If NOS pre or power tubes became unavailable altogether, what new tubes would you buy?


Hey tuberollers, 

I'm curious to see what happens if there's a gun to your head, or more practically all NOS tubes disappear (dread).  What would you do with your line/pre stage and/or power stage?  

I have tried 5 different NOS 12AU7s and only 1 new 12AU7 in my preamp section (Cifte, RCA black plates (late 50s), Sylvanias, Baldwin organ tubes, Amperex 70s orange globes, and new Chinese stock Primaluna tubes).  In my power section, I have not tried any NOS tubes and 3 types of tubes (stock Chinese Primaluna EL34s, reissue Mullard EL34s, and reissue Gold Lion KT88s).  

Side note: I haven't ventured into NOS power tubes because of the cost and availability/scarcity.  I need 8 of them!

Without having tried anything else, I would be lost on new or reissue 12AU7s.  On the power tube side, I'd be just fine with either the reissue Mullard EL34s or the Gold Lion KT88s.  
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Thanks, @tubegroover . I looked up the Sophia Electric 6SN7's and they are compared to a VT-231, so that would make them closer in sonics to NOS. The fact that you are using them in your Modwright/Oppo tells me they must sound more enjoyable than the other new production tubes.

Although they are not inexpensive...hope they last longer than NOS 6SN7's.
A cautionary note about the Sophia 6SN7: See the following thread from 2012, in which I and another member both reported that it caused hum problems in our VAC Renaissance amplifiers, which I determined was due to excessive heater-to-cathode leakage.

https://forum.audiogon.com/discussions/vac-30-30-sophia-6sn7-s/

As I said in that thread:
The heater-to-cathode leakage in my Sophia’s, as measured on my vintage Hickok tube tester, was as low as 3 or 4 megohms on some sections of some of the tubes, and was in the 5 to 10 megohm area on most of the others.
I recall that Ralph (Atmasphere) commented some time ago in another thread that he rejects any tube measuring less than 10 megohms.

Also, I’ll mention that on my Hickok 800a tester all of the vintage 6SN7 tubes I have measure well above 10 megohms, and in many cases are high enough to be unmeasurable.

What I had purchased was a matched quad of Sophia’s "grade A" version of the tube ($100 per tube), with their optional one year warranty ($18 per tube at that time, which I see they’ve increased to $20). To update the history I reported in the other thread, I eventually had Sophia exchange the four tubes for a new matched quad, under the warranty. The replacement tubes worked well for a few months, even though their heater-to-cathode leakage did not measure a great deal better than on the first set. After a few months, though, the replacement tubes developed the same hum problem, and I retired them to my tube collection.

If I had speakers that were significantly less efficient (mine are 97.5 db/1 watt/1 meter), or if I had used the tubes in a different amplifier or other component, it seems quite conceivable that I would not have observed this problem.

Best regards,
-- Al

Thanks to all who have stayed with the initial question and purpose of the thread.  I thought about deleting the thread because of the direction the thread went. 

People, at least me, really do run searches on forum threads with the objective of finding answers.  Now, if someone searches and finds this thread they will get less answers about new tubes that people like as alternative to the NOS tubes that are expensive and scarce.  

Raul should start his own thread.  Too bad.
@almarg , I remember your issue with the Sophia's and maybe they can't tolerate voltage levels in some amps. Tubegroover is having good results in a low current device; a CDP.
Which makes me wonder if the Sophia's would hold up in a single gain stage preamp. 
Al, although the high sensitivity of your speakers reveal the issue with hum, the specs of these tubes don't lie.

Hi Lowrider,

Heater-to-cathode leakage is not a specified parameter in the case of most tubes. For example, that parameter does not appear in the GE datasheet that is linked to in Sophia’s description of their 6SN7. Also, it’s not a voltage issue in this case, because even before they were placed in my amp all or nearly all of the eight tubes I received did not meet the 10 megohm criterion that Atmasphere cited as the minimum he would consider to be acceptable. And their measurements did not change much if at all during the time I was using the tubes in my amp.

What I and the other member reported in the thread I linked to is either a design issue or a quality control issue, albeit one that apparently would not manifest itself in many applications.

Best regards,
-- Al