Blonde Bassman Wow a lotta gain

[FenderRoads]

I recently acquired a 64 Blonde Bassman 6g6 B....

I understand that the treble control on the bass channel increases the gain but wow. I do not know if the large amount of noise I am hearing with any treble setting beyond 12 O'clock (or straight up) is normal.

OK, the noise floor as high as it is when compared to the guitar's volume or rather the signal to noise ratio could possibly be what Leo meant to deliver but... I kinda doubt it...

Now I do not have a reference Blonde Bassman to compare this to so I am trying to get a feel for whether I should take it to a tech.

Any advice would be greatly appreciated

[Leo_Gnardo]

I'll bet you half a peach that it's been modified. The standard Bass pre on the whiteys is a standard triode into a cathode follower resulting in less gain, not more. A more authorotative sound for bass, which doesn't need gain. Let's see a snap of the interior, focusing on the bass pre stage. If you're using it for guitar you might want to keep it the way it is if you like the tone & extra gain.

White Bassman was reported to be a favorite of Craig Chaquico (Jefferson Starship), before 5 of his were wrecked onstage by rioting fans in Germany back in the 80's.

[Jazz P Bass]

On my '61-62 Blonde Bassman I have the bass & treble set at 3.

[FenderRoads]

Thanks Leo G

[acorkos]

your bass channel preamp has 2 resistors that are different from the stock schematic
you have a 220K (red-red-yellow-silver) where the wire from pin 8 of V1 connects to the circuitboard....stock value is 1M (brown-black-green-silver)
you also have a 1M (brown-black-green-silver) where the schematic indicates a 470K (yellow-violet-yellow-silver)...where the bass channel preamp mixes with the normal channel...follow the yellow wire that crosses the middle of the board from left to right

not sure if these changes will make a difference...those resistors appear like they left the factory that way

http://www.thevintagesound.com/ffg/s...g6-b_schem.gif

[FenderRoads]

your bass channel preamp has 2 resistors that are different from the stock schematic
you have a 220K (red-red-yellow-silver) where the wire from pin 8 of V1 connects to the circuitboard....stock value is 1M (brown-black-green-silver)
you also have a 1M (brown-black-green-silver) where the schematic indicates a 470K (yellow-violet-yellow-silver)...where the bass channel preamp mixes with the normal channel...follow the yellow wire that crosses the middle of the board from left to right

not sure if these changes will make a difference...those resistors appear like they left the factory that way

http://www.thevintagesound.com/ffg/s...g6-b_schem.gif

Thanks for those observations. Perhaps I should put the amp back to spec? and then see where to go from there?
....right now I dont know what is causing what.

[Leo_Gnardo]

Excellent photos! Have you measured resistors to make sure they're what they claim to be?

Before seeing the photo I thought maybe someone had cascaded triodes to get whopping gain. Now we can see that's not the case.

I doubt the alternate values have a whole lot to do with the unexpected extra gain you're reporting. A little gain change yes, a lot, no. Once you've confirmed the preamp resistors are what they claim to be, you could try swapping the 2 oddballs to schematic values. Changing 2 resistors, you could know in 5 minutes - - - Unless 1) you're happy with the tone regardless of noise level or 2) you don't want to disturb "original factory connections" which may reduce the value of the amp to a collector.

[FenderRoads]

Excellent photos! Have you measured resistors to make sure they're what they claim to be?

Before seeing the photo I thought maybe someone had cascaded triodes to get whopping gain. Now we can see that's not the case.

I doubt the alternate values have a whole lot to do with the unexpected extra gain you're reporting. A little gain change yes, a lot, no. Once you've confirmed the preamp resistors are what they claim to be, you could try swapping the 2 oddballs to schematic values. Changing 2 resistors, you could know in 5 minutes - - - Unless 1) you're happy with the tone regardless of noise level or 2) you don't want to disturb "original factory connections" which may reduce the value of the amp to a collector.

Thanks for comments...Maybe the issue is not so much the unexpected gain... but the associated hiss noise I hear at treble settings above 5 or 6. It is entirely possible that as I do not have another blonde for reference the gain is normal... it is the noise that worries me, and the fact that I seem to be missing bass on the bass channel.

I think I will change the 2 resistors and anything else to conform with the schematic.... I do not like disturbing the factory solder joints but would rather know this amp sounds right