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by daverj
Thu May 28, 2015 10:44 am
Forum: Modular Synth General Discussion
Topic: oscilloscope newb confused, enlighten me please
Replies: 8
Views: 870

This is not a normal oscilloscope. It looks like a piece of specialty test equipment used by ham radio people.

Apparently it can be used as an oscilloscope to some degree by connecting an external signal into the "Vert" jack on the back and setting the function switch to "sine".
by daverj
Wed May 27, 2015 12:54 pm
Forum: Video Synthesis
Topic: Voltage to Current Converter for Video Bandwidth?
Replies: 6
Views: 685

It's a video vectorscope with separate X/Y inputs? Cool. Yes, it should be able to pass about 1.2MHz signals, or maybe a bit higher. That's the maximum bandwidth of the U and V signals used in PAL. Not full video (luminance) bandwidth, but still well past audio. It should have bandwidth specs define...
by daverj
Wed May 27, 2015 12:27 pm
Forum: Music Tech DIY
Topic: [PROJECT] 8x8 (16x16) MIDI control true summing matrix mixer
Replies: 58
Views: 5936

Those are interesting buttons. Do you have a part number/manufacturer, or a data sheet?
by daverj
Wed May 27, 2015 12:20 pm
Forum: Music Tech DIY
Topic: Missing-rail protection
Replies: 4
Views: 879

A power rail shorted to ground, causing a regulator to go into current limit, will generally supply a low impedance to the rail and the rail is unlikely to go into a reverse voltage. A power connector to the module plugged in wrong, or a broken wire to the power supply could cause an open rail. The ...
by daverj
Wed May 27, 2015 11:39 am
Forum: Music Tech DIY
Topic: Help with adjustable reference voltage regulator
Replies: 6
Views: 410

Are you building this using a PCB, or making it on a protoboard or breadboard? Layout of the parts around that regulator are critical. What kind of load are you testing it with? If I am reading the scope correctly it looks like the Vin has peaks at about 12v and the bottom of ripple is at 6v. First,...
by daverj
Wed May 27, 2015 10:48 am
Forum: Eurorack Modules
Topic: Known issues with popular modules?
Replies: 133
Views: 6235

But this whole line of discussion was precipitated by reports of people actually blowing up modules because the keyed ends of their cables were on wrong. This implies that there are manufacturers out there who think it's OK to rely on the header keys alone to protect their products. Long before key...
by daverj
Tue May 26, 2015 4:02 pm
Forum: Eurorack Modules
Topic: TipTop Station 252 still in production?
Replies: 4
Views: 242

It's still listed on their web site. Maybe send them an email and ask?
by daverj
Tue May 26, 2015 3:47 pm
Forum: Video Synthesis
Topic: Voltage to Current Converter for Video Bandwidth?
Replies: 6
Views: 685

Bandwidth limiting might come from further on inside the display. Many vector displays were never intended to handle wide bandwidth signals. They are meant to draw small shapes created by short slewed signals. When you are feeding in signals to either the positive or negative inputs, what are you do...
by daverj
Tue May 26, 2015 3:24 pm
Forum: Music Tech DIY
Topic: 15VDC to +-15V "converter"
Replies: 16
Views: 825

The HCC15-3 made by Power-One, Bel, Condor, International Power, and probably others can be set to supply either +/-15v at 3000ma per rail or +/-12v at 3400ma per rail. also known as HCC15 or HCC15-3-AG. Similar supplies come in different sizes with different currents by replacing the "CC" with "AA"...
by daverj
Tue May 26, 2015 2:52 pm
Forum: Eurorack Modules
Topic: mystery power issue
Replies: 52
Views: 5659

I see however that both the outlets in my apartment and the cable from the adapter are earthed. they look like this (earth is the top and bottom metal): That is right, as long as your apartment is properly wired. You can get plug in testers with 3 LEDs to show that. what elso would be needed in ord...
by daverj
Tue May 26, 2015 2:19 pm
Forum: Eurorack Modules
Topic: Known issues with popular modules?
Replies: 133
Views: 6235

All module manufacturers are aware of those keyed power distribution systems. Unfortunately not all it seems. I have no problem with manufacturers making distro boards without keyed headers. I just have an issue with module manufacturers that supply ribbon cables that won't work correctly with keye...
by daverj
Tue May 26, 2015 2:06 pm
Forum: Modular Synth General Discussion
Topic: Clear and present rig threat
Replies: 7
Views: 680

Have you tried peeing all over it to mark your territory?
by daverj
Mon May 25, 2015 6:20 pm
Forum: Video Synthesis
Topic: DIY Schematics: Simple Video VCA, Crossfader and Mixer
Replies: 36
Views: 12144

