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Old 3rd October 2011, 07:14 PM   #1
jema is offline jema  Sweden
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Default Small tube amp based on 6N6P

Hello!

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:
Click the image to open in full size.

Please comment!

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

/M

Last edited by jema; 3rd October 2011 at 07:35 PM. Reason: Trafo.
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Old 3rd October 2011, 07:38 PM   #2
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Location: Midland, Michigan
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.
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Old 3rd October 2011, 07:42 PM   #3
jema is offline jema  Sweden
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Quote:
Originally Posted by Frank Berry View Post
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.
Thanks for your very quick reply!
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
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Old 3rd October 2011, 07:47 PM   #4
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I have lots of patience.
Take your time and create a work of art.
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Old 3rd October 2011, 07:57 PM   #5
jema is offline jema  Sweden
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Can I use this input stage?
Click the image to open in full size.

Would seem a little strange though?
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Old 6th April 2016, 06:33 PM   #6
adason is offline adason  United States
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jema, any progress, its been some time
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Old 7th April 2016, 02:23 PM   #7
rongon is offline rongon  United States
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Location: Across the river from Rip's big old tree...
6N6P is roughly similar to ECC99, but with 6.3V heater only. Its electrical characteristics are pretty close to 5687 as well.

http://www.lampizator.eu/UPGRADE/RU-6N6P.pdf

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...

--
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Old 7th April 2016, 05:03 PM   #8
ericj is offline ericj  United States
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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.
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Old 7th April 2016, 10:14 PM   #9
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Join Date: Mar 2006
Location: michigan
Quote:
Originally Posted by jema View Post
Hello!

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:
Click the image to open in full size.

Please comment!

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

/M
Let me level with you here. While it's kind of neat to build these cute little under powered amps that may be used in a small surrounding,asking a driver to do the job of an output tube is pushing it..Being this is your first DIY project,why not build an EL Cheapo that has much more versatility in that you can use it to power most any speaker 89db and above.Once you source the power and audio transformers for this project,you are going to have all this mass and expense that may run more money than the higher wattage PP amp and then you will no doubt be defeating some of your intended purpose..I'm not saying don't build the amp in question but it is very limited in what it can accomplish. JMHO.
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Old 7th April 2016, 10:16 PM   #10
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Default I live about 20 miles from you.

Quote:
Originally Posted by Frank Berry View Post
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.
I'm in Saginaw.
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