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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: Re: Filament bias and PP DHT posted by andy evans on January 26, 2007 at 03:56:12:
Hi Andy ,
I may take you up on your offer , I have a dozen type 46 . Got any globes ? No CCS anywhere in this amp apart from in the B+ feed to the driver (2 x 105V gas regs not shown in the diagram) . The whole point is that the LL1635 interstage can only tolerate 1mA of unbalanced DC . Even tightly matched valves will drift with age so there needs to be some form of adjustment . In the diagram each filament has it's own DC supply , the pots provide a small amount of balancing . If the pots are removed then the '-' of each filament would be joined together , reversing the 'phase' of one filament will allow a change of 2.5V of bias . Alternatively the 3A/110A running at lower current can be used without any balancing , but the output stage will no longer be able to be driven hard into A2 . Ra for the 3A/110A is also higher than I'd like (5k) compared to the 46 (2.3k) . Sowter 8920 were delivered this morning and I've had an offer on the LL1635 . Chassis bashing will commence early nest week so I need to pull my finger out ;)cheers
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Follow Ups
- Re: Filament bias and PP DHT - fatbottle 04:42:02 01/26/07 (3)
- Re: Filament bias and PP DHT - andy evans 12:11:28 01/26/07 (2)
- Re: Filament bias and PP DHT - fatbottle 13:07:55 01/26/07 (1)
- Re: Filament bias and PP DHT - andy evans 14:42:28 01/26/07 (0)
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