The best method is to get an oscilloscope and then test new modules first by sending the outputs to the scope. If everything looks good then connect it to other modules.
by daverj
Mon May 25, 2015 11:07 am
Forum: Eurorack Modules
Topic: Could this damage a module?
Replies: 5
Views: 438

It's unlikely that you will hurt anything by feeding a bipolar signal into a unipolar input. But in many cases, if the input is expecting a unipolar signal, it will ignore anything going below zero volts. So depending on the design, the lower part of the signal might or might not have any effect on ...
by daverj
Mon May 25, 2015 11:00 am
Forum: Modular Synth General Discussion
Topic: AC/DC current in a modular synth
Replies: 9
Views: 2161

In the old days, as well as now, there is no distinction in many systems between audio and CV. Either can go into any input. Because of that most inputs are DC coupled. There are a few exceptions where having a DC voltage on the signal goes against, or interferes with the function of the input for i...
by daverj
Sun May 24, 2015 3:40 pm
Forum: Eurorack Modules
Topic: Pittsburgh 208 case power shutting off
Replies: 8
Views: 452

Have you gone to all of the manufacturer's web sites and verified the current requirements of all of your modules? The values entered at Modulargrid are entered by users and are often entered wrong.
by daverj
Sun May 24, 2015 3:20 pm
Forum: Modular Synth General Discussion
Topic: AC/DC current in a modular synth
Replies: 9
Views: 2161

DC = a voltage that doesn't change AC = a voltage that changes, sometimes in repeating patterns, but not always. A DMM is not a good way to measure signals from a modular. You really need an oscilloscope. When a DMM is set to a DC scale it is displaying an average of the voltage over a period of tim...
by daverj
Sat May 23, 2015 5:14 pm
Forum: Eurorack Modules
Topic: Where do you buy your euro colored patch cables? (EU)
Replies: 6
Views: 373

It helps if you fill in a location in your profile so people know what country or even what continent you are in. The answers may change based on that.
by daverj
Sat May 23, 2015 4:17 pm
Forum: Video Synthesis
Topic: DIY Schematics: Simple Video VCA, Crossfader and Mixer
Replies: 36
Views: 12144

So if I'm building one of these on a blank pcb and powering it with an external 12V power supply... Whats the purpose of the 5v rail in eurorack? Do I need a 5v power supply as well? The 5v rail in Euro is an optional rail, usually used by Euro modules that need power for digital circuits. It's not...
by daverj
Sat May 23, 2015 3:09 pm
Forum: Music Tech DIY
Topic: itead fail...
Replies: 18
Views: 810

setsun8 wrote:I thought that Seeed and itead used the same factory, but I could be wrong.
If they are combining your design with other peoples designs into larger panels before going to the PCB fab house, they can create errors in that step.
by daverj
Sat May 23, 2015 3:02 pm
Forum: Music Tech DIY
Topic: [PROJECT] 8x8 (16x16) MIDI control true summing matrix mixer
Replies: 58
Views: 5936

When you say "true summing", you mean unity gain mixing? ie: if two inputs are at +5v the output is at +10v? If so, the problem is that you will be clipping signals that are in the +/-5v input range once you go past two inputs mixed together, since your mixed outputs can't go beyond the power rails....
by daverj
Sat May 23, 2015 12:04 pm
Forum: Eurorack Modules
Topic: Why are all eurorack prices the same?
Replies: 162
Views: 10898

But still, most people claim that the main cost of eurorack modules comes from the panel and the panel-mount controls. On really cheap modules, the panel, panel parts, and PCB might be a large part of the parts cost. On more complex modules they are still expensive parts, but not the main cost. The...
by daverj
Fri May 22, 2015 11:20 am
Forum: Music Tech DIY
Topic: Ancient batteries with full voltage...?
Replies: 6
Views: 399

The 2032 is guaranteed to hold a charge for a minimum of 10 years. I have some that I bought 20 years ago and never used, and they are just like new. Be aware that sometimes with no load, or very little load, a battery can show a decent voltage, but might drop a lot under even a light load. A good ...
by daverj
Thu May 21, 2015 9:41 pm
Forum: Music Tech DIY
Topic: Ancient batteries with full voltage...?
Replies: 6
Views: 399

The 2032 is guaranteed to hold a charge for a minimum of 10 years. I have some that I bought 20 years ago and never used, and they are just like new. Be aware that sometimes with no load, or very little load, a battery can show a decent voltage, but might drop a lot under even a light load. A good v...
by daverj
Thu May 21, 2015 9:29 pm
Forum: Eurorack Modules
Topic: the DIY cases thread!
Replies: 2551
Views: 502838

Love the pics here. I thought my woodworking skills were good, but I am blown away by the quality of some of these. On a slightly different tack - I am thinking of making a small control skiff using acrylic. I was planning to use 10mm thick - there is a local supplier that will cut it to order via ...

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