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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 Raab on July 17, 2005 at 17:37:25:
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..Ah, yeah. With the newer DACs, they have the protection diodes on the output to keep the voltage at the output from being any higher than a diode drop so you've gotta keep the maximum output voltage well below that.
I dunno, you sure the newer chips are really an "upgrade"? :)
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).Gotcha. Thanks.
You allergic to sand at all? Here's an ultra simple amp that's among a number of others I've been experimenting with for a while now that's worked quite well for me in the "flea power" range.
The tube's ultimately the controlling element in this arrangement, unlike typical hybrid circuits where a tube stage is simply cascaded into a solid state stage and what the tube's doing is little more than a "serving suggestion," the transistor stage just going on and doing what it wants to do. In this arrangement, the tube does what it wants to do and the transistor provides a channel to allow for significantly more current handling to drive the speaker without having to use a step-down trannie.
Not that I've anything against transformers. Just that I prefer to stagger them between active stages (i.e. passive/active/passive/active, etc.) rather than having two passive elements tied together, such as a transformer and speaker. But that's just me. :)
Oh, this circuit has some DC offset but I didn't bother adding a cap to the schematic because I'm using a two-way speaker and just put a cap on the woofer in the speaker and use the inherent cap coupling of the high pass crossover and drive it straight off the amp's output.
I guess you can't be too allergic to sand if you're uing the Pimm CCS which if I recall uses MOSFETs, no? :)
se
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Follow Ups
- Re: what difference does it make? - Steve Eddy 23:41:01 07/17/05 (0)
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