Not a Bug Euro Uber presence bug?

[kit dunborg]

Hi,
I might have found a bug with the Euro Uber Model.

There is a low frequency hum as soon as I lower presence to around 2.5.
Stock settings except that I selected the Recto Straight impedance curve. With any other curve I've tested (I didn't cycle through all of them) the hum did not occur.

Preset attached.

 

[fuzzydude]

That Recto Straight Speaker Impedance Curve definitely seems to make it happen.

 

[yek]

It’s just the combination of amp model and impedance curve that can make this happen.

 

[CrimsonKing]

 

[FractalAudio]

It's not a bug. The Uber has massive amounts of negative feedback and an RLC resonant network in the feedback. If the speaker impedance is highly resonant at the same frequency as the network (as is the Recto Straight) then the power amp becomes an oscillator if you turn the Presence down enough. I suspect the real amp would behave the same way but I'm simply not inclined at this time to lug a Recto cab up here to prove it.

You can do the following:
1. Reduce Depth
2. Reduce Negative Feedback
3. Use a different speaker impedance curve

 

[kit dunborg]

Thanks for clarifying and providing a workaround, Cliff!

So, with the low hum being the note "D", I can see Bogners marketing department using this to their advantage:
" Buy and Uber and with the right cab, play songs in "D", thanks to our new technology called APPG (Automatic Pedal Point Generation)!"

 

[CrimsonKing]

Thanks for clarifying and providing a workaround, Cliff!

So, with the low hum being the note "D", I can see Bogners marketing department using this to their advantage:
" Buy and Uber and with the right cab, play songs in "D", thanks to our new technology called APPG (Automatic Pedal Point Generation)!"

Or just play a Tool song. They're all in D minor.