[JackarlTwo]

OK - back to real tubes again. In these days of ever escalating prices of desirable tubes I have found a garden variety RCA 6SN7GT that IMHO is a top tier tube. This tube should be inexpensive but it is a little hard to find but not because it is rare; I'll explain:
This 6SN7GT tube is from the late sixties. RCA made several different such tubes, but I only found one variant that sounds great. This variant has a little heater wire above the top mica and black parallel plates. All the ones I have seen have red print on the base. There are also rebranded such tubes that should make them even cheaper (I have pair Stromberg-Carlson branded ones - S-C was a radio manufacturer). The problem is that most such tubes when pictured in the ads don't show that little heater wire. Here is a spotters guide:

My tube in action; more pictures below:




If anyone has this variant, please try it and let me know what you think of the sound.

I've been using these tubes for a while now. Sounds pretty close the RCA VT-231 gray glass I have, but not as rolled off up top I think. Very good sound imo, especially for the relatively good price.

 

[mordy]

I've been using these tubes for a while now. Sounds pretty close the RCA VT-231 gray glass I have, but not as rolled off up top I think. Very good sound imo, especially for the relatively good price.

Glad you like them. IMHO this tube is a sleeper and deserves a little recognition.

 

[Jon L]

Glad you like them. IMHO this tube is a sleeper and deserves a little recognition.

These RCA tubes seem to be late 1960's 6SN7GTB's not 6SN7GT per se..

 

[mordy]

These RCA tubes seem to be late 1960's 6SN7GTB's not 6SN7GT per se..

Yes, you are right - GTB.

 

[Jon L]

Yes, you are right - GTB.

I ordered a pair to complete my 6SN7 collection, but I have sold off all my tube gear using 6SN7's. What a crazy addiction..

 

[TLO]

I ordered a pair to complete my 6SN7 collection, but I have sold off all my tube gear using 6SN7's. What a crazy addiction..

It's OK, you may send your collection of 6SN7 to me. I will help you to give them some love in my rotation...

 

[bcowen]

This is the bent "central" pin I'm worried about, but I've tried the tube for hours and no issues. The base itself and tube is super rigid.

The 'center pin' I think you're referring to is the bottom of the glass bulb. It's not bent, that's just the way it formed when it was manufactured. Don't try to straighten it, you'll just break the glass and the tube will be dead forever.

Highly recommend the octal key replacements mentioned earlier. Orient correctly, add a couple drops of super glue, and you're as good as new without having to worry about inserting the tube incorrectly in the future. Having a couple spares won't hurt either, as you'll likely break another center pin at some point. Not that I speak from experience or anything...

 

[JackarlTwo]

The 'center pin' I think you're referring to is the bottom of the glass bulb. It's not bent, that's just the way it formed when it was manufactured. Don't try to straighten it, you'll just break the glass and the tube will be dead forever.

Highly recommend the octal key replacements mentioned earlier. Orient correctly, add a couple drops of super glue, and you're as good as new without having to worry about inserting the tube incorrectly in the future. Having a couple spares won't hurt either, as you'll likely break another center pin at some point. Not that I speak from experience or anything...

Yeah I quickly noticed it's just a part of the glass, I wasn't sure if it was supposed to be bent like that. For now I just use a marker to easier identify the correct orientation.

 

[tdadawa]

I would like some feedback on the difference in sound between 1940's era RCA 6SN7-VT231 and Sylvania 6SN7-VT231 if at all possible. Right now I'll using Sylvania 6SN7GTB in the late 50's early 60's era.

 

[steve468]

I would like some feedback on the difference in sound between 1940's era RCA 6NS7-VT231 and Sylvania 6NS7-VT231 if at all possible. Right now I'll using Sylvania 6SN7GTB in the late 50's early 60's era.

The difference to my ears is probably not as great as you might expect. I personally prefer the Sylvanias for their more even, neutral and natural sound. The RCA are a touch more "fun" sounding, with more present mid-bass (again, small differences). But I thought the treble with the RCAs was a bit wonky, like a bit harsh. To my ears, in my amp, in my system, etc.

You'll probably find both tubes more "toobey"/warmer and more natural than your GTB, by a bit.

 

[tdadawa]

The difference to my ears is probably not as great as you might expect. I personally prefer the Sylvanias for their more even, neutral and natural sound. The RCA are a touch more "fun" sounding, with more present mid-bass (again, small differences). But I thought the treble with the RCAs was a bit wonky, like a bit harsh. To my ears, in my amp, in my system, etc.

You'll probably find both tubes more "toobey"/warmer and more natural than your GTB, by a bit.

Thanks Steve, You might have noticed I slipped on my keyboard and said 6NS7 instead of 6SN7 so I corrected it. Right now my Baldwin 6SN7GTB tubes sound quite toobey compared to my 6922 style tubes I use.

 

[steve468]

Thanks Steve, You might have noticed I slipped on my keyboard and said 6NS7 instead of 6SN7 so I corrected it. Right now my Baldwin 6SN7GTB tubes sound quite toobey compared to my 6922 style tubes I use.

Hah! I didn’t notice. And you gots to be careful with tubes, maybe there was a 6NS7 that’s been lost to time.

 

[TLO]

The difference to my ears is probably not as great as you might expect. I personally prefer the Sylvanias for their more even, neutral and natural sound. The RCA are a touch more "fun" sounding, with more present mid-bass (again, small differences). But I thought the treble with the RCAs was a bit wonky, like a bit harsh. To my ears, in my amp, in my system, etc.

You'll probably find both tubes more "toobey"/warmer and more natural than your GTB, by a bit.

Just curious, what is the date code on your RCA VT-231?

 

[steve468]

Just curious, what is the date code on your RCA VT-231?

On the one tube it says H4E, which I read as an OEM tube from either August 1944 or 1959 - apparently RCA just arbitrarily started repeating date codes after 15 years. ‘Cause why not? The other in the pair is all rubbed off.

 

[TLO]

On the one tube it says H4E, which I read as an OEM tube from either August 1944 or 1959 - apparently RCA just arbitrarily started repeating date codes after 15 years. ‘Cause why not? The other in the pair is all rubbed off.

I believe H4E is 1944 Jul-Aug as from 1947, RCA started using all numbers for dating. Dont mind me, have you checked for microphonic? I asked because I have multiple pairs from 1942-1944 and they dont sound harsh on 2 amps I have tried so far. One thing I have observed is this RCA smoked glass is slightly microphonic if placed in certain socket position but not in another. They are a bit sensitive to micro-vibration when current passes through. Just a thought.