[triod750]

	6N12S ​
Name 6N12S Type Double triode Application LF voltage amplification Cathode type oxide,indirect heating Envelope glass Mass,g 45 Filament voltage,V 6,3 Filament current,A 0,83-0,97 Anode voltage,V 180 Anode current,A 0,015-0,031 Anode power,W 4,2 Grid1 voltage,V minus 7 Steepness,mA/V 4,8-8,0 Microphnic noise,mV 250 Gain 14,0-20,0 Socket type rsh5-1

 

[mordy]

Thanks for the infos mordy .Yes the Photons i have a pair of the ladder type pattern from 1952 . got a few pairs from 60"s

You are halfway there already lol....
ATM I am listening six 50's Foton 6H8S + a RCA 6N7G. The Fotons are very quiet and they have a very even frequency response and great detailed layering.The presentation is both musical and detailed and relaxing - you can just enjoy the music, or, concentrate on details in the music; they are all there. Somehow the background instruments are becoming clearer as well.
This combo runs very cool and with the fans on the amp is almost the same temperature as the room temperature - 27C vs 25C. And that is after leaving it on 15 hours straight.
Glenn once told me that you could exceed the capacity of the GOTL with an additional ampere (in my case 14A instead of 13A) by using fan cooling which
may be good to know, although with this setup it certainly isn't needed.

 

[MIKELAP]

I will give it a try got plenty of 6N7 .ive been using 4 -6BL7 with the double adapter which is 3A \channel and my amp is rated at 3A\channel but doesnt seem to get hot ,then again i dont use these all the time .When you talk about using a fan that's what i do when im using my Russian 6C33C tube SET amp for speakers the damm things go up to 400F. Dont have to use a fan but damm it get's hot Thanks mordy

 

[chrisdrop]

A quick survey of opinions; Do you plug in headphones before turning amp on, or after? Power down the amp with the headphones plugged in?

Bottlehead & other amps suggestion is that you should turn amp on/ off with headphones plugged in and that this is less disturbing noise than otherwise.

My practice with the GOTL is only ever turn on/ off the amp w/ the headphones unplugged, but perhaps I have it backwards with this amp too!

 

[gibosi]

A quick survey of opinions; Do you plug in headphones before turning amp on, or after? Power down the amp with the headphones plugged in?

Bottlehead & other amps suggestion is that you should turn amp on/ off with headphones plugged in and that this is less disturbing noise than otherwise.

My practice with the GOTL is only ever turn on/ off the amp w/ the headphones unplugged, but perhaps I have it backwards with this amp too!

Your practice is correct. The OTL doesn't care if the headphones are plugged in or not. But if a tube blows when the amp is turned on or off, your headphones may not survive. And if you have the headphones on your head, your ears could be damaged. So protect your headphones and your ears. Disconnect your headphones before turning the amp on and before turning it off.

 

[mordy]

Your practice is correct. The OTL doesn't care if the headphones are plugged in or not. But if a tube blows when the amp is turned on or off, your headphones may not survive. And if you have the headphones on your head, your ears could be damaged. So protect your headphones and your ears. Disconnect your headphones before turning the amp on and before turning it off.

I do exactly what Chrisdrop does, with one more caveat: When first plugging in the headphones I always start with an inexpensive pair in case something untoward happens.
Once I know that everything is how it should be I switch to the headphones of choice. I don’t wait more than a minute or so, and yes, it is tedious, but sure beats a blown driver in an expensive headphone.

 

[triod750]

Received a 6N12S from Bulgaria today. It is from 1956 and I wanted to know if there is a difference since they have a slightly different construction from the ones presented by gibosi. The side supports are at a level below the top mica and the bottles are about 4mm shorter. I am waiting for another from Moldovia that is upheld in customs. I put it in after cleaning the pins and it is silent. At least until the music is flowing. I cannot guarantee that the sound is of lesser quality than from the newer ones. Old people like me can say that tubes from 1962 are new, or at least newer. If I were to describe how they sound I would probably say that they are something in between Melz 6N8S/6H8C and 5687. But I don't want to say anything about how they sound. They are interesting and worth trying for anyone so inclined. They remind me of playing vinyl. It's very easy to differentiate between bad and good recordings.

But don't pay much attention to this. My hearing is slightly impaired and I don't have a GOTL. I just listen to music, right now a piano concerto. These 6N12S really make the most of the grand piano. It's quite obvious how powerful that instrument is.

 

[triod750]

This short bottle tube is most likely used and much more matured than the 1962 ones were. They needed a lot of time to become relaxed. They might even develop still after about 150 hours. Just a guess from what I am hearing now.

 

[canfabulous]

A quick survey of opinions; Do you plug in headphones before turning amp on, or after? Power down the amp with the headphones plugged in?

