More Neutron Filter Questions

[primalphunk]

1. Has anyone managed to make a nice sounding Neutron filter using the H11F3 option?  I have been reading all I can find here at this site about this project and so far it seems that the two H11F3s may not be the best way to go.  Mine is not finished yet but I'm dreading the very real possibility that I may have serious problems when I finally get to test it.  

2.  Are there known errors in the wiring for the switches of RG's neutron filter pdf file?  It seems like one of the DPDT toggle switches is not being used fully.  Here's a link to that pdf if you are curious.  http://www.generalguitargadgets.com/v2/diagrams/neutron_filter.pdf .  As with my last question it seems that some earlier posts on this topic hint at the possibility of some kind of a problem so I am just taking a shot in the dark at where that may be.

[primalphunk]

Hmmmm...Guess my questions are unbearable stupid.  Anyone have time to help someone who should probably still be on the bunny slopes?   :?

[R.G.]

1. Has anyone managed to make a nice sounding Neutron filter using the H11F3 option? I have been reading all I can find here at this site about this project and so far it seems that the two H11F3s may not be the best way to go. Mine is not finished yet but I'm dreading the very real possibility that I may have serious problems when I finally get to test it.

Then bag them and use the LED/LDR options. It's not worth dreading. I put the H11Fxx in there for as many options as possible. The H11 stuff has problems with signal level and gets distorted. However, in this application, the distortion is not all that bad. I stuck one in on my test model. I didn't like it as much as the LDRs. So don't do that.

Better yet, put a 14 pin socket in that position, use a 14 pin header for the variable resistor elements and make a couple of different ones to try. That's why the layout is done that way.

2. Are there known errors in the wiring for the switches of RG's neutron filter pdf file? It seems like one of the DPDT toggle switches is not being used fully.

You're right - the switches are not being used fully. However, since a DPDT toggle is specified for the direction reverser pot, and a DPDT with only one Throw used works for the capacitor switches, I specified the same switch. You can use a DPST switch for the capacitors if you like.

I got an electro cap turned around in an earlier version of the board, but I think this one's been pretty well worked out by now. Lots of people built it before I licensed it to GGG.[/quote]

[primalphunk]

Thanks for the response RG.  I stopped dreading my likely failure with this project and went ahead with the thing using the parts I originally bought.  After trying my first run with the h11f3 and getting way too much distortion I have decided to get the Hammatsu(sp) opto trip from small bear and I also think I need to try a different chip for the charge pump.  Mine is whining a little even after the chokes.  Do you know if the Max1044 sold at Small Bear is the right one to go to?  

I posted my first run build report and I think these two things may just polish it right up.

[yano]

If you require bipolar power, the MAX1044 will do the trick, I've never ran into problems using these.

[gez]

If you're just going to run guitars through this effect then perhaps you might consider re-jigging the circuit for single supply.  Recently I've been running SVFs on single supplies and have had no problems at all with headroom, I even got away with a 5V supply and CMOS op-amps (not that I used it in the end, but you don't need huge headroom in these circuits if you're just using it for guitar).

[primalphunk]

If you're just going to run guitars through this effect then perhaps you might consider re-jigging the circuit for single supply.  Recently I've been running SVFs on single supplies and have had no problems at all with headroom, I even got away with a 5V supply and CMOS op-amps (not that I used it in the end, but you don't need huge headroom in these circuits if you're just using it for guitar).

SVF...huh?  What's that?  I'm a peabrain that may have just gotten lucky on a Neutron build.  I don't understand the theory very well at all.  Each of the projects that I have done so far is like a dot to dot coloring book for me...  :?  A very confusing dot to dot at that...heheheh

[SaBer]

If you're just going to run guitars through this effect then perhaps you might consider re-jigging the circuit for single supply.  Recently I've been running SVFs on single supplies and have had no problems at all with headroom, I even got away with a 5V supply and CMOS op-amps (not that I used it in the end, but you don't need huge headroom in these circuits if you're just using it for guitar).

