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Name That Tube!

David_NC

David_NC

Super Member
I've been running my Dynaco ST-70 on some cheap JJ EL34's while I was getting it sorted out, tested, etc. Last night, I traded them out for the ones that came with it. It looks like much of the printing on the tubes has been removed. The 7199's are Tung-Sol, and the GZ34 is labeled Dynaco, so it wouldn't surprise me if the EL34's are pretty old, if not original. I'm curious if anyone recognizes them from these pics:
Tube 1.jpg Tube 2.jpg
 
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Lavane said:
It looks like a 6CA7 "fat boy". That might narrow it down a bit being made in the US.
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I was hoping I'd be able to make out what the tealish writing used to say, but this was the best one, sadly.
However, that gave me a start. They appear to be Philips ECG's. Thanks!
Philips 6CA7.jpg
 
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From what I found, it's either Sylvania or GE. Some are branded RCA, but are just rebranded Sylvania. The European versions of the 6CA7 didn't have the fat bottle. EH however now makes a fat bottle version. It seems the old US made 6CA7 's are getting harder to find.
 
Have you tried fogging the glass with your breath? Sometimes that works with faded lettering. Or putting it in the freezer for a few minutes.
 
I will say they sound a bit smoother than the JJ's. I had to crank the bias pots way down to get them to 1.56v, whatever that means.
That pic is from an eBay auction that ended back in August for $351 for a set of four that obviously look better than mine. There were 23 bids on them, so I guess they are good or at least desirable!
 
David_NC said:
I will say they sound a bit smoother than the JJ's. I had to crank the bias pots way down to get them to 1.56v, whatever that means.
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The 6CA7 is supposed to be a nice sounding tube. I haven't tried them in my ST-70 yet. The JJ KT-77's are a good sounding tube at a low price. I'm using them now. I liked them over the el34's and KT-88's I tried. But people that have used the 6ca7 fanboys seem to like them.
 
They say made.in the US though. I found a blurb stating Amprex/Philip's made these , or other companies owned by them. It also.stated the Amprex/Philip's used two D getters. Those have two round disc getters.
 
Lavane said:
The 6CA7 is supposed to be a nice sounding tube. I haven't tried them in my ST-70 yet. The JJ KT-77's are a good sounding tube at a low price. I'm using them now. I liked them over the el34's and KT-88's I tried. But people that have used the 6ca7 fanboys seem to like them.
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I was noticing a bit of distortion at higher levels, which isn't surprising; my speakers are not efficient at all. I thought to try these and see if they were a bit stronger, and they may be a little, but mostly they sound fuller and smoother, though the JJ's are def decent and cheap. I got a deal on this amp, and having a good set of tubes (including 7199's) makes it an even better one. Give the 6CA7's a try, if you come across some for a reasonable price; I'd be curious of your observations.
 
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