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Old 4th October 2007, 06:34 AM   #1
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Default 6S19P budget SE.

Should be OK for a bit over 2W. No scanner so I'll describe the circuit, from the OPT towards the back.

OPT: Edcor XSE10-16-8K, run into an 8 ohm output for a 4K primary Z.

B+: 310V (allow 5V for OPT loss)

6S19P. Bias at 85Vk, 220Va-k, 40mA with one 100R/1W + 2K/10W, bypassed with 220uF/160V and .22uF/400V Solen. I'm counting on a voltage swing of 150V pk-pk to bring this puppy to full output power.

5687 Driver: RC coupled to 6S19P grid with .47uF 400V + 220K 1/2W. It itself is a standard grounded-cathode stage, direct-coupled from the previous stage, so Rk (unbypassed) will have to be high enough to bypass past the grid voltage, which biased is the high cathode voltage of the top tube in the SRPP. I assume a 5687 has enough grunt to handle a 6S19P.

6N2P (12AX7) Input. SRPP layout. Haven't decided the identical resistor values, but the bottom resistor IS bypassed by a healthy-sized electrolytic and 1/1000 value film cap for higher gain. I'm considering implementing feedback, so I'd probably want to split the bottom resistor into two resistances in series, the one closer to the cathode unbypassed, so I can run feedback to that spot. Input to the 6N2P is straight from the RCA jack, except for a 10K 1/2W carbon composition grid stopper right at the tube socket.

The layout of this amp will probably be a single 5687 in the middle, with a 6N2P to the left and right and a 6S19P at the extreme ends.

The PSU should only need to be around 150mA 350V (choke-input). A 273BX at 350V 175mA should do nicely. A further 1.5H 56R LC filter will be used for each channel's B+, with the capacitor bypassed by a Solen film type. A further LC will feed the 5687 driver, with probably around 15H 1K and 100uF. A last RC tacked off of that will feed the 6N2P SRPP.

All PSU caps will be generic electrolytics.

This amp shouldn't cost too much. I have the 5687's and 6S19P's and just need two 12AX7-types. The OPT's are the cheap Edcors. It'd be nice to splurge on a DIY Enclosures 1712
( http://www.diyenclosures.com/products/chassis/diy1712/ )
BUT it's $115 and might go against the budget-2A3 mentality of this amp - Hammond aluminum seems more my speed. I love symmetry also so might want to just use one 5687 per channel paralleled - quite a lot of current available. Heater voltage should just work out. The 6S19P's will take 2 amps, and if I use two 5687's, that's 1.8 more for a total of 3.8. That leaves just .6A for each 6N2P, which is fine since they take only 340mA each to heat.

How does this sound? Let me know if I ought to sketch this out. I would come up with better values but I left TubeCAD at home...
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Old 4th October 2007, 12:59 PM   #2
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Looks good. I made a SE amp with the 6S19P's bigger brother..and it made for a fine sounding amp. I did not get all of the power out of it...because I just drove it with a 6n1p...sounded great. The 4k primary is maybe a little high..and you'll have very little power? (But I assume you have efficient speakers)

Why not try 3 6s19p paralled and go OTL?
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Old 4th October 2007, 03:04 PM   #3
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4K isn't that low, I agree, but it made a very nice loadline across the curves. Start at 390V and divide through by 4K and you'll see what I mean.

http://tubedata.tigahost.com/tubedat...13/6/6S19P.pdf

As for going OTL, each tube has a plate resistance of 400 ohms. I'd need quite a few tubes in order to get decent power.
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Old 4th October 2007, 03:21 PM   #4
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4 per channel..http://www.transcendentsound.com/singleended.htm
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Old 4th October 2007, 05:37 PM   #5
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I'd probably want about 6 per channel for a bit more power. Why not make it 8 while I'm at it. My only question is how you'd ever manage to drive so many tubes at once.
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Old 13th October 2007, 03:41 PM   #6
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I assume that a 5K OPT impedance would also work? Power output should remain pretty much the same right, maybe 2W or so? One other thing: if I build it really nicely, do you think there might be a pretty decent market for an amp such as this? In case it's too little power for me, I mean. I bet it won't be, though, since my speakers are quite efficient. If I ever changed speakers, though, it might be problematic
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