I have recently finished assembling of low power SE amp with YO-186 (UO-186) tubes at the output. This tube is driven by the stage shown here. The one 6N6P tube driver stage provides up to 60V RMS signal and high voltage amplification, that is enough for driving also DHT tubes as 2A3, 300B, 6B4G, 6S4S and similar. At the output of the SE amp I have installed resistive voltage divider 12R/1R, and the lower 1R resistor serves as a signal source for Denon 9200 headphones. I am very satisfied with result. High quality low power listening to speakers, and also high quality listening to headphones are provided by such amp.
Yes, that is a perfect survey of 6n6p specific features. But, it seems that author is dealing only with a regular kind of 6n6p produced by Novosibirsk plant. This kind is relatively cheap and not brilliant sound wise. Better kind was produced by Foton plant in Tashkent during 1962-1966 period. These are better sound wise and 10 times more expensive. I have dozens of those by Novosibirsk plant, and only few by Foton.
Any curves/datasheet for the Foton 6N6p available?
I purchased some Novosibirsk 6N6p off Ebay (round cup like getter) and was disappointed by their curves on the curve Tracer. Definitely not looking up to the ECC99. E182CC, 7044, 7119 tubes mentioned on those sale sites. ECC99 and 6H30p leaving them all behind. I am hesitant to purchase the Foton versions to test due to the higher price, when some spectacular ( and mostly unknown, off the old $1 list) US tubes have remarkable linearity (below).
I purchased some Novosibirsk 6N6p off Ebay (round cup like getter) and was disappointed by their curves on the curve Tracer. Definitely not looking up to the ECC99. E182CC, 7044, 7119 tubes mentioned on those sale sites. ECC99 and 6H30p leaving them all behind. I am hesitant to purchase the Foton versions to test due to the higher price, when some spectacular ( and mostly unknown, off the old $1 list) US tubes have remarkable linearity (below).
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I went and traced against each other: 6n6P (Novosibirsk) , 12FV7 (RCA), and 6463 (GE)
These tubes are nearly identical clones as far as curves go. Then I traced ECC99, and it had 10% higher and more constant Mu, lower Rp and higher gm, with less curve "rollover" (ie., 2nd H). But then it costs 2 to 4 x as much as the others.
Then again, it all depends on what you -want- from the tube. The lowly 12AU7 can do 2nd H cancellation as driver to the output stage, it's so "bad" (curve rollover) (for a non LTP driver). Probably why it was so popular in tube amps.
These tubes are nearly identical clones as far as curves go. Then I traced ECC99, and it had 10% higher and more constant Mu, lower Rp and higher gm, with less curve "rollover" (ie., 2nd H). But then it costs 2 to 4 x as much as the others.
Then again, it all depends on what you -want- from the tube. The lowly 12AU7 can do 2nd H cancellation as driver to the output stage, it's so "bad" (curve rollover) (for a non LTP driver). Probably why it was so popular in tube amps.
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Thanks for your info. I do not intend to make any promotion to 6n6p in this thread. I simply report about good sound result obtained. Quite probably with ECC99 result could be even better.
The issue with 6n6p and with all small Russian tubes is a big spread of measured characteristics. In my opinion, from big quantity of the same kind tubes, 10-20% are simply a trash and should be excluded from any sales. About 20-30% correspond to datasheet or even better. Remaining 60% are so so. I would say, that buying tubes untested, without even simplest measurements, is a big risk. Or, one could buy 10 times more than needed, and then to select some best ones.
Would you care to post the full schematic? I have an cache of YO186 and do really enjoy their sound as I currently use them and am interested to try your circuit.
The design is not optimal, maybe it could be simplified a bit. But I wanted to be sure in low hum voltage at the output. I could not provide very detailed complete schematics, but some main features are as follows.
I used two independent Power Supplies based on VO-188 Russian DHT tube rectifies. Each PS includes filaments heating toroidal transformer and EI vintage anode transformer (from German 1930's radio receivers). One PS serves for both channels 6N6P tubes, another PS is for both channels YO-186 tubes. Channels separation is arranged like in this picture. No electrolytics. Values could be a bit different, if to use existing parts. Grounding is arrange as star ground (same grounding point for both channels).
YO-186 stages are in higher voltage low current mode (40mA 380V). Output transformers are 9K for 4 Ohms load. This allows higher output power and lower output impedance for 4 Ohms load. I do not expect that many diyers coud use YO-186, therefor the issue of the output stage is up to individual design.
For headphones, I used 12+1 Ohms resistive voltage divider connected to the output. Then signal voltage is taken from 1 Ohms resistor. Quite comfortable for Denon 9200. For other kinds of headphones, voltage divider could be adjusted.
