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Woo Audio 1 Tube Q: 6AS7/6080

post #1 of 12
2/14/05 at 12:26am
Thread Starter 
How come 6AS7 and 6080 tubes are so hard to find? Most of the online tube stores do not sell the 6AS7 or 6080, and one's that do sell them sell unbranded 6080's or a variation of the 6AS7 (6AS7G). Is the 6AS7G tube the equivalent of the 6AS7?

Thanks,
- Steve
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post #2 of 12
2/14/05 at 1:00am
There are many around. Do a google with the tube you want. The 6AS7 is a straight sided tube like the 6080 and the 6AS7G is an ST shape, a much taller tube with shoulders about 3/4 of the way up on the glass. Tube World has a lot of tubes and pictures, just scan down the page until you get the the number you want.

John

http://www.tubeworld.com
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post #3 of 12
2/14/05 at 1:14am
Thread Starter 
Ok, but are the 6AS7 and 6AS7G interchangeable?
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post #4 of 12
2/14/05 at 8:12am
Quote:
Originally Posted by Steve Coal
Ok, but are the 6AS7 and 6AS7G interchangeable?

Yes.
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post #5 of 12
2/14/05 at 8:47am
Quote:
Ok, but are the 6AS7 and 6AS7G interchangeable?
They are the same tube but some prefer the st version. I am using a 5998, which measures somewhat different but the voltages work out fine and I like the sound (in my Woo3)

John
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post #6 of 12
2/14/05 at 8:52am
I like the st version better. The 6520 is another similar tube like the 5998.
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post #7 of 12
2/14/05 at 9:40am
Quote:
Originally Posted by sacd lover
I like the st version better. The 6520 is another similar tube like the 5998.
So which one you think is the best sounding one in this group? 7236-6528A-6520-5998-6AS7G-6336?
Need to get one of the above for the Wheatfield Audio HA-2.
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post #8 of 12
2/14/05 at 4:37pm
Quote:
Originally Posted by gurus
So which one you think is the best sounding one in this group? 7236-6528A-6520-5998-6AS7G-6336?
Need to get one of the above for the Wheatfield Audio HA-2.
I think its more a matter of who made the tube. These tubes are all similar or you couldnt generally substitute them for one another. But be careful because some tubes in this group are just different enough you will want to verify your Wheatfield can use them.

The Bendix and tung sols made tubes are my favorites from this group. I like the tung sol 6080 as well and this 6080 tube is the one actually listed in all the tube manuals as the drop in replacement for the 6as7. The 6080 is a better made tube than the 6as7g IMO, but I think the tung sol 6as7g sounds a little more open in the circuits I have heard them in. Mostly you will find RCA, GE, JAN Philips or Sylvanias available for sale. From that group I like the RCA's and Sylvanias best. The 6336 is a highly regarded tube that I have never used. They are around but you pay a premium for them; expect $50 or so per tube for a 6336. The 7236/6528/5998 can all be tough to find.
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post #9 of 12
2/15/05 at 1:31pm
On the 6528 I would be careful with twice the current demand of the filament. I did find one and would love to give it a listen but I have no idea what the current capabilities are of the Woo3 and have never gotten a real answer to this from the manufacture.

John
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post #10 of 12
2/15/05 at 11:21pm
All the mentioned tubes are notorious for having poorly matched triode sections, as much as 40% out. You would have to find a dealer with a large batch of your choice of tube to come up with a tube that is well matched. Either that or run dual attenuators.

If I had or was considering a Woo, Wheatfield, or Eddie Current I would seriously inquire about having it set up for a Western Electric 421A. Superior sound and the sections already come from the factory matched. An Eddie Current HD25 with a WE 421A would be my dream amp at this point, assuming it was a viable option which it should be.
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post #11 of 12
2/15/05 at 11:38pm
Quote:
Originally Posted by timoteus
All the mentioned tubes are notorious for having poorly matched triode sections, as much as 40% out. You would have to find a dealer with a large batch of your choice of tube to come up with a tube that is well matched. Either that or run dual attenuators.

If I had or was considering a Woo, Wheatfield, or Eddie Current I would seriously inquire about having it set up for a Western Electric 421A. Superior sound and the sections already come from the factory matched. An Eddie Current HD25 with a WE 421A would be my dream amp at this point, assuming it was a viable option which it should be.
421A's are hard to find and cost considerably more than the 6as7 types. I saw some 421A's priced between $70-110 per tube online. I would suspect with their high price and limited availability thats why the builders are reluctant to use them; especially for amps like the Woo and Eddie Current that are priced around $500-600. Still, I can see your point given you would only need one and some of the 6sn7 prices are way beyond the asking price for a WE 421A.
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post #12 of 12
2/16/05 at 12:47am
Yes, 421A's would be great. They are matched so close. Sometimes identical but I don't know if that includes the current draw but most likely it does. The 421's are supposed to be the same measuring as 5998's and the 5998 drops right into the Woo3. I measured the plate voltage and bias of the 5998 in the Woo3 without any changes to the cathode resistor, which is set up for the 6080 and it was within a couple of volts on the plate. This is a cathode follower type setup and the plate of the power tube should be about double the voltage on the input tube, which it is. The cathode is about 10 volts difference, which is where it is with the 6080. So from this the 421A should be fine.

What would be fun would be the 6528 but it has twice the current draw for the filament and I have no idea if the transformer on the Woo3 can handle that. I would not try it untill I found out from the manufacture. I have a 6528 with great big graphite plates. Some like the graphite plates and some don't. I would determine that for myself. I am going to get some 6080's with graphite also.

John
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