Let's Build A Uni-Vibe: Introducing The Pадио Москва (Radio Moscow) Atmospheric Modulator - Sound Sample Added 2/1/2022

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Re: Let's Build A Uni-Vibe: Introducing The Pадио Москва (Radio Moscow) Atmospheric Modulator

Post by Bg »

An example from this morning…
9D4A2E07-7021-407A-956D-5654DADDBA28.png
9D4A2E07-7021-407A-956D-5654DADDBA28.png (375.02 KiB) Viewed 1021 times
So, is that low alcohol or no alcohol at all? mmmm, no alcohol, do you want to try it? Noooooooooo.

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Re: Let's Build A Uni-Vibe: Introducing The Pадио Москва (Radio Moscow) Atmospheric Modulator

Post by FuzzMonkey »

Bg wrote: Wed Dec 15, 2021 5:30 am An example from this morning…
Thanks for that.

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Re: Let's Build A Uni-Vibe: Introducing The Pадио Москва (Radio Moscow) Atmospheric Modulator

Post by Conway »

Damn, I've been really missing those Russianbrides.com posts...
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Re: Let's Build A Uni-Vibe: Introducing The Pадио Москва (Radio Moscow) Atmospheric Modulator

Post by murky »

Bg wrote: Tue Dec 14, 2021 8:57 pm Yeah I tend to hit delete at the first glimpse if Russian in a thread title ;)
In Russia - thread deletes you.....

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Re: Let's Build A Uni-Vibe: Introducing The Pадио Москва (Radio Moscow) Atmospheric Modulator

Post by Miza »

Just watch first 1:16 - hilarious!
Nothing to see here.

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Re: Let's Build A Uni-Vibe: Introducing The Pадио Москва (Radio Moscow) Atmospheric Modulator

Post by FuzzMonkey »

I got a chance today to assemble and test what is probably the least exciting part of my Uni-Vibe build but one of the most important. That being the power supply. So I did little research to determine what were the actual voltages found inside as I wanted to stay as close to the original as possible.

The original units used AC mains power. Meaning you'd need to plug the unit into the wall directly. But who wants that in this day and age? As if batteries weren't bad enough. That incoming AC power was then stepped down by the internal transformer to between 14 and 18-volts AC and then rectified to approximately 21 to 22-volts DC.

A non-filtered version of this voltage is sent to the LFO section as it didn't matter if there was any ripple left in it as the LFO section doesn't contain any audio path whatsoever so noise is of no concern. This measured around 19-20-volts DC under load. And the heavily filtered voltage sent to the audio section measures around 17-volts DC.

Armed with this information, I rounded up a little and settled on 20-volts DC to power the LFO section and 18-volts DC to power the audio section.

Below: The assembled dual power supply.
Image

The dual power supply I designed for this build takes a standard Boss-style, center-negative, 9-volt DC power supply that is then stepped up to by a charge pump to approximately 24-volts. Two separate voltage regulators then step the voltage back down to the required 20-volts and 18-volts respectively.

I made sure to include plenty of filtering as well as non-sacrificial reverse polarity protection in case the wrong type of power supply is ever plugged in by mistake. Non-sacrificial means that nothing burns out i.e. a diode and potentially causes damage to the PCB or stops the pedal from working altogether until it gets repaired.

One thing that I need to consider when it comes time for a PCB revision is some form of over-voltage protection. Having recently completed a spate of pedal repairs where an 18-volt power supply has been plugged into a pedal(s) by accident that is only designed for 9-volt power supply; many of which had some form of charge pump inside. And since the charge pump I've used has a maximum input of voltage of 15-volts and accidents do happen. It is something I'd like to include.

~ Blake

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Re: Let's Build A Uni-Vibe: Introducing The Pадио Москва (Radio Moscow) Atmospheric Modulator

Post by FuzzMonkey »

I've been busy these last few days with work and clearing the workbench of the last few pre-Christmas projects and repairs. So I haven't had as much time as I'd like to work on this. However, I did find time to quickly assemble some of the off-board components for the Uni-Vibe project. Things like the two speed controls, the intensity control, the volume control, and the three LED boards.

Below: (top row; from left to right) The two speed controls, the intensity control, and the volume control. (bottom row; from left to right) the bicolour mode/speed LED, the bicolour input model LED, and the bicolour bypass LED.
Image

Since the LFO of the Uni-Vibe is rather unique in the fact that as the speed of the modulation increases so does the strength/intensity of the signal being generated. Therefore, I decided to have two separate speed controls (that will be foot-switchable) to take advantage of this. That way you can have one speed control set on a slower, less intense setting and the other, on a faster more intense setting without having to bend over to adjust any of the controls. Just tap a footswitch and the speed seamlessly switches between the two.