SVF...huh?  What's that?  I'm a peabrain that may have just gotten lucky on a Neutron build.  I don't understand the theory very well at all.  Each of the projects that I have done so far is like a dot to dot coloring book for me...  :?  A very confusing dot to dot at that...heheheh

State variable filter. A filter that divides your signal to three parts: low-, high-, and band-pass. The frequency can be controlled both by the resistance and the capacitance. Read "the thechnology of envelope controlled filters" at GEO for more info about EFC's or google for SVF's. You should be able to find something. (If you are intrested...)

[Bilbo]

Hullo All,
my first post to this very helpful site. I am gathering the parts to build a Neutron with single battery supply, in the Optional Parts there are listed 2 680uH inductors. Where do these go? is it J8 and J9

Thanks

[petemoore]

  LDR's are cool in this one.
   There are many ways to make light:
  Env Detection of guitar signal is one.
  Envelope dection of anything else [like wah treadle is another.
  LFO: wah sweeping is an alternative.
  And there are various ways to accomplish and or integrate these interactions between the Neutron LDR[s and LED[s.

[R.G.]

in the Optional Parts there are listed 2 680uH inductors. Where do these go? is it J8 and J9

The inductors replace the jumpers to the lower left of U3. You can and maybe should replace the MAX1044 with an LT1054. The MAX1044 has been found to die when +9V in gets a bit high. The 1054 is more durable.

[Bilbo]

Hullo, Bilbo here again,
I have nearly finished my Neutron Filter but am not quite sure how to wire the VTL5C3 thingys. I have a Rev.1.01D pcb.
Not quite clear on the pdf, but as I am only learning could one of you kind people advise me.
Kind regards
Bilbo

[K Zustang]

Hi there,

I am also on my way to building the Neutron on the same GGG PCB.
I bought all the parts except for the optocouplers and after reading every square ft of material on this thing I might go with the VTL5C3 option.

1. I am not quite sure I understand exactly how to do this. 2 H11F3 parts would have been the best option if it worked for everybody, but so many people report bad results that I believe I'll play it safe. It is option 3 on the PDF file and it requires 2 LED/LDR optos like the VTL5C3 which are available at Small Bear.
pretty much straightforward it looks like the two parts which look like each has 2 connections connect to the 8, 10 and 12, 14 pins of the "14 pin" U100/101.

2. Should these parts be matched? is there anything someone can assist as to tips on how to mount them?

3. Would anyone recommend something else which can be found these days at Small Bear?

Thanks
Doron

[Mustachio]

Hey I've been meaning to post about this subject. I built RG's neutron a few months ago and went thru all the reading I could find and did some testing with diff components.

From what I remember RG mentioned something about the forward voltage of new leds compared to old leds back when mutron first made this circuit. I first had used a newer style high bright blue then an amber led with 2 LDR's and I got it to work after reading another guys info on his diy mutron ldr/led roll. To get it to work right with most regular leds you need a 120K or so resistor compared to the 10K the build doc calls for.


The search function isnt working for me right now so I cant pull up the thread. But it was a super smart guy on here that made his own dual ldr/single led and used an epoxy resin inside a fuse case body. My theory is his worked so well because the epoxy will defuse and spread the light out to be even across both LDR's. and he also was the one to mention using a 120K resistor with this set up. Which worked for me and sounded great but it seemed to have too much gain and didn't seem perfect even though I could get a good sound in low pass but not great in bp or hp.

In RG's info he mentioned using an IC Socket with a cover which I could not find stocked anywhere and he mentioned putting something reflective inside this is what lead me to the idea of spread out defused light. and why the epoxy worked so well for the other guy.

I recently ended up ordering a bunch of different leds from mouser with an order to do some testing . This is why, and what it may benefit in this circuit. So as well as a lower forward voltage this led I found is a flat top with a Fresnel lens. So it will spread out the light instead of being more intense in the center like most leds we use. This LED works great with a resistor under 10K I think I settled on some where between 6-8K it seems to hit both ldrs even inside some shrink tubing. I didn't use any epoxy either just 2 ldr's and one led and my Mutron III now sounds perfect and works as close to the original that I can tell in all modes BP and HP are very usable now.

Here's the model number of the LDR's you can get from tayda or thaishine only ones they stock but you can probably find the same or similar from small bear who is a great supplier.

