Ludwig Phase II Clone Tech Notes

[pinkjimiphoton]

guys, (dino especially) do you think this will make an acceptable replacement for the fuzz repeat slider?

http://www.bourns.com/data/global/pdfs/pta.pdf

i'm looking specifically at pda1543....seems like the dimensions should be close enough for rocknroll...

thanks!

[R.G.]

One of the things I considered when doing the PCB layout was laying out a controls PCB with just the slide pots and switches on it. I discarded that because re-making the original front panel is not likely to be something a cloner would do. But it should be possible to re-fit that whole panel, perhaps minus the light show on the switches, with a PCB that holds slider pots and rocker switches, and perhaps some LEDs to take the place of the indicators.

The big deal with linear pots is always how they get mounted. They absolutely have to match up with slots in the panel for the slide knobs in both length and position. It can be challenging. A real friend in figuring this out is a set of dial calipers or digital calipers like from Harbor freight. This lets you measure slot width and length, as well as slot-to-slot position accurately.

[pinkjimiphoton]

wellp, i gotta go by harbor frieght anyways...lol

the tough thing for me is that all the damn measurements are in millimeters, and i just plain can't seem to get the conversion down!!

[R.G.]

the tough thing for me is that all the damn measurements are in millimeters, and i just plain can't seem to get the conversion down!!

It takes a long time to get that working. I keep a calculator on my desk. There are 25.4 millimeters per inch, so to make inches out of a millimeter measurement, divide millimeters by 25.4. To get millimeters when you have inches, *multiply* by 25.4. All you have to have is (a) a calculator to do the arithmetic and (b) remember one inch is 25.4 millimeters.

Of course, the digital calipers flip between inches and millimeters with a button the front. That helps, too!

[digi2t]

Hey Jimi,

I'm at work right now, but I've printed the page, and I'll check the dimensions tonight. I think the one with 45mm of travel should do it, I seem to recall that the original had 50mm. 2.5mm less travel at either end souldn't be a problem. I just need to check if you'll have enough meat at the end of the slots to drill for the mounting screws. If so, you can drill and chamfer two holes in the chassis under the face plate, and use M2 X 3mm flathead socket cap screws. The face plate will cover up the works.

On a different note, can across this; http://www.bourns.com/data/global/pdfs/3048.pdf. That would make a neat pedal pot, if one had the room.

Get that to ya tonight bro.

[oldschoolanalog]

the tough thing for me is that all the damn measurements are in millimeters, and i just plain can't seem to get the conversion down!!

You can just work in metric. Get a good cm/mm ruler & calipers like RG described.
Not having to convert measurements saves time.

[digi2t]

Yup, many hardware stores sell cheap digital verniers. I've got a 6" digital, that i picked up for 10 bux. It's real handy, just a touch of a button, and you can switch between inch or metric.

I've seen them as cheap as 8 bux around here. Probably find one real cheap on EBay.

[pinkjimiphoton]

i'm gonna head out as soon as the vertigo clears enough to drive (meniere's disease. wear earplugs if ya play loud, please!!!) and hit harbor frieght.
should be able to get some for about 10 bux.

still haven't had a chance yet to go chasing grounds, maybe i will tonite tho. peace!

[pinkjimiphoton]

i got some digital calipers, so will check it out tonite. got parts for another overdrive pedal i built and gave away, a little 1 knobber 386 that uses just about nothing...i should just be able to squeeeeeeeeeeeeeeeeeeeeeeze it onto my secondary pedalboard..

[Keppy]

At high frequencies, electrolytic capacitors quit looking like capacitors and begin behaving like inductors. That's where all this business of bypassing electrolytic caps with small ceramic caps comes from.

I assumed that was what C7 was for. Do I need to put another small value cap somewhere on the emitter side of Q6?

At high frequencies, the diodes can't turn on and off fast enough, and can emit little squawks of RF trying to do so.

I was only going to use the diodes (well, one of them) for the tiny voltage drop it would give me. Should I bypass them? I'm unclear as to the impact of RF on an audio signal/circuit, outside of the AM radio station I pick up when I'm breadboarding. 

