"Broken radio" -like note ends with 3 different OD pedals

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"Broken radio" -like note ends with 3 different OD pedals

Postby vvv » 02 Apr 2014, 04:40

Same problem with three different builds. SHOD, Hotcake and with BJFE Honey Bee.

http://tagboardeffects.blogspot.fi/2012 ... out-2.html

All of them have the same very bad, unnatural and gating decay. With Sweet honey OD I tried a few different opamps with no help. Original pedals decay and fade the notes much smoother and the nature of the overdrive is also more sophisticated in the originals.

Anybody else had this problem? What should I try first?

Short example:

http://s000.tinyupload.com/?file_id=785 ... 7702011227
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby vvv » 16 Apr 2014, 14:44

Just finished Klon Centaur -clone and almost unbeliveably it has just the same kind of decay problem. Really nobody has ever experienced anything like this? I´ve made a few clones that do work really well but how can pedal this different to each other have the same problem? On this one, swapping the opamps changes the decay and some 072´s work better but not perfectly.

Am I repeatedly doing something wrong or what is this about?

Take a listen:

http://s000.tinyupload.com/?file_id=006 ... 7925442347
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby Intripped » 16 Apr 2014, 15:00

...a problem with your amp/cone?
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby vvv » 16 Apr 2014, 15:26

Nono, I have a good bunch of working ones that I´ve build and that sound just sounds like bad clipping.
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby DrNomis » 17 Apr 2014, 05:57

Check the voltages on the Op-Amp IC pins, and also on any transistor E,C,B connections, are the Op-Amp ICs and transistors biasing up like they're supposed to?...... :hmmm:


Also is your amp working like it's supposed to?, the same result with different pedals seems to suggest to me that it could be a fault in the amp you're using....... :hmmm:
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby vvv » 17 Apr 2014, 06:03

That biasing-thing is also my guess. Where can I find info about how it´s done? All the ones I build that work right seem to be non-opamp pedals (like Big muffs).
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby DrNomis » 18 Apr 2014, 04:04

You could try doing a search for threads about Op-Amp IC biasing, usually in a circuit which involves at least 1 Op-Amp IC, like for example a JRC4558D, or a TLO72CP, running off a single +9V supply rail, there is usually two resistors connected in series going from the +9V Supply rail to circuit ground, these two resistors are normally made identical in value (anything from about 10k to maybe 22k or a bit more) the purpose of these two resistors is to provide a bias supply which is about half the +9V Supply rail, or +4.5V, this +4.5V bias supply usually goes to one of the input pins on each side of the JRC4558D or TLO72CP IC, the JRC4558D and TLO72CP have exactly the same pinout and contain two Op-Amps which have a + input and a - input, and an output, applying the +4.5V to one of the inputs and connecting the other input to circuit ground biases the output pin to half the supply voltage, there is usually a resistor that connects from the output to the input which has the +4.5V bias supply applied to it as well, have a look at the schematics for the stompboxes you have built and see if you can find the two +4.5V bias supply resistors and then trace out the circuit paths which connect the +4.5V bias supply to the Op-Amp IC pins...... :thumbsup


Use a multimeter to check whether the bias supply is correct and that the Op-Amp ICs are biasing up correctly...... :thumbsup
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby John Coloccia » 20 Apr 2014, 02:27

In addition to all that, I've sometimes gotten similar bad results on prototypes when I've botched up the decoupling caps.
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby DrNomis » 20 Apr 2014, 06:42

If one of the coupling caps goes leaky that can upset the biasing of the next Op-Amp stage after the coupling cap, the output of the Op-Amp stage will either go towards the supply rail, or will drop towards circuit ground depending on how the Op-Amp stage is configured (assuming it's running off a +9V supply rail)...... :thumbsup
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby John Coloccia » 20 Apr 2014, 20:00

Actually, I really was thinking about the decoupling caps on the power supply, but a coupling cap could definitely botch things up too!
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby vvv » 21 Apr 2014, 14:47

