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Post by myles on Apr 7, 2008 18:40:09 GMT -7
I have a question about the ratings on EL-84's. I have a set of JJ's that have 21/4.5 on the box. These two numbers are far enough away from the 40-42 rating mentioned above that I have no idea what they mean! Can anyone shed a little light on what that 21/4.5 means? I would need to know what the plate voltage and bias settings were to come up with those numbers. Without knowing that the numbers mean nothing other than if they are the same on two boxes the tubes are matched. But ... they could be very weak tubes that match or ones that will draw too much current and burn up ... yet still matched. Find out from the vendor how they were tested .... the machine used to test or better than that; the voltages on the plate and bias and IF those numbers are supposed to be plate current in mA and transconductance.
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Post by Deleted on Apr 9, 2008 8:42:53 GMT -7
Myles - I called the distributor who sells to my local dealer, and all he could tell me was that they are using a Maxi Matcher, and they use a Yellow Jacket to adapt the EL-84 to the socket. They said the plate voltage is fixed in these machines, but couldn't tell me the actual number.
Does this help?
Thanks -
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Post by myles on Apr 9, 2008 9:52:34 GMT -7
Myles - I called the distributor who sells to my local dealer, and all he could tell me was that they are using a Maxi Matcher, and they use a Yellow Jacket to adapt the EL-84 to the socket. They said the plate voltage is fixed in these machines, but couldn't tell me the actual number. Does this help? Thanks - This helps a TON .... You can tell them this .... The Maxi Matcher on the EL84 setting use a plate voltage of 325 (when set properly .... there is a 325v and 400v setting) and the 325 volts setting is specified to be use with the 12 volt bias setting for the EL84. Yhe Yellow jacket adaptor is fine, it does nothing more than allow 9 pin tubes to be tested in an 8 pin large octal socket. In simple terms .... bottom line: Set Maximatcher for 325 plate volts -12 bias volts Find EL84S tubes with plate current displayed on MM at 38 - 42 So ... that 21.5 or whatever, if on the MM was very weak. In fact, the lowest range for EL84 tubes on the MM is 25. I am surprised they sent out a tube that was this weak. That 4.5 was probably the transconductance which should read 3.5 or higher.
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Post by Deleted on Apr 9, 2008 17:42:09 GMT -7
Thanks for the info, Myles. If I understand what you're saying, if they did set the MM for 325v and -12 bias volts, these JJ's are a 1 (or lower?) on the GT scale? The distributor mentioned they have three or four people testing these, and I wonder if they all set their MM's up the same. Could an operator have set the MM at a different value that would make these tubes hotter than we think they are?
I'm new to the world of EL-84's, and I have no way to
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Post by myles on Apr 10, 2008 9:43:21 GMT -7
Thanks for the info, Myles. If I understand what you're saying, if they did set the MM for 325v and -12 bias volts, these JJ's are a 1 (or lower?) on the GT scale? The distributor mentioned they have three or four people testing these, and I wonder if they all set their MM's up the same. Could an operator have set the MM at a different value that would make these tubes hotter than we think they are? I'm new to the world of EL-84's, and I have no way to Rather than try to compare static ratings or numbers with dynamic ones that measure the tube over the entire operating range and where it distorts let's just accept that the tubes you received, if tested at 325/-12 are very weak by any standard and would not work well at all in your amp.
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Post by Deleted on Apr 10, 2008 14:09:51 GMT -7
I'm having one heck of a time getting information on these tubes! The distributor is CE, and I tried to call Steve to ask him about their ratings, but he's not in today.
** Edited to remove a bit of a rant. Suffice it to say, the guy I spoke with at CE is nowhere near as helpful as you've been, Myles. I'll stick with GT's. At least I'll be able to buy tubes and have a rough idea of what I'm buying.
Thanks again for your help, Myles.
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Post by myles on Apr 14, 2008 17:24:33 GMT -7
I'm having one heck of a time getting information on these tubes! The distributor is CE, and I tried to call Steve to ask him about their ratings, but he's not in today. ** Edited to remove a bit of a rant. Suffice it to say, the guy I spoke with at CE is nowhere near as helpful as you've been, Myles. I'll stick with GT's. At least I'll be able to buy tubes and have a rough idea of what I'm buying. Thanks again for your help, Myles. You are welcome. The folks at CE have a scale that I gave to them and the other folks should have it to. Just tell anybody there that on an EL84 JJ on the 325v -12v setting you want something that reads as close to "42" as possible.
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