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Hi, everyone. 

I used to hang out here in a small way some years ago, but got really busy and haven't had much spare time to drop in for a long time.  This is a great group and one of the best forums anywhere on the 'net, so I hope to be able to spend more time here as I come up for air after being really, really busy for a long time.  The purpose of my post is to make it clear that I now have an affiliation to disclose.

Many of you know that building pedals can go, well, shall we just say "beyond what you first intended".  Perhaps even beyond that.  That's what has been keeping me busy for some time now.  Somewhere along the way, I had an idea about building pedals that grew and morphed into something bigger than I originally planned.  I'm now in the early stages of launching that idea as a business.  What makes what I'm doing a bit different from most others is that I'm only developing rack effects, no pedals.  You can check it out at www.gerlttechnologies.com.  I know I don't need to explain it to this group – you'll get it right away, everyone does.  I've taken my gear to a few guitar shows to get early feedback, and am happy that the feedback has been overwhelmingly positive from players, about both the idea and the sound.  Would love to hear your comments as I begin to spread the word.  The website needs work, but basic info is there, except product videos – still have to get going on those. 

Anyway, that's it.  I hope you find it interesting.  This is one of my first public postings about what I'm doing, and it seems only natural to do it here where my effects-building interest began to develop into a serious condition that probably needs some sort of treatment, if it is not already too late.  If any of you are in the Dallas area, I'll probably be at the Dallas International Guitar Festival again this year in May, although I have some scheduling issues to sort out first.  If you're there, stop by the booth to check it out in person and say "hi".  I have some pics from the shows I've attended at my Facebook page "Gerlt Technologies".  I don't know what's in store for me, but I've really been enjoying what I'm doing, and being able to share it with others.

Cheers,

Bill

Hey, flanger and MN3007 experts out there.  I've goofed something up and am stuck trying to find the fix.  I'm looking for any hints on where to go next.

I have been debugging on this for days, so I have tried many, many things and have a lot of interesting notes and details I could share.  But I keep ending up stuck at the same place, so I need to get kicked out of my rut.  I'll try to leave out as much as possible here but the specific details I'm providing are all a part of my problem.  Feel free to ask anything else.  I will not be offended - embarrassed quite possibly, thankful most definitely, but not offended :^)

First, I'm building a Deluxe Electric Mistress.  I have my own boards.  The LFO is on a separate board from the main FX circuit.  I have built a few of these recently, and they all worked first time.  Then I made some board changes to try some mods in the mixing and output section.  While I was at it, I switched from using a single bias trimmer for opamps and BBD to separate ones, adding the requisite bias resistor, dc blocking cap, etc.  I also added ground plane pours on both sides of the board.  Now, when I build the board, I get no MN3007 output no matter how I try to bias it.  I also built a new LFO board to go with the new FX board.  All I did on the new LFO board was add a CLR and blinking LED, and ground plane pours on both sides of the board.  Those are the only changes between the working and non-working boards.

Since I have working versions using earlier versions of the board, I can try out MN3007 chips.  I am using known good MN3007 chips that work fine on other boards.  I can also switch to one of my earlier known good LFO boards, to eliminate the entire new LFO as a problem.  However, my new LFO board does work fine with an earlier FX board.  An earlier known good LFO board does NOT make my new FX board work.  Just FYI, the LFO is used by some Electric Mistress or Deluxe Electric Mistress, I can't remember which.  It is very similar to the one in Current Lover, and has the CD4049 on the end to drive the BBD.  And the timing cap is adjusted to get the speeds I want for my MN3007.  Anyway, because of this info, I believe I can say that neither the LFO or MN3007 are the problem.   

Here's the data that has me stuck.  These are the measurements taken directly on the pins of the MN3007 in my non-working board.

                pin 1 (ground):                  14.50V 
                pin 2 (clock 1):                   aprox 8.0 – 9.5V as the LFO varies, with Filter Matrix switched to manual, I get 30KHz at the extreme slow end and 340K at the extreme fast end (sometimes I go as wide as 25-440K).  I can hear the clock throbbing.
                pin 3 (input):                      my bias lets me adjust from 0v to 14V (I measured it).  I have clear, strong audio signal at this pin
                pin 4 (Vgg):                         goes to a 10uF cap to ground (oriented correctly), and usually has about 1.0 – 1.5V, sometimes as low as a few 100 mV if I've been measuring it and discharging the cap
                pin 5 (V+):                           0V
                pin 6 (clock 2):                   identical to pin in all measurements
                pin 7 (output):                   0V
                pin 8 (output):                   0V

When I search for output signal while adjusting the bias, once in a great while I get a little heavily distorted clock noise when the bias is somewhere near 4.5V.  But it goes away very quickly, like it is being drained to ground or fading out somehow.  I cannot make it happen twice.  Once it stops, then I can't get it back until "later" – letting it sit, power cycling, something will eventually "reset" it and I'll hear it again briefly.

