Aion Radian (Rangemaster clone) - Noise Issues

[psb962]

First build, first post on this forum. I've always wanted a rangemaster, so went with the kit from Aion FX. Excellent quality, great instructions.

Build photos are below. It works (miracles do happen) but I'm now trying to eradicate noise - specifically a 42Hz 'digital' buzz that is audible when guitar vol is turned to zero. The noise is present both on battery and on dc power (boss wallwart).

The design uses a TC1044SCPA chargepump. Is that likely to be a the cause of the noise?

I intend to disassemble the pedal in the week and resolder all the power related connections, and all the components connected to ground. Any better ideas?

[FSFX]

Any traditional type of Rangemaster circuit is likely to suffer from noise due to it being the most minimalistic common emitter amplifier circuit that you can ever make.
That is fine when it is used the way an original DRM was designed to work with just a battery and internally with positive ground for a PNP transistor.
The main issues in the design of it that make it noisy are:
1. The bias voltage divider network can couple noise from the power supply into the base of the transistor where it is then amplified and appears on the output, and
2. The output level pot connects directly to the power supply so that when it is turned to its lowest level, any noise on the power supply gets fed direct to the output.

In the original DRM which ran off of an internal 9v battery, these design features did not cause any real problem.
The only characteristic noise in the original DRM was when the level pot was adjusted when connected to an amp as the  pot carries DC and will produce a 'scratchy' sound when turned.

I addressed all of these issues when I did the design of my improved version of the Rangemaster that not only solves the noise issues but uses a PNP transistor (like an OC44) and runs directly off of a standard negative ground pedal power supply without using any power inversion such as a charge pump.

I posted details of this here a day or two ago.

I would suggest you check for an noise on the power supply and even with a battery make sure that you have adequate power supply decoupling on your pedal to filter any power supply noise.

Charge pumps are inherently noisy if not used correctly and some bad ones are being sold. So I would suggest you try with another charge pump IC if you can.

[ElectricDruid]

Why put a charge pump in a Rangemaster clone? That seems like an odd choice. Not only is it taking the thing *further away* from the original, but it's also one of the worst circuits you could choose to add power-switcher noise to!

Don't get it. Aah well. As I get older that happens more and more. I used to be with it, but then they changed what it was. Now what I'm with isn't it anymore and what's it seems weird and scary.

[antonis]

Just Welcome..

[FiveseveN]

Why put a charge pump in a Rangemaster clone?

It provides -9V: DC/DC Adjustable Charge Pump Voltage Converter, 1.5V to 12V in, -12V to -1.5V / 20 mA out. It's the solution Aion went for, presumably to keep it compatible with their wrapper (switch and jacks) daughterboards. That probably means the battery also goes through the converter even though it doesn't need to. @psb962, could you bypass it to check if that's indeed the culprit? And welcome to the forum indeed!

[FSFX]

Why put a charge pump in a Rangemaster clone?

It provides -9V

The Rangemaster is an inherently noisy design if not run direct from a battery.
Having anything like a charge pump providing power is just making the noise issues worse.
It is easy to make the Rangemaster work off +9volts without resorting to a noisy charge pump.

And please don't tell me that using the changes I suggest means that it is no longer a Rangemaster clone because adding a charge pump also means it is not a true Rangemaster clone.

If you really want a Rangemaster clone then you have to build it like this. Anything else is not a clone of the circuit.

[aion]

Build photos are below. It works (miracles do happen) but I'm now trying to eradicate noise - specifically a 42Hz 'digital' buzz that is audible when guitar vol is turned to zero. The noise is present both on battery and on dc power (boss wallwart).

This sounds like it's an input impedance issue. With the guitar at zero, the input signal is extremely high impedance and becomes exponentially more susceptible to interference like switching noise. You can confirm this by putting a buffer in front and seeing if it goes away. If there's something active between the guitar and the RM input then the RM is still seeing a low-impedance signal regardless of the guitar's volume.

I've experienced this type of thing with several pedals including commercial ones like Boss, and would say it's just a thing that happens unfortunately. It's more reliable all around to use a volume pedal.

Why put a charge pump in a Rangemaster clone? That seems like an odd choice. Not only is it taking the thing *further away* from the original, but it's also one of the worst circuits you could choose to add power-switcher noise to!

