Author Topic: Choral Reef with a MN3005?  (Read 782 times)

Aentons

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Choral Reef with a MN3005?
« on: May 14, 2019, 02:03:17 PM »
What would it take to run the Choral Reef as a delay with an mn3005? Has anyone tried doing a drop in?

selfdestroyer

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Re: Choral Reef with a MN3005?
« Reply #1 on: May 14, 2019, 03:29:50 PM »
What would it take to run the Choral Reef as a delay with an mn3005? Has anyone tried doing a drop in?

In the build doc is says "There is no substitute for the MN3008 in this build. You cannot use an MN3208 or one of the new Xvive MN3005."

Sorry man!

Aentons

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Re: Choral Reef with a MN3005?
« Reply #2 on: May 14, 2019, 03:35:54 PM »
Yep I know the new chips are a bit different but Im talkin bout an old an mn3005. Or like using one of the mn3008 doubling daughter board. It's purely to get more delay time and turn it into a modulated delay rather than using it strictly for chorus

I dont have a 3005 or a second 3008 or I'd give it a try

Scruffie

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Re: Choral Reef with a MN3005?
« Reply #3 on: May 14, 2019, 04:03:06 PM »
There's no working difference between an old MN3005 or Xvive one or using two MN3008.

It will 'work' but what would hold it back is the max clock frequency, the 4047 should be able to drive it to about 200kHz IIRC which is around 10mS. So you will probably find the range switch superfluous and have to stick to the 220pF clock cap, maybe going down to 100pF depending on the width pot range. So you'll lose all the shorter delay times basically.
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Aentons

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Re: Choral Reef with a MN3005?
« Reply #4 on: May 14, 2019, 04:21:30 PM »
But you could use a different clock and caps for longer times, right?

Scruffie

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Re: Choral Reef with a MN3005?
« Reply #5 on: May 14, 2019, 04:41:59 PM »
You don't need a different clock for longer times, for shorter you would need to buffer it with a 4049.

I can't be bothered to calculate the filtering right now but the Small Clone was 5kHz-ish IIRC so I'll assume it's the same so 10kHz is the absolute minimum usable clock frequency which is about 200mS and that is going to be unuseably noisy, 15kHz is probably as low as you can go which is around 130mS and even that's going to be very noisy.

I would just build a delay pedal with modulation, this isn't designed to be a delay.
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Aentons

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Re: Choral Reef with a MN3005?
« Reply #6 on: May 14, 2019, 09:11:31 PM »
Ok, sorry, forgive me, i'm new at this and trying to learn. Sorry if im a bit stubborn and a little thick headed. If you don't mind, please help me to understand why it wouldn't be a good fit.

Just for frame of reference, I have been looking at Tonal Recall/Memory Man schematic and it uses an MN3005 and CD4047 combo.


..for shorter you would need to buffer it with a 4049.
I don't understand why it would need a buffer for shorter frequency, especially if we don't want it's frequency in the audio spectrum like below 15k


...the Small Clone was 5kHz-ish IIRC so I'll assume it's the same...
Correct me if i'm wrong but I think the screenshot shows the Choral Reef's post filtering which appears to be fairly steep between 4-5kHz


...so 10kHz is the absolute minimum usable clock frequency which is about 200mS and that is going to be unuseably noisy, 15kHz is probably as low as you can go which is around 130mS and even that's going to be very noisy.
I have zero experience here... why is it noisy if the clock is running at 15k and everything above 5k is being cut? Also, is that 130ms @ 15k for the 3008 or the 3005?

Thanks again!

Scruffie

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Re: Choral Reef with a MN3005?
« Reply #7 on: May 15, 2019, 04:57:40 AM »
Ok, sorry, forgive me, i'm new at this and trying to learn. Sorry if im a bit stubborn and a little thick headed. If you don't mind, please help me to understand why it wouldn't be a good fit.

Just for frame of reference, I have been looking at Tonal Recall/Memory Man schematic and it uses an MN3005 and CD4047 combo.


..for shorter you would need to buffer it with a 4049.
I don't understand why it would need a buffer for shorter frequency, especially if we don't want it's frequency in the audio spectrum like below 15k
I was talking about shorter delay times, so higher clock frequency.

Quote
...the Small Clone was 5kHz-ish IIRC so I'll assume it's the same...
Correct me if i'm wrong but I think the screenshot shows the Choral Reef's post filtering which appears to be fairly steep between 4-5kHz

Quote
...so 10kHz is the absolute minimum usable clock frequency which is about 200mS and that is going to be unuseably noisy, 15kHz is probably as low as you can go which is around 130mS and even that's going to be very noisy.
I have zero experience here... why is it noisy if the clock is running at 15k and everything above 5k is being cut? Also, is that 130ms @ 15k for the 3008 or the 3005?

