Knocking up a couple of double-distortion boxes using a single CD4049UBE. Aside from the normal stuff you'd do for any op-amp (smart layouts, decent grounding scheme, decoupling right near the IC, etc), are there any tips/tricks/best practice things that help tame some of the hiss?

I've seen the suggestions of rolling off plenty of top end at the start and progressively less as things go to help keep noise down, and some cryptic references to stuff like using some of the unused inverters in parallel with the gain stages to keep noise down but aside from that not much else hex inverter-specific

Yeah, it will add more top end than you need for this sort of application, so keeping it in check with feedback caps will be your best ally.

Some useful ideas here:  https://www.diystompboxes.com/smfforum/index.php?topic=69145.40

Quote from: Mark Hammer on June 25, 2024, 08:57:48 AMYeah, it will add more top end than you need for this sort of application, so keeping it in check with feedback caps will be your best ally.

Some useful ideas here:  https://www.diystompboxes.com/smfforum/index.php?topic=69145.40

Cool, have read through that (and a few others talking about noise), but there was plenty of just general advice.

I'm also guessing that being able to increase the gain at the first amplifying stage (probably op-amp), and reduce the gain of the inverter stages is probably a good idea too?

*I* like it partly because it provides an opportunity for shaping the tone before it hits the first inverter section.  As is always true of drive pedals, the signal out that we hear is a function of the properties of the signal feeding any clipping elements.

There are certainly other ways to do that, but that's the one I like.

Hi,

Quote from: drdn0 on June 26, 2024, 02:21:30 AMI'm also guessing that being able to increase the gain at the first amplifying stage (probably op-amp), and reduce the gain of the inverter stages is probably a good idea too?

You didn't provide a schematic, but you said "inverter stageS", plural, so I'm assuming multi a stage overdrive/distortion.

Note that each stage clips and distorts and change the signal individually and feed the result to the next one.
I.e. Unless you have lots of headroom, having 3 stages of gain 4x, 4x->4x->4x, does not sound the same as 16x->2x->2x.

That said, a few pedals do this. Opamp gain and tone shaping, one or two inverters, more tone shaping.

Quote from: marcelomd on June 26, 2024, 02:30:13 PMHi,

Quote from: drdn0 on June 26, 2024, 02:21:30 AMI'm also guessing that being able to increase the gain at the first amplifying stage (probably op-amp), and reduce the gain of the inverter stages is probably a good idea too?

You didn't provide a schematic, but you said "inverter stageS", plural, so I'm assuming multi a stage overdrive/distortion.

Note that each stage clips and distorts and change the signal individually and feed the result to the next one.
I.e. Unless you have lots of headroom, having 3 stages of gain 4x, 4x->4x->4x, does not sound the same as 16x->2x->2x.

That said, a few pedals do this. Opamp gain and tone shaping, one or two inverters, more tone shaping.

It's something along the lines of a Double D, but instead of a buffer at the front I was planning on using a low (ish) fixed-gain JFET stage at the front, and reducing the gain of the proceeding inverter stages.

No need for it to sound the 'same' as I'm not exactly copying anything, but I have a real bugbear with pedals with excessively high noise floors.