Lots of RM clones use charge pumps as voltage inverters to allow the rest of the circuit to stay as original as possible. I've been doing it this way for maybe 8 years now and this is the first I've heard of anyone having any noise issues (and this one isn't a normal use case).

With today's pedalboards it's not really feasible to have battery-only pedals... they're semi-permanently affixed to the board and sometimes really hard to remove, so having to remember to unplug the input every time you're done is just not something you can ask of people.

It is easy to make the Rangemaster work off +9volts without resorting to a noisy charge pump.

Easy, but not without significant downsides. Either you use flip the polarity of the whole circuit and use NPN transistors, or reverse-wire the DC jack and prevent it being used with daisy chains. The charge pump is more complicated, especially for such an otherwise simple circuit, but it works well in this application.

[FiveseveN]

With the guitar at zero, the input signal is extremely high impedance

A short to ground is not high impedance, it's the furthest thing from being susceptible to interference.

[FSFX]

... Either you use flip the polarity of the whole circuit and use NPN transistors, or reverse-wire the DC jack and prevent it being used with daisy chains ...

The Rangemaster uses less than half a milliamp at 9 volts so its power requirements are negligible and in fact the LED indicator if fitted will probably consume ten times the power that the actual circuit does.

The design I published still uses a PNP germanium transistor but flips the circuit and has a few additions to allow it to run direct from +9 volts. It performs and sounds exactly the same as an original PNP positive ground DRM. That is why I built reference circuits such as an original clone to verify that it performed virtually identically when used in the studio and analysed on audio analysis equipment. So it is easy to make a PNP version that runs off of a standard negative ground pedal power supply without using a charge pump. It also benefits from a better PSRR.       

[psb962]

Why put a charge pump in a Rangemaster clone?

It provides -9V: DC/DC Adjustable Charge Pump Voltage Converter, 1.5V to 12V in, -12V to -1.5V / 20 mA out. It's the solution Aion went for, presumably to keep it compatible with their wrapper (switch and jacks) daughterboards. That probably means the battery also goes through the converter even though it doesn't need to. @psb962, could you bypass it to check if that's indeed the culprit? And welcome to the forum indeed!

The 3 PCB layout proves that the battery (or the DC jack) goes through the converter. Power from the i/o board goes over a connector to the footswitch board, and on that board the only voltages are +9v, GND, jack in, jack out, and mainboard in and out. So all the conversion from +9v to -9v happens on board 3, battery or DC jack regardless.

[psb962]

Build photos are below. It works (miracles do happen) but I'm now trying to eradicate noise - specifically a 42Hz 'digital' buzz that is audible when guitar vol is turned to zero. The noise is present both on battery and on dc power (boss wallwart).

This sounds like it's an input impedance issue. With the guitar at zero, the input signal is extremely high impedance and becomes exponentially more susceptible to interference like switching noise. You can confirm this by putting a buffer in front and seeing if it goes away. If there's something active between the guitar and the RM input then the RM is still seeing a low-impedance signal regardless of the guitar's volume.

I've experienced this type of thing with several pedals including commercial ones like Boss, and would say it's just a thing that happens unfortunately. It's more reliable all around to use a volume pedal.

Why put a charge pump in a Rangemaster clone? That seems like an odd choice. Not only is it taking the thing *further away* from the original, but it's also one of the worst circuits you could choose to add power-switcher noise to!

Lots of RM clones use charge pumps as voltage inverters to allow the rest of the circuit to stay as original as possible. I've been doing it this way for maybe 8 years now and this is the first I've heard of anyone having any noise issues (and this one isn't a normal use case).

With today's pedalboards it's not really feasible to have battery-only pedals... they're semi-permanently affixed to the board and sometimes really hard to remove, so having to remember to unplug the input every time you're done is just not something you can ask of people.

It is easy to make the Rangemaster work off +9volts without resorting to a noisy charge pump.

Easy, but not without significant downsides. Either you use flip the polarity of the whole circuit and use NPN transistors, or reverse-wire the DC jack and prevent it being used with daisy chains. The charge pump is more complicated, especially for such an otherwise simple circuit, but it works well in this application.

