Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: RadioComm on February 23, 2023, 02:55:17 pm
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Hello,
Finished preparation for my Smoking Joe I build. I will be using a mid 80's SS amp, that I will degut (photo attached).
Also based on previous knowledge I aquired on this forum (thanks everyone), I have made the following changes to the layout:
* Moved the grid stopper/leak resistor off the board and closer to V1
* Added a boost switch
Questions:
1) Any comments on the boost switch would greatly be appreciated.
2) Also in the original layout/schematic (in the pdf file), there is a discrepancy in the value of the master volume pot between the layout and the schematic. Layout has it at 1M-Audio, and the schematic has it a 500K-Audio.
Did a search and found many 'opinions':
* Some say it affects treble (I can't see why)
* Others say no, since placed after volume and tone stack (I'm on-board with that). These folks really believe that there won't be much of a difference between the two values (I think I see why).
* Very strong opinions on whether to use a linear pot or an audio one.
Not sure which direction to take. Please help...
Otherwise just need to scrounge for whatever parts I already have, and order the rest, and I'm good to go.
Much thanks.
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I think it's dangerous to connect the screen resistor between pins 1 and 9. Some EL84/6BQ5 tubes have pins 1 and 2 internally connected. I have some of them.
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I think it's dangerous to connect the screen resistor between pins 1 and 9. Some EL84/6BQ5 tubes have pins 1 and 2 internally connected. I have some of them.
Oh yeah... I remember you mentioning that in the following thread:
https://el34world.com/Forum/index.php?topic=28393.msg312549#msg312549
So I'm guessing hook up pin 8 and 9 instead?
Thanks so much sluckey.
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Hello,
I'm considering using a 3 position rotary switch for boost control. What amperage should I be considering?
I've found this one at 0.05A (answered in the question section):
https://www.amazon.com/uxcell-Position-Selectable-Channel-Selector/dp/B07JLPFM5W/ref=sr_1_6?keywords=uxcell+2P3T+2+Pole+3+Position&qid=1677450484&sr=8-6
Thanks again.
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You'll be dealing with 1mA to 2mA, so any switch you find will be suitable. I like these switches...
https://www.tubesandmore.com/products/switch-rotary-3-poles-3-position
Much cheaper too.
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You'll be dealing with 1mA to 2mA, so any switch you find will be suitable. I like these switches...
https://www.tubesandmore.com/products/switch-rotary-3-poles-3-position
Much cheaper too.
Perfect! Thanks so much Sluckey.