For headphones, I used 12+1 Ohms resistive voltage divider connected to the output. Then signal voltage is taken from 1 Ohms resistor. Quite comfortable for Denon 9200. For other kinds of headphones, voltage divider could be adjusted.
Vladimir: A few days ago I came across a somewhat "haphazard" schematic that someone on YouTube had designed that is for a low-power -- headphone amplifier -- where the 6N6 valves drive the headphones directly without using a transformer. I have attached a PDF file of this schematic which also includes some of my "discovery" information as I was researching this project.
I just accidentally came across your "6N6 Driver" schematic as I was searching for an English-version 6N6 datasheet (I am not fluent in reading Russian) and your driver circuit seems much simpler than the schematic I had come across earlier. My question to you is: Can you design a complete "Stereo Headphone Amplifier Circuit" including its power-supply? The YouTube schematic I had come across uses a 12AU7 in its first-stage and a 6N6 in its output stage. The output uses a 220uF/450V capacitor to decouple the 6N6 from the headphones. How would you perform this function?
I am -- NOT -- a "Circuit Designer" by any stretch of the imagination, BUT.....my expertise is in performing both the mechanical design of electronic chassis -- AND -- all of the Printed Circuit Board designs by only working from a completed schematic!!! That's what I do. I will attach a PDF file that contains a variety of my equipment designs I have accomplished for a variety of companies.
What I am thinking of is..........if you are willing to come up with a complete, working and -- simple -- "Stereo Headphone Amplifier" schematic, I will work with you in turning your schematic into a "DIY" project that others could easily then build on their own. This would include a complete BOM, GERBER files for either self-etchers or sending out to a PCB-fab shop and either some off-the-shelf enclosure (i.e., BUD, Hammond, etc.) or maybe an aluminum extrusion enclosure by one of the vendors I am familiar with.
WHAT DO YOU THINK OF THIS IDEA??? COOL, HUH??? You can reach me directly at: arrakis.zexelon@gmail.com
I am looking forward to your response. TAKE CARE!!!
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Your proposal came as a surprise to me, because preparing more detailed information for assembling an amplifier using UO-186 tubes does not make much sense due to the very small quantity of available tubes. I myself am very interested in buying additional quantities of these tubes for myself. Now I am busy with a new project on rare GKE-100 tubes, but this project is again more for personal educational purposes than for the proposal of mass assembly of such amplifiers. I am very pleased that my posts on the DIYAUDIO website are of some interest. However, there is an expediency factor that limits the possibility of detailed development and documentation of some of my developments. If were will be some definite questions, I for sure would be glad to discuss them. I hope for your understanding.
Hi, I'm new here, I've been looking for a circuit similar to Shishido's 2a3 direct coupled SE. I have a pair of 6N6P at home, is it possible to modify your design into a direct coupled type? Thank you. 😀
This Shishido's schematics is quite good and reasonable, but for me personally it has some limitations. Voltage amplification factor of one 12AX7 is not enough, if one needs to use 9K for 4 Ohms speakers output transformer. I also do not like 12AX7 because of it's pass band roll off starting from 12 kHz. In general, it is not a problem to direct couple output stage to my 6N6P driver, but I would not do it and would not advise to others, since one would need to solve expensive problem with high voltage power supply (and one should account for low power efficiency and high heat dissipation). Standard rectifier tube solution can become not applicable for such a task. Maybe one will need to use a bridge solution with 4 pcs of rectifier tubes. I am 100% sure, that removing of one good interstage capacitor does not worth all the mess with high voltage power supply and other schematics complications..
oh... one more, pardon my limited knowledge on this, what is the value of R6? Wattage of the rest of unmarked resistors and suitable voltage rating of caps. Thanks.
330K value of R6 would be OK. Gread leak resistor for UO-186 is 100K. C3 value of 1uF is OK in this case. I used shunting for C3, first 0,01uF 500V silver-mica cap closest to a "consumer", then 1uF foil film cap is attached to it. I always use "reverse" shunting, i.e. closest cap is that with smallest value and best quality, then other caps of bigger values. Wattage of unmarked resistors is 0,25-0,5W. The marked resistors indicated real dissipated power on them. At choosing power ratings of the resistors, one should multiply dissipated power by factor 3...5. Otherwise resistor will be very hot and shortly serving.
I would also like to repeat here, that good sounding 6N6P tubes are those by Foton plant produced in the years 1960-1965.
Multiple cheap 6N6P by Novosibirsk plant, present on the market, are all garbage soundwise, they could be use only at prototyping stage.
Multiple cheap 6N6P by Novosibirsk plant, present on the market, are all garbage soundwise, they could be use only at prototyping stage.