Replace 12AU7 with 6SN7 ?

Amiglick,

I'm just curious, but since you said that you are using the Triton as an amp only, already driving it with a 6SN7 based pre-amp, is your motivation to reduce your system's footprint by eliminating the separate pre-amp?

You are fortunate too to be supported by a "tube guy" in whom you have confidence, but since that is already the case, it left me wondering what advice you intended to solicit here? The members that responded with their technical advice certainly seemed conscientious and I'm sure would be willing to again provide their learned council, but perhaps you were looking for comments related to some other aspect of your project?

Your project is an interesting one, though, as the Triton 3 design includes 6SJ7 tubes along with the 12AU7s. I have been told that the 6SN7 tube provides greater resolution than the 12AX7 family, and perhaps that is why Ayon included a tube from the 6SN7 family in the current design. But that makes me wonder if there is another option to your project, which would be to sell your Triton and preamp and get a Triton 3 which has been designed to include a tube from that family. That would certainly seem like a less risky proposition. I have owned 6SN7 based preamps and had the opportunity to try RCA and Sylvania tubes, but I have no idea if the 6SJ7 will afford much of an opportunity for tube rolling. If that is one of your goals then the Triton 3 may not be an attractive option. But since you already have a 6SN7 based preamp, the motivation for your project remains unclear to me.

Prior to getting my Triton 1 I mentioned to the salesman that I was going to replace the NOS 12AU7s that they had put in the unit with the Telefunken tubes from my mono blocks. His reply was to caution me to make sure they were good tubes since the Triton "takes its tubes seriously." Exactly what he meant by that I don't know, or even if it is a meaningful statement, but I would certainly take from his remark that changing tube types in the piece would not be a good idea.

Finally, if increased resolution is your goal, it is my understanding that the 6H30P tube provides greater resolution than the 6SN7, so maybe a preamp like a Rogue Athena or Hera 2 would be an option.

Regardless, best of luck with your project and I hope you will post the results, especially regarding the resulting sound of your system.

Almarg

Al, thank you for your professional analysis.
The facts are:
"the component is designed to operate the 12AU7 at 6.3 volts (with the two halves of the filament in parallel), AND the power transformer can comfortably supply the doubled filament current that would be required by TWO tubes"

I am closely supported by a well experienced "TUBE" guy and it gives me confidence in what I am doing.

I will replace 2 tubes and monitor the changes (if any).
If the change will reflect subtle improvement, I will consider to modify the equipment so it will handle the replacement of all the SIX tubes.

I will post my results here for the benefit of the 12AU7 users.

Thank you all.

I

Reynolds853

Thank you for your post.
I have a preamp. which use 6SN7 tubes.
The NOS 6SN7 have an outstanding timbre which I want to implement also in the TRITON by replacing the 12AU7.
In the TRITON I use 12AU7 NOS Amperex from the 50's.

Regards.

Amiglick,

I own a Triton 1 and if you don't mind me asking, I'm curious about what is your goal for considering this change?

Also, what 12AU7s are you presently running in the amp?

Simply replacing 12AU7s by 6SN7s would double the filament current drawn (3.6 amps vs 1.8 amps for 6 tubes). That could easily burn out the power transformer if its rating is marginal.

The above statement is correct. Unless you can measure this yourself, and are capable of modifying your amp yourself, then don't try to swap out the tubes. Overall the amp would operate but you don't know how the current will effect the other parts in the amp. Most tubes will operate in a range and obviously if it all matches, the better the unit should sound. Therefore, the manufacturer should know what is best for their design.

Happy Listening.

"I am not going out of my way to be rude, I would just think that the manufacturer's word would trump anyone else's. "

Al's an exception.

Ghostrider, just saw your post. Great minds think alike!

Regards,
-- Al

Yogi and Mofi, yes, the 12 and the 6 are the filament voltages that the tubes are designed to be operated with. Obviously, applying 12 volts to a 6 volt filament would result in pyrotechnics.

Looking at a tube manual I have, though, I see that the 12AU7 apparently has a center-tapped filament, and its filament has two ratings, 12.6 volts at 0.15 amps, or 6.3 volts at 0.3 amps. The 6SN7 rating is 6.3 volts at 0.6 amps.

I would surmise, therefore, that SOME designs operate the 12AU7 by applying 6.3 volts between the center tap of the filament and both of its end points, thereby operating the two halves of the filament in parallel.

Other specs on the two tubes are generally in the same approximate ballpark, except that the 6SN7 can handle higher power levels, especially in its GTA and GTB variants, which are also rated to be able to handle considerably higher voltage levels.

So IF the adapter steps down 12 volts to 6 volts, OR IF the component is designed to operate the 12AU7 at 6.3 volts (with the two halves of the filament in parallel), AND IF the power transformer can comfortably supply the doubled filament current that would be required by the SIX tubes, it may be within reason to make this substitution. However, unless one is familiar with the details of the design of both the specific component and the adapter, and unless one knows exactly what one is doing, disaster is being invited.

Regards,
-- Al

12AU7 and related 9 pin triodes have a center tapped filament that can run on 12 or 6 volts depending on whether the segments are wired in series or parallel. In most amps they run on 6 volts as that saves having a special 12 volt secondary winding on the power transformer.

6SN7 draws 600 ma of filament current. A 12AU7 draws 300 ma filament current in parallel mode (6 volt operation).

Simply replacing 12AU7s by 6SN7s would double the filament current drawn (3.6 amps vs 1.8 amps for 6 tubes). That could easily burn out the power transformer if its rating is marginal.

I would follow the manufacturer's recommendation as mentioned above.

Yogi, that is correct as I understand it also. I can't see how you could use a 6 volt tube in a 12 volt position even with an adapter, unless that adapter also steps down the voltage?

I could be wrong but I thought the 12 and 6 mean the voltage of those tubes!

+1 for Rich, I agree. There are so many different 12au7's available. It makes better sense to just try a different 12au7.

With all due respect, do you think that anything that any of us could offer as an opinion to you would mean more than what the manufacturer said to you as fact? I am not going out of my way to be rude, I would just think that the manufacturer's word would trump anyone else's.

Rich

I cannot say anything about your unit but I am using a Modwright transporter with converters to use 6SN7s instead of the 9 pin dual triodes that it was originally designed for. It works fine. Of course in this case, the designer himself makes the converter and now sells the product w 6SN7s as factory tubes.