Deleted
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Post by Deleted on Apr 14, 2015 14:14:42 GMT
This is a great discussion but I know my limits.
What does "Gm" refer to?
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Post by ronzo56 on Apr 14, 2015 14:21:08 GMT
Frans, I think this one is for you.
OK, I'm slow, but I'm catching on. I test a tube today and it tests strong for that tube type. By August it could be dead. I test a different tube, same tube type today. It tests only good. But it could last for years before it dies. So for the money the "strong" tube may or may not be worth the considerable additional money that some sellers are charging nor are the NOS never been used tubes. Just good or bad luck as to life? More or less. Lesson over.
Thanks.
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solderdude
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measureutternutter
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Post by solderdude on Apr 14, 2015 15:40:39 GMT
There is always bad luck and good fortune ... and everything in between.
In general though tubes that test 'strong' should have quite some life in them, perhaps even more than those that test 'good'.
Tubes that test 'good' could also work well for many, many years to come.
from Wiki:
Transconductance is a property of certain electronic components.
Conductance is the reciprocal of resistance; transconductance is the ratio of the current variation at the output to the voltage variation at the input.
It is written as gm.
For direct current, transconductance is defined as follows:
g_m = Delta Iout \ Delta Vin
For small signal alternating current, the definition is simpler:
g_m = Iout\Vin
Vin is the input voltage on the grid.
Iout is the anode current.
It is only fairly linear over a small range.
At full swing it is far from linear and that's what gives it the specific sound.
Gm combined with anode resistance translates into gain.
When a current flows through a resistor a voltage is the result.
So I out x R anode = V out.
Now we have both Vin and Vout and the ratio between the 2 is the gain.
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Deleted
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Post by Deleted on Apr 14, 2015 16:38:46 GMT
Thanks Frans. Now I get it  |
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Post by ronzo56 on Apr 18, 2015 2:35:09 GMT
The 1945 Ken Rad VT-231 arrived. I have only listened to three songs but the difference is apparent immediately. The dobro on Eric Clapton Unplugged sounds like a real dobro for the first time through headphones. I tried playing a dobro guitar for a while so I have a good idea of what it sounds like. More to come.
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Deleted
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Post by Deleted on Apr 26, 2015 0:11:30 GMT
I'm really enjoying my Sylvania 6SN7GTA. It's an odd one because it's almost entirely chrome. I think that's called the flashing but I might be wrong. Either way, it's very smooth sounding with a fairly large sound-stage. It's certainly a step up from the JJ ECC82 which I find to be a bit too hot in the treble for my tastes. I also have a National Union 6SN7GT but that hasn't had much head-time thus far. One downside of the adapter is that the LED doesn't shine up & through it.  Gordon. |
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Deleted
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Post by Deleted on Apr 26, 2015 10:53:53 GMT
This is a left-field question so apologies for going slightly off-topic. Has anyone got any ideas of a way to store multiple valves? Some kind of rack or something, either bespoke or makeshift will do. Actually, bespoke is likely to be expensive so something makeshift would be better for me. I see a lot of valves in my future  Gordon. |
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Deleted
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Post by Deleted on Apr 26, 2015 12:22:50 GMT
That's an excellent idea Mick! I can get the tubing relatively easy as I have loads of connections in the plumbing trade. Your idea has led me to think of how to line the inside of the tube and I'm thinking about car sound isolation foam. I'm about to order some 3mm thick stuff for my doors and that should work great inside the plastic tube if glued down with Copydex. I can even thread the ends to accept caps.
Nice one mate, thanks.
Gordon.
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Post by musicman on Apr 29, 2015 0:41:25 GMT
The 1945 Ken Rad VT-231 arrived. I have only listened to three songs but the difference is apparent immediately. The dobro on Eric Clapton Unplugged sounds like a real dobro for the first time through headphones. I tried playing a dobro guitar for a while so I have a good idea of what it sounds like. More to come. I know what you mean, the Ken Rad I have is the best by far of the tubes that I have. I keep trying my other tubes so I don't wear the Ken Rad out to soon, but have to get back to it in the end. My thanks to Jeremy for helping me acquire this one, it is a keeper. Have not bought any more tubes since getting this one, besides I have enough to last longer than I will be alive, so I am enjoying the Ken Rad, the Sylvania 6SN7GTA I bought from Jeremy is also top notch so I am good for awhile. |
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Deleted
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Post by Deleted on May 1, 2015 18:07:36 GMT
I now have these valves to play with..  Amazingly they all sound different. Not massively but noticeably all the same. I was previously loving the Chrome Dome on the right but the GE on the left is absolutely awesome! It seems to have much more bite to it. Faster transients. The snare on John Mayer's Gravity in particular sounds spectacular! Mick gave me that one so thanks Mick. It's wonderful. I believe it's a VT231 but I'd have to scroll back a bit to find out what this actually denotes. This particular example is built in Canada for the Canadian Armed Forces and dates from 1945. 70 years old! Colour me impressed. Gordon. |
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oldson
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Post by oldson on May 1, 2015 19:05:41 GMT
Great, hope it takes your mind off things for at least a little while.... difficult as it may be at this sad time. ATB. Mick. music helps, without a doubt. |
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Deleted
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Post by Deleted on May 1, 2015 19:41:40 GMT
Actually? I'm not sad. Not really. The funeral went really well. I'd prefer to dwell on the good times. My Dad was my best friend and not many guys can say that in my experience.
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Post by musicman on May 4, 2015 1:39:46 GMT
Hope you have many more happy memories to come, I know when I lost my dad years ago, my thoughts turned to things I had not thought about in so long, but they were fresh as the day they were born. Best of the best
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Deleted
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Post by Deleted on May 4, 2015 2:36:12 GMT
Thanks mate. Aye, I'm dealing with it not too bad actually.
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Post by musicman on May 6, 2015 14:21:51 GMT
you do learn to cope after awhile, I have been down that road so many times now, I know what to expect and when. Worst year, I lost 5 family members in one year, one right after the other, went from the fourth eldest to the eldest in one year. Now only four of us left from the original family, holidays don't require extra places at the table, just a smaller table. You will have the worst pass before you know it, the ache will always be there, put the lose can be put in it's own place, all the best my friend, Don
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