6B4G JAN: Are they really 6B4Gs?

2nd harmonics for the masses

6B4G JAN: Are they really 6B4Gs?

Postby hembrook » Thu Dec 06, 2007 7:38 am

I got a quartet of 6B4Gs on ebay pretty cheap (less than $10 a pop). They are Sylvania JAN date coded 7452 (i.e. late 1974). I ran across this add:

http://www.boiaudioworks.com/index.php? ... a35035fd37

They state:

6B4G JAN NOS Philipps ECG $10.00

TRIODE, POWER
Wait, wait. Before you get too excited, please read the following first!

This is not a directly heated 6B4G, but a 6B4G replacement. It is pentode that is triode connected internally. The tube has the same pinout as DHT 6B4G, and works quite well as a 6B4G. Recommended for DYIers.

So is it really a 6B4G, or a tube that electrically does the same work? I wonder what it will sound like.

Insight appreciated
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Postby mesherm » Thu Dec 06, 2007 8:28 am

It is probably a 6AV5 internally modified to act as a 6B4G, same pinout. 6AV5s were used as TV sweep tubes. As to whether it will sound the same, I have no clue.
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Postby TomMcNally » Thu Dec 06, 2007 9:10 am

Here is what Triode says in their ebay ad for those:


We have up for Auction a Matched Pair of N.O.S. JAN Sylvania 6B4G Power. We got an email from a customer who said these are really, "6av5s internally triode strapped and sold to the government as 6b4g to fulfill a contract". Either way tubes are ready for your amp!!
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I suppose if electrically they are the same, then OK...

Postby hembrook » Thu Dec 06, 2007 9:48 am

It will be interesting to taste test against my 6A5Gs.
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Re: I suppose if electrically they are the same, then OK...

Postby hembrook » Wed Mar 05, 2008 6:42 am

hembrook wrote:It will be interesting to taste test against my 6A5Gs.

Which I did. the 6A5Gs definitely hum less, which is a good thing for me. Both tubes sound very nice. If I can get rid of the hum, then these are a real cost conscious choice at <$10 a pop.
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Postby EWBrown » Fri Mar 06, 2009 8:06 am

Or you could re-wire the sockets for 6AV5 / 6AV5GA and go with those for around $4-5 (or even less) a pop $)

I've been quietly gathering up some GE and Dumont 6AV5GAs and 12AV5GAs for future projects. I look for the "solid plate" versions, no "peep holes" in the plates, and they should be good for pushing well beyond 11 Watts plate dissipation [:)

/ed B
Last edited by EWBrown on Sun Feb 22, 2015 8:46 pm, edited 1 time in total.
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Postby katabatic » Sat Jul 21, 2012 8:51 am

Sorry to bring up an old thread, but I just came across some of these puppies, and what's not completely clear from the thread is: will these work ok in a Get*Set*Go as a substitute for 'real' 6b4g/6c4c's, or will there be performance/longevity/explosion issues? Thanks....

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Postby Shannon Parks » Sat Jul 21, 2012 6:00 pm

You won't have a problem. I presume these are 6AV5s rewired as a 6B4G, and they actually test pretty well (as a triode strap).

Some recent tests:
http://www.diytube.com/phpBB2/viewtopic.php?p=44283

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Postby EWBrown » Sat Jul 21, 2012 8:16 pm

Image

It definitely looks like a Sylvania "large bulb" 6AV5GA to me, just a different base pinout.

/ed B

BTW the price for these has rocketed from $10 to $18 over the past five years... =:o :'(
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Re: 6B4G JAN: Are they really 6B4Gs?

Postby jwhitmor » Mon Jan 26, 2015 6:07 pm

Old thread, but they are still selling these (JAN 6B4G) on E-bay, except they are more expensive now.

Well for me... It begs the question: If we are triode connecting our 6AV5 tubes with a 100 ohm resistor, how did Sylvania make a 6B4 by just crossing a few wires in the base? (???)
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Re: 6B4G JAN: Are they really 6B4Gs?

Postby EWBrown » Mon Jan 26, 2015 6:14 pm

They just tied the plate and screen grid leads together, it is fairly unlikely that they would have added the resistor.

/ed B
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Re: 6B4G JAN: Are they really 6B4Gs?

Postby jwhitmor » Tue Jan 27, 2015 9:11 am

I guess if the tube does not oscillate, then the resistor is not needed, and if it does, then maybe find another tube. As for the suppressor grid, Sylvania probably wired it to a cathode pin. A multimeter would find if either of the cathode pins has a near zero resistance connection to G3.
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Re: 6B4G JAN: Are they really 6B4Gs?

Postby jwhitmor » Sun Feb 22, 2015 4:10 pm

I had a problem with low level AC hum in my speakers when I tried the JAN 6B4G. Other than the hum, they worked fine. I have no hum when I use any other tubes, so maybe the JAN 6B4G tubes were the cause. I would be interested in any other person's experience with these tubes.
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Re: 6B4G JAN: Are they really 6B4Gs?

Postby EWBrown » Sun Feb 22, 2015 8:48 pm

The 6B4G JANs probably have the (6AV5GA) cathode connected directly to one of the filament pins, that imbalance could induce a hum problem. =:o
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