What happens if I use 6550's with a 40 Watt OPT?

[RJ Guitars]

Dumble Guru's... I'm slowing plugging along on a Dumble Lite. I've got a Thordarson 200ma 350-0-350 Power transformer and a 40 watt 6.6 K Ohm OPT. The OPT has a 4,8, and 16 Ohm tap.

I'd like to hear EL34's, 6L6's, and 6550's and sort out which one I like best. Will I damage something (mostly worried about the OPT) if I use 6550's in this amp?

I know each tube type will bias different and I'll have to tweak, but I've got time to do that, just don't want to ruin parts.

I don't need the maximum wattage if that makes any difference.

Thanks

RJ

[VacuumVoodoo]

6550s are current hogs and your power transformer seems on the weak side for 2x6550 current wise.
At best you may try cathode biased configuration for a 40W amp. see p2 on the DATASHEET
It's a hot biased class AB1 so you may not have enough DC current, (170mA DC idle up to total ca 200mA DC at full power)

In worst case the power transformer will overheat or/and go south, make sure the mains fuse is correctly rated for the transformer in question.

[Funkalicousgroove]

I'd shy away from 6550's,

withhe PT you are using, you'll get around 450 VDC on the plates, Biasing at 70% they'll each draw 60mA at idle, I think that may be a bit stressful on both trannies, I doubt that they'd go up in smoke right away, but it would reduce their usable life. What's the current rating of your OT?, What about your filament wind

[RJ Guitars]

Thanks guys, it sounds like I might need 2 completely different trannies from what I've got if I want to mess with the 6550's... I don't need the watts but I was curious if my setup could handle them and give me another tone option...

My OPT is a Hammond 1650H - 40 Watt - 6,600 ct - 200 ma. per side - 4-8-16 ohm.

I'm sure I can get by on EL-34's and 6L6's - I rarely have anyone saying "could you turn that up to 11, I can't hear you"

Thanks again

rj

[Zippy]

Power handling on a transformer is related directly to its current-carrying capacity. If you don't run enough signal into the 6550s to generate the current, you'd be alright. It'd be like running a hotrodded, big bore V-8 with a fuel restrictor plate in. Problem in your case is if the signal gets away and draws enough current to do some damage.

If you were running lower voltages such that the high power condition wasn't possible, it'd be different. I'd say save the 6550s for when you have a sufficiently robust set of transformers or, at least, a lower voltage power supply.

+1 for adding fuse protection to the the OT.