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Old 28th October 2006, 04:38 AM   #1
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Default 6P14P Amp Scratch Build

I have 10 of this russian tube coming on the way and I figured i'd spend some time trying to design a pretty simple phase splitter to drive these nice tubes. After crunching a few numbers with the help of ( http://www.aikenamps.com/LongTailPairDesign.htm ), I came up with the following schematic:

Click the image to open in full size.

Basically I looked at a 6P14P datasheet and used a max voltage of 450 and a 4K load to draw my load line, and ended up with 250V and ~37mA. how does she look?

edit: i haven't designed the CCS part but I'm thinking about using a LM317.
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Old 29th October 2006, 02:14 PM   #2
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update: i'm using a 5965 instead of a 12AT7, with a plate load of 27K on top and 30K on bottom, with a bias resistor of 300R and a tail resistor of 8.2K. i'm going to bias each 6P14P individually using a resistor plus a pot to get near 190R per tube, because of their being unmatched. i'll bypass each 190-ohm combo resistor with a 470uF cap, which might be on the big side but idk if there are rules for it.
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Old 29th October 2006, 06:19 PM   #3
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Hi sorenj07, nice tube. It did service fixed-bias/triode-mode into the 5Kohm output of my little SE for a long time. Tough as nails. I eventually settled on a 'high and cold bias', current somewhere in the low 30 ma range and Vplate around 350 (under 11 watts plate dissipation.) SE second harmonic distortion was higher, which shouldn't be an issue in push-pull, but harmonics above the third or fourth fell throught the floor. I recall UL as following the same pattern. A couple side benefits of a higher B+ are greater output power and the opportunity to raise the driver anode loads for lower distortion as well.
The old measurements aren't well labelled but none of the graphs show the third harmonic above 0.1% at 1 watt, which should translate to roughly 4 watts push-pull (triode mode though.) The amp's since been converted to 6CW5 and can't be re-run. I recommend giving 'high and cold' a spin if you have a variable supply.
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Old 30th October 2006, 04:04 PM   #4
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unfortunately i've decided to go the all-russian route, and will probably use the 6N1P in the phase splitter. right now i'm looking at a 140V plate + 60V grid, 4mA bias point, with 12K plate load on it's 4.4K plate resistance. the nice thing is, though, that if i don't like this sound, there are a million things I can do to mod this splitter section, even switching out tubes
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Old 4th November 2006, 03:09 AM   #5
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Default 6p14p

Greeting,
Where did you get the 6p14p tubes? I think I would like to try them in my Scott 222D, the 7189's I now have are getting flat, and replacements are to expensive. Did you buy them in matched pairs? Were you able to check them to see how good of a match they were? Some sellers charge you extra and never match.

Scott
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Old 4th November 2006, 04:26 AM   #6
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they haven't come yet. I ordered a lot of 10 off of ebay, just search "6P14P lot" and you'll find many choices. The 6P14P-EV is a more rugged military version, and probably more desireable (mine are just regular I think). My latest design allows for individual tube biasing, because the tubes, although new, are unmatched.

Click the image to open in full size.

some notes on the schem. the 6N23P (6DJ8 equivalent) is biased at -1.75V, 4mA per tube. the 6P14P's here are biased at -6V, 40mA per tube. my PSU consists of a 285-0 285-0 half-wave rectified by a pair of 6V3-A's, into a pi filter consisting of 4.7uF 630V, a 193K, and 200uF 400V. the 290V is taken off a 1K 2W resistor and a 10uF cap for a tiny bit more smoothing. i might stick a small choke i plan on rewinding out of a wall wart somewhere in there as well. low dcr, low henries
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Old 14th November 2006, 11:16 PM   #7
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I'm now aware that the approach that I took to biasing might well have been erroneous, but not as much as I thought. I might well still bias each tube at 150 ohms, because the ST-35 biases its EL84's at 95 ohms for both tubes i.e. 190 ohms for two, and it has a higher B+ voltage I think (higher than 305). We'll see what happens, and I can always tweak later
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Old 15th November 2006, 12:36 AM   #8
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Default 6p14

Solenj07:

First, I want to make a correction on your brain. The tube 6P14 is not from Russian, It's from China. The tube marked with letter J is designed for military use.

I've been using this tube for decade, It's a good tube, miniature 9 pin, equivalent to 6bq5, el84, but not a replacement for 7189. which 7189 can withstand higher voltage, above 420VDC.

If use 6p14 in SE application, the Max. Voltage must not exceeds 300VDC, If in PP application, It'd better to use 320VDC, otherwise the tubes will lost time in Ur service. ( shorter Life ).

I think you better to replace RCA or GE tubes for your ST-35, the voltage used in ST-35 as high as 420V. only American tube can stand these high Voltages. Other brand are too expensive like Mullard, Tele.

In comparison to RCA, Mullard, Telefunken, Valvo, Tosibha, Siemens, Yugoslavia, Russian--- etc.

The Audiophile will consider Telefunken, Mullard would perform the best.





WISH YOU ENJOY ELECTRON TUBE FROM CHINA
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Old 15th November 2006, 01:22 AM   #9
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Default Re: 6p14

Quote:
Originally posted by mitwrong
Solenj07:
First, I want to make a correction on your brain. The tube 6P14 is not from Russian, It's from China. The tube marked with letter J is designed for military use.
Umm, if you just do a quick search on eBay for "6P14P" and something strange shows up. - either the 6P14P is really Russian, or there are a lot of those tubes moving into the Russian federation from China for some reason i think the extra "P" at the end indicates that it's the Russian version.

Also, a Google search for "6P14P" somehow only comes up with Russian datasheets and websites. Hmm...

Quote:
Originally posted by mitwrong
I've been using this tube for decade, It's a good tube, miniature 9 pin, equivalent to 6bq5, el84, but not a replacement for 7189. which 7189 can withstand higher voltage, above 420VDC.

If use 6p14 in SE application, the Max. Voltage must not exceeds 300VDC, If in PP application, It'd better to use 320VDC, otherwise the tubes will lost time in Ur service. ( shorter Life ).

I think you better to replace RCA or GE tubes for your ST-35, the voltage used in ST-35 as high as 420V. only American tube can stand these high Voltages. Other brand are too expensive like Mullard, Tele.

Well, if it were a ST35 that I were building, that would be one thing, but since I simulate my B+ at around 305VDC, not 420V, and it'll be push pull - hopefully I'm in the clear? thanks for the warning though
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Old 15th November 2006, 06:54 AM   #10
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This little snippet has some useful info...

http://www.vaughnaudio.com/carina-FAQ.html#Q7

I got a dozen of these tubes from a Ukrainian vendor.

6P14P is the english tranliteration, they are really 6pi14pi.

They seem to work well (so far trialled in my RH84)

dave
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