Tap Tempo LFO Chip

[R.G.]

LFOs, like tremolos, are another of those places where it is apparently simple to do something, but the longer you look at it, the more complex getting it to run actually is.

In LFOs, the issue is almost never how to get a low frequency waveform to do your modulation. Rather, the issue is getting that waveform, whether current, voltage, or digital number stream, to do an audibly good job of manipulating whatever modulation you're trying to do. Just getting a voltage of a suitable size, shape and frequency is the simple, trivial, easy part of the job. And it's almost certainly why you're still waiting for someone to publish a tap tempo delay. 

Getting from LFO to delay time requires another trip into the digital realm to get the analog waveform to modulate a clock speed, somehow.

This turns out not to be difficult, as it's all prior art. But the prior art is not one which has been applied to effects much.

And, as it turns out, this is good for the broader effects community. Getting a patent is only the simple first step in protecting intellectual property. Defending a patent is where the rubber meets the road, and it's powerfully difficult to defend a patent where there exists prior art. It can be done, but the courts usually slice off any protection for anything which has even a whiff of prior art, leaving protection for something so narrow it's easy to work around.

At least that's how it worked back when Fender, Gibson, Vox, Marshall, Baldwin, Standell, yada, yada were sparring over amps with patents. Who knows today, when anything, especially government favor, can be bought?

[doc_drop]

Oh well. I will just keep setting my delays by ear...and never getting it spot on. (Or cheat using software delay.)

I remember when this chip was first mentioned and a few people discussed how to control the delay. It sounded like it still might be possible. Did anyone make any progress?

[R.G.]

I remember when this chip was first mentioned and a few people discussed how to control the delay. It sounded like it still might be possible. Did anyone make any progress?

Yes, but those are the subject of *my* patents.

[doc_drop]

       

[Cliff Schecht]

8 bit pwm? that's suxx

Not sure what you are talking about, MV-53 does NOT use Pulse Width Modulation at all.  Instead it has an on-board Digital Analog Converter [DAC] that has 16-bit resolution and the output sample rate is well over a million samples per second (1.23 MHz).

The output is so clean, even at a 13 second interval, it will bring tears of joy to your eyes!

That IS nice! Care to share what micro you're using?

[MoltenVoltage]

Here is a link to the MV-53 VCF schematic:
http://www.moltenvoltage.com/downloads/MV-53_-_VCF_Schematic_-_Molten_Voltage_v1.bmp

The VCF portion is a modified version of the VCF half of the modular Dr.Q by R.G. Keen, Jack Orman, and Mark Hammer.  A few values have been tweaked and a Gain control added.  A switchable Pop filter has also been added which is sometimes desirable when the LFO jumps from 0-9 volts or vice-versa while using a sawtooth or square wave.

Finally, the Op Amp has been changed to a TS912 Rail to Rail which gives a wider frequency range.  It's worth mentioning that, with the CEILING control on zero, the FLOOR control lets you dial in a frequency and use the VCF circuit as a terrific-sounding Boost.

In case you missed it, here is the MV-53 Tremolo schematic:
http://www.moltenvoltage.com/downloads/MV-53_Tremolo_Schematic_v1.jpg

[Taylor]

Oh well. I will just keep setting my delays by ear...and never getting it spot on. (Or cheat using software delay.)

I remember when this chip was first mentioned and a few people discussed how to control the delay. It sounded like it still might be possible. Did anyone make any progress?

Pretty sure this is working:

http://www.diystompboxes.com/smfforum/index.php?topic=75740.0

[doc_drop]

Thanks Taylor. I will have to go back and read through that thread. Maybe there is still hope. I keep thinking of things like a Magnus Modulus where both the delay and tremelo could be tap tempo'd but at different beat divisions... But of course I have no idea how to impliment something like that. Time to do some reading.

[gena_p1]

8 bit pwm? that's suxx

Not sure what you are talking about, MV-53 does NOT use Pulse Width Modulation at all.  Instead it has an on-board Digital Analog Converter [DAC] that has 16-bit resolution and the output sample rate is well over a million samples per second (1.23 MHz).

The output is so clean, even at a 13 second interval, it will bring tears of joy to your eyes!

ооh, sorry, I saw couple of PWM analogs, and was sured, this is another one.
You did great work!

[Taylor]

Thanks Taylor. I will have to go back and read through that thread. Maybe there is still hope. I keep thinking of things like a Magnus Modulus where both the delay and tremelo could be tap tempo'd but at different beat divisions... But of course I have no idea how to impliment something like that. Time to do some reading.

