Keeley Halo

Hi guys, some days ago I made a preset from scratch watching the video of Andy Timmons and TPS, for my AZ Prestige HSS. I copy the great work that guitarnerdswe an others did about Halo and want to share with you. I hope it's ok.

The preset was made for my Ibanez AZ HSS, so maybe you have to tweak a little bit. I put a Graphic EQ because my guitar doesn't have a treble bleed so, using the volume pot in 5 aprox, made my sound a little darker. I spend my time in the 2d scene, TBH. My initial idea was to emulate four stages of gain, just like Andy.

I hope you like it. I made a quickly record of the sound of the preset with my AZ.


Cheers!!

I’ve been throwing a volume pedal before the amp in the Axe for guitar rollback volume changes instead of using my guitars. None of my guitars have the treble bleed mod and using a volume pedal in this way solves that.
 
Howdy Folks!
I have read through most of the comments and analysis and its truly been a delight. The Halo sound developed from what Andy Timmons showed us he enjoyed, namely the Strymon Timeline and Memory Men, and discussions about how he wanted the sound characteristics to improve. Craighton Hale developed the schematic and circuit board and Aaron Tackett was the DSP programmer. After reading this thread I thought it would be best if we gave a very transparent and revealing description of our process, especially since there were so many creative approaches in trying to replicate the sound. So, I asked Aaron to produce a block diagram of the Halo effect.
Enjoy!
rk

[text from the pdf attached file is copied below]
The input signal is ran into a non-linearity for saturation control and then
low pass filtered. The cutoff frequency of the filter is dependent upon the
amount of saturation, ranging from 2725Hz to 8750Hz.
The saturated and filtered input is ran into Del1 which has a delay time

ratio of 0.75:1 to Del2. The output of the delay is ran through two single-
order filters, an HPF ranging from 0Hz to 300Hz and an LPF ranging

from 1000Hz to 8750Hz.
The filtered output is then modulated up to 9ms at full depth. The left
Del1 is modulated using a cosine while the right Del1 is modulated with a
sine lfo whose rate ranges from 0.1Hz to 10Hz. This modulated output
is then scaled by the feedback control and fed back to the input of Del1.

The saturated and filtered input is combined with the Del1 output. The
sum of these signals’ phase is changed by 180 degrees and ran into
Del2. The output of the delay is ran through two single-order filters, an
HPF ranging from 0Hz to 300Hz and an LPF ranging from 1000Hz to
8750Hz.
The filtered output is then modulated up to 15ms at full depth. Del2’s lfo
is based on the rate control, with the lfo cross-fading between sine and
cosine for the left and right. Essentially at certain points throughout the
sweep of the rate control the lfos for Del2 left and right will either be in
sync or 90 degrees out of phase. This modulated output is then scaled
by the feedback control and fed back to the input of Del2.
Thanks for checking in! Very much appreciated :) I have some questions though, if that's ok?

1. How steep is the LPF after the initial saturation? Is it correct to assume that more saturation = lower cut off point for the HPF?

2. Does the HPF in the feedback loop start at 0 Hz, and then go up to 1 Hz, 2, 3, etc, or does it jump straight up to higher frequency (say 20-30 Hz) when it's activated?

3. What are the tapers of the HPF and LPF controls/knobs inside the feedback loop? Looking at the setting for the tone of the Halo preset in the manual and assuming a 10A log taper, I guesstimated around a 2 kHz cut off for the LPF filter (don't know if this is correct though).

4. Is there only one LFO with different outputs that control all the modulation (one global speed)? Like, is the right side of delay 1 and left side of delay 2 in sync (both are sines from how I interpret the text, even though the block diagram says sine/cos for delay 1 right side).

5. The modulation for delay 2, do you mean that the phase relationship between the left and right side is either 0 or 90 degrees, or does it vary smoothly depending on the setting of the rate control, making in between values as 45 degrees possible?
 
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I’ve been throwing a volume pedal before the amp in the Axe for guitar rollback volume changes instead of using my guitars. None of my guitars have the treble bleed mod and using a volume pedal in this way solves that.
I will give it a try later. Thanks for the tip.
 
