[Ktechlab-devel] Use case analysis, 2A3 amp. =P

[Glen]

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I care about the tubes. They're important for what I want to do as well.

Ugh, modeling transformers. Has to happen, but ugh!

If the instantaneous approximation doesn't work, what would you suggest?
I'll need to hit response up to 20Hz, but to simulate RF frequencies I
dunno about. The current simulator uses a QTimer to fire the steps, and
in the code it says this is limited to 1000 per sec. I don't know if
it's still a limit, though.

- --GC


Alan Grimes wrote:
> A few posts ago, I think I sketched out a 2A3 amp I was working on.
> 
> First the reference material:
> 
> http://www.circuitcellar.com/microchip2007/winners/MT2209.html
> (design is VERY different from mine, the key items are the SMPS and the
> file formats for source code and schematics...)
> 
> http://www.jensen-transformers.com/as/as088.pdf
> 
> http://cinemag.biz/line_input/line_input.html
> http://cinemag.biz/line_input/CMLI-15-15B.pdf
> 
> http://edcorusa.com/products/transformers/cxpp/cxpp50-8-3_4k.html
> (I might custom order a pair with a smaller core to keep the size of the
> amp down...)
> 
> http://scottbecker.net/tube/sheets/049/2/2A3.pdf
> http://scottbecker.net/tube/sheets/093/6/6SL7GT.pdf
> http://scottbecker.net/tube/sheets/137/6/6SN7GTA.pdf
> 
> First issue is the tubes, but then nobody cares about tubes so we'll
> simply mention it and move on...
> 
> Second issue are the transformers and the complex AF features of them
> such as bandwidth and frequency dependent phase delay....
> 
> This brings up a critical issue with the simulator.
> 
> Right now it attempts to do an instant-by instant approimation. This
> gives it a frequency ceiling of 1khz... =\ To go further, it needs to be
> able to switch to static analysis techniques to approximate filter
> responses clear out to 200khz or so. Furthermore, it needs to be able to
> compute general parameters of frequencies all the way into RF. -- this
> is critical to the SMPS design...
> 
> Morgan Jones (no on-line reference, I'm aware of), uses voltage
> regulators all over the place to drop as much as 150 volts off the B+
> rail for the voltage gain and driver of his amp... =P
> 
> The power supply for the amp I'm thinking of needs a 300V B+ rail, a
> secondary B+ rail at around 150v, a B- rail of -300v (maybe even
> -350v!), three separate 6.3v supplies, and four monster-current 2.5v
> supplies... So that's like 10 supplies, or maybe 9 and and absurdly tall
> regulator, not to mention the startup ordering required to safely bring
> up the very expensive output tubes... (they need to be warmed up and the
> B+ should be brought up slowly...)
> 
> Conventional SMPS design software only allows you to specify voltages up
> to a pathetic 100v! =(      sad.
> 
> So a major benchmark for the Ktechlab simulator will be the ability to
> simulate any of the major SMPS topologies and come with reference
> designs for PFC input and DC-DC converters with output voltages all the
> way up to 1.5 KV.
> 
> First, however, we need to design and implement the new parts library. =(
> 

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