Reisong A10: Technical review.

[BMC]

Did you mod an A10 or A12? I have an A10. I'm capable of handling a solder iron and following instructions, but I have an A10 and fumble on the 6N2J to 12AX7 rewire. I am currently using adapters, but if I am reading through this stuff right, I need to rewire the pins.

Cheers!

I have the A10. I did not rewire the heater pins for 12AX7, since I have adapters and also like to use 6N2P tubes sometimes. The instructions work no matter which way you wire the heaters.

This mod is 100% worth it. Good luck!

 

[JohnLA]

The socket rewire is very simple. On both tubes, Pins 1,2,3,6,7 and 8 are the same. The only thing that changes is the heater wiring.

The 6n2 has the 6.3v heater wires hooked up to pins 4 and 5. To use a 12AX7 at 6.3v you just disconnect the wire from pin 5 and move it to Pin 9. If the 6N2 has Pin 9 (which is an internal shield) connected somewhere, remove that connection. Then just connect pins 4 and 5 together.

So for the 12AX7 one wire goes to Pins 4 and 5 and the other goes to Pin 9.

Remember, pins are numbered clockwise when viewed from the bottom.

I have the A10. I did not rewire the heater pins for 12AX7, since I have adapters and also like to use 6N2P tubes sometimes. The instructions work no matter which way you wire the heaters.

This mod is 100% worth it. Good luck!

Thanks, guys! I'm leaning toward re-wire as I don't suspect I'd go back to stock and would always roll 12AX7s.

I'm putting my Mouser order together for the mod as we speak. =)

Cheers!

 

[FlaCharlie]

Thanks, guys! I'm leaning toward re-wire as I don't suspect I'd go back to stock and would always roll 12AX7s.

I'm putting my Mouser order together for the mod as we speak. =)

Just a head's up . . . Digi-Key has a free shipping option, which is especially handy with small parts orders where the shipping can sometimes cost as much or more than the parts being ordered. No minimum purchase and no handling charge.

http://www.audiokarma.org/forums/in...hipping-on-parts-orders.739513/#post-10018562

 

[opnly bafld]

Just a head's up . . . Digi-Key has a free shipping option, which is especially handy with small parts orders where the shipping can sometimes cost as much or more than the parts being ordered

Now you tell me (never saw the thread linked).

I bought 4 LEDs for a Kegger/Blueglow build, only needed 2, but for the price $1.11 ea. and shipping $6.99, why not get a couple extra?

 

[FlaCharlie]

Now you tell me (never saw the thread linked).

I bought 4 LEDs for a Kegger/Blueglow build, only needed 2, but for the price $1.11 ea. and shipping $6.99, why not get a couple extra?

Sorry you missed it, I try to post about this as much as I can. I've probably posted the link in at least 100 threads . . . actually, I just did a search and it's now been 137 times. And, no, I'm not compensated in any way.

 

[JohnLA]

The socket rewire is very simple. On both tubes, Pins 1,2,3,6,7 and 8 are the same. The only thing that changes is the heater wiring.

The 6n2 has the 6.3v heater wires hooked up to pins 4 and 5. To use a 12AX7 at 6.3v you just disconnect the wire from pin 5 and move it to Pin 9. If the 6N2 has Pin 9 (which is an internal shield) connected somewhere, remove that connection. Then just connect pins 4 and 5 together.

So for the 12AX7 one wire goes to Pins 4 and 5 and the other goes to Pin 9.

Remember, pins are numbered clockwise when viewed from the bottom.

Started mods this evening. Output tubes are done. I have also cleared out the input tubes and will pick up the work on those tomorrow.

However, I have a question regarding the 12AX7 rewire. I did the right side (bottom) first, same as Steph. I moved the wire from the 5 pin to the 9 pin. I left the wire on the 4 pin connected and then joined the 4 and 5 pins together with some wire.

