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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 438

post #6556 of 8774

You should be able to connect the negative output of one regulator to the negative output of the other and then carry that wire onto the chassis screw.

post #6557 of 8774

I just did that, before I read your post. Did not notice a reduction in high volume hum. Anyhow, I want to thank you all for your kind words and encouragement.

 

I have one RCA 6AS7 from Dec 1973. I could try it together with the RCA 6080 or look for a second one. Recently, somebody closed out a whole bunch of 6AS7 tubes and the prices and demand went down temporarily, and I was able to buy this tube (from a different source) for a couple of bucks.

 

As hypnos 1 writes, it is amazing how much more we have been able to get out this humble little amp. However, in the sense of fairness I cannot take any credit for coming up with the idea of using 6SN7 tubes for power tubes. I think one of the first people to try it was Artsi with Russian 6SN7 equivalents. All the ideas with extenders, voltage regulators, and pulling the wires through a drilled hole in the extender came from knowledgeable people on this forum. The heat shrink trick I got from YouTube.

 

I did discover the 6832 tube, but the credit goes to Oskari who provided a link to an extensive list of  sub miniature tubes with specs. I picked out a dual triode with specs similar to the 6SN7 tube. Actually, I picked out half a dozen tubes, and then scanned Ebay to see what was available. Some of them I could not find, and the 6832 was the best buy.

 

Part of the fun of tube rolling in my case is to find unknown and/or inexpensive tubes with superior sonic characteristics. (And a secret desire to turn my MKIII into a MK9).

 

Could be that this goal has been met - the sound I now get from my amp feels just right and continues to astound me. Saw a post of somebody selling 900 pieces of the 6832s for $1800. Wonder if David Zhe Zhe would be receptive to build a modified MKIII with this tube as driver. Nah, the little bugger does not have any visual impact... Maybe install a dummy orange glow tube LOL!

 

 

http://jimmyauw.com/wp-content/uploads/2009/04/0a3_.jpg 

post #6558 of 8774
That orange glow tube is a voltage regulator of the sub 100V variety, they have no filaments and are filled with gas.

Basically a tube version of the Zener diode.
post #6559 of 8774

Thanks TD - I just thought it would be a good suggestion to get the visual appeal for a tube amp using the tiny subminiature tube as a driver....

post #6560 of 8774

Similar to Mordy, I reviewed the list of sub-miniatures that Oskari provided, and based on specifications, availability and documented use in audio applications (per Google), I believe the 7963, 6832 and 6021 are the best choices to run in our Little Dots. Indeed, a number of us have already found the 6832 to be a very good tube. And if you are willing to take my word for it, the 7963 is also a very good tube. This leaves the 6021.

 

So.... In this morning's mail, a Sylvania Gold Brand 6021A arrived, manufactured in 1961 and sporting a D-getter. A search on eBay for this tube reveals that all the major US brands and a couple of European brands marketed this tube. As there exists a Sylvania datasheet for the 6021, I am quite certain that Sylvania did, in fact, manufacture this tube. However, I do not know if all these other companies manufactured their own tubes, or if they are simply rebrands. By way of comparision, I am quite sure that only Sylvania manufactured the 7963 and only Raytheon manufactured the 6832...

 

Fortunately, the 7963, 6832 and 6021 all have the same pin-out, so once you figure out how to mount one into your base of choice, mounting the others should be easy. I intend to mount this tube into an octal base, like the 7963 and 6832. However, the 6021 has another little wrinkle that the others apparently do not have, a Russian counterpart, the 6N16B. And wouldn't you know, the pin-out on the Russian tube is different! Moreover, there exists an ultra premium version, the 6N16B-VR, which has 9 leads, instead of 8, the extra lead being attached to an electrostatic shield. According to a number of reports via Google, this ultra premium Russian tube is better than any of the US-made 6021's. I have some on their way to me from Russia... and with some luck, they might arrive before the snow falls. lol :)

 

In the meantime, I am curious to learn how this 6021 compares to the 7963 and 6832.

 

post #6561 of 8774
Quote:
Originally Posted by mordy View Post

 

I did discover the 6832 tube, but the credit goes to Oskari who provided a link to an extensive list of  sub miniature tubes with specs.

 

I don't think I did. Have I completely forgotten? Perhaps it was Artsi.

post #6562 of 8774

Well..... here it is again, if anyone is interested:

 

http://pw2.netcom.com/~wa2ise/radios/penciltubes.html

post #6563 of 8774
Quote:
Originally Posted by mordy View Post
 

I just did that, before I read your post. Did not notice a reduction in high volume hum. Anyhow, I want to thank you all for your kind words and encouragement.

