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Hi everyone, I've been lurking around here for a few years, but this is my first post. I'll try to make it as short and sweet as possible.
I recently built a tweed bassman clone out of parts I had compiled over the years. With the volume below about 2 (and when played with a light attack) the amp has a great clean sound. However, when the power tubes start to break up, the distortion sounds pretty unpleasant. The lows are extremely loose and flabby, and the highs are shrill and can be ear-piercingly harsh when the volume is cranked.
The tranny that's in there right now is providing a B+ of about 500V and about 498V on the screen grids (the rectifier is solid state). Now, I'd like to mention that I've got a pair of JJ 6L6's in it at the moment, which have a max plate and screen voltage of 500V and 450V respectively. I realize that this is less than ideal, but I can't afford a new set of tubes right now, and the amp I typically gig with is currently out of commission. As soon as I can get some funds together, I have plans to put in a center tapped tranny and either retrofit it with a tube rectifier or use a zener to drop B+ down to around 430V or thereabouts. This was a project I sort of had on the back burner for a while, and I never really planned to have to gig with it before I could get the power supply voltage down to a reasonable, but my hands are tied at the moment.
The question I have is, could operating the power tubes so near (or in the case of the screens, so far above) their maximum ratings cause the crappy-sounding breakup I'm hearing? If not, what could potentially be the culprit. For reference, I built this thing pretty true to the 5f6-a schematic. Also, the power tubes are idling at about 21W per tube. Thanks!
I recently built a tweed bassman clone out of parts I had compiled over the years. With the volume below about 2 (and when played with a light attack) the amp has a great clean sound. However, when the power tubes start to break up, the distortion sounds pretty unpleasant. The lows are extremely loose and flabby, and the highs are shrill and can be ear-piercingly harsh when the volume is cranked.
The tranny that's in there right now is providing a B+ of about 500V and about 498V on the screen grids (the rectifier is solid state). Now, I'd like to mention that I've got a pair of JJ 6L6's in it at the moment, which have a max plate and screen voltage of 500V and 450V respectively. I realize that this is less than ideal, but I can't afford a new set of tubes right now, and the amp I typically gig with is currently out of commission. As soon as I can get some funds together, I have plans to put in a center tapped tranny and either retrofit it with a tube rectifier or use a zener to drop B+ down to around 430V or thereabouts. This was a project I sort of had on the back burner for a while, and I never really planned to have to gig with it before I could get the power supply voltage down to a reasonable, but my hands are tied at the moment.
The question I have is, could operating the power tubes so near (or in the case of the screens, so far above) their maximum ratings cause the crappy-sounding breakup I'm hearing? If not, what could potentially be the culprit. For reference, I built this thing pretty true to the 5f6-a schematic. Also, the power tubes are idling at about 21W per tube. Thanks!
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