Haible Subtle Chorus Adjustment

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Spoontex
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Haible Subtle Chorus Adjustment

Post by Spoontex »

Hi,

I've just finished the build of the Haible Subtle Chorus. It apparently works. The effect is very subtle and I can't hear any difference between the modes. now I want to adjust the trimmers.

I understand that I need to adjust 5 trimmers:

BBD Bias, and BBD clock x2 for both channels and the LFO Offset.

I've got to adjust the BBD Bias and Clock, sending 1k signal to the input. But I didn't get any signal in the pin 7 of U14 that is for adjust de LFO.

I read a thread from an old Electronics Music Forum:

This is for a symmetrical LFO shape at pin 7 of U14.

Apply signal and check a point after the BBD (like U6, pin 6) for clipping. Increase level and adjust R15 for symmetrical clipping.

Without input signal, check wiper of R24 for remaining needles from clock signal. Adjust R24 to minimize these.

Anybody that have build the Subtle Chorus can help me?

Thanks.
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bloke_zero
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Re: Haible Subtle Chorus Adjustment

Post by bloke_zero »

No direct experience, but sometimes input material makes a big difference on whether you can hear the effect changes.
Spoontex
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Re: Haible Subtle Chorus Adjustment

Post by Spoontex »

I know, the fact is that I didn't know what to search and expect of this trimmer... and I don't know if it's necessary in case of only Dim D build...

Thanks.
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KSS
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Re: Haible Subtle Chorus Adjustment

Post by KSS »

Thanks for starting the thread. Below is a slightly trimmed part of my PM response.
Spoontex wrote: II've just finished the build of the subtle chorus. And I adjust the BBD's. But I didn't know how to adjust the LFO Offset. I read an old electronic forum that Haible say: is for symmetrical shape at pin 7 of u14, but in this pin I didn't get anything. Can you help me please?
Lucky for you I had the schematics on my hard drive.

IC 14 is part of the 'extra' LFO used in Option A builds.
U16 and U14a are your typical integrator-Schmitt trigger triangle square osc-LFO with U15a acting as a variable resistor to give VC of rate. You should see the output of this LFO on pin1 of U14.

The second half of U15 is used as a VCA between the LFO and the second half of U14 is used as an intermediate buffer of the now VCA -level adjusted LFO output. This is what you should see on U14,pin7. <--and this is a clue. If the VCA -U15b- is closed then you won't have any signal at the U14 buffer!

Check first for the LFO output at U14, pin1. Once you know that is present then you can look U14, pin 7. But if you have no CV from either the Depth pot or Depth CV jack -which opens the U15B VCA through R113 and R114- then you won't have any signal at the U14pin7 output.

I don't mind helping but I *very* much prefer questions like this be asked as a post on MW since then others can benefit from our shared experience.

Edit: I just remembered something that might have created your confusion! Jurgen used the German? form of the numeral 1 in his shcematics and if you're looking at one of those and don't realize it., then it's easy to see his intended number 1 to look like what most people would say is a 7. <--His hand written 1's look like 7's!

Someone copying his schematic or notes might make the same mistake.

The LFO output is at pin 1, and that's where you would attach a meter -or VCO to act as an audible voltmeter!- to see or hear the offset as you adust the trim.

Everything above this edit is still true and useful, but I think you might have been looking at pin 7 when Jurgen intended pin 1. <--To be clear, you *can* still see the LFO and trim it's output from pin7 of U14, but you'll have to have the U15B VCA open to do so!
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Spoontex
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Re: Haible Subtle Chorus Adjustment

Post by Spoontex »

I send a sine wave ( 1k ) to the input in mono mode and I have this square signal on pin1 ( u14 ), on pin 7 I have nothing. I build the Dim D version, only Main Board + BBD board, for instance I don't need any option A or B ( I think ). So, If I adjust the LFO Offset trimmer, this square signal only up and down a bit. I get multimeter and measure the voltage on that trimmer and I set, more or less, 0V on the center.

The other thing is, when I send the test sine wave signal, I see more level on one channel than the other channel ( I upload a video ) in bypass mode the signal is equal on booth channels.

I hear a pop when I change the mode ( 1 to 6 ), and an intention of more effect.

It's possible that I omit something?

I don't know...

Thanks.

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KSS
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Re: Haible Subtle Chorus Adjustment

Post by KSS »

Do you have a control voltage in the Depth jack? PCB connector feeds R114
Do you have a Depth pot? PCB connector feeds R113.

The shifting square shows your LFO offset trim is working correctly.

