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New project 300B
New project 300B
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Old 13th April 2018, 11:37 AM   #1
xcicc is offline xcicc  Italy
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Default New project 300B

hello to everyone, rummaging through old hard drives I found this amp scheme. I do not remember who designed it or anything. I'd like to build it, I'm going to ask you that you're definitely more experienced than me, does it seem like a very good project?
Thanks
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Old 13th April 2018, 12:37 PM   #2
waltube is offline waltube  Italy
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I don't like that project. The 300B must be driven from linear stuff similar to it. In this way the first stage with 6922 in srpp and the second stage with 6H30 also in srpp is a good choiche. in case you can use a single E88C (not E88CC) in SRPP, it is a very interesting solution because is involed only one amplification stage to drive the 300B why not E88C

Walter
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Old 13th April 2018, 01:24 PM   #3
artosalo is offline artosalo  Finland
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To me it looks that ECL82 is used proper way. It is especially know as a very linear tube. And also refreshing to see a project of 300B with intention to better performance, i.e. with NFB.
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Old 13th April 2018, 01:46 PM   #4
xcicc is offline xcicc  Italy
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Hello yes, I agree with your analysis thanks
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Old 13th April 2018, 01:47 PM   #5
xcicc is offline xcicc  Italy
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.... I add that in my opinion 90% for a good tube amp are the output transformers. Correct me if I'm wrong
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Old 13th April 2018, 01:50 PM   #6
mbrennwa is offline mbrennwa  Switzerland
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Quote:
Originally Posted by artosalo View Post
And also refreshing to see a project of 300B with intention to better performance, i.e. with NFB.
+1
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Old 13th April 2018, 04:45 PM   #7
Adolf Corkscrew is offline Adolf Corkscrew  Finland
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Am I the only one here a wee bit concerned about how those screen and control grids are connected in the pentode half of the ECL82? I fail to see how connecting the control grid directly to the anode would not end up in a spectacular failure of the tube.
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Old 13th April 2018, 04:53 PM   #8
xcicc is offline xcicc  Italy
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Sure? I have serious doubts about it. How should it be connected?
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Old 13th April 2018, 05:09 PM   #9
Adolf Corkscrew is offline Adolf Corkscrew  Finland
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They're the wrong way around. The control grid (g1) should be connected where the screen is now, and the screen grid tied to the anode. That makes the pentode section behave as a triode.
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Old 13th April 2018, 05:35 PM   #10
waltube is offline waltube  Italy
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Maybe is an error on drawining the circuit. The intention is to use the pentode as triode. In addition this circuit is using a 5u4 with 310+310 vac (and a mix of fixed an cathode bias) the Vdc is low to reach a right power. In every case I can't undersand the use of a pentode as triode when there are other stuff bettere than this solution

Last, the OT must be a the best this to justify the money to buy a pair of 300B

Walter

Last edited by waltube; 13th April 2018 at 05:47 PM.
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