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300B driving 845
300B driving 845
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Old 12th July 2018, 11:26 AM   #11
gabdx is offline gabdx  Canada
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magic sound comes from the amplification stages,

To me I want to listen to the 845 tube distortion, not the 300B + the 845, maybe if you want to have a soup. I prefer to have dinner.
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Old 14th July 2018, 01:29 AM   #12
deafbykhorns is offline deafbykhorns  United States
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I sure like my 300b driving a gm70
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Old 14th July 2018, 01:04 PM   #13
wredny is online now wredny
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What kind of load do you use for 300b, interstage?
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Old 15th July 2018, 12:31 PM   #14
deafbykhorns is offline deafbykhorns  United States
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Custom Monolith Magnetics interstage. I tried several other methods and this was the most dramatic change. I suspect it would be similar with the 845
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Old 15th July 2018, 09:51 PM   #15
wredny is online now wredny
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You read me like a book. I bought chinese 300b 845 amp as sort of kit and playground. It's capacitor coupled and according to my calculation does very poor job in driving power tube. I was going to go with replacing 7500 ohm resistor with choke but after looking at the prices I figured I might as well go with the 1:1 interstage and give it some room for a2 operation. Can you gents recommend an affordable interstage for testing purpose that would work in my application? 300b supply is 410V.
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Old 16th July 2018, 12:42 AM   #16
deafbykhorns is offline deafbykhorns  United States
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I used a Hammond for testing but ended up with the monolith magnetics (custom). The Hammond are limited to 25ma but thats not actually a bad thing, distortion is low. I also tried a pair of Silk which you can easily run up to 60-70ma. The monolith was best because the additional inductance. All of these allow some a2 operation My supply was about the same voltage which was ideal. I actually used a 2.5v 40watt 2A3 JJ tube with great results
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Old 16th July 2018, 08:41 AM   #17
wredny is online now wredny
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Thanks a lot! Any expirience with lundahl IS?
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Old 16th July 2018, 11:13 AM   #18
Celsius is offline Celsius  Spain
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I have made three different amps with the 211. For me the magic and clear sound has been with 6e5p triode > 2a3 > 211

2a3 have many cheap options with really very good sound, 10y maybe is the best but with less option to buy.


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Old 16th July 2018, 12:10 PM   #19
deafbykhorns is offline deafbykhorns  United States
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Quote:
Originally Posted by Celsius View Post
I have made three different amps with the 211. For me the magic and clear sound has been with 6e5p triode > 2a3 > 211

2a3 have many cheap options with really very good sound, 10y maybe is the best but with less option to buy.

Absolutely!!!
My setup is a 6E5P-JJ2A3-GM70


wredny--
A Lundahl 2753 at 25ma might work (about the same as the hammond IT)
Or you could use a 1671
Both the above would require the cathode resistor be changed (assuming its cathode biased)
A LL1677 is rated for a 300B but its a 1:2 step up
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Old 16th July 2018, 12:46 PM   #20
wredny is online now wredny
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My plan is to try jj2a3 once 300b I got are done.

Lundahls you mentioned are exactly the ones I was considering but I was hoping to get practical feedback, especially in occasional a2 ops. Do you think it's better to stick with higher inductance or current?

Step-up would increase impedance too much...
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