That's just stellar @AlbertA, nice work.
Wish it didn't take so many blocks.
Maybe we'll get a factory block for something like this some day
I mean I could totally see this in the Multi-tap delay block, as it already has modes with four delay lines.

Thanks for checking in! Very much appreciated :) I have some questions though, if that's ok?

1. How steep is the HPF after the initial saturation? Is it correct to assume that more saturation = lower cut off point for the HPF?
Do you mean lowpass? From the manual:
"SATURATE - Acts as tape compression and saturation,
allowing you to mimic the grit and feel of vintage
tape delay units. Additional low pass filtering is also
introduced as saturation is increased."


I take that to mean that yeah the low pass cutoff is decreased.

3. What are the tapers of the HPF and LPF controls inside the feedback loop? Looking at the setting in the manual and assuming a 10A log taper, I guesstimated around a 2 kHz cut off for the LPF filter (don't know if this is correct though).
It wasn't clear from the question but I take it you mean you are estimating 2KHz cutoff for the LPF in the feedback loop for Preset 1A? based on a 10A log taper and where the Tone controls sits for that preset?


4. Is there only one LFO with different outputs that control all the modulation (one global speed)? Like, is the right side of delay 1 and left side of delay 2 in sync (both are sines from how I interpret the text, even though the block diagram says sine/cos for delay 1 right side).
I interpreted to be, Del1 L and Del R are always out of phase 90 degrees (cosine = sine + 90 degree shift). Del 2 L and R LFO are apart by 90 degrees.

Then Del 1 and Del 2 LFO can be 90 degrees out of shift between them but maintaining the 90 degree shift between L and R.
By cross-fade I'm assuming it's a weighted sum of cos and sin - i.e. a*sin(x)+b*cos(x) for Del2 L and a*cos(x)+b*sin(x) for Del 2 right


5. The modulation for delay 2, do you mean that the phase relationship between the left and right side is either 0 or 90 degrees, or does it vary smoothly depending on the setting of the rate control, making in between values as 45 degrees possible?
I interpreted as between L and R LFO's it's always 90 degrees. Between Del 1 and Del2 LFOs is where they would in one extreme, it'll be sin for Del2 L at the same time Del2 R is cosine or at the other extreme Del2 L will be cosine and DeL2 R will be sine.
 
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So given the interpretation above for the cross-fade - we can use the Source 1 + Source 2 feature of the modifier setup to emulate it.

I've used LFO 1, from the controllers section, where LFO1A = sine and LFO 1B = cosine (since Output B Phase is set to 90 deg).

  • Del1 L is simulated by Delay Block 1 L
  • Del2 L is simulated by Delay Block 1 R.
  • Del1 R is simulated by Delay Block 2 L
  • Del2 R is simulated by Delay Block 2 R.

  • Delay Block 1 Time L is assigned a modifier source of LFO1B (cosine)
  • Delay Block 2 Time L is assigned a modifier source of LFO1A (sine)
  • Delay Block 1 Time R is assigned a modifier with source 1 = LFO1A (sin) and source 2 = LFO1B (cos), operation is set to "Src1 + Src2"
  • Delay Block 2 Time R is assigned a modifier with source 1 = LFO1B(cos) and source 2 = LFO1A(sin), operation is set to "Src1 + Src2"
We can then use the Modifier Scale 1 and Scale 2 in both blocks to simulate the cross-fade. For example:
  • One extreme, Scale 1 set to 100%, Scale 2 = 0%
    • This simulates Del 2 LFO being 90 deg out of shift with Del 1 LFO.
  • Other extreme, Scale 1 set to 0%, Scale 2 = 100%
    • This simulates Del 2 LFO being in sync with Del 1 LFO
  • Then for anything in between, we can set Scale 1 and Scale 2 on both blocks to add up to 100%, for example, (50%, 50%) or (20%, 80%) or (80%,20%) - you get the idea.

Left-channel-Del2-setup.pngRight-channel-Del2-setup.png

Attached is an updated preset that sets it to 50%

 

Attachments

  • Timmy Andons.syx
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Do you mean lowpass? From the manual:
"SATURATE - Acts as tape compression and saturation,
allowing you to mimic the grit and feel of vintage
tape delay units. Additional low pass filtering is also
introduced as saturation is increased."


I take that to mean that yeah the low pass cutoff is decreased.
Yes, I meant LPF after saturation. Nicely spotted!

