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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: Re: what difference does it make? posted by Steve Eddy on July 16, 2005 at 13:51:51:
Oh, well if the 1:2 of your current input trannie already gives you sufficient voltage gain, and your tube stage is already a CF, then it looks to me like you're already there. No?Yes, with the current DAC chips I am, but they are old 16-bits 1543s and can power pretty much everything exept speakers. I like them because they are powerful and sounds good, but also keeps in mind that someday I'll upgrade to AD or Burr/PCM multibit DACs and with those chips voltage on DAC pins needs to be kept incredible low (as low as possible really), so a really high turns MC stepup transformer at in the range 1:20 plus is needed (Like the amorphous Lundahl stepups) to get a good enough voltage for a single triode swing a speaker, while keeping the DAC voltage low.. extremely high-μ..
Tubes aren't my strong point so forgive the question here, but why do you need the autoformer? Are you using it as a step-down because the CF doesn't have the juice to drive the load directly?
Yes. A triode cannot drive the small speaker load directly, it just can't pass the current on a low voltage swing but with the low voltage grid swing (from the stepup xformer) you control the B+ anode voltage of the triode (that's how a triode works). This is high voltage low current. the CF cap removes DC and the Step down autoformer trade voltage for current. This way you can get a swing with Watt (P=UI, U=RI) into a low load/impedance (speaker).
No shit? Are you running that critter full range? Or are you taking advantage of the CF cap that you need to have anyway and using that to set a high pass cutoff point?
No I do not take advantage of the cap as filter. It is in fact a very good idea thought but a plate choke with low inductance (about 1-2Hy) must be used as load to make sure the tube only is loaded at frequencies taken out at the CF. Should work good though if oversizing the CF cap and thus determining low-freq rollof with the plate choke without risking to load the tube.. I like the idea very much. I use a CCS so I take out all frequencies. I run full range but I put very moderate power levels into them and take neccesary precatiouns. They should really be run with a series cap for safety. Like amplifiers should be run with fuses..
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Follow Ups
- Re: what difference does it make? - Raab 17:37:25 07/17/05 (1)
- Re: what difference does it make? - Steve Eddy 23:41:01 07/17/05 (0)
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