Hi everyone! I just built a Chrome Dome distortion, but having an issue. It works mostly, but somehow when I change the tone knob, it cuts the volume and sounds quite dull in the middle and if I turns it back and forth a bit, then the volume comes back and it sounds normal again. I already checked the tone knob and other components multiple times but couldn't figure out. If anyone can help, it will be really appreciated. Thank you guys!
Chrome Dome Distortion
- Thread starter blivjc
- Start date
Mcknib
Well-known member
Sure do Chuck
I'll try this then a red fasel just to see what it does I expect it'll just act like a wah when turned
I do have an old Gould OS255 15mhz oscilloscope which I've never used I just usually audio probe problems so don't have a clue with the o scope but I'll fire it up and maybe start learning and hopefully get some useful info
I'll try this then a red fasel just to see what it does I expect it'll just act like a wah when turned
I do have an old Gould OS255 15mhz oscilloscope which I've never used I just usually audio probe problems so don't have a clue with the o scope but I'll fire it up and maybe start learning and hopefully get some useful info
Mcknib
Well-known member
Chuck
I can confirm that your solution works thank you very much for your advice and knowledge
Unfortunately mine has developed another fault nothing major or related to the 10K fix but it hindered me in my testing, my volume kept cutting out and from the old wiggle test I've got a dodgy connection on lug 1 it wouldn't alter volume or dump signal to ground, once I held it in place several times and rotated the tone pot through its range the dead spot had gone
So when I get a minute I'll sort the volume
Thanks again Chuck I know this has appeared on another couple of forums so I'll pass on your fix with credit to you
I can confirm that your solution works thank you very much for your advice and knowledge
Unfortunately mine has developed another fault nothing major or related to the 10K fix but it hindered me in my testing, my volume kept cutting out and from the old wiggle test I've got a dodgy connection on lug 1 it wouldn't alter volume or dump signal to ground, once I held it in place several times and rotated the tone pot through its range the dead spot had gone
So when I get a minute I'll sort the volume
Thanks again Chuck I know this has appeared on another couple of forums so I'll pass on your fix with credit to you
Chuck D. Bones
Circuit Wizard
I like the 10K resistor fix better than the 1nF capacitor fix because it addresses the problem directly. No guarantees that the 1nF fix will even work, it's a band-aid at best, just something to try.
dawson
Well-known member
Fixed that weird 'dead spot' in the TONE control with @Chuck D. Bones' 10k resistor in series with C7- thanks a lot 2019 Chuck!!
This circuit is fucking bonkers- I love it.
This circuit is fucking bonkers- I love it.
Chuck D. Bones
Circuit Wizard
I should have also mentioned that pins 9, 11 & 14 of IC1 must be grounded. Leaving the inputs to a CMOS gate floating is a rookie mistake.
Bricksnbeatles
Member known well
Thinking of finally building this one since it’s low parts count and I have the board laying around since 2020— glad I found the details about the fixes. Anything else worth implementing to improve performance?
Chuck D. Bones
Circuit Wizard
It is what it is. The 10K resistor and grounding the unused inputs on IC1 are all that's required to prevent problems. There are plenty of component value tweaks one could make to tailor the tone. Don't waste your money on an expen$ive inductor. Socket IC1. All of the current production (Texas Instruments) CD4049s I've tried are noisy, some worse than others. If you can find a vintage RCA, National or Fairchild, use one of those. Running IC1 on 9V was not smart IMHO; it works better at 4 or 5V and draws a lot less power. Fixing that requires cutting traces.
dawson
Well-known member
It'd be more useful to me if it were louder. My build sits around unity- same as the demo I watched of the original.
That's the only thing I'd change, but since I don't have a fix to suggest other than maybe stacking it with a boost, I'm just complaining
That's the only thing I'd change, but since I don't have a fix to suggest other than maybe stacking it with a boost, I'm just complaining
Chuck D. Bones
Circuit Wizard
Increasing the volume is easy. Make R20 larger. Try 68K. don't go over 150K.
something else to try: If the tone is too harsh, increase C9 to 100pF or higher to roll-off some of the extreme high-end. At 22pF, C9 cuts the treble above 48KHz. Your dog won't even hear that.
something else to try: If the tone is too harsh, increase C9 to 100pF or higher to roll-off some of the extreme high-end. At 22pF, C9 cuts the treble above 48KHz. Your dog won't even hear that.
Feral Feline
Well-known member
@Chuck D. Bones — I'm guessing that when tenting the 10k it doesn't matter which side of C7 it's on?
