Small tube amp based on 6N6P
I'm thinking of building a small mono-speaker with integrated amp.
The speaker element I will use is a 4", and has a sensibility of 94dB.
Does anyone have a very simple and good schematics or idea for how to build the amp?
I haven't decided if I should go with PP or SE, would you think SE could be power enough?
Maybe this schematic is something to use? The SE looks quite easy, though I don't understand the "Parallel"-thing:
Could this be a good transformer to use?
Link to datasheet
What do you think of these speakers?
Link to product page of speakers
Here are some info on the 6N6P
Introduction to 6N6P
I've looked at the specifications for the 6N6P.
It's an interesting tube and may sound good as the output stage in a SE configuration.
Both sections in parallel.
You'll need another stage or two to drive the 6N6P.
What are your thoughts on the input/driver stage(s).
I've built a couple of SE amplifiers using 6BM8 triode/pentodes and with 6DN7 dissimilar triodes.
I have no experience with the 6N6P tube.
I'd like to know the outcome of your project.
Since this is my first DIY-tube-experience, I'm not sure what I need. I thought the 6N6P tube it self was enough for a so small speaker, I'm thinking 4-6 watt. I might need to study the SE theory first...
I hope you have patience ;)
I have lots of patience.
Take your time and create a work of art.
Can I use this input stage?
Would seem a little strange though?
jema, any progress, its been some time
6N6P is roughly similar to ECC99, but with 6.3V heater only. Its electrical characteristics are pretty close to 5687 as well.
Figuring its rp is about 2k ohms (at most common op points), paralleled you'd get rp = 1k ohms. Plate dissipation for both plates combined is spec'd at 8W. Mu is about 20. Max plate voltage is 300V.
Using that info, you could actually use two 6N6P bottles per channel to make a push-pull-parallel (PPP) amp with B+ supply of 300V. Each 6N6P section should be set to draw 12.5mA quiescent, so each bottle (two paralleled triode sections) would draw 25mA. I figure the grid bias will need to be about -15V. For cathode-bias, the plate-cathode voltage would be 285V. That works out to a bit over 7W plate dissipation per 6N6P bottle.
Since the driver would only need to deliver 30V peak, it might be possible to use a 6DJ8 in a concertina (cathodyne) configuration as the driver -- if you don't use a global negative feedback network around the circuit. The driver stage's plate current would need to be fairly high, since the input capacitance of the 6N6P is fairly high (Cmiller is more than 100pF per triode section, so >200pF per bottle paralleled). Maybe couple a 6DJ8 section to a MOSFET concertina phase splitter?
A 20W PP OPT with impedance of maybe 6k6:VC should work. I'd expect no more than about 3.5W per channel. 8k:VC would give you a little less power, a little lower distortion.
One thing to keep in mind is that 6N6P uses a lot of heater power, 6.3V at 750mA per bottle. If you did the PPP idea above, you'd use 3A of heater power per channel, which is about the same heater power a pair of EL34 or KT88 would use.
Anyway, just thinking out loud. I've used this tube as a single-ended line stage and as a differential PP driver, but not as an output tube. Might be worth a try...
And 6n6p-I has a 900mA heater.
I have an OTL headphone amp that uses one 6n1p-ev and one 6n6p-i per channel. Works great.
6k6 sounds about right for PPP 6n6p. The 6n6p PP output circuits I've seen used a 12k opt. Edcor's XPP15-8CT-7.6K might be a good one for PPP 6n6p.
I live about 20 miles from you.
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