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Are all inverter created equal?

11/8/1999 3:47 PM
Mark Hammer	Are all inverter created equal? We've established that one needs to be careful about the category of 4049 (select unbuffered), but I'm wondering how much variation there is WITHIN a category of the same. Bear in mind that inverters are intended to invert logic signals (from high to low oe low to high), and that they have been co-opted to serve in a linear design with the Insanity Box, Hot Tubes, Tube Sound Fuzz, Hot Harmonics and the late Charles Fisher's design that showed up in EM last year. I may be speaking naively here, but it strikes me that it would be quite feasible for 4049's to meet spec for their intended function, but vary considerably with respect to their unintended function. More succinctly, is it possible that one needs to pop in a few different 4049's from a batch and select by ear? There are obviously more factors to consider, but I'm curious as to whether we have been assuming more consistency in linear functioning from 4049's than is warranted. Jack raises the use of the 4007. I'm wondering if anyone has ever considered the 4069, which is also a hex-inverter chip. The MXR Envelope Filter uses this for its linear sections as well as its clock-generating and switched-capacitor filter circuitry. P.S.: Aron, the IB design is kinda cool. I like the idea of having 3 different potential distortion elements to tweak - sort of a greatest hits! RG and I were kicking around the relative merits of the two basic implementations of CMOS inverter distortion for quite a few years now. I think it started somewhere in 93 on alt.guitar, with a discussion of the two different Anderton Tube Sound Fuzz designs, and my preference for the tone of the one where an op-amp pre-amp stage slammed the first inverter, as opposed to demanding the inverter to generate all the gain and distortion. That led to the posted schematic that is attributed to me, but is really just a fine tuning of Craig's original design. On paper, your design refines the basic features, and - in a sense - uses the logic of the BMP (2 successive clipping stages) in a creative way; clever touch. Stellan's Slow Finger is also a nice design, in terms of flexibility, but its obvious focus is CMOS-flavoured clipping. Honest to goodness, the longer I follow this stuff, the more I realize that creating distortion is completely analogous to making soup. It's all in the simmering and seasoning of the right ingredients.

11/8/1999 3:47 PM

Mark Hammer

Are all inverter created equal?

We've established that one needs to be careful about the category of 4049 (select unbuffered), but I'm wondering how much variation there is WITHIN a category of the same.

Bear in mind that inverters are intended to invert logic signals (from high to low oe low to high), and that they have been co-opted to serve in a linear design with the Insanity Box, Hot Tubes, Tube Sound Fuzz, Hot Harmonics and the late Charles Fisher's design that showed up in EM last year. I may be speaking naively here, but it strikes me that it would be quite feasible for 4049's to meet spec for their intended function, but vary considerably with respect to their *unintended* function. More succinctly, is it possible that one needs to pop in a few different 4049's from a batch and select by ear? There are obviously more factors to consider, but I'm curious as to whether we have been assuming more consistency in linear functioning from 4049's than is warranted.

Jack raises the use of the 4007. I'm wondering if anyone has ever considered the 4069, which is also a hex-inverter chip. The MXR Envelope Filter uses this for its linear sections as well as its clock-generating and switched-capacitor filter circuitry.

P.S.: Aron, the IB design is kinda cool. I like the idea of having 3 different potential distortion elements to tweak - sort of a greatest hits! RG and I were kicking around the relative merits of the two basic implementations of CMOS inverter distortion for quite a few years now. I think it started somewhere in 93 on alt.guitar, with a discussion of the two different Anderton Tube Sound Fuzz designs, and my preference for the tone of the one where an op-amp pre-amp stage slammed the first inverter, as opposed to demanding the inverter to generate all the gain and distortion. That led to the posted schematic that is attributed to me, but is really just a fine tuning of Craig's original design. On paper, your design refines the basic features, and - in a sense - uses the logic of the BMP (2 successive clipping stages) in a creative way; clever touch. Stellan's Slow Finger is also a nice design, in terms of flexibility, but its obvious focus is CMOS-flavoured clipping.

Honest to goodness, the longer I follow this stuff, the more I realize that creating distortion is completely analogous to making soup. It's all in the simmering and seasoning of the right ingredients.

11/8/1999 4:05 PM

GFR

quote:
"I may be speaking naively here, but it strikes me that it would be quite feasible for 4049's to meet spec for their intended function, but vary considerably with respect to their *unintended* function."

That happens indeed.

quote:
"More succinctly, is it possible that one needs to pop in a few different 4049's from a batch and select by ear? "

Sure.

quote:
"I'm wondering if anyone has ever considered the 4069,"

I have a magazine project of a compressor that uses the 4069. I also have an all-cmos phaser that uses 4069 cmos inverters for everything - no other active device. And there's the "Guitar Note Expander" that could do distortion, compression, expansion, and frequency dependant cmpression or expansion. This appeared on ETI and used a 4007.

quote:
"The MXR Envelope Filter uses this for its linear sections as well as its clock-generating and switched-capacitor filter circuitry."