Not much to say about the intensity and volume controls; pretty standard stuff. Just a 100kB pot for the volume control and a 50kB pot to control the intensity. I do love those 9mm Alpha pots, however! I even found some 100kC dual pots for the speed controls! I've got some miniature chicken-head knobs for them too.

There are a couple of bicolour LEDs to provide visual feedback on the status of the pedal in terms of the different modes I have planned. The first is a speed indicator LED that blinks on and off to match both the speed and intensity of the modulation. One colour represents the chorus mode that everyone associates with the Uni-Vibe and the other colour, the lesser-known vibrato mode.

The second bicolour LED is the status LED for the bypass. I’m planning on having two modes of bypass; one being a relay-based true bypass (pretty standard stuff once again) and the being akin to the ‘Cancel’ mode of the original unit when the signal from the LFO was shorted to ground and in effect turned off the bulb inside, cancelling the modulation. The signal from the guitar stills travels through the preamp and the phase-shifting circuitry but since the bulb is not actively producing any light to influence the LDR (or light-dependent resistor) there is no phasing taking place. Not exactly what you’d call ‘bypass’ in the traditional sense, but an ode to the original.

I’m also planning on having ability to be able to select between two different input modes. The ‘Vintage/Modern’ modes are commonly found on other Vibe pedals on the market. The preamp itself drives the phasing shifting circuitry as well as provides the dry signal that gets mixed together with the wet signal to provide the Uni-Vibe classic sound (the vibrato mode is purely the wet signal). The ‘Vintage’ mode provides a warmer, slightly darker tone with a little less output and is the 'stock' circuitry as found in the original. The ‘Modern’ mode provides a bright tone with more output and clarity. Again, the bicolour LED help to provide visual feedback to what input mode is currently being used.

There will be more to come soon so stay tuned!

~ Blake.

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Re: Let's Build A Uni-Vibe: Introducing The Pадио Москва (Radio Moscow) Atmospheric Modulator

Post by FuzzMonkey »

With the Christmas rush at work over and the big day itself now been and gone, I finally got the chance to sit down and begin assembling the main PCB for my Uni-Vibe build.

I think the board itself looks great. I'm happy with the layout (as is my OCD in terms of look), but there are a couple of refinements I need to make. Nothing major at this stage; just a couple of component footprints that need to change, some spelling errors, etc. I did, however, make a mistake when it came to trim pots. I created the components myself in Eagle, and when it came time to assign the pin connections, I managed to label them incorrectly. But nothing soldering a jumper wire across them won't fix.

I took a straight to PCB approach on this one. The only things I really experimented with on a breadboard were the handful of mods I planned to incorporate in the build. I had spent some time working on a mod for the Phase 90 that replaced the stock op-amp based LFO section with that of the original Uni-Vibe, complete with LDRs and lightbulb. This started me on this path in the first place, so I was able to successfully prove a lot of concepts while working on that mod.

Below: Time to get those SMD soldering chops down.
Image

In the audio section, for example, a couple of values of resistors were changed in the pre-amp section to provide unity gain when switching between the effect and bypass mode in order to prevent that perceived drop in volume commonly found in modulation effects. There is also a FET at the input to allow me to increase the input impedance of the pre-amp for the Vintage/Modern modes I've already talked about in my last post. Other than that, the entire audio section is the same as the original in terms of using an all-transistor based topology. No op-amps here.

Below: The completed audio section.
Image

I did, however, forget to order one particular value of resistor; a 68k used in the final stage of the audio section and had to ab-lib with a through-hole resistor until the SMD version arrives. Along with another part that I also forgot to order for another little project.

Below: Ad-libbing with a through-hole resistor until the SMD version arrives.
Image

The LFO section also has a couple of mods. The first is the Offset trim pot used to adjust to the off-time of the lightbulb that, when used in conjunction with the traditional Gain trim pot allows you to better dial the effect the LFO has on the lightbulb in order to find the sweet spot for the LDRs in terms of brightness and responsiveness.

There is an op-amp in the LFO section (Ye Gods!) to buffer the signal coming from the LFO so as not to load it down on its way to the transistor that drives the lightbulb in order to better run the LED that matches the speed and intensity. There is also a trim pot to dial in that LED to match the LFO in order for it to best represent what you hear.

The transistors used for the LFO and to drive the lightbulb are both Darlington transistors as 1. it saves on a part as the transistors used in the LFO are arranged in a Darlington configuration on the original anyway and 2. it is better suited to driving the blub due to the ability to handle more current.

