Ludwig Phase II Clone Debugging and Miscellany

[R.G.]

So... I guess this means you are ready for the SMD Ludwig then Jimmy? 

Be very careful what you want...

[pinkjimiphoton]

lol.... naaah, greg, i'll start digging thru the scrap piles at the dump for components by the light of the silvery moon

[Govmnt_Lacky]

So... I guess this means you are ready for the SMD Ludwig then Jimmy?  

Be very careful what you want...

I would give it a go for sure!  

Building one that is.... I can't design for crap 

[pinkjimiphoton]

you just need a breadboard, and a willingness to let the magick smoke out, greg

that said, built my very first "commercial" fuzz of my own design tonite. if *I* can do that, i think pretty much anyone with opposable thumbs can do it.

[Keppy]

Here's the list of needed documentation updates since my earlier posts disappeared:

1) Fix the swapped inputs on the wiring diagram.
2) Add a 13-15V zener from R64/39/40 (cathode) to ground (anode).
3) Switch the labeling on the Fuzz and Animation toggles, unless you want to flip the switch positions to match the original.
4) Jumper R7 when using the 6027 to ground the cathode.
5) First page of the build doc still mentions a 5k rocker pot; should be 10k
6) Pg. 17 refers to the bases of the UJT backwards, though the diagram for the PUT is correct.
7) The square set of holes for Q6 is incorrect.

Mods I dreamed up (but haven't tried):

1) Rocker Bypass: Use a DPDT in the rocker pedal to switch from using the rocker pot to a manual pot set to the sweet spot for "yoy." Swap the two non-grounded legs of the pots. An LED can be inserted in series from the "cold" lug of the pot to ground to keep the wiper from grounding out.
2) Speed mod: Increase C2 and/or the Rate pot to increase the range of available speeds.

Various updates:

I found one more bug in the documentation. CF1 is backwards on the layout. EDIT: I was looking at it wrong. Never mind.

Last year I only tried the 6027 with a flipflop on the breadboard, but I've now built a working Phase II with it, so it's completely verified.

I've also verified the rocker bypass mod mentioned above, with the LED indicator.

The speed mod didn't extend the range significantly. Also, slowing it down doesn't slow down the transitions, it just lengthens the time between them, so extremely slow settings don't sound great anyway.

[Keppy]

Also, check my math, but RF28 looks to me like it's dissipating more than .25W. Two 6.8k .25W resistors in parallel would be well within their rating though.

[Govmnt_Lacky]

Necro update!!

It looks like the 2nd run pdf on Geofx still has an error on the PnP transfer for Q6. If Q6 is mounted to the component side of the PCB then the Base leg is not connected to anything. The Collector and Emitter are fine but the Base is just floating.

This does not apply if you connect it via the trace side.

[digi2t]

Necro update!!

It looks like the 2nd run pdf on Geofx still has an error on the PnP transfer for Q6. If Q6 is mounted to the component side of the PCB then the Base leg is not connected to anything. The Collector and Emitter are fine but the Base is just floating.

This does not apply if you connect it via the trace side.

Email sent.

The second run of PCB's were double sided, with jumper traces on the component side. Unfortunately, the jumper for the B pads of Q6 is not displayed in the build doc, only the trace jumpers. You need to put one in. On the PCB's, the Q6B trace is there.

[~arph]

I still have to build it too... Got the PCB, parts and everything..

[Govmnt_Lacky]

Thanks Dino... I fixed the Q6B issue and it seems to have done the trick.... almost  Sent you an email on the subject but... will reference it here as well for others.

I finished the build and I am seeing good voltage from Q6, trimmers all set to the recommended starting points, and I tuned RF29 so that there was exactly 3.80VDC on the wiper.

I get great formants from all 3 channels BUT.. I am getting bad LFO bleedover when in Animate mode. This is after incorporating the 15V Zener fix.

Looking for recommendations.

[digi2t]

Are you in Fuzz Repeat mode?
What is the level of the Fuzz Repeat pot?

The diode is there to prevent percussion repeat bleed into the audio when in FFM mode. In certain settings, the percussion repeats is part of the charm function.

[Govmnt_Lacky]

Are you in Fuzz Repeat mode?
What is the level of the Fuzz Repeat pot?

The diode is there to prevent percussion repeat bleed into the audio when in FFM mode. In certain settings, the percussion repeats is part of the charm function.

This is with Fuzz off. The LFO bleed is only in the 3 formant channels when Animate is on. When in Parallel, Counter, or Vowel mode I get a nasty LFO bleed when the strings are muted.

