RG Neutron, questions and issues

[Moxienator]

Hi folks! Im currently building the Nuetron filter from the GGG board, and am having major issues with it. Still a noob, and I don't yet have a multimeter, soooo... yeah, there's that, but anyway..

The issue is complete lack of any sort of sweep. I put in a B250k pot for Rx, and used the chokes for the single battery option, as well as using the VTL5C3's.

Maybe this is a stupid question, but should I ground each pot like in a guitar? In all the research I did, I couldn't find any info on that.

I'm not at the breaking point yet, but soon this thing may end up as "Target Practice". I've read the Tech of Auto Wah, pored over the Neutron build article, built a couple smaller projects (which seem to work), and can't seem to get where I'm having the issue. I'll try grounding the pots tomorrow.

Anyone still building this? All the other threads on this have seen birthdays.... Help? Advice?

[SonicVI]

First thing I'd check if you get no sweep is the vactrols. Make sure you have them soldered in the correct way.

[Moxienator]

Thanks Sonic. I'll double check that ASAP!

PS- Any idea wether i should ground all pots? Do I need to ground switches?

[Morocotopo]

Without a multimeter you can´t do much more than look at the thing and swear. Buy a cheap chinese one, not much money, and you´ll have a tool that you´ll use forever.

[GibsonGM]

Do it.   

http://www.extech.com/instruments/product.asp?catid=49&prodid=289

[Moxienator]

Sonic, you hit the nail on the head. Thank you!

The Freakin' VTL's were backwards. how embarrassing!
I switched them around, and had to decrease the Rx/Sweep Pot from a B250k to a B50k i found lying around, and presto! Sweep.

I know guys, I know. I need a multi meter. I WILL get one, and soon. The next build to start is the Azabache, and a meter is a must have for it.

The Neutron works great, but has a high pitched whine that starts in the BP setting and is louder in the HP setting.
Its not insanely loud, but very noticeable.

I have the inductors/chokes in place for j8 & j9 (i think those were the jumpers replaced anyway, as this build has taken me almost a year), and am using the single battery option.

I'll be "cleaning up" the wiring as much as possible, but am still not sure about grounding pots/switches. The schematic in RG's booklet show
both pots only having two connections and no lugs grounded, but what about the case of the pot? could this decrease the whine?

I may even decrease the Rx/Sweep pot to a 10k when i put in the next order at small bear. This should be enough for the VTL option. Again, this pot also only has two lugs connected to the board, and is not grounded. Ill try grounding the case of the pot and see where that goes.

[SonicVI]

The only reason you'd need to ground a pot is to ground the enclosure if you arent using metal frame jacks. The high pitch whine is coming from the charge pump. Which charge pimp IC are you using?

[mistahead]

I wish Pimp ICs were more common...

Like the newmojo of the digital world.

[Moxienator]

Those Pimp IC's keep smacking around the resistors and whatnot. Unruly lot to say the least! But they also have Pots.....

Sonic, Im using the Max1044A charge pump.

Copy that on the grounding. Thanks!

[Moxienator]

oh yeah, and REAL P.I.M.P. IC's pop Caps. Werd.

Going to noodle around with the Neutron tonight, and see if I can crank the amp to '2' tonight.... oh man, here goes.

I ordered some new pots and such, Im basically just going to clean up the wiring a bit, since its a really nice mess.

The sweep knob is kind of hard to keep in place, so its being replaced by a B25K with 11 detents. I figure that way, my bassist and I can fool around with it and actually dial in the correct "sweep" for the instrument.

I've got some ideas on what I like to call "Weaponizing the Neutron Filter" that I think might actually work.
Using a push/pull pot for bypass and "Peak", and a small second board.
On the board are a trimpot for "Gain" - set at unity gain, a B25K trimpot for "sweep" wired into RX, C14 (two caps in parallel), and R21 leading to the output.
Put jumpers in for "Range" and "Direction". Add a small battery switch that utilizes the "on board" power option, and mount into an instrument.  
Any one tried anything like this before?  