This always reminds me of the new ground planes I added.  I've gone back and visually followed every trace and hole looking for ground plane issues on the FX board (new unpopulated one).  I've even done continuity checks on every single hole.  All seems well.  On my board, there is a trace connecting pins 7 and 8, which then goes on to the rest of my circuit through a cap.  Not only is there no sound at pins 7/8, there is nothing at or past the cap (taking all my new board mods out of play except for the biasing and ground plane changes).  Right now I am testing a board that has nothing populated past that cap. 

Being suspicious of a bad ground plane connection, I tried 2 things.  First, I removed the MN3007 completely and put a jumper from pin 3 (input) to (pin 7).  I get audio at pin 7 and after the cap.  The board is not grounding it out.

I also reseated the MN3007, but with pins 7 and 8 bent out so they did not seat in the socket.  Then I tried to bias.  Almost, but not quite, the same thing happened as before.  I actually got audio on the output pins very briefly as I turned the bias voltage down toward 4.5 – 5V.  But it faded away just like the "distorted clock noise" did with those pins fully socketed.  Could be a fluke, or it could be that whatever is happening just happens a little faster when those 2 pins are socketed.  I expect the "heavily distorted clock noise" is really faint, heavily distorted audio.

I also replaced the 10uF cap from Vgg to ground with a jumper.  Since I've done that, I haven't heard even the little bit of fading clock/signal noise that I used to have.  But I didn't always have that noise before, so this may not mean much.  The only difference I noticed after this change is that instead of 0V on the output pins, I have around 150mV.  But that may be coincidental.  I think I've seen tiny voltages like that from time to time, which keeps me thinking that I'm somehow draining to ground somewhere.  But that somewhere seems to be between pin 3 and pin 7/8...

I also backed out my biasing change.  I took out the resistor on the input line to my bias trimmer and replaced the DC blocking cap I had added with a jumper.  My bias is now coming in on the output from an opamp, as it does in my working board.  No difference at all, other than which biasing trimmer I use to search for signal.

Also, note that all my MN3007 measurements (except the missing output on pin 7 and pin are identical to measurements I've taken from one of my working builds on the previous board version.

I've built a lot of pedals, so I'm careful and reasonably proficient, but still have much to learn.  I've checked all my usual methods of goofing up, many times, carefully.  I've removed/replaced components, reflowed solder, looked for bridges/bad joints, and lots and lots of debugging.  I've even built multiple of these non-functioning boards to further reduce the chances of soldering errors and bad components.  I'm only populating the minimum part of the circuit needed to test for MN3007 output.  Everywhere I have probed or tested, I seem to have good/expected values with the exception of those two output pins.  This is true for each board and experiment I've tried.  I haven't found anything wrong anywhere.  That just means I'm overlooking or misunderstanding something, of course.  I've even been suspicious of my probe, and tested it :^)

So that's the hole I'm stuck in.  Everything seems good for my known good MN3007, yet I can't get it to give me any output.  Everything feels like some sort of grounding problem, or just a lack of effort on the part of my MN3007 :^)  I'm sure there is something I'm not measuring that matters on the MN3007 pins.  What could I look for there that would shed light on why the MN3007 refuses to pass signal?

Hi,

I have this version of an Electric Mistress on my breadboard:  http://www.metzgerralf.de/elekt/stomp/mistress/images/1976-electric-mistress-v2-schematic.gif

I'm trying to stay true to the original, but there are a few differences:

I'm using an MN3007, wired in like Current Lover, including the output filtering and transistor, CD4049, etc.  However, I didn't include the trimpot on pin3 to the BBD.  In this schematic, the signal is already biased coming out of the opamp into pin3. 

I'm also running at about 14.7V regulated.  My power comes from an LT1054 charge pump and 15V regulator.  My bias sits at 7.35V.  I don't need the LM741/BC309 stuff as a result.