One thing I just discovered (going through the build in my head) is that I installed both the resistor AND the trimmer for RF26  I am gonna have to cut out the actual resistor and try tweaking with the trimmer.

Is there any way to cut down/out the LFO bleed in the formants?

[digi2t]

In FFM mode, you should not be getting percussive repeats (tock, tock, tock). Especially if the Fuzz Repeats pot is at zero.

RF26 is either trimmer or resistor. If memory serves me, if using the trimmer then you place a jumper across where the resistor goes DO NOT INSTALL ANYTHING WHERE THE RESISTOR GOES. RF26 is a simple input control for how much signal hits the filters. With hot pups or input signals, it helps cut down on filter distortion.

Unrelated; RF29, 3.80v is a point that I've found gives the best all around performance in mostof the units that have crossed my bench. You can play with it, between 3.70v, and 3.90v, while sweeping the treadle through the range, and in different FFM modes (parallel, counter, vowel). You'll notice that the frequency range will change quite a bit with even a 0.05v change. Since there will always be tolerances in all the components (and there are LOTS of components in here), you're unit might sound even better at a slightly different voltage setting. Try it, and see.

[Govmnt_Lacky]

In FFM mode, you should not be getting percussive repeats (tock, tock, tock). Especially if the Fuzz Repeats pot is at zero.

RF26 is either trimmer or resistor. If memory serves me, if using the trimmer then you place a jumper across where the resistor goes. RF26 is a simple input control for how much signal hits the filters. With hot pups or input signals, it helps cut down on filter distortion.

Unrelated; RF29, 3.80v is a point that I've found gives the best all around performance in mostof the units that have crossed my bench. You can play with it, between 3.70v, and 3.90v, while sweeping the treadle through the range, and in different FFM modes (parallel, counter, vowel). You'll notice that the frequency range will change quite a bit with even a 0.05v change. Since there will always be tolerances in all the components (and there are LOTS of components in here), you're unit might sound even better at a slightly different voltage setting. Try it, and see.

You do NOT want to short out the 1/4W resistor slot for RF26! It is an either/or scenario. Shorting it will result in FULL signal going to the filter board all the time.

I will need to cut out the 1/4W resistor, leave that spot open, and use the trimmer to dial in the proper audio level to the filters.

As for the RF29 setting.... as I stated before, I have it set to 3.80VDC dead on and I love the sound of the 3 formants (Parallel, Counter, and Vowel) I just want to get rid of the LFO bleedover.

I'm gonna send you an email for further guidance. Keep a lookout 

[digi2t]

In FFM mode, you should not be getting percussive repeats (tock, tock, tock). Especially if the Fuzz Repeats pot is at zero.

RF26 is either trimmer or resistor. If memory serves me, if using the trimmer then you place a jumper across where the resistor goes. RF26 is a simple input control for how much signal hits the filters. With hot pups or input signals, it helps cut down on filter distortion.

Unrelated; RF29, 3.80v is a point that I've found gives the best all around performance in mostof the units that have crossed my bench. You can play with it, between 3.70v, and 3.90v, while sweeping the treadle through the range, and in different FFM modes (parallel, counter, vowel). You'll notice that the frequency range will change quite a bit with even a 0.05v change. Since there will always be tolerances in all the components (and there are LOTS of components in here), you're unit might sound even better at a slightly different voltage setting. Try it, and see.

You do NOT want to short out the 1/4W resistor slot for RF26! It is an either/or scenario. Shorting it will result in FULL signal going to the filter board all the time.

I will need to cut out the 1/4W resistor, leave that spot open, and use the trimmer to dial in the proper audio level to the filters.

As for the RF29 setting.... as I stated before, I have it set to 3.80VDC dead on and I love the sound of the 3 formants (Parallel, Counter, and Vowel) I just want to get rid of the LFO bleedover.

I'm gonna send you an email for further guidance. Keep a lookout 

Absolutely correct! You beat me to the correction rewrite.   

[Keppy]

I get great formants from all 3 channels BUT.. I am getting bad LFO bleedover when in Animate mode.

Just to be clear, you're talking about popping sounds, right? There's a whole host of things the LFO can cause in Animate mode:

- Filter sweeps (the intended effect, will have all the usual hissy-ness of sweeping filters when you're not actively playing)
- Filter squeals (only at the extremes of the sweep, need to be tuned out with all the trimpots)
- Fuzz repeats (monotonous ticking sounds, but kinda intentional-sounding, should go away when switched off)
- Actual LFO bleed (LOUD ticking noise, definitely not used for music ever)

The first two are normal in a build (at least until it's tuned up). The third is normal, but should be selectable. Does the sound you're experiencing sound like fuzz repeats, only they won't switch off (even with the fuzz off)? Or does it sound like straight-up, jumping-several-volts-at-once LFO tick? Or something else?