OK. Thanks a lot for these. Could it be that bias fine-tuning would be necessary in some cases? Like do they do that in commercial pedals as if they use some specific batch of opamps that they know how to bias them excatly? Also I´m not sure if everyone who builds clones can hear those little imperfections in their builds.
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby vvv » 29 Apr 2014, 19:23

I´m yet to familiarize with the biasing-thing, instead, I built a few more pedals and I still haven´t got a single lo/medium gain overdrive to sound right. From 20+ built pedals only fuzzes and some higain overdrives and distortions have sounded like they should. I think many builders just don´t care about their builds sounding wrong or they can´t hear it. I´d really like to hear a sound clip of some Vero-built lo-gain overdrive pedal where somebody plays an open chord gain set quite low and lets it ring and fade out.

It would be good to know what circuits are more sensitive to those problems and just skip building those because I have already spent quite a lot of time with builds I never got to work right...

Maybe I should do some build I have already build once this time using higher quality components and even try to do one with same brand components to a pre-made PCB to see if that makes a difference.

Do you always do biasing in every build to get things right? Is it like a basic prosedure in building?
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby DrNomis » 29 Apr 2014, 19:47

vvv wrote:OK. Thanks a lot for these. Could it be that bias fine-tuning would be necessary in some cases? Like do they do that in commercial pedals as if they use some specific batch of opamps that they know how to bias them excatly? Also I´m not sure if everyone who builds clones can hear those little imperfections in their builds.



Not really since most passive electronic components are usually made so that their actual values measure to within a certain percentage +/- the marked value, this percentage is called Tolerance, for example electrolytic caps are usually made so that they measure anywhere from 10 to 20 % +/- their marked value, resistors are made so measure anywhere from 1 to 10 % =/- their marked values, it's only in special cases where low-tolerance components will be used in a circuit, most of the ICs used in commercially manufactured stompboxes are bog standard, higher quality semiconductors tend to be fairly expensive so manufacturers would tend to use the bog standard ICs to keep costs down so they can increase their profit-margin, personally, I think any effects of the imperfections on the sound of a stompbox would probably be hard for us to hear unless the imperfections are fairly severe to the point where the imperfections are the result of a faulty component...... :thumbsup
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby DrNomis » 29 Apr 2014, 19:58

vvv wrote:I´m yet to familiarize with the biasing-thing, instead, I built a few more pedals and I still haven´t got a single lo/medium gain overdrive to sound right. From 20+ built pedals only fuzzes and some higain overdrives and distortions have sounded like they should. I think many builders just don´t care about their builds sounding wrong or they can´t hear it. I´d really like to hear a sound clip of some Vero-built lo-gain overdrive pedal where somebody plays an open chord gain set quite low and lets it ring and fade out.

It would be good to know what circuits are more sensitive to those problems and just skip building those because I have already spent quite a lot of time with builds I never got to work right...

Maybe I should do some build I have already build once this time using higher quality components and even try to do one with same brand components to a pre-made PCB to see if that makes a difference.

Do you always do biasing in every build to get things right? Is it like a basic prosedure in building?



Most of the time the biasing is pre-set by the circuit designer as in the case of voltage-divider biasing in a Rangemaster circuit for example, but even though the designer of the Rangemaster circuit chose resistor values of 470k and 68k, it doesn't mean these values are set in stone, if you were to build a Rangemaster using a randomly selected Germanium transistor, it may bias correctly with those resistor values, then again it may not in which case you might need to tweak the resistor values a bit until the transistor does bias correctly, it depends on the operational characteristics of the transistor, that is what I think is the fun part of Electronics, building a circuit and then tweaking it to get it working better...... :thumbsup
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby vvv » 29 Apr 2014, 20:22

DrNomis wrote:I think any effects of the imperfections on the sound of a stompbox would probably be hard for us to hear unless the imperfections are fairly severe to the point where the imperfections are the result of a faulty component...... :thumbsup


Yes, most of the builds I call "broken" can sound just fine like with only single note played, maybe just lacks some sustain, but some specific chord might give really ugly fading. That´s what makes me think most builders think their builds work just fine.

