Hello:
I would like to change the drive tube from a 12ax7 to a Russian 6n2p. could someone help me out with which traces to split and jump. I am thinking I should split the link between 4 and 5 on the drive tube and jump from pin 4 to pin 2 on the output tube. not sure what to do with pin 9 on the drive tube. Marc could you help me out here? a diagram would help.
Thanks
I would like to change the drive tube from a 12ax7 to a Russian 6n2p. could someone help me out with which traces to split and jump. I am thinking I should split the link between 4 and 5 on the drive tube and jump from pin 4 to pin 2 on the output tube. not sure what to do with pin 9 on the drive tube. Marc could you help me out here? a diagram would help.
Thanks
Hi SCD,
So, why do you want to switch to another tube type? If you are going to change to another type entirely, why not try some others that are unknown in this circuit? After all, you seem determined to strike out into the unknown by yourself, but with help. The bias will be different too, so you have to do more than get the heater right.
-Chris
Did I miss something here, or did you just change the rules?
So, why do you want to switch to another tube type? If you are going to change to another type entirely, why not try some others that are unknown in this circuit? After all, you seem determined to strike out into the unknown by yourself, but with help. The bias will be different too, so you have to do more than get the heater right.
-Chris
Hello Chris:
For a moderator, I would not characterize your comments as entirely helpful or useful.
From what I have read 6n2p and 12ax7 have quite similar characteristic. The primary difference being the heater wiring.
The reason I asked in the earlier post is because I have a few 6n2p that I would like to try on this board. I am having a little trouble reading both sides of the board at once and was asking for a little help as to which traces should be cut and or jumped.
I did not think it would be this challenging
Have a nice day
For a moderator, I would not characterize your comments as entirely helpful or useful.
From what I have read 6n2p and 12ax7 have quite similar characteristic. The primary difference being the heater wiring.
The reason I asked in the earlier post is because I have a few 6n2p that I would like to try on this board. I am having a little trouble reading both sides of the board at once and was asking for a little help as to which traces should be cut and or jumped.
I did not think it would be this challenging
Have a nice day
Hello SCD,
Moderators are just regular members with a lot of extra work to do. Without the hat symbol we are posting as regular members.
Now, your last post makes perfect sense and I wouldn't have a problem with it. However, the way your information was presented was like pulling teeth to get it all. Now, for the first time you can be given the type of response that you were actually searching for. I was hoping you would recognise how incomplete your questions actually were, and it did result in now complete request for information. Read back ans see how it developed.
Okay, so you want to repin the existing layout for a new tube type. What I would recommend you do is look up a 12AX7A and the 6n2p and note the differences between them. It's pretty basic stuff to figure out and maybe you just need confidence in order to do this yourself. It's important to learn when you can.
The 12AX7A is here: https://frank.pocnet.net/sheets/049/1/12AX7A.pdf
The 6n2p is here: http://www.mif.pg.gda.pl/homepages/frank/sheets/112/6/6N2PEV.pdf
The heater connections for the 12AX7A would be pins 4 and 5 for a 12.6 volt series connection that you now have. The heater connections for the 6n2p are pins 4 and 5 as well. Just change the 12.6 volt supply to the 6.3 volt supply you need to use. You don't need to cut any traces at all.
Now that I've told you how to deal with the heaters, next you need to go over the rest of the pin assignments and suggest how you might do this (make an effort please). On thing you won't know is the connection on pin 9. On the 6n2p it is a shield that goes to signal ground. On the 12AX7A it is the centre tap for the heater and is probably not connected to anything on your board. The rest of the connections will be two sets of cathode, grid and plate. Just match them up between the tubes. It doesn't matter which is assigned triode 1 and 2. Just match all the elements of the same section together. You'll be able to do this on your own, then just ask if your solution is correct.
Best, Chris
Moderators are just regular members with a lot of extra work to do. Without the hat symbol we are posting as regular members.
Now, your last post makes perfect sense and I wouldn't have a problem with it. However, the way your information was presented was like pulling teeth to get it all. Now, for the first time you can be given the type of response that you were actually searching for. I was hoping you would recognise how incomplete your questions actually were, and it did result in now complete request for information. Read back ans see how it developed.
Okay, so you want to repin the existing layout for a new tube type. What I would recommend you do is look up a 12AX7A and the 6n2p and note the differences between them. It's pretty basic stuff to figure out and maybe you just need confidence in order to do this yourself. It's important to learn when you can.
The 12AX7A is here: https://frank.pocnet.net/sheets/049/1/12AX7A.pdf
The 6n2p is here: http://www.mif.pg.gda.pl/homepages/frank/sheets/112/6/6N2PEV.pdf
The heater connections for the 12AX7A would be pins 4 and 5 for a 12.6 volt series connection that you now have. The heater connections for the 6n2p are pins 4 and 5 as well. Just change the 12.6 volt supply to the 6.3 volt supply you need to use. You don't need to cut any traces at all.