You could even use the original "buffered bypass" of the original! For all the Deadheads in here... thats the key, I think.

[R O Tiree]

Reference the whining sound... is it the charge pump? That operates at 10kHz or lower (depending on the current it's supplying... bigger current draw = lower clock freq). Try it with just 2 x batteries and see if the whining stops. If so, then I might be tempted to change the 7660 charge pump for a MAX1440 - with the MAX chip, you can tie pins 1 and 8 together which multiplies the charge pump clock freq by 6, taking it well ouitside audio range.  The other thing you might try is bigger smoothing caps.  There's a note in the 7660 datasheet about using 100µF caps if running it hard.

[Moxienator]

That sounds great, but I'm already using the MAX1044A chip.

[Moxienator]

OK! We officially have Wah!

I replaced the "sweep" control ( Rx ) pot from a B50k to a B25k that has 11 detents. The wah is perfect.
For any of you working with this pedal using the VTL's i suggest using this setup as it worked for me.
I may try and go down to 10k, just to see what happens.

The detents on the pot make it easy to "reset" the effect if it gets turned by accident, and they WORK.
I was having to fiddle around a lot with the settings, because i would take it someplace and en route, it
would get bumped or jostled and the knobs would be all over the place, but no more.
Its also nice if you want to let someone else use it on a different instrument. They can set the sweep they
like and when theyre done, you can easily switch it back. Realistically, all the knobs should have detents.

[Moxienator]

BUMP!!!

Hey guys! I finally fixed my Neutron issue.

The board was wired correctly, including the charge pump, but the grounds were the issue.

My Neutron has a "sweep" pot for Rx, and a 3PDT true bypass pcb from SBE.

What I did was add a small piece of perfboard to the back of a pot with double sided foam tape (My new best friend) and connected all the grounds to it.
The ground connection were from the Input Jack, Output Jack, and the 3PDT pcb.

This IMMEDIATELY cleared up the high pitched whine sound.

Now I can pull off the 70's Jerry sounds with the SD '59.

[Kipper4]

Do you have a final schematic for this or a build doc please.
This is defo on my build list .
Thanks

[Mustachio]

Here ya go Rich,

http://www.geofex.com/PCB_layouts/Layouts/neutronpub.pdf

It's really a great fun pedal. Theres a few threads and posts about making your own vactrol for this build.

I personally suggest using a 4mm LED with a fresnel lens and the ldr's from tayda. I advise against the Rx sweep pot.

[Kipper4]

Cheers Jim.
I guess you have built this then.
I'm a big reggae/ska fan so I'm thinking this is the ultimate controllable filter for this application.
Looking forward to it.
I'll look up those ldr/led threads

[Moxienator]

Really? I like the RX pot. It lets me dial in the pedal when I change from an SG to a Strat. The single coils seem to lack enough "umph" to drive the filter.

[Mustachio]

I hear ya about the difference when going from single coils to humbuckers. But it seemed better to just turn the gain up on the pedal and adjust the peak range to taste which is subtle.

When I built mine I used sockets for the led/ldr and Rx . I used a 50K pot to adjust Rx and played with it a while and found there was a sweet spot that sounded best to my ears and popped in a resistor as close to that value as I could and it worked perfect!

Now if you use sockets and an LED you can look and see what that Rx is doing to the LED , to high the LED stays lit a little to much leaving you at the upper range of the sweep and giving a smaller sweep range. To low and the LED doesnt get bright enough to reach the end of the sweep and limits your range again. That's why I think the sweet spot is the way to go , set and forget.

Like you mentioned if the Rx pot gets moved around from transporting or bumping it you might loose that perfect sound when  ya get to your gig and not have enough time to fine tune it before your set starts. I like pots with detent's and its a good idea to keep your settings in place

What about a on/on dtdp switch with a set resistor for humbuckers or single coils ?