JazzVinyl
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Didn't Skunk Works help design and test the SR-71 spy plane (that could fly at mach 6)?
2359glenn | studio
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Didn't Skunk Works help design and test the SR-71 spy plane (that could fly at mach 6)?
mordy
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All right, here is the story. Some time back I bought two 6336 tubes and in the package were two of those metal circle-like things.
They have been sitting there for a while, and then it dawned upon me that they must be heat sinks or tube coolers that slip over the glass. Just like the radiators in a house increase the heat dissipation from the pipes by providing more surface area, the tube heat sinks extend the surface area for more heat dissipation from the glass.
The 6336 tubes are two 6AS7 tubes in one envelope and draw 5A, and they get really hot.
The heat sinks are flexible and the one pictured had been stretched out to fit the larger glass envelope of the 6336 tube, but the second one had not been stretched out, and it fit handily over a 6080 tube.
Another shot:
In order for the stretched out one to fit , I had to push it together with a little piece of wire around it.
The 6336 is rated at 250C, and the spec sheet mentions cooling. I have a pair of graphite Bendix 6080WB (rated up to 300C) in my GOTL , and I decided to make an experiment and measure if the tube coolers make a difference.
(BTW, I just saw an ad for a single Bendix 6080WB for a mind staggering $700!
What is the tube world coming to?
https://www.ebay.com/itm/RARE-6080-...692158?hash=item2aef41c83e:g:GSAAAOSwA~5fN10K)
But I digress - back to the experiment:
Stage one: I let the amp warm up an hour and then measure the spot with the highest tube temperature with an infrared thermometer.
Stage two: Let the amp cool off and then warm up an hour with the tube coolers in place and measured tube temperatures.
Stage three: Let the amp cool off and then measured the temperature after an hour with my two 4" fans blowing on the amp and tubes.
Stage four: Let the amp cool off, and then measured after an hour with both the tube coolers in place and the fans on.
Room temperature 24C, amp playing with headphones. All tubes in socket savers (that further reduces the tube temperatures). My experience is that even date matched tubes vary a little in how hot they get, so I averaged out both tubes.
Disclaimer: Test equipment not calibrated fancy stuff, but the main points borne out are the relative reductions of heat.
1) Amp left on its own - Bendix temp 203C
2) Tubes with tube coolers attached - temp 146C
3) Fans on, no tube coolers - temp 149C
4) Tube coolers and fans on - temp 119C
The question is what the best operating temperature range is of the tubes - I have only seen upper limits mentioned, but possibly too low a temperature will impact function. Would like to hear from others about this.
Tried to find a seller for these flexible tube heat sinks. Could not find anything for sale that is flexible and can fit several sizes of tubes, but I found something called Pearl Tube coolers. They come in fixed sizes, and you need to size them to your tubes. The company claims that their coolers can double the service life of tubes:
https://www.pearl-hifi.com/03_Prod_Serv/Coolers/Coolers.html
You can buy them here:
https://www.partsconnexion.com/pearl-tube-coolers.html
But.....
Comes JACtubes and throws in a wrench. He states that tube coolers are a bad idea because they change the heat dissipation characteristics of the glass part of the tube versus the part where the pins are attached. The materials used in sealing the pins have the same heat expansion as the tube glass, and by cooling the tube glass you change this relationship and microscopic channels can open up that very slowly lead to loss of vacuum:
https://jacmusic.com/techcorner/ARTICLES/English/COOLTUBES/Not-using-cooler-elements.pdf
I need to hear from you which way to go. Perhaps fans are better since the air blows on all parts of the tube, whereas the heat sinks/tube coolers only affect the glass.
Also need to know how much the tube can be cooled without loss of performance (which I know can happen).
They have been sitting there for a while, and then it dawned upon me that they must be heat sinks or tube coolers that slip over the glass. Just like the radiators in a house increase the heat dissipation from the pipes by providing more surface area, the tube heat sinks extend the surface area for more heat dissipation from the glass.
The 6336 tubes are two 6AS7 tubes in one envelope and draw 5A, and they get really hot.
The heat sinks are flexible and the one pictured had been stretched out to fit the larger glass envelope of the 6336 tube, but the second one had not been stretched out, and it fit handily over a 6080 tube.
Another shot:
In order for the stretched out one to fit , I had to push it together with a little piece of wire around it.
The 6336 is rated at 250C, and the spec sheet mentions cooling. I have a pair of graphite Bendix 6080WB (rated up to 300C) in my GOTL , and I decided to make an experiment and measure if the tube coolers make a difference.
(BTW, I just saw an ad for a single Bendix 6080WB for a mind staggering $700!
What is the tube world coming to?
https://www.ebay.com/itm/RARE-6080-...692158?hash=item2aef41c83e:g:GSAAAOSwA~5fN10K)
But I digress - back to the experiment:
Stage one: I let the amp warm up an hour and then measure the spot with the highest tube temperature with an infrared thermometer.
Stage two: Let the amp cool off and then warm up an hour with the tube coolers in place and measured tube temperatures.
Stage three: Let the amp cool off and then measured the temperature after an hour with my two 4" fans blowing on the amp and tubes.
Stage four: Let the amp cool off, and then measured after an hour with both the tube coolers in place and the fans on.
Room temperature 24C, amp playing with headphones. All tubes in socket savers (that further reduces the tube temperatures). My experience is that even date matched tubes vary a little in how hot they get, so I averaged out both tubes.
Disclaimer: Test equipment not calibrated fancy stuff, but the main points borne out are the relative reductions of heat.