NOW, the left side bottom has the wires coming in the from the heaters, as well as wires that join over to the right side output tube. I assume task is the same... wires in and out both get moved from 5 to 9, 4 wires stay same, and join the 4 and 5. However, as I untwisted the wires joining the two output tubes--to get a little more length I need to move the wire--I noticed that the wires are opposite. So, before moving, the 5 pin on the left was wired to the 4 pin on the right, and vice versa. I assume this is a circuit thing, I'm no electrician, and moving the wires on the left side is simply same as I did on right, regardless. But I just want to make sure that this is in fact the case and I'm not supposed to reverse the wires or do something else.

IMG_0404

• JohnLA
• Jan 3, 2022

A10 stock output tube wiring

Thanks again for your time and help.

Cheers!

JG

 

[FlaCharlie]

I have a question regarding the 12AX7 rewire. I did the right side (bottom) first, same as Steph. I moved the wire from the 5 pin to the 9 pin. I left the wire on the 4 pin connected and then joined the 4 and 5 pins together with some wire.

NOW, the left side bottom has the wires coming in the from the heaters, as well as wires that join over to the right side output tube. I assume task is the same... wires in and out both get moved from 5 to 9, 4 wires stay same, and join the 4 and 5. However, as I untwisted the wires joining the two output tubes--to get a little more length I need to move the wire--I noticed that the wires are opposite. So, before moving, the 5 pin on the left was wired to the 4 pin on the right, and vice versa. I assume this is a circuit thing, I'm no electrician, and moving the wires on the left side is simply same as I did on right, regardless. But I just want to make sure that this is in fact the case and I'm not supposed to reverse the wires or do something else.

IMG_0404

• JohnLA
• Jan 3, 2022

A10 stock output tube wiring

Thanks again for your time and help.

Cheers!

JG

Since pins 4 and 5 are now connected when using a 12AX7 it doesn't matter if the wire itself goes to 4 or 5. Just think of the combination of 4/5 as a single pin. The other wire goes to pin 9.

 

[JohnLA]

Since pins 4 and 5 are now connected when using a 12AX7 it doesn't matter if the wire itself goes to 4 or 5. Just think of the combination of 4/5 as a single pin. The other wire goes to pin 9.

Got it. So at the end of the day, if I move the wires from 5 to 9 on each, I will wind up with pin 9 on the left connected to pin 4/5 on the right, and pin 4/5 on the left connected to pin 9 on the right, correct? Meaning, this would be wired in series, right?

IMG_0405

• JohnLA
• Jan 3, 2022

A10 after 12AX7 conversion?

 

[FlaCharlie]

Got it. So at the end of the day, if I move the wires from 5 to 9 on each, I will wind up with pin 9 on the left connected to pin 4/5 on the right, and pin 4/5 on the left connected to pin 9 on the right, correct? Meaning, this would be wired in series, right?

IMG_0405

• JohnLA
• Jan 3, 2022

A10 after 12AX7 conversion?

No, although I'm not sure if it would really make any difference since it's AC.

Make a connection from pin 4/5 on one tube to 4/5 on the other tube. Make a connection from pin 9 on one tube to pin 9 on the other tube.

The connection is in parallel.

 

[JohnLA]

No, although I'm not sure if it would really make any difference since it's AC.

Make a connection from pin 4/5 on one tube to 4/5 on the other tube. Make a connection from pin 9 on one tube to pin 9 on the other tube.

The connection is in parallel.

Ah. Ok. Thanks again for your time and help.

Cheers!

JG

 

[g-t-i]

Great discussion here. Since only one side (pin 123triode+49heater) is used anyway ... why connect 4/5 together to heat the unused side filament?? Would it be better to just connect heater to pin 4+9 on both sides? It will ease the PT load a little bit also.
And would it also benefit if the unused Pin 678+5 are all tied together and to ground?? (Is this the right way to do it to avoid any interferences/cathode poisoning for using one side only?? Opinion differs on this for what I have read.)

(I am not going to complicate it further to suggest wiring it up using opposite triode side for the left and right 12AX7 so that he can swap the 12AX7 when it gets old (if he is considering rolling megabucks NOS rare 12AX7 tube it might make sense?)

