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6P14P Amp Scratch Build

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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:

An externally hosted image should be here but it was not working when we last tested it.


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.
 
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.
 
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.
 
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 :)
 
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
 
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.

An externally hosted image should be here but it was not working when we last tested it.


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 :D
 
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 :)
 
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.


:bigeyes: :bigeyes: :smash: :smash: :smash:


WISH YOU ENJOY ELECTRON TUBE FROM CHINA
 
Re: 6p14

mitwrong said:
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...

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 :)
 
Update: Got a pair of Z565 OPT's from Doug over at AK, and laid out my potential config. Tubes seem really close to each other, which is making me think that I might have to go with a clunky-looking 16x8x3" Hammond aluminum box...

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


Yes, those 6V3-A's are unequal heights, and one is slanty, but those deadbeats at Triode aren't shipping me the other two that I ordered. They're a buck each, but it's the principle of the thing :mad:
 
Re: 6p14

mitwrong said:
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.


It is true. Russian (rather Soviet Union) tubes during copying in China lose one letter in numbering system :)
6p14p - 6p14
6n1p - 6n1
 
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Thanks to this thread I bought some 6P14P-ER on eBay to try in my old Realistic Stereodyne 40 which isn't too kind to current production 6BQ5. It ran the originals quite a bit hotter than recommended and the replacement JJ's barely handle it even at significantly reduced Vp.

The original design voltage was about 390V and with modern line voltages it is now slightly over 400V. :xeye: In addition I'll use a small value power resistor (22 - 100 ohms) from the power transformer ct to ground to drop some volts as needed.
 
Major update. After using the 16x8x3 Hammond after all, I'm using .047uF orange drops on the positive side, and .1uF orange drops on the negative. I guessed that the yellow wire on the Z565's was the 8-ohm tap, and not the orange one, because it had slightly higher resistance. I also soldered a free-hanging 10K 1/4W resistor to put some moderate feedback to the bottom of the cathode.

Biasing. I'm still seeing around 300V B+ to the CT, and will probably use a resistor network of 130 ohms + 10 ohms + 0-20 ohm pot on each, bypassed with a 470uF cap. My design center was 150 ohms per tube for 40mA, -6V. It'll be easy to change to a CCS though, because the whole bias network for each tube will be on individual stand-off perfboards near each 6P14P :)

I have drilled most of the holes, not those for the bias boards, and wired up the heaters, and it looks pretty sweet. One of the 6V3-A's lights up A LOT more than the other, also it is much shorter (I need to get more of those things). I'll post pics as soon as I bite the bullet and buy a $40 charger for those pesky proprietary batteries.
 
Update: put the thing together, the actual measured bias is a bit weird, but i matched the tubes to .1mA of each other so it should be good. Bass is absolutely pounding, without being muddy. the high end is a bit darker than before but still seems plenty clear.

Measurements:
B+: 274V
B++: 260V

Tubes 1-2 (left): 48.0mA each
Tubes 3-4 (right) 48.3mA each

I'm not using any feedback, I have a 10K resistor hanging off the hot binding post in case I want to try. What improvements could I expect?

I also notice that my linestage has a lot of hum, probably because the transformers aren't isolated from the chassis with grommets, and the PT and choke are close to each other, with cores parallel .

but yea i'm pretty pumped that it works, pics soon (ttiwwop)
 
Well, I had the 16-ohm tap connected to the output jack, and now that I connected the 8-ohm tap, bass is less dominant and treble has reappeared, so everything feels in balance. Great to listen to :D. Hum/noise with inputs shorted are absolutely nil.

Here are some pics, at long last.

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.
 
Very nice build! I may have to try your schematic out, as I found an ebayer selling 6P14P (Sovtek EL84s?) and picked up 40 of them at $2/each. eBay is definitely the place to get them, as the web shops are selling them for $7+ each!

Now I'm itching to see what can be built with these guys, and your design looks like it uses a lot of parts that I have sitting around. I really just need the PSU iron and the output iron. Maybe using the dynaclone transformers from Triode Electronics?

http://www.triodeelectronics.com/z517wadyoutr.html

If you don't mind me asking, where did you source the toroid from?

Finally (and most importantly), how does it sound?
 
Thanks! I really love how it sounds, and I really didn't feel the need for feedback. You can use a regular 6DJ8 instead of the 6N23P. I basically had the 193K and the PT left over from projects that I kept on changing, so I wanted to throw an amp together cheaply. I got the 6N23P's free, and got the cheap 6P14P's, but was persuaded to not cheap out on the iron. I highly recommend this project to anyone :) But maybe use a 2" box instead, the 3" is kind of clunky :(

As for the iron, I used the Z565's so I recommend those. I'm not sure if the 1650E has UL taps, but if it does, that's definitely a fine transformer to use. Finally, I'm a big fan of Edcor (though I haven't used the transformers I bought from them yet) so definitely give them a look, here. Their 7600 ohm OPT's should probably work, but you can always ask them to make you some 8000-ohm ones.

http://www.edcorusa.com/classx/tube_output/cxpp/cxpp.htm


I'm not sure if the power transformer is any better or worse than Hammond, but its secondary resistance is something like 56 ohms across a 275-0-275V secondary, with current of up to .5A. I like using parts conservatively so it appealed to me. Here's their eBay store. They have recently added many more power transformers to their lineup.

http://stores.ebay.com/Antek-inc

Thanks for your interest! :smash:
 
Well, I'm drawing around 192mA of current through the 6V3-A's and they seem to be holding pretty steady, but it's still kind of disturbing. The amp has worked so far, I rarely listen very loudly. Is it worth replacing each 6V3-A with a paralleled 6CA4 (which I can definitely do) or should I not sweat it?

note: datasheets I've seen for the 6V3-A specify 600-800mA steady peak current and 135mA DC current...
 
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