Thanks again!
Well there's a lot of sources of noise in a delay effect, first of all you have the chips inherent noise specs (S/N etc) which aren't great, don't forget this is pretty old technology now, which is a big reason why we use companders in delays as they bring the signal level up. Then there's sampling noise, the rule is your filtering must always be at least half the clock frequency and then there's audible clock noise as at 10-15kHz we're well in to audio range. An over simplification but I digress.

So we filter the signal, a perfect filter would have a big cliff face and nothing over the desired frequency would get through but they don't work like that. That Choral Reef filter is second order so it's cutting out 12dB per octave, to make life easy let's say it's set at 5kHz and we have a minimum clock frequency of 10kHz, that means that are filter is cutting that frequency by 12dB... that's still quite audible. So when you look at something like the Memory Man or DM-2 you see it uses two filters in series at the output which if they're both second order is now cutting are minimum clock frequency at 24dB, better, but even at max delay time there's still quite a bit of noise coming through but a certain point we cut our losses because we're just simple guitarists.

That's the basics and that's why BBDs went extinct basically, they're a pain and have lots of drawbacks for general purpose circuit design.
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zgrav

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Re: Choral Reef with a MN3005?
« Reply #8 on: May 15, 2019, 08:15:13 AM »
The choral reef is a tight build already with little if any room for larger parts, workarounds, etc.   I think it was optimized to be a chorus pedal and then optimized to fit into a standard VFE build.  One of the nice things about VFE pedals is all of the adjustments you can make with the on-board pots and switches.  The down side of that is there is little room to try any other mods on the board other than same-sized drop-in part substitutions.     

If you want a different kind of effect pedal with a longer modulated delay, I agree with the suggestion above to pick a design and build it from scratch.   

Aentons

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Re: Choral Reef with a MN3005?
« Reply #9 on: May 15, 2019, 10:00:20 AM »
If you want a different kind of effect pedal with a longer modulated delay, I agree with the suggestion above to pick a design and build it from scratch.



Honestly, I'm not really looking for a specific delay. I was just trying to explore the capabilities of the CR. I'd love for the CR switch to be a flanger/chorus/delay switch.

Full disclosure: Something is wrong with the switch on the one i built and i have to open it up, so I wanted to see if there were possibilities for other mods while i was in there.

The choral reef is a tight build already with little if any room for larger parts, workarounds, etc. ...The down side of that is there is little room to try any other mods on the board other than same-sized drop-in part substitutions.     
There is lots of room down where the battery goes!
« Last Edit: May 15, 2019, 10:08:11 AM by Aentons »

benny_profane

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Re: Choral Reef with a MN3005?
« Reply #10 on: May 15, 2019, 01:34:28 PM »
Full disclosure: Something is wrong with the switch on the one i built and i have to open it up, so I wanted to see if there were possibilities for other mods while i was in there.

Whatís this issue youíre having with the switch?

Aentons

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Re: Choral Reef with a MN3005?
« Reply #11 on: May 15, 2019, 01:46:45 PM »
It worked fine for a a few months and then it all of a sudden started doing this. It works fine until I flip the switch and then it pops really loud and sounds like it's gonna melt. It buzzes and hums loudly and makes other weird random popping and other oscillation type noises. I turn it off and right back on and it's back to being fine

benny_profane

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Re: Choral Reef with a MN3005?
« Reply #12 on: May 15, 2019, 01:55:41 PM »
It worked fine for a a few months and then it all of a sudden started doing this. It works fine until I flip the switch and then it pops really loud and sounds like it's gonna melt. It buzzes and hums loudly and makes other weird random popping and other oscillation type noises. I turn it off and right back on and it's back to being fine
Hmm this build has given me a bunch of dumb problems (from my errors), but I havenít had to deal with that. You havenít opened it up yet for diagnostics?

Aentons

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Re: Choral Reef with a MN3005?
« Reply #13 on: May 15, 2019, 05:26:59 PM »
Hmm this build has given me a bunch of dumb problems (from my errors), but I havenít had to deal with that. You havenít opened it up yet for diagnostics?

Sorry to hear that. As zgrav said before, It is quite tight in there. I've built a few of the VFE projects and the only problem I've had so far is metal touching metal so I'm hoping that's what my issue is this time too. I have not opened it up yet.

Aentons

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Re: Choral Reef with a MN3005?
« Reply #14 on: May 16, 2019, 02:42:35 PM »
I opened it, looks like I may need to clean it up a bit. I remember it being difficult to get the switch to line up properly so I might reflow those points.
« Last Edit: May 16, 2019, 02:45:17 PM by Aentons »