Ludwig Phase II Clone Tech Notes

[R.G.]

Just got through looking at this. I subbed in a footprint which is a composite of the three most common trimmer footprints. One of them wasn't the Bourns 3266 series, but with the link I checked. It fits the smallest of the three possibles. So yes - 10 turns will work as long as they don't have too low a dissipation for the current that's going through them. I haven't checked power dissipation on all the resistors and pots.

[digi2t]

OK, we might be getting closer to the hand of God here. Just had another exchange with the guy whose close to the Ludwigs, and he's found the name, and is getting in touch with, the guy who actually brought this sucker to life back in the day.

Hopefully, I'll be able to get the setup info, and we'll be able to REALLY know what this baby is supposed to sound like. Besides, all those trimmers STILL have me perplexed!

[R.G.]

OK, we might be getting closer to the hand of God here. Just had another exchange with the guy whose close to the Ludwigs, and he's found the name, and is getting in touch with, the guy who actually brought this sucker to life back in the day.

Hopefully, I'll be able to get the setup info, and we'll be able to REALLY know what this baby is supposed to sound like. Besides, all those trimmers STILL have me perplexed!

It would be interesting to see how the filters are supposed to work. Generally a circuit's function pops out at me, but these are unusual in that I can't directly relate them to one of the normal active filters in my head.

Some of the trimmers are obvious in function. Others are only guessable until we get one running.

[toneman]

It would be interesting to see how the filters are supposed to work. Generally a circuit's function pops out at me, but these are unusual in that I can't directly relate them to one of the normal active filters in my head.

I hear U there.
IMO, It's drawn really caddywompus 

Yes, that's a "REAL" word 

http://en.wiktionary.org/wiki/caddywompus

Yeh, I don't see those filters, YET 
Gonna have to redraw the whole thing to wrap my head around it 

May all your hazes be purple!
afn

[pinkjimiphoton]

i think once the clone is built, we're gonna be surprised at just how much acid the designers were doing...lol.
can't wait!

[pinkjimiphoton]

just checkin' in guys...analogman has contributed some more stuff on the other thread, so check it out when ya can!

[R.G.]

It sounds like Keppy is nearly on line. When he gets it fired up, we'll have what we need to put the icing on the cake, I think. I'm watching.

[digi2t]

If Kep nails this, I'm havin' a brewsky in his honor. Then another for R.G. Then another for Jimi. Then anotherlkao forjpjdf lalaijfa;;adsk......................

[pinkjimiphoton]

me too....hic!!

[R.G.]

I've zeroed in on the problem, if not the solution. It's the transistor in that add-on amplifier. If I connect an audio probe to the base, I get signal. To the collector or the emitter, nada. Voltage reads full supply on the collector, nothing on the base or emitter. I am currently using a 2N5551 in that spot.

Earlier posts mentioned an undocumented resistor (1Meg, I think) that R.G. speculated might be used to bias that transistor. What can you guys tell me about that? I'll see if I can find the post...

Good work isolating that. That add-on always bothered me.

Fortunately, we can just nail it. It's acting just like I thought it would be doing from the schematic. A quick bit of simulation shows that a 1M from collector to base on the add-on transistor makes it have gain and not be blocked. Paste that in if you can. Perhaps the back side of the PCB. I can draw up where to put it if you want.

[digi2t]

Crap... I should have posted this here, in the tech notes. Here it is again, my sincerest apologies for the double up.

Are you talking about this?;



If so, it consists of 47k and 10k resistors, 0.1uF cap, and a 2N4401 tranny. Maybe the 2N5551 isn't cutting the mustard?

I was looking at the schem again, and I'd like to run something by you guys, insofar as the volume output of the unit is concerned. On the fall plate diagram, point 6 (to my untrained eye) seems to be the output of the unit. It goes through the terminal strip/amplifer section, and then out. Resistor R73 sits between point 6, and ground. Wouldn't this resistor directly affect the output level of the unit? If so, could we switch between two different resistances, via the formant switches to A) Bring the volumes to unity, and maybe B) Make the unit a bit louder overall? Or maybe a balance pot arrangement, allowing the user to vary the balance between fuzz, and fuzz/formant output. 

