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2359glenn | studio - Page 89

post #1321 of 10139
Quote:
Originally Posted by Xcalibur255 View Post

I'll try to chime in here with my limited understanding.

 

I think the way to know with certainly what the B+ (plate voltage) of an amp is would be to actually measure it.  This is a fixed value that is determined by the power supply design of the amp.  There is usually some loss (called voltage sag or drop) that happens in the rectifier tube which gets accounted for in the overall design, and the intent is to arrive at a specific voltage that the tube in question needs to be ideally biased.  Technically you can run a tube over or under its nominal plate voltage, with some consequences for doing the former, but I think most designers shoot for whatever the nominal value is as specified in the tube data sheet.  Whatever value results in the most linear operation without exceeding maximum values is ideal.

 

So we get various "drop in" substitute tubes because their pin out is the same as the one originally designed for the amp, they want a plate voltage that is the same or similar to the original tube, and the other electrical parameters are close enough that the circuit still behaves as it was designed to. 

 

Thanks for the explanation.

post #1322 of 10139
Quote:
Originally Posted by Xcalibur255 View Post

I'll try to chime in here with my limited understanding.

 

I think the way to know with certainly what the B+ (plate voltage) of an amp is would be to actually measure it.  This is a fixed value that is determined by the power supply design of the amp.  There is usually some loss (called voltage sag or drop) that happens in the rectifier tube which gets accounted for in the overall design, and the intent is to arrive at a specific voltage that the tube in question needs to be ideally biased.  Technically you can run a tube over or under its nominal plate voltage, with some consequences for doing the former, but I think most designers shoot for whatever the nominal value is as specified in the tube data sheet.  Whatever value results in the most linear operation without exceeding maximum values is ideal.

 

So we get various "drop in" substitute tubes because their pin out is the same as the one originally designed for the amp, they want a plate voltage that is the same or similar to the original tube, and the other electrical parameters are close enough that the circuit still behaves as it was designed to. 

 

OMG. So this is what goes on when I'm listening to music. Thank goodness we have the techs to explain this. Great explanation Xcalibur255. :)

post #1323 of 10139
Thread Starter 
Quote:
Originally Posted by Xcalibur255 View Post

Quote:
Originally Posted by Silent One View Post

 

If memory serves, we had two different experiences in two different states. He had the "X" mod and I didn't. I thought the presentation the tube offered was rather pedestrian and passed on it. With a revised amp, maybe I'll revisit it.

I'd be happy to try it again if anybody would like.  My memory of the tube was that it was very good at some things and not so good at others, overall being too much of a compromise to use on a daily basis.  I recall the bass quality being terrific and the detail good but the imaging was wonky and flat.

 

Yes, that is my memory of tongue_smile.gif your memory - mixed results with the tube. And we both walked away from giving it full-time duties...

post #1324 of 10139

You can get a measurment by using a test socket and a DMM.

 

If you measure across pins 3 & 4 for the first section and 6 & 7 for the second you'll know what the plate voltage is.

 

My amp has a plate voltage under 250V, which is the max for a 6SL7.

post #1325 of 10139
Thread Starter 

So, when will you announce?

post #1326 of 10139

Are you referring to the new tube?

post #1327 of 10139
Thread Starter 

Happy yeah...

post #1328 of 10139

eek.gif

 

The suspense!!

post #1329 of 10139
Quote:
Originally Posted by Silent One View Post

Happy yeah...

 

 

My dear SO, I am very surprised you are ever so thorough and you missed it!

post #1330 of 10139
Thread Starter 
Quote:
Originally Posted by rosgr63 View Post

Quote:
Originally Posted by Silent One View Post

Happy yeah...

 

 

My dear SO, I am very surprised you are ever so thorough and you missed it!

 

I just returned home with great preoccupation - forgot everything that happened earlier today. biggrin.gif Perhaps, I'll re-read the thread...

post #1331 of 10139

No need, just read Glenn's tube list, it's there!

post #1332 of 10139

I missed it too. I blame work! It was interfering with my forum comprehension...riiiiiight...rolleyes.gif

post #1333 of 10139

Well you are both forgiven..............deadhorse.gif

post #1334 of 10139
Thread Starter 

Great! 'Cause I remember reading the list now...redface.gif the B65 has me intrigued. Doesn't Osram make a sexy aluminum base I'm always bothering you guys about due to its price?


Edited by Silent One - 12/10/12 at 11:47pm
post #1335 of 10139

Come on which is the new tube?

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