Thanks. That's a new one on me. Maybe I need to be checking bias more often.M Fowler wrote:Separate bias for each tube since the matched tubes we get today don't stay matched for long.
express external bias-pot option question?
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Re: express external bias-pot option question?
Re: express external bias-pot option question?
Well I imagine the amps circuit isn't exactly balanced either so that would be a reason the tubes are not the same. Even so matched tubes is no guarantee of a perfect match when the amp is operating.
Some enjoy a little mismatch for tone purposes I have read. But what the heck do I know, I'm no expert in tube matching or tube amplication engineering.
Mark
Some enjoy a little mismatch for tone purposes I have read. But what the heck do I know, I'm no expert in tube matching or tube amplication engineering.
Mark
Re: express external bias-pot option question?
M Fowler wrote:Well I imagine the amps circuit isn't exactly balanced either so that would be a reason the tubes are not the same. Even so matched tubes is no guarantee of a perfect match when the amp is operating.
Some enjoy a little mismatch for tone purposes I have read. But what the heck do I know, I'm no expert in tube matching or tube amplication engineering.
Mark
Having a separate bias for each tube sounds like a great idea. If a mismatch is desired, dial it in. If not, get each output tube at the exact desired bias point regardless of other circuit/tube vagaries.
Is there any downside to it?
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Re: express external bias-pot option question?
Plus you can run unmatched output tubes.
Re: express external bias-pot option question?
Yes the whole point for me is I want to run individual bias pots to set each tube and not to soley rely on match tubes sets. I would still get a matched set but then I could keep them idling correctly not just each pair.
Mark
Mark
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Re: express external bias-pot option question?
That would be the way to go. In the existing "express" BOM files found here it, indeed, calls for two trimmers in the external biasing options' list of parts. I'm going to assume that's for each tube? I've still yet to see exactly how this is implemented in the circuit. Has anyone done this (trimmer for each tube)?
Re: express external bias-pot option question?
Has instructions been posted anywhere? i cant seem to find any.
Thanks
That would be the way to go. In the existing "express" BOM files found here it, indeed, calls for two trimmers in the external biasing options' list of parts. I'm going to assume that's for each tube? I've still yet to see exactly how this is implemented in the circuit. Has anyone done this (trimmer for each tube)?
Thanks
That would be the way to go. In the existing "express" BOM files found here it, indeed, calls for two trimmers in the external biasing options' list of parts. I'm going to assume that's for each tube? I've still yet to see exactly how this is implemented in the circuit. Has anyone done this (trimmer for each tube)?
Re: express external bias-pot option question?
Notice on the attached the 220K/220K resistors are separated going to their own bias circuit and pot.
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