Many circuits I've seen use a large/small cap arrangement to filter the power supply, with values similar to C7, C8, C11. The OCD, for example, uses nearly the same values in a 3-cap filter arrangement, except the small cap is 100nF instead of 10nF. What I'm trying to say is, the filtering on the Phase II is so similar to what I've seen on other high-gain circuits (in my tiny experience  ) that I'm not aware of what problems could arise in this design.

I feel a geofex article link coming on...

I was tired when I wrote this. I meant the collector side of Q6.

[digi2t]

OK, a quick gander at my unit vis-a-vis the slide pot you're eyeing. The screw thing won't work because the slot on the unit is longer than the distance between screw holes on the pot. It MIGHT fit between the face and backplane though, but it might be really tight. I measured aprox. 6mm of space between the two, and the pot is listed as 5.5mm thickness. Then, I'm not sure where the connection points on the pot may end up, where the aluminium backplane is concerned. It's a tough call. I looked around today, and I could only find 45mm travel pots. The original is 50mm, which is aprox. 2", so you won't have to mess with the slot. Just mounting it will be a bit tricky.

If you can get one on the cheap, especially a thinner one which you could shim in there, I would try it.

[digi2t]

OK... another option for the slider pot replacement.

Screw all of them. Change them all out for 60mm travel pots. Just stretch out the slots a bit, and mount them using screws, as I previously mentioned. You'll have enough meat at the ends of the slots for the screws that way.

I don't have the unit in front of me, but I believe that aluminium plate inside serves only to hold the slider pots. If you can ditch it, go with 3 new pots i.e. PTA6043.

I know it's a bitch to ditch/mod original parts. I love to keep things stock if I can, but finding a hen's tooth is bad enough. Trying to find the filling is a whole other game brother!

On another front, I've started to layout a vero version of the Colorsound Vocalizer. Just ordered the IC's, and 22K dual gang pot (that sucka was pricey, coming from England!). Just need to find an old wah to gut now.

As you can all see, I like to keep my plate full....

[R.G.]

I was tired when I wrote this. I meant the collector side of Q6.

No biggie. A 0.1uF monolithic ceramic on *both* collector and emitter would not be amiss, with either the stock or an external switching power supply.

[pinkjimiphoton]

hi guys, here's a demo of my ludwig...it's a little darker sounding than dino's....but i think you'll get an idea of some of the possibilities this thing has to offer!!

enjoy...then let's build us some!!

[R.G.]

Did some more reading on formants and phonemes.

The "yoy-yoy-yoy" sound is composed of "eee-O-eee-O-eee-O..." strung together.

The all-IC approach seems to work too. I set myself the task of making it run through a whole string of vowel phonemes instead of alternating between two, so getting the formants to move exactly through the middle of the formant regions is keeping my mind busy.

[digi2t]

Hey R.G.,
Speaking of IC's, I've just completed a vero of the Colorsound Vocalizer. I was wondering if the Ludwig would work along the same principles of the Colorsound's IC layout.

I started a thread on it here; http://www.diystompboxes.com/smfforum/index.php?topic=92202.0

[pinkjimiphoton]

if anyone can figure it out, it's you, r.g.!!

the counter switch seems to be the "yoyoyoyoy" switch, the vowel seems to do the others.

as i recall way back when, you could actually get it to cycle thru most of the vowel sounds. i haven't been able to tweak that in in mine yet however.

[pinkjimiphoton]

nice dino! lookin' forward to checking out that thread, and hopefully building one!!

[R.G.]

At Keppy's request, I added a second position for a TO-220 darlington transistor for Q6 on the console board. Good idea Kep! I like selective population options.

On the console/slider thing:
I also like making PCBs that make controls and switches easy.  I started, then stopped, on a PCB that would take stock Bourns slider pots and e-switch switched to fake a front panel, realizing that it would only be useful on two boxes I know of, those being the ones in captivity.

However, it's almost trivially easy to do something like that, trivially as in once you know where the holes in the panel are and what parts you want to use to replace the stock ones, just do the mechanical layout for the switch/slider holes and then apply resist pen, you can re-make a control panel. It's work, and needs attention to detail, but it can be done.

[digi2t]

R.G., don't get bent out of shape with sliders, pots, switches, etc. Personally, if one is to create his/her clone, just offboard wiring from the board would be the best option. They can create their own control scheme then. Let's keep it simple.... and compact.