Weird low resonance

pneil2

pneil2

Inspired
Hey guys,

I'm building patches for my new XL and have run into an odd problem.

It's a vox patch based on the "Aye Cee 30" preset. I'm using the "2x12 Class A Blues Mix" Ultra Res I R. The problem is that when I play a D chord, I heard a low D tone (below my low E) and I'm playing a 6 string! It's a note that doesn't even exist on my guitar.

I searched other thread and didn't find this exact issue. I can change the low cut frequency on the cabinet and make it go away, but by the time the resonance goes away, all the lows are sucked completely out of the cab. I also tried turning down the bass and the depth on the amp with no effect. Some other cabs show this behavior and some don't.

I really like this amp/cab combo and would really like to make it work. Any tips?
 
This low D (73 Hz) is the result of a sub-frequency produced by your open d string (147 Hz) and the a on the g string (220 hz) in the D chord : 220Hz-147Hz=73Hz.
Lowering SAG and setting B+ Time Constant higher might help.
 
Hucky said:
This low D (73 Hz) is the result of a sub-frequency produced by your open d string (147 Hz) and the a on the g string (220 hz) in the D chord : 220Hz-147Hz=73Hz.
Lowering SAG and setting B+ Time Constant higher might help.
Click to expand...

The ghost bass D note does occur exactly when the two notes you mention. Also when the higher D on the B string and the A are picked. Neither the sag or the B + time constant seem to have a discernible effect on the ghost tone.
 
It can also depend on ac psu simulation.
On a real vox you get ghostnotes from singlenotes as well.
If you do not like it change psu sim from ac to dc.

pneil2 said:
Hey guys,

I'm building patches for my new XL and have run into an odd problem.

It's a vox patch based on the "Aye Cee 30" preset. I'm using the "2x12 Class A Blues Mix" Ultra Res I R. The problem is that when I play a D chord, I heard a low D tone (below my low E) and I'm playing a 6 string! It's a note that doesn't even exist on my guitar.

I searched other thread and didn't find this exact issue. I can change the low cut frequency on the cabinet and make it go away, but by the time the resonance goes away, all the lows are sucked completely out of the cab. I also tried turning down the bass and the depth on the amp with no effect. Some other cabs show this behavior and some don't.

I really like this amp/cab combo and would really like to make it work. Any tips?
Click to expand...
 
Cliff:

"Note that high values of Sag along with low B+ Time Constant values can cause “ghost notes” when the supply type is AC (as in a real amp). Lower B+ Time Constant values will make the amp feel “faster” but too low can cause ghost notes."

"Those old amps make ghost notes. My 100W Plexi has some ghost notes that are louder than the fundamental. The easiest way to eliminate them (if you don't like/want them) is to simply set the Supply Type to DC. However, IMO, the ghost notes are a large part of the character of these designs and removing them isn't desirable. Don't over-analyze it. Recognize that certain designs produce ghost notes and embrace it."
 
It might just be an intermodulation product along with a strong resonance in the IR. Whenever you put two tones through distortion you produce the sum and difference of the two frequencies. These are called intermodulation products. A fun way to demonstrate this is to play, for example, the high E at the 12th fret, 1st string and then bend the D on the B string up until it's just slight below an E. You'll hear the difference frequency move down as you bend up.

IIRC the resonant frequency of those old Vox speakers is around 75 Hz. So if you are playing a D chord you are getting the difference between the root and the 5th and this is right at the resonance of the speaker.

If I were playing and noticed this my reaction would be "cool".

You can probably dial it out by putting a high-Q peaking EQ at the suspect frequency and pulling it down a bit.
 
Yeah, it wouldn't really bother me if it was actually in the range of the instrument I was playing and didn't only happen strongly at one frequency. If it happened at more points it might be ok. At one point, it's just distracting.

Cliff, thanks for the idea about EQing it out. That's perfect I since it's outside the range of what I'm trying to hit. I should be able to minimize it a bit without too much impact to the rest of the sound.

Thanks all,
 
Joero6 said:
pneil2 Let us know if the EQ fixes the problem for you, I am curious about this one. Joero
Click to expand...

Joero6,

The EQ worked fine. I used a peaking PEQ and just notched the 73Hz band. I can A/B between the two settings and the rest of the tone is virtually untouched. The only difference (to my ears) is that the low D ghost tone is less obvious.

Thanks all!
 
The resonance on those old Vox speakers is really pronounced. The resonance is very prominent and, in fact, was one of the motivations behind UltraRes as I was finding that existing IR technology was insufficient to capture the resonant peak.
 
FractalAudio said:
The resonance on those old Vox speakers is really pronounced. The resonance is very prominent and, in fact, was one of the motivations behind UltraRes as I was finding that existing IR technology was insufficient to capture the resonant peak.
Click to expand...

I believe it. I've been pleasantly surprised by the UltraRes IR's. I confess that my initial response was "oh, sounds cool, but it's probably a pretty esoteric difference". I was totally wrong. I liked the previous IR's (even in the Ultra) but there where a few area's (usually at low frequencies) where they just weren't quite "right". Some of the lower register "squawks" like Jeff Beck used to play (Blow by Blow era stuff) just didn't come across as sounding entirely correct. You've nailed it now. Thank you for all of the hard work.
 
FractalAudio said:
The resonance on those old Vox speakers is really pronounced. The resonance is very prominent and, in fact, was one of the motivations behind UltraRes as I was finding that existing IR technology was insufficient to capture the resonant peak.
Click to expand...

That might explain why I was so convinced ultra res was better but many people couldn't hear much of a difference as I'm mainly a Vox/celestion user.
 
Had/have this issue with Valvetech Hayseed 30 - a Vox clone. Took it to my tech who is a bit of a Vox expert & to his surprise all his vintage Voxes did it to. Did an updated mod which came from the manufacturer which seemed to drop off the lower end enough to minimize the issue but I think I want some of that low end back!

As Wolfenstein says, it does help to fatten up the sound & make it a bit more 3D though it can go too far as well under some circumstances.
 
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