Max 300B SE output possible with James 6123HS ? - diyAudio
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Old 16th June 2006, 04:28 AM   #1
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Default Max 300B SE output possible with James 6123HS ?

What is the maximum output I can get with a James 6123HS transformer and ( Electro Harmonix - Gold ) 300B combination ?
I have a EH Gold 2A3 alsoand hope to be able to swap easily to compare the two types of tubes. Parts values will have to be swapped I guess.
I was looking at the JE Labs circuit for the 300B. I like the direct coupled 6SN7 sections as it reduces the number of caps in the signal path. I will probably put in a toroidal power transformer and to avoid interference from the mains supply I'll add a mains input filter.
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Old 16th June 2006, 05:48 AM   #2
arnoldc is online now arnoldc  Philippines
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Here are your 5K operating points for the 300B

Plate Voltage/Grid Bias/Plate Current/Load Resistance/Power Output/2nd Harmonic/3rd Harmonic*

350 -76 50 5000 6.2 30 45
400 -91 40 5000 8.4 26 37
400 -87 60 5000 8.3 30 46
450 -102 50 5000 10.7 27 39
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Old 16th June 2006, 06:09 AM   #3
corbato is offline corbato  India
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Hi Ashok

Pick ur op point! See attached.

I am right now running on the bench 300B RC with 6SJ7. Prior to that it was EF86, 6SN7 in SRPP and of-cource the JE method.

I think my final build will be eaither with 6SJ7's or the EF86's. Its close toss up at this moment, but the the 6SJ7 may just make it.

DELTA PTX and Chokes. GZ34 with CDB Oil cans in the PSU.
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Old 17th June 2006, 01:01 AM   #4
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you can get like 15W or so if you go on the 2.5K tap. I also am using those james OPTs and am also using EH gold 300bs. I just recently switched to the 5K tap and that seems to give better damping than the 3.5K. Its suprising how much power this amp is capable of. i can actually use it with 90db speakers and it sounds pretty good. I run around 430V, 75mA and have a power triode driver. enjoy!
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Old 17th June 2006, 02:07 AM   #5
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Thanks guys.
I think I will go with the 5K load and 450V .I already have the 500V supply caps. A 10% margin looks a bit small but I've seen many commercial amps with similar margins.

Hi Zarniwoop,
Is the output impedance difference audible or was it just a measured difference ?
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