 

[JohnLA]

Great discussion here. Since only one side (pin 123triode+49heater) is used anyway ... why connect 4/5 together to heat the unused side filament?? Would it be better to just connect heater to pin 4+9 on both sides? It will ease the PT load a little bit also.
And would it also benefit if the unused Pin 678+5 are all tied together and to ground?? (Is this the right way to do it to avoid any interferences/cathode poisoning for using one side only?? Opinion differs on this for what I have read.)

(I am not going to complicate it further to suggest wiring it up using opposite triode side for the left and right 12AX7 so that he can swap the 12AX7 when it gets old (if he is considering rolling megabucks NOS rare 12AX7 tube it might make sense?)

Learning a lot here! So, given the 12AX7 pins:

1 - Plate 2
2 - Grid 2
3 - Cathode 2
4 - Filament 2
5 - Filament 1
6 - Plate 1
7 - Grid 1
8 - Cathode 1
9 - Filament Tap

It looks like with the mod, I am using "1" side of tubes. So in order to swap tube sides when needed, I could wire up the "2" side on one of the output sockets based on pin map? So, for example, pin 1 on one side, pin 6 on the other? I assume 4/5 and 9 would stay the same.

Is this correct?

 

[g-t-i]

JohnLA I didn't meant to confuse you more. Just to point out that if you want to rewire your A10's heater to make it into an A12 for 12AX7 use -> you would do as you have confirmed with FLACharlie above which is to connect one wire to pin 9 and other wire to Pin 4+5 tied together. This is the standard 6.3V connection and will draw 300ma current per 12AX7; and you will be heating both filament.
With the exact Skunkie mod -> you are using side "2" of the triode (Pin 1/2/3) ... not side "1" as you wrote above (referring to the pin out description you wrote above). And per Skunkie design you use the exact same side "2" triode for both channel. Just want to make it absolutely clear for you here so you are not confused. This will work just fine as per exact Skunkie mod.

I was just throwing out discussion/suggestion on something extra: Connecting only filament for the side you are using to save total of about 300ma off the Power Transformer. You can do this by connecting only pin 9 and pin 4 to the 2 heater wires (assuming the tube is made per standard which means pin 4 is filament for the pin 1/2/3 side triode (being used) and pin 5 is filament for the pin 6/7/8 side triode). This is optional and same thing as connecting all unused pins to ground is also optional.
On top of that something extra is to be able to do the swap trick. You already have the idea I think from above that is using one side triode on one channel and the other triode on the other channel. I believe this only make sense if you only heat the filament for the triode that is being used on each side. If you heat the filament for the unused triode side as well it will wear it out and there is no point of doing the swap trick anymore imo.

keep it going.

 

[JohnLA]

JohnLA I didn't meant to confuse you more. Just to point out that if you want to rewire your A10's heater to make it into an A12 for 12AX7 use -> you would do as you have confirmed with FLACharlie above which is to connect one wire to pin 9 and other wire to Pin 4+5 tied together. This is the standard 6.3V connection and will draw 300ma current per 12AX7; and you will be heating both filament.
With the exact Skunkie mod -> you are using side "2" of the triode (Pin 1/2/3) ... not side "1" as you wrote above (referring to the pin out description you wrote above). And per Skunkie design you use the exact same side "2" triode for both channel. Just want to make it absolutely clear for you here so you are not confused. This will work just fine as per exact Skunkie mod.

I was just throwing out discussion/suggestion on something extra: Connecting only filament for the side you are using to save total of about 300ma off the Power Transformer. You can do this by connecting only pin 9 and pin 4 to the 2 heater wires (assuming the tube is made per standard which means pin 4 is filament for the pin 1/2/3 side triode (being used) and pin 5 is filament for the pin 6/7/8 side triode). This is optional and same thing as connecting all unused pins to ground is also optional.
On top of that something extra is to be able to do the swap trick. You already have the idea I think from above that is using one side triode on one channel and the other triode on the other channel. I believe this only make sense if you only heat the filament for the triode that is being used on each side. If you heat the filament for the unused triode side as well it will wear it out and there is no point of doing the swap trick anymore imo.

keep it going.

