Here's something from a tube seller site:
The Classic series amps have got to be one of the best working man’s amps ever built. For a production made amp they are built well and sound great. My favorite is the 50-410 I like the quick response of the 10’s.These amps are fixed bias and use EL84 power tubes. They provide a crisp, warm tone when using tubes with a moderate natural plate current draw. If it’s a good blues tone your after then a fairly hot set of EL84’s will give a nice greasy tone with an early saturation. The drive channel is very good adding a nice smooth distortion when using good tubes. With the stock Chinese 12AX7’s or sovteks ( the new EH tubes included, as they are sovteks ) it has a nasty honk! http://www.eurotubes.com/euro-k.htmSo this tells you several things.
1. The Groove Tubes are probably relabled Sovteks of some sort and might give the "nasty honk" mentioned above. This is a taste or opinion situation.
2. This amp is fixed bias and you probably have no idea what heat range those Groove Tubes run. This is a HARD FACT situation.
The Peavey Classic 50 is a Class B (AB), push pull, fixed-bias amp that can be modified by any competent tech to be an adjustable bias amplifier. Basically, Peavey was cheap and used a fixed resistor because it's cheaper than putting a potentiometer (bias adjustment pot) in each amp.
Just plugging tubes into this amp is rather like putting a replacement carborator on your engine WITHOUT any adjustment. It MIGHT be perfect (chances are slim)....it might be close....or it might be completely off.
With tubes, the adjustment can be too high or too low.
Too low will typically make the amp sound non-dimensional and unmusical. Real bland or "cold".....but the tubes will last a long time.
Too high and the amp can sound pretty good (for a while), but the tubes will run hot and not last long...also the tube(s) could self-destruct at anytime and could possible damage other internal components when they do.
On the bright side, Groove Tube/Sovteks tend to take heat abuse better than most other tubes...they just don't sound as good as JJ Teslas IHMO. You might simply try the new tubes and plan to get the situation fixed correctly in the near future (perhaps with a matched quad of JJ's).
Just understand that NOT all amps using EL84 tubes are "plug & play" cathode biased situations you find in lower wattage EL84 applications like many VOX amps and even lower wattage Peavey amps.
If the church can swing it, bring the amp to a tech to have the adjustment pot added and get your new tubes correctly biased for long dependable life. This is true for ANY new tubes regardless of brand.....they're all different. "Matched" tubes are only matched to each other in the quad....you have no idea what your amp is set for without checking the bias.
Destes -- Where are you located?
