frequency shifter

[jhaible]

[lexvortex]

Hi JH,

I have a question about the feedback normalled through the aux in, is it OK to be only able to turn the knob up to 2 maybe 3 before the feedback gets really loud and clips the input?

Thanks,
Dave

[jhaible]

[lexvortex]

Hi JH,

What value resistor would you recommend? Maybe a 3k or so?

Thanks again,
Dave

[jhaible]

[lexvortex]

Thank

I used a 10k log pot for the aux input and I ended up with a 50k resistor in series which got the feedback to self oscillate at about 8 or 9 on the dial which is about what i wanted.

Thanks again,
Dave

[Papareil]

Hello,

I have finished to build the JH-FS1A with full options ...
Long to assemble but really great module



More pictures and infos on my website

http://m.bareille.free.fr/modular1/jh_fs1a/jhfs1a_mb.htm

Thanks,

Marc B.
PAPAREIL SYNTH LABS

[jhaible]

[dingebre]

Jurgen,

Finally all wired and hooked up. Calibration steps 1, 2, and 3 went fine for, but step 4 is not. In the attached photos, yellow is the 1Vpp square wave at about 250 Hz input, Blue is the signal at the CMP OUT pin indicated in the photo. I can reduce the "flat" part to 0.0 essentially, but the other half of the wave keeps ringing.

When I look at pin 6 of U14, I don't see a signal (which I guess is correct since pin 5, the "+" is connected to ground.)

I get about a 100mV pp square wave on U14, and a square wave on Q4

Any ideas? I'm a bit at a loss as to where to start. I've triple checked the panel wiring, I removed the jumpers... I do have everything connected. should I disconnect board 1 from board 2? Should I unplug the wires to the panel?

David

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[jhaible]

[dingebre]

Thanks JH.

Yes, I used a 10K resistor.

I'm still going to poke around the OTA's a little with the scope. I'd like to understand it better and see where the signal changes from the square wave to this thing.

I"ll head onto the other steps and will let you know...

David

[dingebre]

More calibration problems.

I got home too late, and decided to try calibration some more.

1. I found that a big part of the signal in the last scope grab was coming from the "input" connector which connects board 1 and 2. So, I guess have some wire tracing to do. I disconnected the wire between the boards and grounded the input connector on board 1, and was able to affirmatively minimize the signal at CMPOUT. It still has a funny, almost sine shape on the lower half of the pulse, but I could tell when it was minimized. I ended up with a series of small pulses at the leading edge of the input square wave. I can grab an image if needed.

2. I get no signal on DIFF or SUM. I've tried tracing backwards across the various components, but can't seem to find any signal at all. Do you have a suggestion of some pins I can look at? I've looked at inputs/outputs on U14, U15, U18, U17

3. Now, the embarrassing. I shorted something on the side of U6 or U7 that is closest to the edge of the board (pins 1-7) and R8 smoked. From the schematic, I would think I hit -vb3 with a ground wire I had floating around, but I can't see where I could have hit a connection to -vb3 on that side of the chips. I saw a spark and R8 is definitely toast. Could I have hurt either U6 or U7 in the process? I seemed to gather that R8 and R7 were sacrificial to protect against someone like me shorting out a power bus.

I've checked various resistors and capacitors connected to these IC's and I seem to have the right ones. I've double checked that I have the IC's installed properly, too (but i will check again I know that the IC's are not installed all the same way on the boards) I am using LM3700's instead of the LM3600's but I don't think that is the problem.

Now, it's really late and I'm mistyping about every other word....

Thanks,
David

Thanks.
David

[jhaible]

[dingebre]

All fixed, I think.

I thought I'd post this here for group amusement at my expense. After replacing R8, I thought I'd give the calibration another go. total frustration. However, I was also becoming increasingly annoyed at a large amount of noise on the signal. I was attributing it to a noisy probe.

Now the good part. I was shutting down to go to a wedding with my wife and instead of shutting the power down like I usually do, OScope, module, iron, lights, I turned off my fluorescent magnifier light first. The noise went away. When I got back I tried the calibration step 4 with the fluorescent off. Yes, the square wave was already small enough that it was hidden in the noise. So the rest of the calibration went fine, and I think it's actually working the way it should.

I hate fluorescent lights. Any way to filter that noise out of my stuff?

Thanks JH. Very cool stuff.

[jhaible]

[dingebre]

All done! Thanks JH for the design and trouble shooting help and thanks Tobias for the parts kit.

It's a FracRack format, Schaefer panel, 4U (6 inches) wide. I omitted the Mic input in favor of an additional audio level input so I could keep the feedback loop on the Aux. input.

The title is Bulgarian and translates to JH Frequency Shifter.

Now, maybe the phaser(s) or VCO's I've got waiting...

David

[sduck]

Looks fantastic, David!

And yet another FS1a finished -





So far it seems to be working - the led's are lighting up appropriately, and some kind of sound is being processed and passed through, with the knobs all doing things, although I haven't calibrated it yet. I still need another scope probe for the second channel. The wiring is really sloppy, at least compared to some other things I've built - but it works.

And I want to thank Dave Brown for his parts and wiring tips, which I copied faithfully, and his panel design which I copied, but not quite as faithfully. And Jurgen for the excellent design!

[davebr]

[sduck]

It seems to work ok. I just had to make sure that my bracket was close enough to the center. Even with it almost dead center, I had to angle it slightly to keep adequate clearance on both sides.

[jhaible]

[sduck]

Thanks, Jurgen. It's just a Front Panel Express panel. Most people use the default white infill for all the engraving. Adding colors is a one shot price upgrade - I think 7-8$, then you can add any colors infills you want. I balance the added cost by saving money with no infills on a lot of it - on this panel, everything that looks white in the picture is actually not infilled - just etched aluminum, which looks really great in real life. The way I do panels is actually relatively inexpensive - the cheapest fonts they have, as much hpgl as I can use, and no infills whenever possible. This one was a bit more than usual due to all the stuff on it - 106$ (US). Dave Brown's brilliant version, which this is based on, cost 114$ - I didn't think I could make the colors work and be the same or lower, but managed somehow.

[zthee]

I just fired up my frequency shifter - and got some magic smoke
Due to a TL074 in the wrong position in the dome filter.

I've tried the function of the rest of the module, and I get 2 nice triangles - so the oscillator seems to work fine!

But when looking at the CMP out I get a wierd signal - is this due to the dome filter not working? Or should that be OK even though the dome filter is toasted?

Thanks!

[jhaible]

[zthee]

Ah, yes! Thanks.

I think I found the problem though - I have VCO that bleeds into the power lines. Causing my whole system to go banans. I'm gonna have to deal with that before anything else I guess..


Here's a picture of my, not yet functioning, frequency shifter.

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[jhaible]