I am greatly reassured to hear that I'm the first having noise issues with this pedal. I have little doubt that somewhere there is a cold solder joint that is taking something out of circuit that would otherwise make the pedal run silent. This was my first build and I was pleasantly surprised it even worked at all. When my new roll of solder arrives Tuesday I will rework the build and redo a bunch of joints that I suspect as I had to resort to an ancient roll of solder of dubious origin when my regular stuff ran out halfway through.

FYI, I made a model of the Radian schematic in LT Spice to better understand how it works. I see there is a 45kHz pulse on two of the IC pins but that is way out of range so I don't know where my EMI is coming from.

Thanks all for comments. Does anyone have illustrations of ways to shield pedal internals? If my rework doesnt improve the pedal I will try wrapping some of the jumper cables to try and keep the EMI out.

[FSFX]

FYI, I made a model of the Radian schematic in LT Spice to better understand how it works. I see there is a 45kHz pulse on two of the IC pins but that is way out of range so I don't know where my EMI is coming from.

The Radian still has the same PSRR (power supply rejection ratio) problems of the original Rangemaster.
The output level potentiometer connects directly to the power supply (V-) and so any noise on the power supply such as that coming from the charge pump will appear on the output. The maximum level of this noise will be when the level control is at its minimum position.
When you are running an LTSpice simulation of anything like this then you should avoid using ideal components, like ideal capacitors and select an actual manufacturer's type to make sure that you have realistic parasitic components like the series resistance (ESR).
In LTSpice you should also add some realistic value of noise on the voltage source for the power to be able to see if the circuit is tolerant to power supply noise. Just simulating a circuit in LTSpice using 'ideal' components will mislead you into thinking that the circuit is OK when, in fact, the design requires better power filtering or decoupling.   

[aion]

With the guitar at zero, the input signal is extremely high impedance

A short to ground is not high impedance, it's the furthest thing from being susceptible to interference.

Lol, yes. I should have given that a second read before posting it. Impedance rises up to a point as the volume knob is lowered, but then it goes back down once it gets closer to zero.

Thanks all for comments. Does anyone have illustrations of ways to shield pedal internals? If my rework doesnt improve the pedal I will try wrapping some of the jumper cables to try and keep the EMI out.

It's possible it could be fixed by shielding the wires, but it doesn't seem likely (provided the input signal is truly grounded and it's not a case of improper guitar wiring) since a grounded cable isn't carrying anything that can pick up noise. Essentially the base of the transistor is floating, with a capacitor to ground—the input capacitor, whose value depends on the position of the Range switch—but the capacitor's ground is traveling all the way back through the guitar cable and joining up inside the guitar rather than being localized. There could be some strange effects from that as well, not to mention any other number of rig-specific variables.

All that to say, it doesn't mean your build has any issues... it's definitely possible that out of 500+ builds, nobody's ever tried turning the guitar volume all the way down and perhaps this happens in all of them! I just don't think most effects manufacturers would consider this a normal use case or design flaw. A quick search on TGP indicates that this is not uncommon in commercial effects, particularly in germanium fuzzes (charge pump or no) and modulation effects with LFOs. And there's a lot on this forum as well for DIY builds.

The 3 PCB layout proves that the battery (or the DC jack) goes through the converter. Power from the i/o board goes over a connector to the footswitch board, and on that board the only voltages are +9v, GND, jack in, jack out, and mainboard in and out. So all the conversion from +9v to -9v happens on board 3, battery or DC jack regardless.

Correct. I don't think there's a straightforward way to make the battery bypass or disable the charge pump, so yeah, the battery does go through the inverter which is not very efficient. I don't recommend using batteries in conjunction with charge pumps, at least not in the field, but there was enough space in the enclosure and it can be helpful for workbench testing.

[psb962]

I found the source of the 42Hz buzz - it was one of those internet connections where you plug an ethernet cable into an adapter into a power socket. SO now the pedal is quieter, but on a variety of guitars I'm still getting swooshes, pops, and ticks with volume full up (and its worse with it down).

The noise goes down a little if I touch the case - but all jacks have continuity to ground.

So, I'll rework it in next few days. I took it apart and took some closeups of the soldering. If anyone can see any obvious problems, please post. The large connections (pot and switch lugs) are poor as I ran out of my decent solder, but the rest should be ok.

