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Strange experience / class D content

Happy Face

Supporting Member
May 3, 2007
709
512
Portland, Maine
So, I'm in a new project, somewhere close to a Doors tribute band without costumes, wigs etc. I had not planned to stick with it but the band, especially the drummer, is really good.

I pay for a wicked good practice studio with sharp PA, drum kit etc in Portland but the others live out in the burbs so we practice in a sonic hell-hole closer to where they all live.

I was using one of those new 100 watt Fender Rumble combos but everyone was whining that they couldn't hear me. So I brought out a pair of those new Orange 1x12" lite cabs with a 200 watt Taurus class D hybrid that I used to carry as a backup to one of my Orange heads. And for practice at home.

Well, yesterday at practice, Gremlins had taken control of the PA and the work-around limited things a little. Then my amp started cutting out, with the amp protection light happily illuminating. I wasn't driving the amp all that hard, or so I thought, and it kicked right back in after maybe 10 seconds or less.

I figured it was another Gremlin at work drawing down the power to levels where solid state amps complain so I moved it to another plug which, I was told, was on another circuit. For a couple of minutes I looked like a genius but soon enough, it started dropping out again.

It took a while, like 90 minutes, before old blockhead here finally figured out the circuit protection feature on the little amp only kicked in when I played A on the fifth fret of the E string. Open A on the A string? Not a problem. But hit the fifth fret on the E string and you could hear an audible pop and then the amp shut itself off for a few seconds.

Mind you, I was playing a really hot active bass with Darkstar pickups so, in retrospect, I'm not surprised. I'll have to check the pole piece heights etc. In the meanwhile, I'll haul over a nastier amp.

But I just found it interesting that even after so many years of playing, there is always something new that'll come along and challenge you.


Also a good reminder of why I ALWAYS bring a backup amp to shows.
 
Let's hook up that bass to a 'scope, do a Fast Fourier Transform on the signal, and we'll sure as the day is long find out why that fretted A is giving you grief. :)

(However, it could just be that the ghost of ol' Jim was just paying you a visit.)

How are you doing? (I'm a little sad to hear there will be no leather pants with this project.)
 
Hey amigo! I "fondly" remember trying to wiggle into a sharp looking pair of black leather pants back when Marden's was out at the Westgate shopping center. Alas, even employing maximum mind control, those lovely slacks could not be worn by me.

Let's try and get together soon, brother.
 
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Hey amigo! I "fondly" remember trying to wiggle into a sharp looking pair of black leather pants back when Marden's was out at the Westgate shopping center. Alas, even employing maximum mind control, those lovely slacks could not be worn by me.

Let's try and get together soon, brother.

I would like that.

Marden's and black leather pants are causing me some major cognitive dissonance.
 
It's more likely the cab impedance goes a little wonky - fifth fret A will have a different distribution of spectral energy than open A (IOW tone is different).
This is exactly what my first suspicion is too.
 
So, I'm in a new project, somewhere close to a Doors tribute band without costumes, wigs etc. I had not planned to stick with it but the band, especially the drummer, is really good.

I pay for a wicked good practice studio with sharp PA, drum kit etc in Portland but the others live out in the burbs so we practice in a sonic hell-hole closer to where they all live.

I was using one of those new 100 watt Fender Rumble combos but everyone was whining that they couldn't hear me. So I brought out a pair of those new Orange 1x12" lite cabs with a 200 watt Taurus class D hybrid that I used to carry as a backup to one of my Orange heads. And for practice at home.

Well, yesterday at practice, Gremlins had taken control of the PA and the work-around limited things a little. Then my amp started cutting out, with the amp protection light happily illuminating. I wasn't driving the amp all that hard, or so I thought, and it kicked right back in after maybe 10 seconds or less.

I figured it was another Gremlin at work drawing down the power to levels where solid state amps complain so I moved it to another plug which, I was told, was on another circuit. For a couple of minutes I looked like a genius but soon enough, it started dropping out again.

It took a while, like 90 minutes, before old blockhead here finally figured out the circuit protection feature on the little amp only kicked in when I played A on the fifth fret of the E string. Open A on the A string? Not a problem. But hit the fifth fret on the E string and you could hear an audible pop and then the amp shut itself off for a few seconds.

Mind you, I was playing a really hot active bass with Darkstar pickups so, in retrospect, I'm not surprised. I'll have to check the pole piece heights etc. In the meanwhile, I'll haul over a nastier amp.

But I just found it interesting that even after so many years of playing, there is always something new that'll come along and challenge you.


Also a good reminder of why I ALWAYS bring a backup amp to shows.

Why do you think that having a hot active bass with hot pickups would make any difference? As I see it, having a hot bass just means you add less gain at the input of the amp. With a low output bass you add a little more gain at the preamp. In the end it's all the same before it reaches the power amp.
 
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Spectral energy? Way beyond my meagre comprehension. (Though the grizzled old guitarist pondered if the E string has more motion than the A.)

The harmonics in a 5th fret A (fingered) are different than those in an open string - that's why they sound different. They do sound different, right?
 
upload_2019-7-29_9-52-33.jpeg

LOL
 
One explanation might be, the "A" played by stopping the string on 5th fret of the E string, moves a string (with more mass) slightly closer to the pickups in contrast to the open A string whose smaller gauge (less mass) vibrates full scale between the bridge and nut resulting in the distance between this string and the pickup is slightly more. The result could be higher amplitude signal generated by the "A" played fretted E string, which is just enough to overwhelm your amplifier system.
Then the question becomes, "why does this subtle difference overwhelm the amp"?
BTW, is your bass setup properly?
 
One explanation might be, the "A" played by stopping the string on 5th fret of the E string, moves a string (with more mass) slightly closer to the pickups in contrast to the open A string whose smaller gauge (less mass) vibrates full scale between the bridge and nut resulting in the distance between this string and the pickup is slightly more. The result could be higher amplitude signal generated by the "A" played fretted E string, which is just enough to overwhelm your amplifier system.
Then the question becomes, "why does this subtle difference overwhelm the amp"?
BTW, is your bass setup properly?

Thanks. That makes sense and is in-line with the observation from the grizzled old guitar player.