KE10720
this is where I got mine

http://www.ebay.com/itm/3-x-Photo-Conductive-Cell-650nm-LDR-RADIAL-5mm-USA-SELLER-Free-Shipping-/320943738397?pt=LH_DefaultDomain_0&hash=item4ab9bcce1d

The LED I used which works best for me at least is a Lumex Here's the mouser part number 696-ssl-lx433GD

And heres the link to the LED

http://www.mouser.com/ProductDetail/Lumex/SSL-LX433GD/?qs=sGAEpiMZZMs4quMj8r4lmjaw8B5qKY8aX7D4mSD%252b5KI%3d

Id imagine other leds will work well too look for the viewing angle wider the better Im guessing.

Besides that bridge pins 1 and 8 on the charge pump IC and make sure its a SCPA version which has this high freq boost to take the high pitch whine above audible hearing.

Ive read mixed results about the vtl5c3 and its a bit expensive although small bear has a cheap alternitive to the vtl5c3 I want to try soon.

http://www.smallbearelec.com/servlet/Detail?no=1255


I tried at least 5 diff types of LEDS 5 diff LDR's and a VTL5C2 and a VTL5C7 Which had to have the larger 120K resistor at RX instead of 10K. The freshnel led and the KE LDR's are what worked for me best ,I hope this helps ya. Good luck its one of my favorite effects!

[K Zustang]

Wow dude, thanks,

I really want this thing to work right.
I'll check out your remarks and give it a shot.

1. Small Bear's answer was that the work-alike of the VTL5C3 which costs about half, has similar specs.
    It seems like a good choice so I'll order the parts. If it doesn't sound right I'll also go the LED/LDR photocell path. will VTL5C3 also require Rx to be as high as 120k?

2. How can I know if the charge pump using Max1044, LT1054 or 7660S is an SCPA version?

Thanks again, sounds like you nailed it. I will probably need some more help down the road.

Doron

[Mustachio]

Here's a pic of my neutron guts



The big blue thing on the left is my home made LED/LDR

I'm not sure about the VTL5C3's resistor because I haven't tested one I just tried the 2 and 7 series of Vactrol's. I suggest using sockets for the RX I used the lil snap in-line sockets and cut off what ever I need. You can see it in the pic I posted. In the pic It had a 130K resistor I believe I was before I changed the LED and resistor but using the same LDR's and still the same housing so it still looks the same as this pic just 2 parts swapped ( the new Fresnel LED and 8.1K resistor I think I settled on.)

If you socket RX you can use 2 poles of a potentiometer dial it in and then take it out and measure the pot with it in the same position make sure you don't move the dial. then replace it with a resistor as close as you can get to that reading.

And for the charge pump IC you can use a any of the ones you listed but they all have different suffix Some are EPA and CPA but the ones with an S before the last letters is for some super boost option that basicly ups the frequency above 10K so its not audible here's one I recently ordered

http://www.mouser.com/Search/ProductDetail.aspx?R=TC1044SCPAvirtualkey57940000virtualkey579-TC1044SCPA

I used the TC7660SCPA as well works great just bridge pins 1 and 8 Under the board with a small piece of wire.

For the range pot I believe I used a 200K instead of the 150K cause their hard to find but the 200K from mouser works just fine.

Good luck if I can help later down the road just let me know.

[K Zustang]

Thanks man,

I am amazed at the speed I get your replies. This means so much when one is so eager to get answers.

1. your image and the homemade LED/LDR sure looks really cool (!!!) and I will definitely bug you some more if the VTL5C3 yields unacceptable results. However SD at SmallBear assured me that it will work. It seems like the implementation is quite simpler on a 14 pin socket. Do you think the the VTL5C3 should be somehow connected together? should they be covered or is everything going on internally there?
2. The ICL7660S I already have and used for an 9-18V Charge pump a few months ago seems like it has the frequency boost you were talking about. pin 1 connected to +V (pin will boost the oscillator freq from 10kHz to about 35kHz (your chip boosts to 45kHz!). It seems it will do the trick...thanks for the tip.
3. I bought 100k dual gang pots to make a 200k pot instead of the 150k....thanks for the tip.
4. I will also use the 680uH coil chokes on J8 and J9....are these really necessary?
5. I will put a pot for Rx and maybe decide to keep it if the range proves useful. I really want it to be good for guitar, Bass, Harmonica and Keyboards. I thought that each instrument will require different frequency so I might need a switch to get different resistors for different inputs....what do you think?
6. Do you think it would be possible to implement a LED which lights with the envelope and use it as an external indicator on the enclosure?
7.... and last.... I really would like to get this unit to get the envelope trigger from an external source (like the drums mic or an LFO)...do you know where I can stick a second input to the circuit with an input buffer or something?


