A few years back, I picked up a used Sundown tube head for $150 or so. It had two 6L6s, and I surmised that it must be one of the 50W models I'd read about. I subsequently brought it to a local tech to be tuned up, and had him replace the 6L6s with EL34s. Recently, I contacted the designer, Dennis Kager, who, based on the serial number, informed me that this amp was originally equipped with 2 6550s, and was advertised as being 100W.
At this juncture, I'm considering building a new point-point board and using the original transformers, (solid state) power supply, and chassis, mainly because it needs service, and I'm really not all that attached to the current voicings, feature sets, PC board construction, etc.
Not quite sure what I want to do with the output section. I've always liked the sound of EL34s, though right now I'm running fat-bottle 6CA7s. Never been wild about the sound of 6550s, and really don't need that much power anyway. KT66s might be a consideration.
I'm wondering what the implication of using the existing transformers (output and power) will have when applied to these other tubes. My gut feel is that it'll just be a matter of overkill, providing I'm careful about my voltage levels. Is this accurate?
What is the sonic effect of running both preamp and power tubes at higher than normal (but still within spec) voltages?
Thanks,
Joe
6550-->6L6-->EL34 tube mod?
Moderators: pompeiisneaks, Colossal
Re: 6550-->6L6-->EL34 tube mod?
Joe,
I'd start with a couple of more basic questions:
1) Can you actually get real 6550's -- ones that have a reputation for good tone? Some of what is/was being sold are really some other tube type labeled as 6550, probably 6L6.
2) What will you do with a 100W amp, even if you could build it? Are you playing a stadium? 50W provides about 90% of the perceived volume of a 100W amp.
I recognize that everyone's needs, tastes, and desires differ. If it were mine, I wouldn't try to make it into a 100W amp.
As far as your not liking the voicing of the amp, that, in my view, is the best reason for doing something. You probably have a great platform that offers lots of choices. I wouldn't feel locked into the original expectations for this amp.
Just my 2 cents.
I'd start with a couple of more basic questions:
1) Can you actually get real 6550's -- ones that have a reputation for good tone? Some of what is/was being sold are really some other tube type labeled as 6550, probably 6L6.
2) What will you do with a 100W amp, even if you could build it? Are you playing a stadium? 50W provides about 90% of the perceived volume of a 100W amp.
I recognize that everyone's needs, tastes, and desires differ. If it were mine, I wouldn't try to make it into a 100W amp.
As far as your not liking the voicing of the amp, that, in my view, is the best reason for doing something. You probably have a great platform that offers lots of choices. I wouldn't feel locked into the original expectations for this amp.
Just my 2 cents.
Re: 6550-->6L6-->EL34 tube mod?
Hi Phil,
Thanks for the reply. I wasn't considering going for MORE power at all -- quit the contrary. I agree -- don't even have need of a 50W amp, although as I come to appreciate the value of clean headroom, I'm less fixated on overdriving everything all the time. At the moment, I'm leaning toward just working with the fat-bottle 6CA7s that are currently in there, since they're nearly new. Had a blond Bandmaster with KT66s years ago (gasp, had to cut out the bottom of the cabinet to make them fit), and remember liking the tone, so that's my other contender. I briefly considered 6V6s, of which I also have two on hand, but it just seemed like a shame to waste the capabilities of those big transformers on a 22W amp. (Especially since I also have an 18-W Crate -- don't laugh! $150 delivered, tube preamp & poweramp, and a decent tone after some judicious tube substitution.)
Anyway, I'm thinking anything from 35 to 50 W or so would be a reasonable target.
Thanks for the reply. I wasn't considering going for MORE power at all -- quit the contrary. I agree -- don't even have need of a 50W amp, although as I come to appreciate the value of clean headroom, I'm less fixated on overdriving everything all the time. At the moment, I'm leaning toward just working with the fat-bottle 6CA7s that are currently in there, since they're nearly new. Had a blond Bandmaster with KT66s years ago (gasp, had to cut out the bottom of the cabinet to make them fit), and remember liking the tone, so that's my other contender. I briefly considered 6V6s, of which I also have two on hand, but it just seemed like a shame to waste the capabilities of those big transformers on a 22W amp. (Especially since I also have an 18-W Crate -- don't laugh! $150 delivered, tube preamp & poweramp, and a decent tone after some judicious tube substitution.)
Anyway, I'm thinking anything from 35 to 50 W or so would be a reasonable target.