It wasn't clear from the question but I take it you mean you are estimating 2KHz cutoff for the LPF in the feedback loop for Preset 1A? based on a 10A log taper and where the Tone controls sits for that preset?
Correct, I was talking about the taper of the tone control basically. That's how I calculated approx 2 kHz cut off of the Halo preset.

I interpreted to be, Del1 L and Del R are always out of phase 90 degrees (cosine = sine + 90 degree shift). Del 2 L and R LFO are apart by 90 degrees.

Then Del 1 and Del 2 LFO can be 90 degrees out of shift between them but maintaining the 90 degree shift between L and R.
By cross-fade I'm assuming it's a weighted sum of cos and sin - i.e. a*sin(x)+b*cos(x) for Del2 L and a*cos(x)+b*sin(x) for Del 2 right

I think we interpreted the LFO relationship a bit differently. I can't see anything in the text that accompanies the block diagram, that mentions the phase relationship between the modulation of delay 1 and 2 (so basically unknown as of now).

I read delay 1 the same way as you though, that left and right are always 90 degrees out of phase with each other.

I interpreted as between L and R LFO's it's always 90 degrees. Between Del 1 and Del2 LFOs is where they would in one extreme, it'll be sin for Del2 L at the same time Del2 R is cosine or at the other extreme Del2 L will be cosine and DeL2 R will be sine.

From what I gather, delay 2 left and right are either in sync, or 90 degrees out of phase, depending on the rate. So 0.5 kHz might mean they're 90 degrees apart, and 2 kHz rate might mean that they're in sync. If in between values are possible, I don't know (hence my question). But I definitely interpreted Robert's post as once you set the rate, the phase relationship between delay 2 L/R is static.
 
Wow, just wow… @Robert Keeley just drops in and gifts the secret sauce!!! Thank you so much!

I own and owned many Keeley pedals:
Dark Side
George Lynch Time Machine Boost - incredible wiring and dressing BTW
Nova Wah - the original custom swirl painted one
The 4x4 modified Ibanez turbo tube screamer

Awesome, awesome pedals! I’ll have to add the Halo to the list.
 
I think we interpreted the LFO relationship a bit differently. I can't see anything in the text that accompanies the block diagram, that mentions the phase relationship between the modulation of delay 1 and 2 (so basically unknown as of now).
Yeah that's true - should be testable though when I get my pedal.


From what I gather, delay 2 left and right are either in sync, or 90 degrees out of phase, depending on the rate. So 0.5 kHz might mean they're 90 degrees apart, and 2 kHz rate might mean that they're in sync. If in between values are possible, I don't know (hence my question). But I definitely interpreted Robert's post as once you set the rate, the phase relationship between delay 2 L/R is static.
Right, I have a hunch they are cross-faded like a*sin(x)+(1-a)*cos(x) for Del2 L and a*cos(x)+(1-a)*sin(x) for Del2 R - so them coming in sync is just a property of that addition as you increase a.
It's easier to see it visualized:
http://www.mathopenref.com/graphfun...)+(1-a)*sin(x)&sg=f&ah=1&a=0&bh=1&b=0&c=0&d=0

Move the a slider up and down and see how they come and get out of sync up to 90 degrees.

One approach would be to just map a linearly to the rate knob (with whatever taper that knob has) - so that when rate all the way down is a = 1 and rate all the way up, a = 0. Or it could be custom LUT, or some custom shape.
 
Wow, just wow… @Robert Keeley just drops in and gifts the secret sauce!!! Thank you so much!

I own and owned many Keeley pedals:
Dark Side
George Lynch Time Machine Boost - incredible wiring and dressing BTW
Nova Wah - the original custom swirl painted one
The 4x4 modified Ibanez turbo tube screamer

Awesome, awesome pedals! I’ll have to add the Halo to the list.
Those are some of the best ones from the old days! The GL TMB did have amazing wiring, it was like a Matchless amplifier. Arlon Prince swirl paint jobs on a Nova Wah! The good old days for sure! Steve Vai and Joe Satriani were using the 4x4 TS9DX back then! ;-O. The Halo is easily the best thing we've ever done. You'll be proud to add it to the collection sir! <3
 
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