I hate to keep harping on this, but it really is a major weak point of the unit. If I could catagorize the volume output level of the unit, in it's various operating modes, it would be as follows (except for bypass, which is adjustable);
Fuzz - weak
Fuzz + Formants - louder
Formants (no Fuzz) - loudest

And, as a sidebar, I've found that vowel pronunciation can vary on the unit depending on the input signal volume as well. At certain points, with the guitar on full volume, in formant "C"/no fuzz mode the unit will produce bow wow wow, but roll off the guitar volume a bit, and it cleans up to yoy yoy yoy. Almost as if the guitar alone were overdriving the unit. Not something I would necessarily want to correct, but I thought I would put it out there as FYI. I find that it does allow some tonal pallate change on the fly, without having to touch the unit. I'm using a cheap Strat copy with it right now, and I don't think the pups are THAT hot, but I imagine my Motherbuckers loaded Ibanez will probably do a wicked job on this sucker. Maybe an input level pot wouldn't be a bad idea?

Jimi, if you've got the time, could you confirm my statements bro? Thanks!

[R.G.]

Crap... I should have posted this here, in the tech notes. Here it is again, my sincerest apologies for the double up.

No biggie.

Are you talking about this?;

Yep.

If so, it consists of 47k and 10k resistors, 0.1uF cap, and a 2N4401 tranny. Maybe the 2N5551 isn't cutting the mustard?

Yep, that's the circuit. Any chance you could do a quick measurement on the DC collector voltage?

On some of the pics posted here, I noticed a 1M resistor patch-soldered onto the component side of the PCB. I don't know where that goes. But as it turns out, a 1M between collector and base of the add-on transistor biases it so it has a gain of 10 or more. I'm not sure why they'd put the rest of it on that terminal strip and the bias resistor on the PCB; it's just a theory. But it's pretty sure that if the base of the add-on doesn't get some bias, it won't amplify; and the circuit will work as Kep is reporting. I don't think it's the 5551 as much as needing to bias it up.

I was looking at the schem again, and I'd like to run something by you guys, insofar as the volume output of the unit is concerned. On the fall plate diagram, point 6 (to my untrained eye) seems to be the output of the unit. It goes through the terminal strip/amplifer section, and then out. Resistor R73 sits between point 6, and ground. Wouldn't this resistor directly affect the output level of the unit?

Yep.

If so, could we switch between two different resistances, via the formant switches to A) Bring the volumes to unity, and maybe B) Make the unit a bit louder overall? Or maybe a balance pot arrangement, allowing the user to vary the balance between fuzz, and fuzz/formant output. 

I hate to keep harping on this, but it really is a major weak point of the unit. If I could catagorize the volume output level of the unit, in it's various operating modes, it would be as follows (except for bypass, which is adjustable);
Fuzz - weak
Fuzz + Formants - louder
Formants (no Fuzz) - loudest

Yep. Those are possibles. I've kind of been waiting to see if we can get back to a functional clone to start tinkering. But all those are possible.

And, as a sidebar, I've found that vowel pronunciation can vary on the unit depending on the input signal volume as well. At certain points, with the guitar on full volume, in formant "C"/no fuzz mode the unit will produce bow wow wow, but roll off the guitar volume a bit, and it cleans up to yoy yoy yoy. Almost as if the guitar alone were overdriving the unit. Not something I would necessarily want to correct, but I thought I would put it out there as FYI. I find that it does allow some tonal pallate change on the fly, without having to touch the unit. I'm using a cheap Strat copy with it right now, and I don't think the pups are THAT hot, but I imagine my Motherbuckers loaded Ibanez will probably do a wicked job on this sucker. Maybe an input level pot wouldn't be a bad idea?

Interesting. I wonder if the filters overload on big signals and that changes their operating point.

[digi2t]

On some of the pics posted here, I noticed a 1M resistor patch-soldered onto the component side of the PCB.

Could you narrow down the location of this "patch-soldered" 1M resistor? Looking at my board, nothing is jumping out at me.

Tranny readings are;
E = 0.00
B = 0.621
C = 9.60 (avg., fluctuates a bit)

Interesting. I wonder if the filters overload on big signals and that changes their operating point.

I would say that your hitting the proverbial nail on the head. I would even go as far as to say that they are overloading in formant only operation, because the bow wow is a touch distorted, but when I roll back the throttle on the guitar a bit, it cleans up, and yoy yoy yoy appears. I guess maybe back in the day, the pick ups weren't as hot, so they designed the circuit with the average input heat available for the time. Speculation on my part.

