OT distance from speaker
Moderators: pompeiisneaks, Colossal
OT distance from speaker
Just finished my first amp build...finishing up the cabinet now. I realized that my OT is very close to the metal frame of my speaker - maybe 1/16th away. Is this a problem? I know that both have a magnetic field - not sure if this would affect anything or not. Thanks!
Re: OT distance from speaker
A long time ago some very reputable manufacturers actually riveted the OT to the speaker frame, rather than mount the OT on the chassis.
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Stevem
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Re: OT distance from speaker
I just did some mods on a guys Bugrea 22 watter and in my check out of the amp before I got into it I found this.
The 2 EL84 output tubes are located right above the speaker frame by some 2 inches.
with the amp cranked and the reverb up to 50% the amp starts to feed back with the input still shorted, cupping my hand close to the left most 84 as viewed from the rear would send the amp into full on feed back!
upon testing the tubes I expected to find some microphonic tubes, but that was not the case!
so long story short, yes tube layout can be very important.
Also after building a bunch of combo amps I will no longer build a combo of more than 15 to 20 watts just due to the fact that when such a amp is played out more than 3 times a week full on cranked, or some 25 hours a month, your gonna beat up the output tubes without question!
Layout wise you want the output tube(s) as far away from the speaker as you can get it.
But a big part of what effects this choise in a PP type amp is the fact that if you get more than medium gain going on you do not want the output leads off the PI section to be more than some 3 to 4 inches long if they need to run parallel to the tubes, or oscillation issues can crop up big time and or poor tone due to part way phase cancelation!
The 2 EL84 output tubes are located right above the speaker frame by some 2 inches.
with the amp cranked and the reverb up to 50% the amp starts to feed back with the input still shorted, cupping my hand close to the left most 84 as viewed from the rear would send the amp into full on feed back!
upon testing the tubes I expected to find some microphonic tubes, but that was not the case!
so long story short, yes tube layout can be very important.
Also after building a bunch of combo amps I will no longer build a combo of more than 15 to 20 watts just due to the fact that when such a amp is played out more than 3 times a week full on cranked, or some 25 hours a month, your gonna beat up the output tubes without question!
Layout wise you want the output tube(s) as far away from the speaker as you can get it.
But a big part of what effects this choise in a PP type amp is the fact that if you get more than medium gain going on you do not want the output leads off the PI section to be more than some 3 to 4 inches long if they need to run parallel to the tubes, or oscillation issues can crop up big time and or poor tone due to part way phase cancelation!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
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Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!