Thanks again,
I am starting soldering tonight and waiting for some more parts to arrive later on this week.
Hoping to share some good results soon....

Doron

[Mustachio]

Hey no problem I've been meaning to post the info about the led/ldr stuff for a while and always forget. Seen this thread was revived with some one asking so I figured id try to help.


1. The VTL5C3 should work fine just plug it in and go no need to do anything to it like covering or anything .

2. Yup the 7660S is the right one

3. Yup that'll work

4. I don't think you will need the chokes once the charge pump is jumper'd for boost. I didnt need em. But you never know.

5. I dont think leaving a pot for RX is a great idea I know Ive seen it done but I think most people find theres just one sweet spot . And different insturments will just have a diff gain at the input which will be controled by the gain pot so really no need for anything other then a single resistor at RX once you find the sweet spot that works well with your LED/LDR-Vactrol set up.

6. Yes you can add in an LED that lights up and fades out with the effects signal. I think you can right off the area where the led side goes for the vactrols. If you got sockets in there like I do its easy to experiment and pop in a few components.

7. I don't know enough about triggering from external source to give you good info maybe some one else here can help.

Good luck this was a fun project! and one of my favorite of all time pedals!

[K Zustang]

Thanks for your help Mustachio,

OK....got the Neutron up and ready, checked my soldering and rechecked all connections. Put a 50k pot on Rx (Smallbear suggested 20k-30k with the VTL5C3 work-alike).


Turned it on....and what do you know....IT WORKS!
I played around with Rx to get the sweep right and it sounds OK. t is around 17k-20k according to my taste. No whining from the DC power supply and the overall playability of the unit is quite good from first impression.

A few things I noticed right away which need attention.
1. The connections of the Gain and Peak pots are reversed when going according to the GEO/GGG schematic. This is although I did get a 1M rev. log pot. No a big problem to reverse the lugs.
2. The Gain is very sensitive.
3. I get distortion when envelope is fully open. I tweaked Rx but apart from changing the sweep range it didn't affect the distortion. Clean sound is achieved by playing softer or rolling off the volume on the guitar.
4. The overall circuit is quite noisy. there's a noticeable hiss and some RF noises which may be attenuated once I box the circuit.

I am continuing to tweak Rx using Single coils, Humbuckers, vocals, keyboards and Bass guitars. I hope I can get this thing to sing perfectly.

Any suggestions?
Thanks,
Doron

[Mustachio]

Nice! Congrats on it working.

Ok here's a few things to try , might work might not.

reverse the wiring on your pots so they work the right way. should have a lil different sweep.

The gain on mine seemed sensitive as well, but reversing the wiring having a diff sweep seems to make it a bit better. And try lowering the RX to maybe around 10k-12k this will be less sensitive, but now raise the gain pot so it triggers the sweep stronger. I think there's a happy medium in there between the 2. Maybe ...

There is a small amount of distortion or warble even on the original I think it sounds great on mine but its not very strong or apparent I wouldn't really call it distortion its more like diff frequency's muddying up in the background. Yours may sound diff then mine though. Mine sounds pleasant and pretty clean but if I strike a nice Dminor chord in the second position and let it ring out it has a nice warm growl.

I do think mine may have sounded more distorted before I fine tunes up different areas of the pedal like pots and rx and getting the ldr/led set up right.

The noise is probably the charge pump IC (its like a high pitched whine). You got the right ic's the scpa version right ? You will have to bridge pins 1 and 8. Then the noise will be gone and it will be silent and probably solve lots of issues with noise and maybe make the distortion less apparent and like the smooth growl since some of that power noise will be gone and not accentuating the distortion. I just soldered a clipped end of a resistor lead on the under side of the board between pins 1 and 8.

Its probably my favorite pedal good luck fine tuning it man!