Hi, i want to build a simple el84 pp amp. I have a 8k output transformer (without UL) 2 el84 and a ecc82. Is this a good schematic?
Has the ecc82 a proper gain for a input a .5Vrms at full power? If i have 2 nputs, one a CD player, and the other is a Computer, which has a minor output, how can i have a equal level at the same volume?
Thanks for any ansower and sorry for any grammatical error, i'm an italian student and i don't know english very well.
Has the ecc82 a proper gain for a input a .5Vrms at full power? If i have 2 nputs, one a CD player, and the other is a Computer, which has a minor output, how can i have a equal level at the same volume?
Thanks for any ansower and sorry for any grammatical error, i'm an italian student and i don't know english very well.
Change input resistor /68 k/ to 1-2-5 kohm.
First make power supply /with load resistor 200 k to ground/, then output stage and check mode, then phase splitter and check and then input stage.
/I doubt about 470 k between first plate and grid of second triod/.
First make power supply /with load resistor 200 k to ground/, then output stage and check mode, then phase splitter and check and then input stage.
/I doubt about 470 k between first plate and grid of second triod/.
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as shown the gain of the first triode will be ~10x or so, which is not really enough. Better choice will be 6DJ8, 6N1P, or even ECC81 due to higher gain and better linearity.
Also- as shown you have no connection to G2- you need to figure out what connection you wish to make, as triode and pentode have different drive considerations.
Also- as shown you have no connection to G2- you need to figure out what connection you wish to make, as triode and pentode have different drive considerations.
Need much lower plate and cathode resistors for the 12AU7.
Should decouple the power supply between 12AX7 and 12AU7.
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Fisher used the 12DW7 (7247) tube in similar circuit ... It's half a 12AX7 and half 12AU7 .... The tube is confused and does not know what it wants to be...LOL
Look at the schematic for Fisher SA-100 amplifier with the 7189 tubes....
Look at the schematic for Fisher SA-100 amplifier with the 7189 tubes....
Sylvania ones sound good for Hi-Fi...
The best sounding are the Telefunken ones that Fisher used, no surprise...
RCA I believe are made by GE..... GE are good but just OK for audio applications...your mileage may vary....
In their last couple of years of production, Dynaco supplied
four brand new Telefunken 12AX7A tubes with each PAS-3X kit.
For around 130US total.
There is a new production JJ 12DW7 available widely for about $15. There's also an Electro-Harmonix new production tube for about $25, and NOS goes for generally higher prices. I would build the circuit with some JJs and listen, then maybe go with some higher priced tubes. Apparently there were Mullards (likely very pricey when available) and some USA brands.
JJ makes them if you are on a budget. I have not used them so I can't comment on quality or anything subjective.
May I ask the obvious question! Why not use a proven EL84/8k design? Look up Baby Huey which is probably the ultimate design of its kind at the moment. Could be built without UL.
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I have many JJ 12DW7s. I use them as X7 voltage gain to U7 cathode follower driving a 6V6 or 6L6 in an SE Amp with NFB.
They perform the same as separate 12AX7s and 12AU7s.
I have not tried them with U7 as concertina. I would expect them to perform as well as they do in cathode follower mode
They are convenient for mono blocks.
Steve
They perform the same as separate 12AX7s and 12AU7s.
I have not tried them with U7 as concertina. I would expect them to perform as well as they do in cathode follower mode
They are convenient for mono blocks.
Steve
Can i build an amp with the preamp of this schematic and a Pentode connected push pull (i need 15W)?
The preamp tube 6n1p is equivalent to e88cc?
No, it isn't. In some circuits and situations it's close enough to work, but it has way less transconductance and needs twice the heater power.
6N23P = ECC88
6n1p is kind of like a lower gm version of a 6922, closer to something like a 6BQ7. It has similar mu to the 6922 but otherwise it's sort of its own thing, but some say it's close to a lower mu ECC81. Lovely tube either way, in applications like this they are perfect.
I have two e88cc at home, can i use this for this circuit or i need to change some value?
I've redrawn the amp using E88CC as input tube, and AC coupling (easier for me than figuring out DC operating points. I don't use SPICE) and a vertical output since it's easier to draw in SchemeIt.
I also added a gNFB loop since you'll want one if using pentodes... the higher you make the 2k gNFB resistor, the lower the gNFB will be. You don't have much gain to work with, and I picked 2k arbitrarily. Try and adjust if needed. when you get the feedback ratio right, then you can test for the value of the compensation capacitor (10kHz square wave looks goo on a scope, no ringing or overshoot).
Enjoy.
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