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Bassman 100 compressor question

B

BassUrges

Mar 14, 2016
1,336
3,042
Denver
#1
I have a Bassman 100 15" combo (see picture--lots of amps using this name). I will be using it essentially as a stage monitor next month with most sound coming from the PA from the amp XLR.

My question, which the user's manual doesn't address, is whether the built in compressor also compresses the XLR out. I'll be doing some JPJ lines which are frankly above my ability level, and some smoothing of dynamics would be nice.

I may wind up with a compressor pedal but budget and simplicity push me towards the built-in if I can use it.
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#2
BassUrges said:
I have a Bassman 100 15" combo (see picture--lots of amps using this name). I will be using it essentially as a stage monitor next month with most sound coming from the PA from the amp XLR.

My question, which the user's manual doesn't address, is whether the built in compressor also compresses the XLR out. I'll be doing some JPJ lines which are frankly above my ability level, and some smoothing of dynamics would be nice.

I may wind up with a compressor pedal but budget and simplicity push me towards the built-in if I can use it.
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It would depend if the XLR is pre or post compression.
Obvious answers, I know.
Do you have a signal path diagram for your amp that shows where the XLR output is related to the compression circuits?
 
#6
So I'm up way too late thinking about a question that won't be relevant for a couple of months, but I found something that purports to be a Fender Bassman 200 schematic on a non-Fender website. It shows the compressor coming before the FX loop, and the "post" XLR send coming after the effects loop. (Pre comes before everything--just a little buffering and out it goes, so if you used the FX loop it wouldn't show up in the PA).

Assuming the schematic is correct and assuming the design of the 100 is the same (and it sure looks to be), then there's the answer: compressor does affect the XLR out if you use "post EQ."

Sound guy should super be pleased to get a post signal.
 

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#7
I've been studying the schematic a bit more and discovered that the "post eq" output comes after both gain AND master volume, while the "pre," as I mentioned, does not (and is more of a true DI). Which is incredibly annoying, because who's to say j won't want to fiddle with volume at some point? Pretty sure the sound guy doesn't want me messing with his levels.

So I'm back to considering a pedal, not that it's a good time to drop the cash.
 
#8
BassUrges said:
I've been studying the schematic a bit more and discovered that the "post eq" output comes after both gain AND master volume, while the "pre," as I mentioned, does not (and is more of a true DI). Which is incredibly annoying, because who's to say j won't want to fiddle with volume at some point? Pretty sure the sound guy doesn't want me messing with his levels.

So I'm back to considering a pedal, not that it's a good time to drop the cash.
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I know it's not the same amp, but I have the Rumble 200 combo and the D.I. is post.
It has a ground lift switch but no pre/post. That may be a Fenderish philosophy, (though the new Class D Bassman has pre/post) or it might just be that you get one switch, and they choose ground lift for the Rumbles.

I just scored the schematic for my 200 and started looking at the possibility of modding it so the switch is pre/post rather than ground lift. (Might be more of an undertaking than I want, but it looks do-able.)
What I don't get us why people get all up in my face for suggesting that I would like to have the option of pre/post.
Why is what I want for my amp any of their concern, especially when it involves having it both ways?
 
#9
Most solid state amps of that vintage have the compression immediately before the power amp. It's not meant to be an effect, it's a protection ciruit. Peavey was the first mfr I recall offering this, they called it "Distortion Detection Technology" (DDT) and on some of their amps you could switch it off, though most had it always on. I still see this sort of feature on occasion, like the protection limiters used in some class D amps.

Anyway, it should be after any line outs or DIs.
 

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