Now that I've told you how to deal with the heaters, next you need to go over the rest of the pin assignments and suggest how you might do this (make an effort please). On thing you won't know is the connection on pin 9. On the 6n2p it is a shield that goes to signal ground. On the 12AX7A it is the centre tap for the heater and is probably not connected to anything on your board. The rest of the connections will be two sets of cathode, grid and plate. Just match them up between the tubes. It doesn't matter which is assigned triode 1 and 2. Just match all the elements of the same section together. You'll be able to do this on your own, then just ask if your solution is correct.
Best, Chris
Hi TheGimp,
Sort of, but it never hurts to check and make certain. Who knows what the capacitance is between elements (I haven't checked). Same goes for the other parameters. Always check to make certain instead of accepting the fact that you get sound and it works. This is DIY, there is no excuse for not getting very good performance.
You can just ask, but you will get better information if you attempt to figure some things out on your own first.
-Chris
Sort of, but it never hurts to check and make certain. Who knows what the capacitance is between elements (I haven't checked). Same goes for the other parameters. Always check to make certain instead of accepting the fact that you get sound and it works. This is DIY, there is no excuse for not getting very good performance.
You can just ask, but you will get better information if you attempt to figure some things out on your own first.
-Chris
Hello again Chris: My question starts at post 2101. Perhaps I should have stated clearly I am using the circuit board that bandol83 put together.
I have reviewed the spec sheets for the two tubes. My question is referencing the circuit board. I have characterized my question as a statement to hopefully make it a bit more clear.
?? In order to use the 6n2p as a drive tube with this board: On the drive tube section of the board the trace between pin 4 and 5 needs to be split. + and - 6.3vdc applied to these pins. The trace from Pin 9 needs to be split and connected to signal ground.
Perhaps someone familiar with the circuit board can help out and confirm that this correct.
Thank you
I have reviewed the spec sheets for the two tubes. My question is referencing the circuit board. I have characterized my question as a statement to hopefully make it a bit more clear.
?? In order to use the 6n2p as a drive tube with this board: On the drive tube section of the board the trace between pin 4 and 5 needs to be split. + and - 6.3vdc applied to these pins. The trace from Pin 9 needs to be split and connected to signal ground.
Perhaps someone familiar with the circuit board can help out and confirm that this correct.
Thank you
Hi SCD,
I looked at Marcs PCB layout (Rev 2). Confirm that is what you have. The 6.3V heater supply is wired between pin 9 and pin 4 with pin 4 linked to pin 5. Cut track betwen pins 4 and 5 leaving pin 4 connected to trace. Wire pin 5 to other side of heater supply at pin 7 of V2 OR pin 2 of V3. Cut track to pin 9. Wire pin 9 to 0V wherever most convenient. Maybe inside end (closest to PCB centre) of either R43 or R44.
Looks like you have understood the requirements OK.
Cheers,
Ian
I looked at Marcs PCB layout (Rev 2). Confirm that is what you have. The 6.3V heater supply is wired between pin 9 and pin 4 with pin 4 linked to pin 5. Cut track betwen pins 4 and 5 leaving pin 4 connected to trace. Wire pin 5 to other side of heater supply at pin 7 of V2 OR pin 2 of V3. Cut track to pin 9. Wire pin 9 to 0V wherever most convenient. Maybe inside end (closest to PCB centre) of either R43 or R44.
Looks like you have understood the requirements OK.
Cheers,
Ian
Hi KP93300,
Again I didn't answer very fast, but it's holidays and strange enough I am more busy now, things will be better in September
Anyway, at least I answer
For the output tubes I have tested EL34 of course, KT88 and 6CA7. I was not very happy with the KT88 from JJ. may be the high voltage of about 350 V with my first custom transformer was not enough for them ? The EL34 were old Telefunken and sound good but finally I still prefer the new production 6CA7 from JJ... I am now using the Toroidy 250 VA transformer which has two high voltage output at 275 & 330 V AC. On the actual board I am limited to 400 V DC because of the capacitors, but I may build a new one with the PCB from the Group Buy 3 made by Prasi with 500 V capacitors and off board bridge to add external bigger capacitors to take advantage of the higher voltage of 460 V DC...
I haven't tested the KT77, but someone on the forum says that they are very good too ? The 6550 could be interesting too, I use them in my Jolida amplifier but I didn't tested them in the EL34 Baby Huey !