[R.G.]

It's here, just to the right of that black-knobbed trimmer in the middle of the board. It's in Jimi's pics of the internals.



I can't tell exactly where it goes, but it's in the area of the PCB that takes off to the output, and coincidentally the area where I stuffed in the external circuit in the PCB Keppy is working on now.  I speculated that it may be just connected to a DC point that feeds a little bias current into the output connection. That would bias up the external transistor enough to amplify, maybe.

[digi2t]

PHEW!!! I thought my eyes were going bad there for a bit.

I don't have that "add-on" on my board. Someone must have tried to get creative with Jimi's unit. Mine has only the 150K, as per the diagram.

Jimi, can you have a gander and see where the two ends of the darker piggy-back resistor go? The light colored R33 one is the original (same as mine, color bands match resistance too). The band colors off the darker one would be nice as well, not too clear in the pic. Just by the pic, it doesen't make sense to me that they bridged the 150K with a 1M 

[pinkjimiphoton]

hi guys, that r 33 resistor is indeed bridged with a 1 meg...it's definitely stock, so i'm imagining it was to bias something... it's tieing the base and collector of q7 on the schematic, i'm still enough of a newb to have no idea what that part of the circuit is doing...but i'd imagine higher resistance equals higher gain?

i'm gonna be on the road mostly the next two days, i'll try and open it up on saturday when i finally get some down time.

[pinkjimiphoton]

there's something going on with what dino reports as to volume drops, for sure.
when mine had broken, and the 150r trimmer (r65) was not passing signal, i got hella fuzz by adjusting trimmers r62, 55 and 41. i could get SCREAMIN' loud fuzz out of it by playing with them, but as soon as i fixed the trimmer and got the formant working again, the fuzz kinda whimpered out again. i'm assuming they're "stealing" a lot of the fuzz gain to make the formant filters work? maybe they aren't two discrete parts of the circuit, but happy coincidences of one?

R.G.?  help a newb out? any ideas?

[digi2t]

hi guys, that r 33 resistor is indeed bridged with a 1 meg...it's definitely stock, so i'm imagining it was to bias something... it's tieing the base and collector of q7 on the schematic, i'm still enough of a newb to have no idea what that part of the circuit is doing...but i'd imagine higher resistance equals higher gain?

i'm gonna be on the road mostly the next two days, i'll try and open it up on saturday when i finally get some down time.

Correct me if I'm wrong, but that makes no sense whatsoever. If they are indeed in parallel, the signal will still prefer to travel through the 150K, rather that the 1M, rendering the 1M useless. Path of least resistance.

My kids follow the same principle when it comes to cleaning up

[pinkjimiphoton]

maybe it has to do with the division of being parallelled?  what's 1,000,000 divided by 150?

i get 6666.666666666666666666666666666666666666666666667 ohms.

i think my calculator is broke!!

[Keppy]

I've zeroed in on the problem, if not the solution. It's the transistor in that add-on amplifier. If I connect an audio probe to the base, I get signal. To the collector or the emitter, nada. Voltage reads full supply on the collector, nothing on the base or emitter. I am currently using a 2N5551 in that spot.

Earlier posts mentioned an undocumented resistor (1Meg, I think) that R.G. speculated might be used to bias that transistor. What can you guys tell me about that? I'll see if I can find the post...

Good work isolating that. That add-on always bothered me.

Fortunately, we can just nail it. It's acting just like I thought it would be doing from the schematic. A quick bit of simulation shows that a 1M from collector to base on the add-on transistor makes it have gain and not be blocked. Paste that in if you can. Perhaps the back side of the PCB. I can draw up where to put it if you want.

Doing this only gave me about .13v on the base. Still no conduction. I could lower the resistor value, but I hesitate to do anything here that is a known departure from the original. Any other ideas? Might I have an error somewhere else creating a voltage divider of the wrong sort?

One thing to note is that Dino's collector reads 9.6v. Mine reads the supply voltage ~35v or so. If anything, though, it seems like that would give me MORE current at the base, not less.

Oddly enough, I'm getting about 3 mV on the emitter, which is grounded. Continuity to ground checked out fine. Hmm.