The pinout of the 6N1P Tubes I used in my build is very similar to the pinout of, say a 12AX7/ECC83 except that the heaters are connected to only pins 4 and 5, pin 9 is internally connected to a shield which is placed in between the two triode sections, so I connected pin 9 of each of the 9-pin sockets to chassis ground.
I did a quick search on Google for some information about the original EarMax miniature tube headphone amplifier, and found this webpage, and I thought that forum members might find it interesting to read, so, here's a link to the webpage:
https://www.tubeampdoctor.com/en/earmax-pro-headphone-amplifier-by-brocksieper
https://www.tubeampdoctor.com/en/earmax-pro-headphone-amplifier-by-brocksieper
Looks cool, a 6DJ8 is similar to a 6N1P, the 6N1P has similar ratings but requires about twice the heater current than the 6DJ8, so both the 6DJ8 and the 6N1P should work in the circuit, I had never tried 6N1P tubes before so i thought it would be cool to give them a try, I like the "sound" they have.
Keep 6N1P as a first tube. Pinout is the same (E88CC, 6N1P, 6N6P, 6N23P). Heathing curent is 750mA for 6N6P. Output impedance will be lower. Find 6N6P from the 60', Foton. Newer tubes sounds worse than the older ones.
https://www.ebay.com/itm/253104280635
https://www.ebay.com/itm/253104280635
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I share Nixie's comment, the current tubes sound worse than the old and the quality control is very poor.
I bought the ones from the link above. Cheap and great sounding. Only now the values on the scheme must be changed, there is some work to be done. And the anode current will be about 20mA for each 6N6P, all together about 50mA. Can the power supply make this possible?
The power transformer I used in my build has an HT secondary winding that can supply up to 115mA, so there should be enough current capacity in the power supply.
I should do some voltage measurements and calculations to work out how much HT current is being drawn from the +HT supply by the two amp circuits in my build.
To my ears, the three Svetlana 6N1P tubes I used in my build do seem to sound really good, the amp is very pleasant to listen to for extended listening sessions, my ears don't seem to get fatigued much at all, there's more than enough volume being produced by the amp even at relatively low volume settings, you really don't need to turn the volume up full at all.
6N6P heaters need 750mA, so you'll need 2.1A from your heater supply. Hammond 269AX only provides 2A 🙁
Yep, that's the only downside, and I really don't want to risk burning-out the power transformer, it already gets quite warm, besides, the amp appears to be working fine as it is.
That transformer secondary is over the limit even with 3 x 6N1P. That is why it is hot.
Power Rating (VA) 40
Primary VAC 115
Primary Frequency 60
A.C. High Voltage Secondary RMS 250V C.T. @ 115ma.
Filament # 1 VAC 6.3V @ 2A
The data sheet of 269AX does not mention 6.3V CT for heating, and in your schematic it is drawn that way?
Power Rating (VA) 40
Primary VAC 115
Primary Frequency 60
A.C. High Voltage Secondary RMS 250V C.T. @ 115ma.
Filament # 1 VAC 6.3V @ 2A
The data sheet of 269AX does not mention 6.3V CT for heating, and in your schematic it is drawn that way?
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It's AC, and there is a diode bridge and a capacitor. In general, for DC you need more AC current (1.41xDC current). In principle, since the transformer has two secondaries, this one "borrows" from the second one, which is not heavily loaded. If 1.8A is required for DC heating, then the secondary should provide at least 2.5A. Additional problem is that when you have a diode bridge and a capacitor, the current is not sinusoidal, and you need to add more reserve to the secondary because it is dimensioned for sinusoidal current. If it is AC heating of the tubes, then the current is sinusoidal.
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oh yea. @DrNomis44 you are overloading your transformer. You can heat 3 6N1P tubes with the 269AX with AC, but for DC you need at least 2.5A supply, and maybe >3A to account for inrush current. Looks like you should use 6DJ8/6N23P, back to the MJ design.
Also, I've never seen heater elevation done with a cap in that way. I would create a voltage divider off the HT supply and connect that to the center tap, or the (-) leg of the circuit if DC. Then you have a bleeder resistor for the HT as well.
For the 6N6P variant, I would use a PT with a slightly higher output voltage, and a much beefier heater supply winding. Over here we have an Antek that makes 280v@90mA and 6.3v@4A at a good price. CLC power supply.
Also, I've never seen heater elevation done with a cap in that way. I would create a voltage divider off the HT supply and connect that to the center tap, or the (-) leg of the circuit if DC. Then you have a bleeder resistor for the HT as well.
For the 6N6P variant, I would use a PT with a slightly higher output voltage, and a much beefier heater supply winding. Over here we have an Antek that makes 280v@90mA and 6.3v@4A at a good price. CLC power supply.