Square output from a BBD is often caused by the bias being incorrectly set.
Spoontex
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Re: Haible Subtle Chorus Adjustment

Post by Spoontex »

KSS wrote: Tue Nov 22, 2022 3:12 pm Do you have a control voltage in the Depth jack? PCB connector feeds R114
Do you have a Depth pot? PCB connector feeds R113.

The shifting square shows your LFO offset trim is working correctly.

Square output from a BBD is often caused by the bias being incorrectly set.
No,

I don't have anything on this connectors:

Phaser
Rate
Race_CV
Depth
Depth_CV

I leave unpopulated.

I need them for the Dim D version?
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KSS
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Re: Haible Subtle Chorus Adjustment

Post by KSS »

You need them if you are using the A option.

Without any rate voltages your LFO modulation will be only one speed. That might be fine but I would certainly want to have an ability to change the modulation rate. The three pin connectors for rate and depth are meant to connect to pots. The two pin connectors are for CV jacks.

The rate will not matter if you do not have any voltage on the Depth connectors. Because the depth CV at these two opens up the VCA which lets the LFO modulation go on to the rest of the circuit.

It's been a *long* time since I built mine -Jurgen was still alive- and I went for the *most* flexibility.
Doing a Dim D only will have presets instead of flexibility and I'm not currently familiar with what that means in relation to your questions or these connectors being used or not in that particular build version.

What I can say is that without these connectors, you must be providing the voltage they would supply to the U15 VCA and variable 'resistor' or you will not have any result from that part of the circuit.

I am basing my replies on the attached schematic.
Attachments
jHSC-03-BBDPCBschematic2B-1024.jpg
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Spoontex
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Re: Haible Subtle Chorus Adjustment

Post by Spoontex »

KSS wrote: Tue Nov 22, 2022 3:42 pm You need them if you are using the A option.

Without any rate voltages your LFO modulation will be only one speed. That might be fine but I would certainly want to have an ability to change the modulation rate. The three pin connectors for rate and depth are meant to connect to pots. The two pin connectors are for CV jacks.

The rate will not matter if you do not have any voltage on the Depth connectors. Because the depth CV at these two opens up the VCA which lets the LFO modulation go on to the rest of the circuit.

It's been a *long* time since I built mine -Jurgen was still alive- and I went for the *most* flexibility.
Doing a Dim D only will have presets instead of flexibility and I'm not currently familiar with what that means in relation to your questions or these connectors being used or not in that particular build version.

What I can say is that without these connectors, you must be providing the voltage they would supply to the U15 VCA and variable 'resistor' or you will not have any result from that part of the circuit.

I am basing my replies on the attached schematic.
100k pots on rate and depth? And I don't understand what are you refer for CV Jacks. Where I connect this Rate_CV and Depth_CV jacks?

And with this configuration I need the rotary switch? Or I can build with booth, Rate, Depth and Rotary?
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KSS
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Re: Haible Subtle Chorus Adjustment

Post by KSS »

Reading Jurgen's note (1) on that schematic says you do not need this A option at all for the Dim D version.

Because this is an 'extra LFO to go with the one already on the main PCB.

When I was answering your PM I looked through the schematics I had saved and stopped when I found one with a U14. Sinc eyou had referenced it in your request. It seems it is not needed for the version you want to build!

Edit: was typing while you replied
I don't know the pots value, I built mine in 2008 and no longer have it.

I'll mod the drawing to show the connections, but it seems that you won;t be using them for a simple Dim d build. It may still help someone later building
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jHSC-03-BBDPCBschematic2B-1024-mod.jpg
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Spoontex
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Re: Haible Subtle Chorus Adjustment

Post by Spoontex »

I suspected... So, on my debug list I delete the LFO Offset.

I need to desolder the Option A components? Or it can be soldered on the PCB?

Now remains the pop when I change the mode with the rotary, and the fact that I have less signal on one channel... When the signal is bypassed I have the same levels on booth channels.

I upload a photo of the rotary.
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Spoontex
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Re: Haible Subtle Chorus Adjustment

Post by Spoontex »

Update:

With a 40Hz square wave I got more balanced output.
Spoontex
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Re: Haible Subtle Chorus Adjustment

Post by Spoontex »

It's possible that the enfasis on the effect when I change the mode ( click ), it's because the rotary switch is BBM non shorting?
Spoontex
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Re: Haible Subtle Chorus Adjustment

Post by Spoontex »

I think that my unit didn't work properly. When I change the mode, I don't see any change on my scope...

Anybody can help me to do some tests? Please... ?

Thanks.
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