In the LFO I subbed in a 3906 for the BC177.  I tried other PNPs and HFEs, but none of that seemed to matter.  Also, in one place there is a 50n cap and in another a 0.5u cap.  I used 47n and 470n instead.  Otherwise, I've duplicated everything else.

It seems to be working.  I have modulated output, controlled by the Rate and Range.  But there isn't enough flanging.  My voltages and behavior are in line with what they should be, everywhere except at the BBD pins 7 and 8.  I have 10V there instead of my bias level of 7.35V like I have at pin 3 - ?   At pin 2 of the MN3007 I get rates of 25-160KHz.  Should be 20-200KHz for the SAD1024, I think.  So I'm a little low.  Plus it needs to be doubled since I'm using the MN3007 with a longer delay.  I'm not familiar with this LFO, but nothing I've tried has adjusted my clock range correctly.  What do I need to do to go from 25-160KHz to 40-400KHz?

I'd like to understand what sets the high and low frequencies so I can adjust them to other values, too.  Any help is greatly appreciated!

Reading the Rage Quit thread reminded me of a couple of times I had problems.  Sometimes (maybe every time?) they are really frustrating stupid things.  Here are a couple of mine – what are yours?

1.  Built a pedal that worked, but was noisy compared to the original vintage version I had.  Debugged on it for a couple of days and nights trying to figure it out.  In the process, tried it in a different location to use a different amp, where it was silent as a mouse.  Turned out I was testing near something that was generating a lot of EMF (big swimming pool motor on the outside of the wall) – everywhere on the planet except where I was testing, it sounded great.

2.  Drilled a hole for a pot that was a little rough, and had to touch it up with a file.  When I finished building the pedal, it didn't work.  Again, debugged for a couple of days, trying everything under the sun, including using a magnifier to look at solder joints, find solder bridges, etc.  At one point, picked up a stronger magnifier and found a microscopic aluminum filing wedged between the solder joints on a electro cap (those pads are really close together).  It was so small I couldn't see it with the other magnifier.  Dusted it off and it worked just fine.

3.  My second Aquaboy build didn't work.  It's complicated, so there's plenty to debug there.  Again, spent a couple of days trying stuff, to no avail.  Finally decided to replace the compandor chip, about the only thing I hadn't replaced at least once.  I had good voltage readings on every pin and no reason to replace it, but sometimes you just gotta try stuff.  When I took it out, I found one leg was folded up underneath it.  I was getting my voltage readings by touching the tops of the legs with my DMM probe.  So probably the only time that chip worked was when I pushed that pin down with my DMM to get a voltage reading, causing the bent leg to touch the pin in the socket.  Unbent the leg and the pedal worked fine.

#@$%^!

Hi,

I finally got around to breadboarding a graphic eq I had been intending to build.  It has 7 bands and a master level.  Basically a GE-7 with regular bypass switching instead of all that Boss switching cruft, with upgraded parts, running at 15v (might be able to push 18, depending on final opamp selection).  I had scored some slider pots for it a long while ago.  I have one of those black 1590BB enclosures that is sort of textured on the outside, so there is plenty of room.  But I haven't come up with a good way to cut the 8 slots.  They have to be pretty accurate or the sliders won't work and look nice, of course.  Have any of you done that before?  How did you do it?  I've had a few ideas, but none that I think will be accurate enough to try.  Maybe I should be looking for a dead 8-slot EQ in nice cosmetic condition    When I had it on my breadboard, I used regular pots to get it going.  That's kinda clunky to use compared to the sliders, especially when I would have to put them in 2 rows to fit across an enclosure.  Also considered a single large rectangular hole, using epoxy or something to make a single assembly out of the sliders, but that's just plain ugly.

Probably the best idea I've had so far is to start each slot by drilling 3-4 holes in a line to create a long hole big enough to get a jigsaw blade into so I could finish the slot with a jigsaw and a metal cutting blade.  I think the blade width would be about right for the slot width.  I'm doubtful that I can control my jigsaw well enough to get nice slots, though.  There is a lot of vibration and tilt to control on a small surface and it will definitely mess up the finish on the enclosure.  Have seen a handle that accepts jigsaw blades (makes it like a keyhole saw) so I could cut them slowly/manually.  That's kinda where I'm at right now, but I'm doubtful it would actually work that well.

Also thought about using a nibbler, but I can't make a clean cut with one, even if it would cut the enclosure.  The one I have would make too wide a slot. 

Most rotary blade tools would probably leave non-vertical cuts at the ends of the slot.  I have to be careful there because I need tiny screw holes right at the ends of the slots to hold the sliders. 

