• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

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valvesound

valvesound

Member
Joined 2011
lexx21 said:
valvesound.... are those ef86 tubes? Did you use a cnc mill to make the pc board?
Click to expand...
Hi lexx, Yes they are EF806's and the PCB is a 'normal' PCB etching without a silkscreen layer. (I prefer it without silkscreen) I endeavored to make a layout as close as possible to point to point wiring but with the advantage of symmetry and having it consistent and reproducible.
 
J

jdrouin

Member
Joined 2012
Reverse-engineered Wright Sound Mono 8. This has been a labor of love to recreate the first tube amps I'd ever heard back in 2001. My friend had his pair modified by George to use the Magnequest/Peerless TFA-204 output transformer (instead of the stock FS-030), so that's what I've done here.

5Y3, 6SN7, 300B; B+ 310V, 300B 260Vak/55mA -- so it's basically a 2A3 amp with a 300B stuck in it. *Very* satisfied with the sound, but I'll keep fiddling with the operating points to try and get a higher 2nd harmonics profile for that "euphonic" sound.


Thanks for looking!
 

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azazello

azazello

Member
Joined 2008
jdrouin said:
Reverse-engineered Wright Sound Mono 8. This has been a labor of love to recreate the first tube amps I'd ever heard back in 2001. My friend had his pair modified by George to use the Magnequest/Peerless TFA-204 output transformer (instead of the stock FS-030), so that's what I've done here.

5Y3, 6SN7, 300B; B+ 310V, 300B 260Vak/55mA -- so it's basically a 2A3 amp with a 300B stuck in it. *Very* satisfied with the sound, but I'll keep fiddling with the operating points to try and get a higher 2nd harmonics profile for that "euphonic" sound.


Thanks for looking!
Click to expand...
Id like to advise You to increase plate current to 80-90 ma and 300 B start sound much better than with 55 ma with wich sound is little bit dry, but You can sense.
 
J

jdrouin

Member
Joined 2012
azazello said:
Id like to advise You to increase plate current to 80-90 ma and 300 B start sound much better than with 55 ma with wich sound is little bit dry, but You can sense.
Click to expand...


Thanks for the suggestion. I’ve breadboarded numerous 300B amps and tried them at a variety of operating points, including above 90mA. To my ears the sound is thick and labored with higher current, but lithe and airy with lower current. My favorite combination was 390Vak/56mA in a WE91A circuit.

But maybe higher current would sound better with higher voltages than I was running back then.

For these amps, the TFA-204 has a maximum DC current of 60mA, so the operating point is limited by that.
 
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