can these preamp tubes be used in a guitar amp?

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KentC

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Posting this in a couple spots to see if I can get some answers here. I was out visiting a flea market today when I came across a couple of baskets full of old vacuum tubes. All different kinds that I have never heard of. The majority of them were old RCA 9 pin tubes. None of them said that they were in the 12AX or ECC family. They all had strange numbers that I have never heard used on any forum I visit, so I'm not sure if any of these could be used in a guitar amp. I had a bunch picked out ready to buy, but I ended up not buying them because I just wasn't sure if they were going to be worth anything. They were very cheap so I was going to take the chance and figured worse comes to worse, I at least have a bunch of NOS tubes. But I chickened out when I started looking online and didnt see anything that said these could be used in a tube amp. Alot of these dad dates ranging from the 50's and 60's, one even said 1947 on the box. So my question is, if I list the marking that were on some of the boxes, can anyone tell me if these are anything that could be used in the preamp section of an amp? I'm pretty ignorant when it comes to tubes so any knowledge anyone has here would be appreciated. Again the majority was all RCA, but there was a couple Tung Sol, GE, Sylvania, and even some old Westinghouse brands which I have never heard. IF anyone cant see the picture, here are some of the markings on the box tops: 5AT8 (or 5ATS.. picture was blury)
6HF8, 6CN7, 6ANBA, 10DE7, 8AW8A, 6DE7, 5CM8, 5X8, 6AU8, 7AU7, 6DX8/ECL84, 6JU8A, 5T8, 5BR8,
10CW5 LL86 (SYLVANIA)

https://imgur.com/a/Py6ec for a picture since I cant get it to embed in the thread.

Py6ec
 
No, it's almost never a good buy. Usually they are old radio or military radio tubes. I know of shops full of these. NOS, but un-useable unless you want to build around them. I don't see anything there worth anything.
 
I've got a datasheet collection, let me run through a review a few of them. I see a few that with heater mods or slight pin-layout changes to an amplifier might be something you can use. I'll report back.
 
6HF8/5AT8 No.

6CN7 - You could use one half of this tube only and ground the un-used pins - it will have similar gain to a 12AU7. The pin layout structure is nothing like a 12AX or ECC series also.

6ANBA - I don't have anything. Closest I've got is 6AN# datasheets. I don't know what this is.

10DE7/6DE7/7AU7 - In the right hands, this tube could act as a potential clean tube. It has very very low gain (1/10'th of a 12AX7's) and the input stage would need to be carefully designed - Ri is less than 1k. The pinout is nothing like a 12AX variant as well. A potential use but complicated to design around - I'd say definitely not something any current amplifier could use.

8AW8A - I don't have anything.

5CM8 - one half of this tube has the same gain as a 12AX7, but the heater voltage for this tube is limited to 4.3V at 600mA hence the first number being a 5. The pinout is nothing like a 12AX7 (It's not hot-swappable).

5X8/6AU8 - Half the gain of a 12Ax7 and half the tube has no use for guitar. Wouldn't be worth your time to bother with it.

6DX8/5BR8 - Not worth your time. Odd Ri requirement.

6JU8A - I don't have anything.

5T8 - This has to be the funkiest damn tube design I have ever seen. I've never in my life seen a circuit that used one of these. Not even close to what you could use with a guitar amplifier design. The cathode is split between two different pins on one triode side and the gain is in the same range as a 12AU7. The heater voltage is low - 4.7V. The other half of the tube has no use for guitar.

10CW5 - I don't have anything.

LL86 - I don't have anything.

This is just a quick look to see what you've got listed and what I have on file. Take my recommendations with a grain of salt - there's limited info on a lot of these and a lot of what I have is based upon datasheets written in russian from the 50's and 60's.

Hope this helps a bit.
 
glpg80":jvbt1kun said:
6HF8/5AT8 No.

6CN7 - You could use one half of this tube only and ground the un-used pins - it will have similar gain to a 12AU7. The pin layout structure is nothing like a 12AX or ECC series also.

6ANBA - I don't have anything. Closest I've got is 6AN# datasheets. I don't know what this is.

10DE7/6DE7/7AU7 - In the right hands, this tube could act as a potential clean tube. It has very very low gain (1/10'th of a 12AX7's) and the input stage would need to be carefully designed - Ri is less than 1k. The pinout is nothing like a 12AX variant as well. A potential use but complicated to design around - I'd say definitely not something any current amplifier could use.

8AW8A - I don't have anything.

5CM8 - one half of this tube has the same gain as a 12AX7, but the heater voltage for this tube is limited to 4.3V at 600mA hence the first number being a 5. The pinout is nothing like a 12AX7 (It's not hot-swappable).

5X8/6AU8 - Half the gain of a 12Ax7 and half the tube has no use for guitar. Wouldn't be worth your time to bother with it.

6DX8/5BR8 - Not worth your time. Odd Ri requirement.

6JU8A - I don't have anything.

5T8 - This has to be the funkiest damn tube design I have ever seen. I've never in my life seen a circuit that used one of these. Not even close to what you could use with a guitar amplifier design. The cathode is split between two different pins on one triode side and the gain is in the same range as a 12AU7. The heater voltage is low - 4.7V. The other half of the tube has no use for guitar.

10CW5 - I don't have anything.

LL86 - I don't have anything.

This is just a quick look to see what you've got listed and what I have on file. Take my recommendations with a grain of salt - there's limited info on a lot of these and a lot of what I have is based upon datasheets written in russian from the 50's and 60's.

Hope this helps a bit.
Click to expand...
So in other words, don’t waste your money. :lol: :LOL:
 
Just in case anyone googles this shit again, at least there's some form of closure :lol: :LOL:
 
It wouldn't be worth the trouble, unless your amp calls for the "#" in the name
of the tube (ie 6dj7)

That # would usually indicate the voltage of said tube as a rule of thumb.

12XXX being 12volt tube...then it's designation/flavor (ax7, at7, au7, bz7, etc)

I would stick to 12v tubes in the preamp section of your amp.
 
Thanks for the replies. I came across these just completely randomly ad was hoping I came across some cool stash of old preamp tubes. But turns out that wasn't the case. Oh well. I may still go back and pick up a few just to have since I'm into old stuff like that. I think they were only asking $1 a piece so why not.
 
^Well if they are only $1, then maybe just buy them as ornaments, or use them to build a little radio or mini stereo so they light up- just a gimmicky fun thing.

Then sell it online and the hipsters will fork out thousands for it!
 
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