Bottlehead & other amps suggestion is that you should turn amp on/ off with headphones plugged in and that this is less disturbing noise than otherwise.

My practice with the GOTL is only ever turn on/ off the amp w/ the headphones unplugged, but perhaps I have it backwards with this amp too!

Same - turn on and off without headphones plugged in, and I always turn the volume knob to zero before plugging/unplugging headphones. Just small habbits to develop as muscle memory and I suspect the latter is more useful day to day as to not accidentally have your head blasted off by a high volume!

 

[L0rdGwyn]

When I had the GOTL, I always turned on before plugging in and unplugged before turning off to ward off evil spirits the specific fear is tube arcing, which the 5998 in particular is prone to, I have had more than a few arc across different OTL amplifiers, never any permanent damage, but others have not been so lucky, including our host. So good practice with OTLs, less of an issue with SET amplifiers since voltages and noise are stepped down across the output transformer.

 

[raindownthunda]

When I had the GOTL, I always turned on before plugging in and unplugged before turning off to ward off evil spirits the specific fear is tube arcing, which the 5998 in particular is prone to, I have had more than a few arc across different OTL amplifiers, never any permanent damage, but others have not been so lucky, including our host. So good practice with OTLs, less of an issue with SET amplifiers since voltages and noise are stepped down across the output transformer.

What is the amount of minimum time you'd feel "safe" letting a 5998 warm up before switching to main headphones? Is it fair to assume that most tubes fail during warm up and that after warm up arcing won't/rarely happen? My routine with my bottlehead crack is to let it warm up for 60 seconds without any headphones plugged in. Then I'll connect an old Sony MDR-V6 to play some music on low for 10 minutes, before switching to a ZMF.

 

[LoryWiv]

Your practice is correct. The OTL doesn't care if the headphones are plugged in or not. But if a tube blows when the amp is turned on or off, your headphones may not survive. And if you have the headphones on your head, your ears could be damaged. So protect your headphones and your ears. Disconnect your headphones before turning the amp on and before turning it off.

This does seem very prudent and rationale, but with some amp designs (not necessarily OTL) there may be a concern as discussed here in an older thread. Pro's and con's, and potentially amp-design specific?

 

[whirlwind]

What is the amount of minimum time you'd feel "safe" letting a 5998 warm up before switching to main headphones? Is it fair to assume that most tubes fail during warm up and that after warm up arcing won't/rarely happen? My routine with my bottlehead crack is to let it warm up for 60 seconds without any headphones plugged in. Then I'll connect an old Sony MDR-V6 to play some music on low for 10 minutes, before switching to a ZMF.

I almost every tube that I have ever had go bad, seemed to happen at start-up.
I did have the filaments burn out in one Tung Sol 5998 while listening to music, one channel just faded away.

 

[L0rdGwyn]

What is the amount of minimum time you'd feel "safe" letting a 5998 warm up before switching to main headphones? Is it fair to assume that most tubes fail during warm up and that after warm up arcing won't/rarely happen? My routine with my bottlehead crack is to let it warm up for 60 seconds without any headphones plugged in. Then I'll connect an old Sony MDR-V6 to play some music on low for 10 minutes, before switching to a ZMF.

I would typically wait about a minute or two, as @whirlwind said, the issues with the 5998 seem to occur during the first 15-20 seconds or so of startup time, IME.

This does seem very prudent and rationale, but with some amp designs (not necessarily OTL) there may be a concern as discussed here in an older thread. Pro's and con's, and potentially amp-design specific?

Yes, there is an issue with OPT coupled designs related to having a load disconnected. In a SET amplifier for example, there is a DC current running through the OPT primary winding at all times. The voltage generated by this current is applied to the load reflected from the secondary of the OPT to the primary (headphones / speakers). If the load is removed during operation, the voltage on the primary can spike to several times the B+ voltage, which can potentially lead to arcing in the OPT transformer and fry it. This is only a real danger if the amplifier is being operating near or at clipping, as in a guitar amplifier, less of a concern with a hifi amplifier as we don't typically listen that loud.

A common method to protect against this is to wire a resistor across the OPT output terminals in parallel with headphones / speakers such that there is always a load reflected to the primary even with no headphones / speakers connected, I use 470ohm in my SET amps. OPT like Lundahl have high voltage insulation ratings too, so the danger of arcing is low. With an OPT coupled amp, the danger would be if it was turned on without a load plugged in, the amp designer did not include any type of protection, the driver tubes are capable of driving the output tubes into clipping / cutoff, and the volume is turned up to the point of clipping / cutoff.

 

[mordy]

Based on all of the above it seems like a good idea to turn down the volume to zero on startup, in addition to the other precautions - easy to do and a no cost option......