Could you post me a schematic?

11/8/1999 5:36 PM
Mark Hammer	I'll be happy to send you a hand-drawn schematic when I get home tonight. It's drawn from a rather crowded PC-board, so I can't vouch for its accuracy (one of the reasons why I haven't given it over to those with schematics archives for posting; this is not the kind of circuit you can easily spot errors in). I'll include a scan of the PC-board itself (trace and parts sides) so you can double check. The ETI circuit sounds interesting as well. I'll trade you scans. I also have a 4049-based compressor circuit that appeared in the Canadian edition of ETI about 15 years ago. I'll try and send that along with the MXR-EF.

11/8/1999 5:36 PM

Mark Hammer

I'll be happy to send you a hand-drawn schematic when I get home tonight. It's drawn from a rather crowded PC-board, so I can't vouch for its accuracy (one of the reasons why I haven't given it over to those with schematics archives for posting; this is not the kind of circuit you can easily spot errors in). I'll include a scan of the PC-board itself (trace and parts sides) so you can double check.

The ETI circuit sounds interesting as well. I'll trade you scans. I also have a 4049-based compressor circuit that appeared in the Canadian edition of ETI about 15 years ago. I'll try and send that along with the MXR-EF.

11/9/1999 12:25 PM
GFR	I've just sent you the scans, please contact me if you can't get them.

11/8/1999 7:37 PM
Aron	>More succinctly, is it possible that one needs to pop in a few different 4049's from a batch and select by ear? I have created a bunch of CD4049-based circuits and (silly me), I use a new 4049 for each circuit - not a reuse of the old one. I have gotten good results from the batch I have bought. They all perform in the same way - same type of frequency response, same gain. BUT, I could easily imagine this being different for other brand chips. Nothing suprises me lately. >Aron, the IB design is kinda cool. Thanks! >I like the idea of having 3 different potential distortion elements to tweak - sort of a greatest hits! Yes, that was the idea. The gain (trim pots) before each section allow you to control the gain per section and therefore adjust the relative amounts of clipping each section contributes. The MiniBooster took on a very smooth distortion when fed from the CMOS circuit. The 3 circuits give this pedal a nice compression - but it still has dynamics for me. >uses the logic of the BMP Yes, that was the idea. Multiple _different_ types of distortion stages. I didn't realize it until Gus pointed it out, but I was going from harder clipping (diodes) to softer (CMOS) to even softer (FET). I did this subconciously on the Insanity but conciously on another Big Muff killer pedal (which sucked). "It's all in the simmering and seasoning of the right ingredients." Yep, like R.G. said "devil is in the details". And another thing -- darn it. These details will change depending on different equipment. That's why DIY will live forever. We need it! I'm very excited because I ordered that transformer from Mouser that I can use for a Varitone circuit. I have this new idea.... I will post it soon!

11/8/1999 7:37 PM

Aron

>More succinctly, is it possible that one needs to pop in a few different 4049's from a batch and select by ear?

I have created a bunch of CD4049-based circuits and (silly me), I use a new 4049 for each circuit - not a reuse of the old one. I have gotten good results from the batch I have bought. They all perform in the same way - same type of frequency response, same gain. BUT, I could easily imagine this being different for other brand chips.

Nothing suprises me lately.

>Aron, the IB design is kinda cool.

Thanks!

>I like the idea of having 3 different potential distortion elements to tweak - sort of a greatest hits!

Yes, that was the idea. The gain (trim pots) before each section allow you to control the gain per section and therefore adjust the relative amounts of clipping each section contributes. The MiniBooster took on a very smooth distortion when fed from the CMOS circuit. The 3 circuits give this pedal a nice compression - but it still has dynamics for me.

>uses the logic of the BMP

Yes, that was the idea. Multiple _different_ types of distortion stages. I didn't realize it until Gus pointed it out, but I was going from harder clipping (diodes) to softer (CMOS) to even softer (FET). I did this subconciously on the Insanity but conciously on another Big Muff killer pedal (which sucked).

"It's all in the simmering and seasoning of the right ingredients."

Yep, like R.G. said "devil is in the details".

And another thing -- darn it. These details will change depending on different equipment. That's why DIY will live forever. We need it!

I'm very excited because I ordered that transformer from Mouser that I can use for a Varitone circuit. I have this new idea.... I will post it soon!

11/8/1999 7:55 PM
Aron	Re: Are all inverter created equal?/Just a Recipe Boy, all of this talk reminds me that a schematic is just like a recipe. The wrong ingredients and different flavors come out. Certain schematics scream out for a parts kit - so that you can get the exact sound. FET Muff, Insanity, SB3 and others come to mind. Aron

11/6/1999 11:21 AM
Aron	Re: Insanity Box (for Aron) Ed, I just put revision 4 of the schematic online. It lists my trim pot values as measured in circuit. This may affect the sound of the circuit a lot.

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