[FSFX]

I found the source of the 42Hz buzz - it was one of those internet connections where you plug an ethernet cable into an adapter into a power socket.e post. The large connections (pot and

This is the whole point of the EMC (Electromagnetic Compatibility) regulations and requirements that exist in the EU and elsewhere.
So many of these DIY pedal designs completely ignore any EMC requirements.

[aion]

So many of these DIY pedal designs completely ignore any EMC requirements.

I would extend that to say "all, or very nearly so". One of the attractions of DIY is that you can make a pedal that works and sounds great without needing any familiarity with FCC or CE regulations, whether designing your own from scratch or building someone else's design. The typical first-timer knows nothing about basic grounding practices, for example, and the amazing part is they don't need to! They might be several builds in before they encounter an issue caused by poor grounding, but once they do, they'll learn a whole lot about it through the process of debugging.

By the same token, I don't think it's reasonable to expect otherwise. That would be contrary to over 30 years of history of this particular community (going back through Ampage to Usenet, where many of our elder statesmen first met up) during which time there has only been the briefest discussion of anything related to CE or FCC compliance, most of which was just dismissing it as "don't bother with it unless and until you go commercial".

This may be a flaw in our collective education, which is why it's great to have people in the community with different areas of expertise. I am sure lots of us would be interested if you could give a crash course in how we could incorporate some of these practices, particularly if it could be distilled down into, say, the 80/20 threshold of which specific items would make the biggest impact for the least added complexity. But this type of stuff just hasn't been part of the conversation before.

[FSFX]

...... I am sure lots of us would be interested if you could give a crash course in how we could incorporate some of these practices ....

I would love to do that.

I have only recently started to post stuff on this forum and comment on other's posts. However, I have been very active on a couple of the FB groups for many years and posted what I thought were understandable explanations of what are often complex or misunderstood aspects of the magical world of electronics to help beginners.

I will write up something regarding EMC, grounding and decoupling if that is needed and hasn't already been covered by the likes of Jack Orman and R G Keen who I know are active here and have published an enormous amount of extremely helpful information for pedal builders.

The scope would be to inform about reducing any EMC related issues with DIY pedals.
For commercial pedal builders who need FCC or EU compliance for EC marking then I think the best advice is for them to read all the relevant published EU and FCC guidance and engage the proper certified testing laboratories or consultants to ensure they meet the regulations for marketing commercial products in the different countries.

[FSFX]

By the same token, I don't think it's reasonable to expect otherwise. That would be contrary to over 30 years .... during which time there has only been the briefest discussion of anything related to CE or FCC compliance ....

Surprisingly (or not) a lot of pedal circuits do incorporate some basic EMC provisions only because people blindly copy what others have done. This includes such things as adding a small resistor in series with the input and a small value capacitor to ground to help filter any RF ingress or egress via the input connection. Also adding a suitable Miller capacitor to a high gain transistor stage or an op amp to limit the high end gain and kill off any parasitic oscillations in the RF spectrum. However, many fail to realise that charge pumps and SMPS supplies fall into the unintentional emissions catagory of the FCC regulations which cover devices generating frequencies above 9kHz. But such things a using ferrite beads has little if any affect in the context of RF filtering with pedals as the inductance produced by simple ferrite beads is way too low to be effective except at VHF and UHF frequencies.

As this is a DIY site then this DIY EMC testing information may be informative and educational to some here.

https://www.emcstandards.co.uk/diy-emc-testing-series-2001

[psb962]

I resoldered the pedal, wrapped conducting tape around the connecter cables to add additional shielding, and rebuilt it. Now, if the guitar is plugged directly into the pedal I still pick up some digital noise from my home internet stuff but less than before. However,  as aion suggested, when I put the pedal after a buffer (my Polytune 3) then there is no digital noise, and the background noise level is about same as my OCD and less than my EHX Big Muff Green Russian.

So I think this issue is solved, and the project complete.

I've wired it into my pedalboard right after the tuner, and its followed by a compressor, phaser, OCD, Muff, then the amp. 

Thank you all for your help. Onto the next project!

[Matthew Sanford]

As this is a DIY site then this DIY EMC testing information may be informative and educational to some here.

https://www.emcstandards.co.uk/diy-emc-testing-series-2001

Thank you for these brilliant (albeit slightly cheeky) guides! Just on part 1 and the information (and cautions) for making emissions testing equipment got me a bit excited to be honest...probably loads of cable company coax around to repurpose