I have some rotary blades that look like drill bits that you can use with a drill to cut sheetrock.  I could put them in my drill press, but I'm not sure they are up to cutting metal and they don't really work that well in softer materials - pretty rough cuts and difficult to control. 

Or maybe a small file - yuck.  Will probably need one anyway to smooth things up after whatever I do...

I know someone that worked in a lab that had a really cool 3D printer that printed titanium or some exotic metal.  Maybe I should sell my house and get one of those - no more drilling enclosures for me!

Hi,

I'm thinking about getting a digital scope, but I'm worried about something and thought I'd ask about your experience with them. 

It seems like most affordable digital scopes take low resolution samples (typically 8bit) at a very high rate, which is probably geared for use on high speed digital circuits. If you are using an 8-bit digital scope for audio work, do you find the granularity of the data values to be acceptable? I don't mean "not bad for the price". I'm trying to understand, cost aside, how well 8bit scopes work for audio analysis. I'm not worried about small display resolutions, since you can typically zoom in until you hit your data resolution.  I'm specifically asking about the sample granularity, not the sampling rate or bandwidth. Decent consumer grade audio recording gear normally gets 24bit samples at 96K or 192K so it sounds good to your ears. 8bit sampling seems crude by comparison.  For a +/-5V AC signal, that's a 10v range divided into 256 values, or about 0.039v resolution in your data.  24bit sampling would give you about 0.0000005v resolution.

Can you clearly see what you can clearly hear, like the difference in a circuit if you swap values of caps in a fuzz feedback loop? Or two different types of clipping diodes in a distortion pedal? If you make small component changes to your pedal, would you expect to be able to see the result on the scope? That sort of stuff.

I'm trying to decide if I get a digital scope, whether 8bits is good enough or I should instead save up for a 16bit model.   I would think 16 bits would be OK.  I hardly ever have pedal stuff over 18v, so let's round up to 20v AC, or a 40v range.  Dividing that by 65536 gives resolution of around 0.0006v. 

If you are happy with your ability to see details with your digital scope, what model are you using?

Thanks!

Hi,

A while back, I built a 15v MN3005 AquaBoy.  All is well with that, very well, in fact!

I also built a 9v AquaBoy to try MN3205s.  It has stock values from the parts list, with jumpers for R55 and R27.  But I can't get any of my 8 MN3205s to bias.  I can't get guitar signal on pins 3/4 at any combination of bias, clock, and cancel settings.  Some even kill the input at pin 7.  I tried biasing them individually in the first BBD position.  None passed signal to pins 3/4.  Then I tried pairs of them, because I've had cases where a single BBD wouldn't bias if the second one wasn't socketed.  But even in pairs, none would bias.  I can bias MN3208's and BL3208's in there OK. 

Is there anything that might cause this, other than bad MN3205s?  There are some comments in the instructions about some resistor tweaks for R27 and R55, but they specifically mention V3205.  Other than getting the power and jumpers set correctly, I didn't see anything that looked specific to MN3205 (or MN3208 or BL3208).  I did try 100K instead of a jumper for R55 and 470K instead of the R27 jumper.  That didn't get the MN3205s to work, either.  I saw something about tweaking R18 and R26 (should that be R19 and R26?), but haven't tried that yet. 

If the build is working fine with 3208s, should I be able to pop them out, replace them with MN3205s, reset all the trimmers, and be good to go if the MN3205s are good?  Or will some tweaks maybe help?  Are jumpers for R27 and R55, and 82K for both R19 and R26 correct?

Thanks!

Hi - Just build my second AquaBoy.  First one was an MN3005 build - it's excellent!

This one is a 9v build to try MN3205s.  I'm powering it with a RoadRage board (LT1054) and a 9v regulator to get nice clean power to it.  Stock build with jumpers horizontal for 9v build.  R13, R14 are 10K.  R27 was 470K, but is currently a jumper.  R55 was 100K but is also currently a jumper.  R37 is 20K.  R56 is 470K.  R58 is a jumper.  D3 is empty.  MN3102 clock.  NE570.

As it sits, I have it running OK with MN3208's.  I cannot get any of my (4) MN3205's to pass any signal on pin 3/4 when only 1 (or both) are socketed.  If I leave a working MN3208 in place for the first BBD and add any of my MN3205's in the second position, not only does the MN3205 not pass any signal, but the signal is completely trashed coming out of the first BBD.  Even the input to the first BBD (pin 7) becomes just loud noise.  Take out the MN3205, and the single MN3208 does what it should.  None of the MN3205's I have will pass signal in either BBD position.  I've learned that sometimes you cannot get them to bias without having both socketed, but even with both socketed, I can't get any signal through them.