For the output transformers I am using two Hammond 1650N, with 4.3 k ohms impedance, that I have since many years and they are very good in this amplifier. I have also made some test with a 4 k Amplimo 3A524 toroidal transformer without UL output to test the stability of the amplifier without global feedback and UL, I have made tests in both triode mode (screen connected to plate) and pentode mode (screen connected to high voltage) and both give good result
I have not tested Toroidy transformer (I will use the CFB version in my next quad KT120 amplifier) but I know at least two persons who have used it and are very happy with them : Jacques, in Belgium use the EL34 6.6 k version and Philippe, few km from me in the south of France use the very nice DEMO version of the KT88 4.3 k version (see post 2076)...
If some others builders use them, please give us your feedback ?
I will receive the top panel soon, I will send pictures when the amplifier will be in the box
Best regard,
Marc
Again I didn't answer very fast, but it's holidays and strange enough I am more busy now, things will be better in September
Anyway, at least I answer
For the output tubes I have tested EL34 of course, KT88 and 6CA7. I was not very happy with the KT88 from JJ. may be the high voltage of about 350 V with my first custom transformer was not enough for them ? The EL34 were old Telefunken and sound good but finally I still prefer the new production 6CA7 from JJ... I am now using the Toroidy 250 VA transformer which has two high voltage output at 275 & 330 V AC. On the actual board I am limited to 400 V DC because of the capacitors, but I may build a new one with the PCB from the Group Buy 3 made by Prasi with 500 V capacitors and off board bridge to add external bigger capacitors to take advantage of the higher voltage of 460 V DC...
I haven't tested the KT77, but someone on the forum says that they are very good too ? The 6550 could be interesting too, I use them in my Jolida amplifier but I didn't tested them in the EL34 Baby Huey !
For the output transformers I am using two Hammond 1650N, with 4.3 k ohms impedance, that I have since many years and they are very good in this amplifier. I have also made some test with a 4 k Amplimo 3A524 toroidal transformer without UL output to test the stability of the amplifier without global feedback and UL, I have made tests in both triode mode (screen connected to plate) and pentode mode (screen connected to high voltage) and both give good result
I have not tested Toroidy transformer (I will use the CFB version in my next quad KT120 amplifier) but I know at least two persons who have used it and are very happy with them : Jacques, in Belgium use the EL34 6.6 k version and Philippe, few km from me in the south of France use the very nice DEMO version of the KT88 4.3 k version (see post 2076)...
If some others builders use them, please give us your feedback ?
I will receive the top panel soon, I will send pictures when the amplifier will be in the box
Best regard,
Marc
Hi SCD,
Yes you are right, you can replace the 12AX7 / ECC83 with the 6N2P, they are compatible except for the heater, not only they are not connected in the same way but the 6N2P need a little higher current too (see datasheet in previous post) !
I didn't implement a jumper solution to accept both tube on this amplifier PCB, but I have done it on other projects for 12AU7 / ECC82 replaced with 6N1P, as you can see below, it is quite simple in fact
The pin 9 of the 6N2P is a screen between both triode and can be connected to ground (GND) or left unconnected.
Best regards,
Marc
Yes you are right, you can replace the 12AX7 / ECC83 with the 6N2P, they are compatible except for the heater, not only they are not connected in the same way but the 6N2P need a little higher current too (see datasheet in previous post) !
I didn't implement a jumper solution to accept both tube on this amplifier PCB, but I have done it on other projects for 12AU7 / ECC82 replaced with 6N1P, as you can see below, it is quite simple in fact
The pin 9 of the 6N2P is a screen between both triode and can be connected to ground (GND) or left unconnected.
Best regards,
Marc
Pin 9 on 6N2P should not be left unconnected, IT should always be grounded see: 6N2P - WHAT THE?????????????
Hi toriversen,
Pin 9 should be connected to an AC ground. That could be any potential within the ratings of the tube as long as it is at AC ground. That means you could connect it to a bias voltage for the heaters (above ground) that is bypassed to ground. Sometimes that is easier than trying to get a connection to real, absolute ground.
-Chris
Pin 9 should be connected to an AC ground. That could be any potential within the ratings of the tube as long as it is at AC ground. That means you could connect it to a bias voltage for the heaters (above ground) that is bypassed to ground. Sometimes that is easier than trying to get a connection to real, absolute ground.
-Chris
Hi toriversen,
Pin 9 does not need to be necessarily connected to the ground, as you can see on my two schematics it is connected to one of the heater lines and there is absolutely no noise or distortion for this reason.
This is based on a description in the Merlin Blencove book on tubes preamplifier and the RIAA amplifier is described in this thread : Merlin RIAA Preamp
Marc
Pin 9 does not need to be necessarily connected to the ground, as you can see on my two schematics it is connected to one of the heater lines and there is absolutely no noise or distortion for this reason.
This is based on a description in the Merlin Blencove book on tubes preamplifier and the RIAA amplifier is described in this thread : Merlin RIAA Preamp
Marc