Yes, my mistake, I should have wrote "2" for pinout side, my bad. I enjoy the learning experience and now know more about my little amp and its underlying parts than I did before! =)

When I first got the amp, I also invested in some much better tubes than with what came. The sound difference was night and day. The other little mod I did at that time was swapping out the coupler caps with some Russian PIOs. At any rate, given the decent relative expense of the tubes I put in, I am quite interested in being able to swap sides when needed, rather than using only one half of the tube.

I think I'm pretty clear now on how to do the additional work, including NOT joining the 4 and 5 pins, as per the Skunkie mod, but connecting the heater wire only to 4 or 5 depending on filament side.

Keeping it going. =)

Cheers!

 

[StepheK]

Right, this is a "further mod" I mentioned but didn't get into, trying to keep this mod as simple as possible. But yes you can totally heat "side A" of one tube and "side B" of the other, tie the unused pins to ground and swap the 12AX7 tubes when they wear out.

I will say I really like the sound I get from these cheap JJ EL34L tubes. I've tried a bunch of different 6CA7, KT77 etc and keep going back to these JJ tubes.

 

[FlaCharlie]

@JohnLA Ooops. I forgot that the @StepheK mod only uses one section of each 12AX7, not both. I just described the standard way to hook up the heaters.

If it were my amp I would go with her optional method and use "side A" of one tube and "side B" of the other so you could swap tubes after a while. This effectively gives you new tubes without having to buy any more.

Of course it really depends on how long you plan to keep the amp and how much use it gets. Input tubes don't wear out as fast as outputs. I've found original input tubes in vintage amps from the 1960s that still test new or nearly new. On the other hand, there's no point in wearing out a section that isn't being used. This would especially be true if you ever try more expensive NOS 12AX7s.

I've never done this but, if you go that route, it seems to me that you would want to ground the unused pins for the plate, grid and cathode but not the unused heater pin, right?

I think (?) that grounding the heater pin of the unused section would still light the heater, just as it would if you were heating the tube using a 12.6v series connection. When you do that (a series connection) you connect one heater wire to Pin 4 and ground Pin 5, leaving Pin 9 (the center tap) disconnected.

 

[Squidward]

Two extreme mods might be to replace the 12AX7 tubes each with 6AV6, or to move the wires and use both sections of a single 12AX7?

Neat mods, Stephe.

 

[StepheK]

I've never done this but, if you go that route, it seems to me that you would want to ground the unused pins for the plate, grid and cathode but not the unused heater pin, right?

Correct, float the unused heater pin.

 

[StepheK]

Two extreme mods might be to replace the 12AX7 tubes each with 6AV6, or to move the wires and use both sections of a single 12AX7?

Neat mods, Stephe.

There are a lot of things you could do, using a pair of triode strapped 6EJ7 pentode tubes comes to mind. Those tubes sound great and are super linear when triode strapped. Kegger designed one of his KT88 amps around them, which I built and loved. I ended up using the similar 6JC6a pentode, triode strapped, in mine.

 

[JohnLA]

@JohnLA I think (?) that grounding the heater pin of the unused section would still light the heater, just as it would if you were heating the tube using a 12.6v series connection. When you do that (a series connection) you connect one heater wire to Pin 4 and ground Pin 5, leaving Pin 9 (the center tap) disconnected.

Correct, float the unused heater pin.

I'm confused a bit. Which pin am I floating? Here's one side of amp example:

IMG_0407

• JohnLA
• Jan 4, 2022

12AX7 wiring one side

So the above example of one of the tubes, I am grounding only 6, 7, 8, and leaving 5 open? Other side tube I'd ground 1,2,3 and leave 4 open. Correct?

OR, do I move the wire on pin 9 back to pin 5, and wire 4 to 4 and 5 to 5 from tube to tube? And then float the 9's?

Thanks for your guys' help. =)

JG