Only other oddity I haven't addressed is that the feedback runs away with the knob at about noon, even if you don't play a note.  This happens with the T1 trimmer set to kill all feedback (full CCW).  I expect my signal is too hot somewhere.  Maybe the R27 and R55 jumpers need to be resistors again to knock a little off

It is possible that the MN3205s are all bad, of course.  But before I conclude that, is there anything unique to the MN3205 build that I should try?  It isn't mentioned much in the instructions.  Since I can run with a pair of MN3208, the build itself is probably OK.  It also runs with a pair of BL3208.

Suppose I wanted to build an AquaBoy DX, but without the modulation.  Is it as easy as:

1.  Leave off everything shown on the schematic in the LFO section AND
2.  Leave off the vactrol, depth pot, and R56 from the Clock section of the schematic.

Thanks!

Hi,

My Aquaboy DX build is having problems.  I think the problem is I missed a couple of points that weren't clear to me in the instructions.  I want to verify those points, as well as get some opinion on whether my misunderstandings are the source of my problem.

Some of my build options, FYI: 
    15v RoadRage with LT1054
    MN3005 BBDs
    3101 clock
    jumper R27, R55, and R58
    R56 is socketed with a 470K in it
    R13 and R14 socketed both with 33K
    R50 and R51 both 8.2K
    NE570 compander
    VTL5C3 vactrol

Everything else is as listed in the BOM.  I put in the extra LED and it adjusts as expected with the Rate knob.  Switch wiring works as expected.  Have triple checked soldering.  Used a meter to measure each component value before soldering it, so pretty confident about part values/placement.  I've built quite a few pedals and am pretty careful, since I've found it's much easier to take the time and do it right than debug and fix it :^)

The symptom is found when trying to set the trimpots.  I set the controls as described in the doc with the 2nd BBD removed.  I used my DMM to "preset" the clock trimmer to 6.5K, but it wouldn't adjust down quite that far.  So I put it back in the middle, which is around 8.5K.  Using an audio probe, I can follow my input signal through to pin 7 on the first BBD.  But I get loud whining and maybe some very, very faint buzz that might possibly be some input signal coming through on pins 3 and 4.  But there is no easily recognizable signal coming through from the input on pin 3 or 4, and no signs of any delay - loud whining instead.  The bias for that BBD does nothing to the sound on those pins.  Adjusting the clock trimmer does change the sound/pitch of the whining.  Voltages on the first BBD are:

pin1 - 8.6v
pin2 - 4.3 v (loud whining sound)
pin 3 - 5.9v (loud whining and maybe very faint buzz/signal)
pin 4 - 5.9v (loud whining and maybe very faint buzz/signal)
pin 5 - 0
pin 6 - 4.3v (whining)
pin 7 - 4.2v (good guitar sound, altered by compander a bit)
pin 8 - 7.9v

I'm obviously not getting my 15v to the BBD.  I know my RoadRage is putting out the 15v (measured it).  The whining frequency matches the clock at around 8.5K.

In searching the forum, it appears that D2 and D3 should both be left out for a 15v MN3005 build.  I think that is my mistake in reading the instructions.  I have both D2 and D3 in place.  I believe that is chopping the power to the BBDs, clock, etc. 

But before I remove those two diodes, I want to verify that I should leave out both D2 and D3 and leave those spots on the board both open (no jumpers).  I believe that is what I should have done.

Secondly, any guesses on whether those diodes (low power) could cause the symptoms I'm seeing?  I tried several MN3005 and MN3008 BBDs and they all behaved the same way.  I don't have another way to test the BBDs, but I think they are OK, particularly the MN3008s.  All 12 BBDs I have could be bad, but I'm discounting that for the moment, particularly if the low voltage could cause my problem.  Maybe a better question is whether anyone happens to know if bad BBDs might behave like this?  I suppose before I remove those diodes, I could test with an MN3205, BL3208, etc, but I'm not sure that's really safe for those other BBDs, or even useful.

That clock trimmer would only get me down to about 6.7K when I turned it all the way.  Not sure if that'll be a problem, or if maybe it'll change once the diodes are removed.

Thanks for any words of experience!