 

I have one RCA 6AS7 from Dec 1973. I could try it together with the RCA 6080 or look for a second one. Recently, somebody closed out a whole bunch of 6AS7 tubes and the prices and demand went down temporarily, and I was able to buy this tube (from a different source) for a couple of bucks.

 

As hypnos 1 writes, it is amazing how much more we have been able to get out this humble little amp. However, in the sense of fairness I cannot take any credit for coming up with the idea of using 6SN7 tubes for power tubes. I think one of the first people to try it was Artsi with Russian 6SN7 equivalents. All the ideas with extenders, voltage regulators, and pulling the wires through a drilled hole in the extender came from knowledgeable people on this forum. The heat shrink trick I got from YouTube.

 

I did discover the 6832 tube, but the credit goes to Oskari who provided a link to an extensive list of  sub miniature tubes with specs. I picked out a dual triode with specs similar to the 6SN7 tube. Actually, I picked out half a dozen tubes, and then scanned Ebay to see what was available. Some of them I could not find, and the 6832 was the best buy.

 

Part of the fun of tube rolling in my case is to find unknown and/or inexpensive tubes with superior sonic characteristics. (And a secret desire to turn my MKIII into a MK9).

 

Could be that this goal has been met - the sound I now get from my amp feels just right and continues to astound me. Saw a post of somebody selling 900 pieces of the 6832s for $1800. Wonder if David Zhe Zhe would be receptive to build a modified MKIII with this tube as driver. Nah, the little bugger does not have any visual impact... Maybe install a dummy orange glow tube LOL!

 

 

http://jimmyauw.com/wp-content/uploads/2009/04/0a3_.jpg 

 

So, mordy, we have artsi (wherever he is now!) to thank...but don't sell yourself short my good man - you were indeed instrumental in bringing the 6SN7 more into focus...

 

And, of course, my comments re GIBOSI 's work on external heater power supplies should be aimed more at enabling the use of 6AS7G/6080 as power tube  (a leap equalled only by the C3G as driver, and now the sub-miniatures) - the 6SN7s not needing it of course...

post #6564 of 8774

mercury.jpg

 

Extra points if you can identify this "tube"

 

 

images?q=tbn:ANd9GcTiW3__aLqz7Bf29vBpIpLckA2ueniAQRTXL2X3uFOmDf2TAv4PaQ

(Another example of same)


Edited by mordy - 6/16/14 at 11:21am
post #6565 of 8774
Quote:
Originally Posted by TrollDragon View Post
 

Still at the back of the bus here, with a pair of 6GU7's as power tubes.

 

 

:beerchug: 

 

Hey there TD...what's this "back of the bus" stuff? The enthusiast that you are should have you right at the FRONT, lol!

 

Que pasa, mi amigo?! :rolleyes:.

post #6566 of 8774
Quote:
Originally Posted by mordy View Post

 

Extra points if you can identify this "tube"

 

Videos of these are pretty awesome. (Plenty on youtube.)

post #6567 of 8774
Quote:
Originally Posted by mordy View Post
  Warning: Spoiler! (Click to show)

mercury.jpg

 

Extra points if you can identify this "tube"

 

 

images?q=tbn:ANd9GcTiW3__aLqz7Bf29vBpIpLckA2ueniAQRTXL2X3uFOmDf2TAv4PaQ

(Another example of same)

It's a mercury arc rectifier. But I don't know any more than that...

post #6568 of 8774

 

post #6569 of 8774
Quote:
Originally Posted by mordy View Post

 

Extra points if you can identify this "tube"

 

Mercury Arc Rectifiers... Honking BIG diodes... :D

 

Here are the type we would use as opposed to the massive Subway power system beasties.

 

There are many models...

http://www.ebay.com/itm/816-mercury-vapor-rectifier-tubes-NOS-RCA-USA-2-pcs-/331235569819

:beerchug:

post #6570 of 8774
Quote:
Originally Posted by hypnos1 View Post
 

 

Hey there TD...what's this "back of the bus" stuff? The enthusiast that you are should have you right at the FRONT, lol!

 

Que pasa, mi amigo?! :rolleyes:.

My enthusiasm is high but unfortunately my wallet does not share the same искренний энтузиазм. :(

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