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Magnavox Tube Radio Has Too Much Bass!!

A

AshTray700

Jan 1, 1970
0
got a magnavox tube table top radio, cleaned and repaired and it works
really well except for the fact that there is just way to much bass that
sometimes it distorts the sound. i know i can find a way to taper it off
what i dont know is why it would do that? is it because the lower
frequencies of today on fm are amplified. (the doors never over basses it)
or is it due to one of those flashlight sized electrolytic capacitors
failing or a vaccume tube on the virge of death, i do notice that the
amplifyer tube gets way hotter than the rest (im not sure if this is
normal or not i dont have much experience with vacuume tubes)
 
N

NSM

Jan 1, 1970
0
| got a magnavox tube table top radio, cleaned and repaired and it works
| really well except for the fact that there is just way to much bass

Most old tube sets were like that. The public was impressed by it. I wasn't.

| that
| sometimes it distorts the sound. i know i can find a way to taper it off
| what i dont know is why it would do that? is it because the lower
| frequencies of today on fm are amplified. (the doors never over basses it)
| or is it due to one of those flashlight sized electrolytic capacitors
| failing or a vaccume tube on the virge of death

No

| , i do notice that the
| amplifyer tube gets way hotter than the rest (im not sure if this is
| normal or not i dont have much experience with vacuume tubes)

Normal. If it won't burn you it's running too cool.

N
 
C

Charles Schuler

Jan 1, 1970
0
AshTray700 said:
got a magnavox tube table top radio, cleaned and repaired and it works
really well except for the fact that there is just way to much bass that
sometimes it distorts the sound. i know i can find a way to taper it off
what i dont know is why it would do that? is it because the lower
frequencies of today on fm are amplified. (the doors never over basses it)
or is it due to one of those flashlight sized electrolytic capacitors
failing or a vaccume tube on the virge of death, i do notice that the
amplifyer tube gets way hotter than the rest (im not sure if this is
normal or not i dont have much experience with vacuume tubes)


It can be "fixed" by changing an audio coupling capacitor to one with a
smaller value. A schematic would be helpful.
 
AshTray700:
The reply by Charles Shuler is correct.... the audio coupling
capacitor that goes to the G1 GRID of the Audio Output tube....
probably a .01 or .02 can be lowered in value to .001 or .002 - - - -
that should thin out the bass response a little. You can play with
that value either higher or lower to get the sound you desire. You
did not mention the model number of the radio so I am just guessing
here... so here are some common Audio Output tube numbers with the pin
number for the G1 grid:
50B5 pin 7
35C5 pin 2, 5
50C5 pin 2, 5
35L6 pin 5
50L6 pin 5
6K6 pin 5
6V6 pin 5
6F6 pin 5
If you need further ideas or need the pin numbers for other tubes
please post again.
electricitym
= = = = = = = = = = = = = = = = =
 
B

Bob

Jan 1, 1970
0
These sets usually had a negative feedback loop, sometimes to the lower end
of the volume control that was lifted from ground by a low value resistor.
It was either designed for that impressive bassy sound or component values
have changed. I would look for a network from the speaker to the volume
control or from the audio output plate to the first AF plate or something
similar and check component values. They usually provided feedback at mid
frequency but none at low frequency so there was more gain for the bass. If
all is as designed, you could modify the feedback loop to reduce the
feedback at mid frequency which makes the bass seem less apparent. You
would also pick up some overall gain.
 
J

jakdedert

Jan 1, 1970
0
Bob said:
These sets usually had a negative feedback loop, sometimes to the
lower end of the volume control that was lifted from ground by a low
value resistor. It was either designed for that impressive bassy
sound or component values have changed. I would look for a network
from the speaker to the volume control or from the audio output plate
to the first AF plate or something similar and check component
values. They usually provided feedback at mid frequency but none at
low frequency so there was more gain for the bass. If all is as
designed, you could modify the feedback loop to reduce the feedback
at mid frequency which makes the bass seem less apparent. You would
also pick up some overall gain.

There is also the possibility that what he describes as 'too much bass' is
in fact, *too little treble*! On a unit this old, almost anything could be
wrong and it probably needs a thorough going-through which would include--at
the very least--replacement of the filter caps and any wax/paper capacitors.

Before all that is done, troubleshooting is pretty futile.

jak
 
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