Hmm. That would be possible but not using any stock chip. I would talk to user "Decc" who made the PTAP. He's a nice guy and knows his stuff. I know he could do something like that, it would only be a matter of rallying enough interested people to convince him.

Presumably the PTAP works for anything which is controlled by a resistance, so in some tremolos where the speed control is a variable resistor, the PTAP would just need to have its tap time-to-resistance slope rescaled (which I imagine would require a lot of testing of the actual circuit).

[sb_grl]

Not sure what you are talking about, MV-53 does NOT use Pulse Width Modulation at all.  Instead it has an on-board Digital Analog Converter [DAC] that has 16-bit resolution and the output sample rate is well over a million samples per second (1.23 MHz).

The output is so clean, even at a 13 second interval, it will bring tears of joy to your eyes!

It looks like you are using a dsPIC device and the 16-bit dac version is 100K sample rate, how do you come up with 1.23M? Are you multiplying the sample rate by the over-sample rate of the delta-sigma converter?

[Cliff Schecht]

That's for MV to know and for you to reverse engineer!

[sb_grl]

That's for MV to know and for you to reverse engineer!

Uh, that is not really a clear comment. I asked as the data sheet is missing a lot of info, what is the error in the dac? Linearity? Setteling time? If the rate they state really is the sample rate times oversample rate of the ds converter, I can get the info from the dsPIC datasheet. If it is not a dsPIC, great, what are the dac specs?

[gena_p1]

I remember when this chip was first mentioned and a few people discussed how to control the delay. It sounded like it still might be possible. Did anyone make any progress?

Yes, but those are the subject of *my* patents.

you are lucky civil world citizens,everything is patented

doc_drop - it's simple enough to make tap tempo on any BBD based delay

[G. Hoffman]

Quantity pricing is on this page:
http://www.moltenvoltage.com/mv-53.html

We can customize the chip with a minimum order of 100.  Additional programming charges will vary based on complexity.  Send us an email and let us know what you have in mind.

Thanks for the interest!

We will get the Phase 90 and Dr. Q schematics posted as soon as we can.

OK, so that's quantity pricing - what about if you want to buy less than 20?  Or are they not available to the general public yet?


Gabriel

[flo]

doc_drop - it's simple enough to make tap tempo on any BBD based delay

Can you please elaborate on this? Perhaps post a link to a schematic / design project? Thanks.

[doc_drop]

Thanks for asking what I was too intimidated to ask, Flo.

I have a BBD chorus (Zombie Chorus), but all my delays are based on PT2399 which is digital and not a bucket brigade type delay chip.  But I am still curious how one would do it for the BBD circuits as well.

[Cliff Schecht]

Bunch of skeptics around these parts!

That's for MV to know and for you to reverse engineer!

Uh, that is not really a clear comment. I asked as the data sheet is missing a lot of info, what is the error in the dac? Linearity? Setteling time? If the rate they state really is the sample rate times oversample rate of the ds converter, I can get the info from the dsPIC datasheet. If it is not a dsPIC, great, what are the dac specs?

All you were supposed to get out of my comment was that MV may not want to share all of that information with the world. If you're going to develop something based off of his product then maybe he'll give you the specs you mention. I would assume he's put the time and effort into making a solid product. All I would really need to develop something based off of his IC is a pinout, a list of what the pins do and the DAC's output current levels. You're asking for things that are proprietary information, if he gives it out then he's going to have a bunch of copycats in no time..

[sb_grl]

Bunch of skeptics around these parts!

All you were supposed to get out of my comment was that MV may not want to share all of that information with the world. If you're going to develop something based off of his product then maybe he'll give you the specs you mention. I would assume he's put the time and effort into making a solid product. All I would really need to develop something based off of his IC is a pinout, a list of what the pins do and the DAC's output current levels. You're asking for things that are proprietary information, if he gives it out then he's going to have a bunch of copycats in no time..

dac specs are proprietary? So I'm just supposed to assume that it is a PERFECT 16-bit dac? 0 error? Instant settling? I would never use a dac, or device that incorporates a dac, that I don't have full specs on, for all I know this chip could be +/-1/4 lsb or +/-13 lsbs. Knowing only current sink/source, the bit width and clock rate (with out really stating which clock he is talking about) is of no use. I am asking for performance specs, not the program code.

[Cliff Schecht]

I have to agree with you there. I wouldn't use a device like this if it wasn't fully characterized. I'd like to see some noise specs and distortion figures myself. A 16-bit DAC, if implemented correctly, is more than adequate for outputting low frequency waveforms. If we only knew what micro he was using...