The 12B4A is excellent in a line stage.
The 6B4G is a desirable directly heated power O/P triode.
The 12AV5 is pentode that can be "strapped" into a triode that strongly resembles the 2A3 and 6B4G in electrical behavior.
The 6AX4 is a damper diode. A pair of 6AX4s will nicely take care of rectification duties in a power amp.
Setting the heater supply up for the 8FQ7 is a bit of a PITA, but once you have that done, it will work in circuits that call for the 6FQ7/6CG7 and 6SN7.
The 6CW5/EL86 is a "12" W. power pentode. A look at the data sheet suggests that you could make a NICE PP power amp around 2 matched pairs.
The 6EJ7 is a sharp cutoff pentode that might be useful in the 2nd gain block of a RIAA preamp. I'm guessing that dampers are needed to hold microphonics down.
The 6B4G is a desirable directly heated power O/P triode.
The 12AV5 is pentode that can be "strapped" into a triode that strongly resembles the 2A3 and 6B4G in electrical behavior.
The 6AX4 is a damper diode. A pair of 6AX4s will nicely take care of rectification duties in a power amp.
Setting the heater supply up for the 8FQ7 is a bit of a PITA, but once you have that done, it will work in circuits that call for the 6FQ7/6CG7 and 6SN7.
The 6CW5/EL86 is a "12" W. power pentode. A look at the data sheet suggests that you could make a NICE PP power amp around 2 matched pairs.
The 6EJ7 is a sharp cutoff pentode that might be useful in the 2nd gain block of a RIAA preamp. I'm guessing that dampers are needed to hold microphonics down.
awesome, thanks for the info, I'll start looking around here as well..
http://tdsl.duncanamps.com/tubesearch.php
http://tdsl.duncanamps.com/tubesearch.php
Nice photos! Let's see more of the 7027s and 7868 output tubes!
That is called the getter, it is a reactive metal deposited in the tube when the air is removed. Its job is to scavenge the last few air molecules. It gradually gets used up over the life of the tube, particularly on the big power tubes. If it looks shiny and new, it generally means the tube is good. If it goes white, the air has leaked in and the tube is junk.
If I were you, I would start looking for matched quads of NEW or testing good output tubes eg 7027 or 7868 and build a push pull amp around them. You could even build a parallel push pull amp (PPP) for lots of power.
many of the other tubes will be useless unless you have a black and white TV, however you can maybe get some of the useful or rare ones tested and sell them to fund your project. That's what I have done in the past...
That is called the getter, it is a reactive metal deposited in the tube when the air is removed. Its job is to scavenge the last few air molecules. It gradually gets used up over the life of the tube, particularly on the big power tubes. If it looks shiny and new, it generally means the tube is good. If it goes white, the air has leaked in and the tube is junk.
If I were you, I would start looking for matched quads of NEW or testing good output tubes eg 7027 or 7868 and build a push pull amp around them. You could even build a parallel push pull amp (PPP) for lots of power.
many of the other tubes will be useless unless you have a black and white TV, however you can maybe get some of the useful or rare ones tested and sell them to fund your project. That's what I have done in the past...
SHiFTY said:
Unfortunately, the Novar sockets OS 7868s fit are extemely scarce. NOS and strong UOS 7868s command GOOD money. For starters, there are plenty of Fisher 400s in service to use 'em. IMO, selling the 7868s off to obtain the funds needed for "iron" and other purchases makes sense.
The 7027s are Octal based and don't present the socket sourcing problem. Being members of the 6L6 family means the drive voltage requirements of the 7027 are substantial. A Mullard style circuit with a 12AT7 in the LTP role should get the job done.
BTW, the 6L6 family is quite tolerant of some control grid current. Class "AB2" operation using DC coupled voltage follower drivers is worth considering.
Makes a very nice triode and according to Chambino in the UK, a pair is capable of about 80W if you abuse the ratings a bit.
http://turneraudio.com.au/2323-triode-integrated-6cm5.html
http://www.chambonino.com/construct/const8.html
did anyone not say anything about the loads of rare GE 6dn7's??? These are hard to find for decent prices!
Sex amp anyone?
as for the 7868's! Keep them! Excellent audio tube, direct equivalent to the 7591 used in a lot of hi-fi amps, different pinout.
AES sells these
http://www.tubesandmore.com/scripts...clients/cemirror/ELEVATOR.FXP?item=P-ST9-254M
for those for $1.95 each, so their NOT expensive and NOT hard to find.
if you do decide to sell them, they will probably bring a lot of money on ebay, but as with any tube you want to sell you need to test/match them first to get a good return on them.
I'm going to tell you right now, a matched quad of 7868's will bring a lot of money ($150+ at the least) for someone looking for a set for their scott or fisher.
Sex amp anyone?
as for the 7868's! Keep them! Excellent audio tube, direct equivalent to the 7591 used in a lot of hi-fi amps, different pinout.
AES sells these
http://www.tubesandmore.com/scripts...clients/cemirror/ELEVATOR.FXP?item=P-ST9-254M
for those for $1.95 each, so their NOT expensive and NOT hard to find.
if you do decide to sell them, they will probably bring a lot of money on ebay, but as with any tube you want to sell you need to test/match them first to get a good return on them.
I'm going to tell you right now, a matched quad of 7868's will bring a lot of money ($150+ at the least) for someone looking for a set for their scott or fisher.
You have a bunch of 6DN7s which are used in the Bottlehead Sex amps. That would be an excellent first project. Very affordable, easy to build and great sounding amp with efficient speakers. Bottlehead building directions are first rate which makes assembly a pleasure if you follow directions.
Dude,
Thanks for teasing this out. I've been worried that Novar sockets were becoming "unobtainium".
AES' poor write up as a compactron socket doesn't help.With this reasonable deal in Novar sockets available, I agree that building 7868 based circuitry is an execellent idea. The 7591 family are very easy to drive. An "El Cheapo" style 12AT7 based splitter/driver will work quite well.
Hello! I am wondering of you read my post? I am offering to take thos 12au7 Conn tubes from you. I am offering you a much better price than your alternative, which is selling them on ebay, or worse throwing them away. It is not true that they are no good in HIFI use. anyway please let me know!
email me, we can work something out.
email me, we can work something out.
I'd be interested in some of the 7027a tubes for my Ampeg. Also any 12au7a, 6k11, 6fq7/6cg7, 12dw7 or 7025 as well. Those old Ampegs have a ton of tubes in them! I also have an old Magnatone that could use any of the following: 7591, 6gh8 and 12ax7a/7025.
If you can't test them, I'd be willing to get several extras so I could test them myself and find good matched ones for my amp. I don't care about printing quality or brand names, just that they work well and don't cost a ton of money. I'm a user, not a collector so you can save the real pretty ones for someone else.
Cheers,
- JJ
If you can't test them, I'd be willing to get several extras so I could test them myself and find good matched ones for my amp. I don't care about printing quality or brand names, just that they work well and don't cost a ton of money. I'm a user, not a collector so you can save the real pretty ones for someone else.
Cheers,
- JJ
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