Finally, I've incorporated a high-side switching scheme for the Cancel function. While the original unit simply shorted the signal from the LFO to ground just before reaching the blub driving transistor. I found during my experiments, that there was often a delay of up to three seconds until the modulation kicked in when using this method. The time did vary depending on where the Speed and Intensity controls were set. A faster, more intense setting meant that more current was passing through the blub and the warm-up time would be reduced this kick-in time and the modulation would take effect sooner. For a slower, less intense setting, it seemed to take an age.

With the high-side switching, I can choke the power reaching the blub right back (again, using a trim pot) until only a trickle is getting through, just enough to keep the bulb warm and dramatically cut down the start-up for the modulation no matter where the Speed and Intensity controls are set but nowhere near enough to affect the LDRs in any way.

Below: The completed LFO section.
Image

Next up is some serious testing time as while it should work in theory, the real world is a different place. Wish me luck.

~ Blake.

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Re: Let's Build A Uni-Vibe: Introducing The Pадио Москва (Radio Moscow) Atmospheric Modulator

Post by jeremyb »

That’s so cool, love all the thought you’ve put into this, I’m sure it will be stellar when finished!!
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Re: Let's Build A Uni-Vibe: Introducing The Pадио Москва (Radio Moscow) Atmospheric Modulator

Post by FuzzMonkey »

jeremyb wrote: Mon Dec 27, 2021 1:29 pm That’s so cool, love all the thought you’ve put into this, I’m sure it will be stellar when finished!!
Thanks Jeremy. I've tried to modernise a classic a little without losing any magic of the orginial that everyone knows and loves.

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Re: Let's Build A Uni-Vibe: Introducing The Pадио Москва (Radio Moscow) Atmospheric Modulator

Post by Cdog »

It's cool to see your progress Blake! Your pcb looks really slick too, Loving the fantail graphic! What sort of bulb are you using? Have you figured out over-voltage protection yet?

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Re: Let's Build A Uni-Vibe: Introducing The Pадио Москва (Radio Moscow) Atmospheric Modulator

Post by FuzzMonkey »

Cdog wrote: Tue Dec 28, 2021 7:54 am It's cool to see your progress Blake! Your pcb looks really slick too, Loving the fantail graphic! What sort of bulb are you using? Have you figured out over-voltage protection yet?
Thanks Corey. I appreciate your kind words.

The bulb I currently have installed is rated at 12-volt with a 20mA current draw and has a C2F filament all contained in a T1-¼ package. From my research, I believe the original units used a bulb with a C2V filament. I'm in the process of tracking some down so we'll see what we can find. If I can find some that are reasonably priced; I'll pick some up out of curiosity if nothing else.

Since yesterday's post, I've fired it up and everything works as it should so far. The LFO is LFOing (see the rather shakey GIF below), the Speed and Intensity controls work as intended, as does the Cancel mode and the Vintage/Modern it passes an audio signal etc. But most importantly it vibes.

Below: The LFO... well... LFOing.
Image

I've hardwired it in Chorus mode for testing purposes with just the single Speed control and Intensity and I am using the Cancel mode as the bypass triggered via a microcontroller which is also used to switch the between the Vintage/Modern input modes.

I haven't figured out the over-voltage protection yet. I had seen this video (see below) on using a crowbar circuit to protect the charge pump a while back and thought it might be a possibility. I've also seen a few other possible solutions after doing some research.



However, the power supply in its current configuration is rather squelchy sounding at the moment and definitely needs to have the filtering beefed up. Especially on the side supplying the audio section. It is potentially under-powered too which is currently playing havoc with the Speed/Intensity LED designed to mimic the status of the bulb as the voltage sags under load when the blub is on compared to when it is off. This would be fine if I wasn't planning on using the Cancel function and leaving the bulb on all the time but I'm not. But once the bulb is turned off, the loading on the LFO changes just enough to throw the LED out of sync compared to when the bulb is on.

I'm sure I'll figure something out given time. But it is all part of the process as I was expecting a few wrinkles to iron out so all part of the fun!

~ Blake.

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Re: Let's Build A Uni-Vibe: Introducing The Pадио Москва (Radio Moscow) Atmospheric Modulator

Post by Cdog »

FuzzMonkey wrote: Tue Dec 28, 2021 10:49 am
Thanks Corey. I appreciate your kind words.