1) Amp left on its own - Bendix temp 203C
2) Tubes with tube coolers attached - temp 146C
3) Fans on, no tube coolers - temp 149C
4) Tube coolers and fans on - temp 119C
The question is what the best operating temperature range is of the tubes - I have only seen upper limits mentioned, but possibly too low a temperature will impact function. Would like to hear from others about this.
Tried to find a seller for these flexible tube heat sinks. Could not find anything for sale that is flexible and can fit several sizes of tubes, but I found something called Pearl Tube coolers. They come in fixed sizes, and you need to size them to your tubes. The company claims that their coolers can double the service life of tubes:
https://www.pearl-hifi.com/03_Prod_Serv/Coolers/Coolers.html
You can buy them here:
https://www.partsconnexion.com/pearl-tube-coolers.html
But.....
Comes JACtubes and throws in a wrench. He states that tube coolers are a bad idea because they change the heat dissipation characteristics of the glass part of the tube versus the part where the pins are attached. The materials used in sealing the pins have the same heat expansion as the tube glass, and by cooling the tube glass you change this relationship and microscopic channels can open up that very slowly lead to loss of vacuum:
https://jacmusic.com/techcorner/ARTICLES/English/COOLTUBES/Not-using-cooler-elements.pdf
I need to hear from you which way to go. Perhaps fans are better since the air blows on all parts of the tube, whereas the heat sinks/tube coolers only affect the glass.
Also need to know how much the tube can be cooled without loss of performance (which I know can happen).
Last edited:
mordy
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Meaning skunk works:
skunk-works
- an experimental laboratory or department of a company or institution, typically smaller than and independent of its main research division.
The Bendix Corporation had a division in Eatontown, NJ called the Red Bank Division. Here they developed vacuum tubes for use in ballistic missiles that could operate at 60,000 feet and under very difficult conditions. - And this of course explains the red print on the Bendix 6080WB tubes:
leftside
Headphoneus Supremus
Group buy? I'd take 4:
https://www.ebay.co.uk/itm/50x-6C5G-CV581-TUBE-BY-COSSOR-GREAT-BRITAIN/363088391811
https://www.ebay.co.uk/itm/50x-6C5G-CV581-TUBE-BY-COSSOR-GREAT-BRITAIN/363088391811
chrisdrop
1000+ Head-Fier
Excited to get some packages in the post yesterday, but I certainly can take a break buying tubes... 7x Sylvania 6BL7s (branded Fivre, but they are Sylvania), 4x Fivre 6C5G, 2x Grey Osram L63 (to replace a pair that I ruined!)
.. time for a break man !!
... sod that - @leftside I'd be in for 2 or 4!
.. time for a break man !!
... sod that - @leftside I'd be in for 2 or 4!
JazzVinyl
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Know the feeling!
You have a heck of a lot of really nice tubes, Chris!!
The 7x 6BL7's that are Fivre->Sylvania - are they the Flat Plate ones?
Here is an interesting roll for you, Chris, using tubes you might already have:
ECC88 + C3g as Driver Triplet and 2x Mullard 6080's...
Kind of the opposite of the normal GOTL take on things, very fast and articulate, not as laid back. A touch of warmth from the 6080's balances this out.
Cheers!!
gibosi
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There are a bunch of different ECC88's. Which are you using in this triplet?
And I'm still running six Melz 6H12C (or 6N12S). Unfortunately, with only two output sockets, it is difficult to directly compare them to 6BX7, swapping tubes in and out of adapters is a major hassle. But my impression is that the Melz are relatively transparent and I find that they allow more euphonic drivers, such as the gray-glass NU, the black glass Brimar or the TS BGRP to shine. Currently enjoying the Tung-Sol very much.
gibosi
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And I should say that I got extremely lucky. I managed to buy ten 6H12C for $15 each, all dated 1962. Looking at the curremt prices of these tubes on eBay, that would be a much more expensive proposition. 
whirlwind
Headphoneus Supremus
There are a bunch of different ECC88's. Which are you using in this triplet?
And I'm still running six Melz 6H12C (or 6N12S). Unfortunately, with only two output sockets, it is difficult to directly compare them to 6BX7, swapping tubes in and out of adapters is a major hassle. But my impression is that the Melz are relatively transparent and I find that they allow more euphonic drivers, such as the gray-glass NU, the black glass Brimar or the TS BGRP to shine. Currently enjoying the Tung-Sol very much.
I sure understand what you are saying about not wanting to fiddle with those adapters to much.
A really transparent power tube is a good thing IMO...you get to listen to your favorite driver tubes and enjoy them for what they are.
Good job getting a matching 10 tubes!
chrisdrop
1000+ Head-Fier
Hey JV, tx for the recommendations. Always warmly welcomed!
I don't have any ECC88s, or Mullard 6080s. I do have C3g and other 6080s (Bendix, GEC, RCA). I wasn't sure about the 'small tubes' vs their larger brethren. I guess some of these smaller tubes are "in-play"! They are generally manufactured later, mid-50s onwards if I recall correctly.
Regarding the 6BL7s, they are all from the same case. I'll need to go through and find which tubes have the least eroded date paint. This is what they look like:
I'd take 4 (or 6 or 8 if needed)!
JazzVinyl
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These are labeled "Amperex" - think you ID'ed as being made by someone else, but I don't remember who. They are 1950's and were not cheap, as I recall...it's a nice tube, buttery smooth aids the more brittle C3g's...
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raindownthunda
500+ Head-Fier
I’d be in for 4 as well.
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another 4 for me...
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