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experimental 6L6G / 6BG6G amp design brainstorm
experimental 6L6G / 6BG6G amp design brainstorm
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Old 20th March 2009, 12:59 PM   #31
whitelabrat is offline whitelabrat  United States
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I've been using 6BG6GA's in a Simple SE for a while now. You won't be disappointed. I've tried a pair of old 6BG6G's and they sounded great, but couldn't take the ~27w dissipation (guessing from tubelabs chart). The GA's may be able to take a good beating depending on the manufacture.

One thing about these 6BG6 tubes is they can take a good high voltage. Anyone have thoughts about using the 640vct power transformer with a bridge rectifier? Electrolytics probably aren't an option any more in a power supply, but they can be gotten reasonably
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Old 20th March 2009, 06:31 PM   #32
chromal is offline chromal  United States
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Default 6L6G/6L6GB/6BG6G/6BG6GA SE OTs

So one of the questions on my mind is the ideal primary impedance for a 6BG6G SE OT. I've read different things, primarily,
6L6GB: A SE Zout = 4600
807: A SE Zout = 6000 for 'autobias resistor,' 5000 for -20v grid bias. autobias? Is that like cathode bias?

I've primarily been looking at Edcor OTs at the suggests of others here and because of their price/performance:


But am not sure which would be the best choice for tube/loudspeaker rolling (I have two pairs of 4ohm and three pairs of 8ohm loudspeakers, would ideally be able to explore both). Should I ask about two secondary output impedences, perhaps, or hook up 8ohm speakers to the 4ohm outputs and hope it's 'close enough' ?
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Old 20th March 2009, 06:49 PM   #33
jean-paul is offline jean-paul  Netherlands
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Chromal, could you send me a pm ?
It's only audio. Member of the non modular PCB design committee
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Old 20th March 2009, 08:32 PM   #34
chromal is offline chromal  United States
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Well, nevermind. I just ordered some Edcor XSE SE OTs. Ouch, 2-3wk turnaround. WEll, I'm glad they seem busy with orders in this economy. If they're not the best choice, ohwell, at least they were cheap at $20 per. (XSE15-4-5K) Although some 'net reviewers suggest they exceed their official specified bandwidth, I sort of balk at the official lofi-ish spec of 70-18kHz. Anyway, I can always drop in CXSE25-4-5K OTs later, if I want.

I also picked up an unlisted Edcor Power Transformer they had with 370-0-370@200mA, 6.3@4A, 5@2A) which I think will make a decent power supply tranny for my Simple SE / 6BG6G project. Still haven't figured out how I would power a stereo version of my 6BG6G class-A PP amp project, nor whether I want an integrated stereo amp or two monoblocks.... I'll continue to muddle forward with my 1-channel class-A PP prototype using my existing power and output trannys.
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Old 20th March 2009, 11:45 PM   #35
chromal is offline chromal  United States
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Here, I've attached a .PNG image of the schematic and a simulation of a possible B+ supply for the 6BG6* class-A(triode) PP 1ch amp. a 4k resistive load is intended to represent two ~42mA (triode-strapped) anode loads on the PP transformer.

the white line is the voltage presented to the OT's primary center tap.

T1 is my 320-0-320@105mA power tranny (320@117 input. my input's more like 120-121, so 333-0-333 in the simulation)

L1 is a hammond 169S 4H 225ma 500v choke.

C1, C2, C3 are 500v caps. (note that C1 and C2 are shown as 'ringing' into the near 550v territory, but what design alterations I could make aren't clear to me...

R2 is intended to represent the OT/tube load at quiescent.

My goal here is to provide a ripple filter and current source for a 325v plate voltage, 42mA Ia per tube, as per the application data for a triode-strapped 6BG6G class-A P/P from tung-sol, which rates each tube at a Zout of 8000 under this configuration.

Is C3 enough of a reservoir at 47uF? I have a bag full of these 47uF@500wvdc electrolytics....
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File Type: png 6bg6g-class_app.png (91.6 KB, 225 views)
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