double check the bias.

Statements like "No biasing needed due to fixed bias" are misleading and in-accurate.

Ultimately, it's your amp, do as you wish.

Dom

 

[espboogie123]

I think you worry too much bro. "No biasing needed due to fixed bias" is a correct statement in that, since the mesa is fixed bias, WE cannot bias unless modded with the resistor out the correct pot in place. Me and my buddies have 4 roadsters and quite a few triple/dual recs and and rarely encountered a red plate mismatch and we have tons of tube swapping. The OP was simple asking if he needed to take to tech to bias... and the answer is no. The SED winged C el34s sound great in the roadster and many amps. I have those as backups as I run the Winged C 6l6s.