The bulb I currently have installed is rated at 12-volt with a 20mA current draw and has a C2F filament all contained in a T1-¼ package. From my research, I believe the original units used a bulb with a C2V filament. I'm in the process of tracking some down so we'll see what we can find. If I can find some that are reasonably priced; I'll pick some up out of curiosity if nothing else.

Since yesterday's post, I've fired it up and everything works as it should so far. The LFO is LFOing (see the rather shakey GIF below), the Speed and Intensity controls work as intended, as does the Cancel mode and the Vintage/Modern it passes an audio signal etc. But most importantly it vibes.
Below: The LFO... well... LFOing.
Image
Vibes! Woo! This is a super cool project bro, and it looks like a considerable amount of effort has gone in so far. The bulb looks cool! I wonder if it would become fragile when hot like tungsten lamps? I honestly have no idea... but I suppose suppose you could perform some mechanical tests... potentially a bulb socket for user replacement would be a good idea?
I haven't figured out the over-voltage protection yet. I had seen this video (see below) on using a crowbar circuit to protect the charge pump a while back and thought it might be a possibility. I've also seen a few other possible solutions after doing some research.

That's a really great video. Crowbar looks like a good option for a few cents in parts... I'm sure most people think plug size is what makes a psu compatible with a device or not. Makes for a better user experience if it doesn't die easily :thumbup:
However, the power supply in its current configuration is rather squelchy sounding at the moment and definitely needs to have the filtering beefed up. Especially on the side supplying the audio section. It is potentially under-powered too which is currently playing havoc with the Speed/Intensity LED designed to mimic the status of the bulb as the voltage sags under load when the blub is on compared to when it is off. This would be fine if I wasn't planning on using the Cancel function and leaving the bulb on all the time but I'm not. But once the bulb is turned off, the loading on the LFO changes just enough to throw the LED out of sync compared to when the bulb is on.
What's the current draw from the charge pump like? That bulb is thirsty. Are you using a 1044/7660 for your charge pump? From memory the LT1054 has better current output, and is a little more robust. :think:

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Re: Let's Build A Uni-Vibe: Introducing The Pадио Москва (Radio Moscow) Atmospheric Modulator

Post by FuzzMonkey »

Cdog wrote: Tue Dec 28, 2021 11:38 am Vibes! Woo! This is a super cool project bro, and it looks like a considerable amount of effort has gone in so far. The bulb looks cool! I wonder if it would become fragile when hot like tungsten lamps? I honestly have no idea... but I suppose suppose you could perform some mechanical tests... potentially a bulb socket for user replacement would be a good idea?

Thanks. I've got an enclosure for the prototype ordered so once it arrives and everything is boxed up I might have to kick in around a bit (literally) to see what happened. The pins on the bulb I am currently using a pretty thin, more like wire than say leads on a ¼ watt resistor so I'd probably need to use a different bulb if I were to socket them. Something with more robust pins. Or even a screw-in type in they make them small enough.
That's a really great video. Crowbar looks like a good option for a few cents in parts... I'm sure most people think plug size is what makes a psu compatible with a device or not. Makes for a better user experience if it doesn't die easily :thumbup:
Yes. Making it as bullet-proof as possible is on my list of goals. Some many pedals with a charge pump have no protection for it whatsoever in terms of over-voltage other than a written warning in the user manual or on a sticker. An with so many pedals out there that can run 18-volts, accidents will and do happen.
What's the current draw from the charge pump like? That bulb is thirsty. Are you using a 1044/7660 for your charge pump? From memory the LT1054 has better current output, and is a little more robust. :think:
I've never been much of a fan of either the 1044 or the 7660. More so the 7660. I am using an LT1054 at the moment which can provide up to 100mA and when using the power supply I designed, the circuit as a whole draws approximately 40mA at the most depending on what the LFO is doing at any given moment. The voltage drops from steady 20-volts with the bulb off to around 17-volts when the bulb is on. But does flutters between that value to down as low as 14-volts. It functions perfectly, other than the noise in the audio path due to insufficient power filtering on the 18-volt rail. It's just screwing up my Speed/Intensity LED.

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Re: Let's Build A Uni-Vibe: Introducing The Pадио Москва (Radio Moscow) Atmospheric Modulator

Post by FuzzMonkey »

Happy New Year first of all. Just a quick post; work and family at this time of year has been more of a priority than pedal building. Crazy; I know.

Anyway, I've talked a lot so far about the technical side of things and my thoughts behind what I've done so far and why. So today (now that I've got the build to a point where it is actually running), I thought it was about time you all heard the thing! So here's a quick sound sample.

My apologies in advance to David Gilmour. :lol: Enjoy!



~ Blake.

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