I'm guessing it's one of the last two since you've been talking to Dino and that seems to be what he's assuming, but it's unclear from your actual posts, so can you clarify?

Assuming that's what it is, can you verify that Q8 base is grounded (via continuity, not 0V) when fuzz repeats are switched off? That would rule out bleed along the intended Fuzz Repeat path.

Basic question: Have you already poked at the physical wiring? This LFO has a huge spike, and wiring capacitance may be enough to cause bleed if the wires cross funny. Not that I've had it happen in this build, but there are an awful lot of ways those wires might bump together.

[Govmnt_Lacky]

Just to be clear, you're talking about popping sounds, right? There's a whole host of things the LFO can cause in Animate mode:

- Filter sweeps (the intended effect, will have all the usual hissy-ness of sweeping filters when you're not actively playing)
- Filter squeals (only at the extremes of the sweep, need to be tuned out with all the trimpots)
- Fuzz repeats (monotonous ticking sounds, but kinda intentional-sounding, should go away when switched off)
- Actual LFO bleed (LOUD ticking noise, definitely not used for music ever)

The first two are normal in a build (at least until it's tuned up). The third is normal, but should be selectable. Does the sound you're experiencing sound like fuzz repeats, only they won't switch off (even with the fuzz off)? Or does it sound like straight-up, jumping-several-volts-at-once LFO tick? Or something else?

I'm guessing it's one of the last two since you've been talking to Dino and that seems to be what he's assuming, but it's unclear from your actual posts, so can you clarify?

Assuming that's what it is, can you verify that Q8 base is grounded (via continuity, not 0V) when fuzz repeats are switched off? That would rule out bleed along the intended Fuzz Repeat path.

Basic question: Have you already poked at the physical wiring? This LFO has a huge spike, and wiring capacitance may be enough to cause bleed if the wires cross funny. Not that I've had it happen in this build, but there are an awful lot of ways those wires might bump together.

I did a quick phone test with Dino last night (and he can chime in here if he wants) and it sounds to me like it is definitely one of the last two.

It is definitely something with the LFO. When I use the external CV pedal I get great... non-ticking formant sound. As soon as I throw the Animate switch on... BOOM! Dino says that there will be some noise but this was definitely much louder than his build.

Some recent updates:

- I did install RF26 (47K) in parallel with the trimmer pot (50K) so it looks like I had a ~16K resistance instead of the stock-ish 47K going into the Filter PCB. I fixed that least night by cutting out the 1/4W 47K resistor and now just have the trimmer in place.

- I also re-adjusted my R20 to coorespond to Dino's initial resistance settings. Also, re-biased RF29 to get the 3.80VDC on the wiper.

Tonight, I am going to re-test and see where I stand. I also want to tackle adjusting the RF55 and RF77 trimmers to tune in the formants a bit. Hoping all of this will get the LFO bleed down a bit.

Finally, Dino did suggest that I may have used an ON-ON-ON switch for the Fuzz Repeats but....... I checked the switch and it is definitely ON-OFF-ON.

[Govmnt_Lacky]

Assuming that's what it is, can you verify that Q8 base is grounded (via continuity, not 0V) when fuzz repeats are switched off? That would rule out bleed along the intended Fuzz Repeat path.

I will add this to the list of items to check tonight 

[Govmnt_Lacky]

A bit of last minute second guessing on my part so a confirmation will go far......

For the DPDT On-Off-On Repeats toggle, can someone confirm that thiss is the proper operation of the switch?

Lets number the switch poles like this:      1   2

                                                              3   4

                                                               5   6

So, when the toggle is UP, then Pole 3 connects to 5 AND pole 4 connects to 6

When the toggle is centered, there is NO contact between any of the poles

When the switch is DWN, Pole 3 connects to 1 AND pole 4 connects to 2.

Correct?
                     

[Govmnt_Lacky]

When in FFM mode, I get continuity between Q8 Base and GND. I lose it when I switch to Repeat or Both mode.

Still no noticeable change in the LFO noise on the formants. Removing the 1/4W R26 resistor and re-adjusting the R26 trimmer did mellow out the sharpness.

Gonna play with the R55 and R77 trimmers to try to dial in some goodness and dial out the badness. More to follow...