10k + 100n = 159.2 Hz on the Muzique calc...
10k + 100n = 159.2 Hz on the Muzique calc...
Bricksnbeatles
Member known well
Got it! Nice and easy fix. Not surprised that it’s not a pinnacle of design/engineering— the guy who runs it didn’t seem like a super professional guy when I was looking into his stuff way back when. A friend of mine got one direct from him in 2013 or so, and it was so shoddy and haphazard looking; like it was thrown together with hot glue.
Might add a pot to control the Q of the filter. Easy enough to do. Otherwise I don’t think it’s work messing with too much based on my memory of how it sounded. Maybe the r20 increase you mentioned since it was pretty weak in output, but otherwise it’s a solid sounding, if not poorly designed, peace of kit to mess around with.
I have a bunch of the cheap inductors from SBP exactly for projects like this. Most measure around 520mH which should be perfect. Interesting to hear about the 4049s— do you find them to be noisy only in CMOS distortion stuff, or also when they’re part of PLL/Octave circuits? I think I have two or three old production ones (Fairchild? I don’t remember, but def not TI; something from the 70s or 80s) that I got in a box of old parts years ago. I’ll give ‘em a try.
Chuck D. Bones
Circuit Wizard
Tenting? Is that Canadian term?
When 2 parts are in series, the order does not matter.
ok... what was the freq before we installed the 10K resistor?
Chuck D. Bones
Circuit Wizard
I guess it's fair to assume that if the manufacturing is iffy, the engineering would be too... where is the pride in making something good?
I'd breadboard it first. My experience with modding CryBaby wahs is that when raising R9 beyond 100K there is no increase in Q. Might even be less, depending on the inductor. If you're shooting for super high Q (which may or may not be desirable), then you need a high Q inductor which means the winding resistance needs to be low. I have some of these sweet babies and the winding resistance is around 30Ω.
CMOS gates were never intended to be used in a linear mode. A few clever guys like Craig Anderton, figured out that certain CMOS gates could be operated in linear mode and wrote about it back in the '70s. After reading that stuff, I experimented with running CMOS inverters in linear mode back then. At the time, there were several manufacturers, RCA, Fairchild, National, Signetics... making CD4000 parts. Fast-forward to today and a few big names (TI, ADI, ON semi) have gobbled up the competition. AFAIK, TI is the only producer of CD4000-series ICs. Their CD4069s and CD4049s are noisy when run in linear mode. Oddly enough, their CD4007s are quiet in linear mode. If you're making octave-down circuits or PLL circuits (like the Boss DF-2), then the CMOS ICs are running in digital mode and therefore analog noise is not a concern. I always socket CMOS parts when running them in linear mode because the datasheet tells us nothing about what to expect in linear mode. The only way to know if a CMOS gate is any good in linear mode is to try it. Maybe a good topic for a separate discussion.
Bricksnbeatles
Member known well
I think it was probably a fluke— probably messed around and made something he liked, then decided to sell them without much of the know-how.
Great info! In this case I’m actually shooting for lower Q, so I’d only be going down in resistance, not up. Probably replace R9 with a 5K resistor and an A250K pot or something like that. Tame it down into more standard variable mid-boost area when the sharp cocked Wah effect isn’t needed. For super high Q stuff, my go to is always the Systech Harmonic Energizer or its angry brother, the Systech Overdrive— I don’t need this to cover the same territory.
Super interesting stuff! I’d definitely love to see you do a whole write up about CMOS chips in linear mode— the Darkglass stuff (AION Maelstrom schematic) could be a really interesting circuit to dissect and compare to the older implementations like the Anderton Tube Sound Fuzz/Red Llama or EHX Hot Tubes.
Feral Feline
Well-known member
I misunderstood a few simple things about how HPF and LPFs are formed; I understand now series order doesn't matter.
When signal's shunted off, such as in this Coda diagram of a Muff tone circuit, it matters:
A little bit more knowledge gained and I'll be close to dangerous...
Well uhh lesseeee
C7 and R15 form a HPF corner freq of 1.1Hz.
Oh yes, mustn't forget...
RE: "Tenting"... Sure could be a Canadian term, I suppose. I couldn't find any examples on the forum until I switched the term to "teepee" and then you get all sorts of hits of @MichaelW and many other forumites teepeeing components.
To the left of the IC, there's two resistors tented/teepeed :
For the Chrome Dome, I would teepee/tent the 10k with C7 cap in C7's location...
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