There must be something they are doing differently in commercial pedals as I have yet to hear a "broken" sounding commercial pedal. They kind of sound "fine tuned" and I have also A/B tested some of clones I build with orginal ones and difference is really clear when tested properly, not just playing single notes etc.
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby gjcamann » 29 Apr 2014, 21:53

I noticed it a little on my SHOD, but I haven't tried the original OP275 chip yet. Some designs are more susceptable to this. I've experienced this big time with the LM386's. It probably doesn't matter in a mix. I think it's more of an op-amp thing, try a transistor based design like a Les Luis.
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby Nocentelli » 29 Apr 2014, 22:30

vvv wrote:Yes, most of the builds I call "broken" can sound just fine like with only single note played, maybe just lacks some sustain, but some specific chord might give really ugly fading. That´s what makes me think most builders think their builds work just fine


There's an element of high gain fuzz masking slight gating on some circuits, but "really ugly fading" is noticeable if it is really ugly.

vvv wrote:There must be something they are doing differently in commercial pedals as I have yet to hear a broken sounding commercial pedal. They kind of sound "fine tuned" and I have also A/B tested some of clones I build with orginal ones and difference is really clear


There are certainly some diy-ers happily using supposed clones that are not actually as the designer intended, caused by build error, erroneous schematic/layout, inaccurate parts, supply voltage, parts with wide tolerances or particular hfe/leakage requirements etc. That said, you really need to be specific: You say you've build 20+ pedals, but specifically the SHOD, honey bee, hotcake and klon sound gated as a low gain OD.

I haven't tried the shod or honeybee but the hotcake is an overdriven opamp, and some people don't really like that sound. It was a bit woolly, and yes maybe a wee bit gated at the very tail of a complex chord, it might depend on the particular opamp used (metal can mojo notwithstanding). The klon is really not to my taste, but I play through quite clean solid state amps: People who pay money for this pedal usually claim it sounds amazing through my very expensive fender tube amp, when used as a booster, with the gain down low. I don't remember it being unpleasant on the decay, just reasonable sounding diode clipping, nothing special. There could be a fault with your build, or maybe you need Bill's special diodes.

Some circuits seem to work fine whatever the parts: Paul Cochrane's Timmy, and the skreddy lunar module for example, work every time, with specified opamp/transistors, or with anything else vaguely suitable.
mmolteratx wrote:absolutely zero commercial use allowed. If I find anyone selling these, I'll fly to your house and kick you in the nads. And you may or may not find yourself in trouble.
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby vvv » 30 Apr 2014, 06:07

gjcamann wrote:I noticed it a little on my SHOD, but I haven't tried the original OP275 chip yet. Some designs are more susceptable to this. I've experienced this big time with the LM386's. It probably doesn't matter in a mix. I think it's more of an op-amp thing, try a transistor based design like a Les Luis.


I´d say the swapping of opamps is usually in vain. When I build Soulsonic Hunny Bunny I tested it first with a few LM301 chips but all of them had gating. Then I ordered some TL071´s and 741´s of different brands being sure that it would fix it (as its so simple circuit theres nothing much that can be wrong), but there was only minimal affect and almost none to the gating-thing. In my experience only Klon Centaur has benefited anyhow from trying different opamps.
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby vvv » 30 Apr 2014, 06:14

Nocentelli wrote:I haven't tried the shod or honeybee but the hotcake is an overdriven opamp, and some people don't really like that sound. It was a bit woolly, and yes maybe a wee bit gated at the very tail of a complex chord, it might depend on the particular opamp used (metal can mojo notwithstanding).


I have the orginal HC and I might not like too much too, but question is about sound being "healthy", not of a personal taste here. Maybe some fuzzes being an exception that might be supposed to sound bad and gated. In overdrives it should be clear when the sound is broken and not working right (like unnatural or short sustain).
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Re: "Broken radio" -like note ends with 3 different OD pedal

Postby vvv » 30 Apr 2014, 06:38

Nocentelli wrote:Some circuits seem to work fine whatever the parts: Paul Cochrane's Timmy, and the skreddy lunar module for example, work every time, with specified opamp/transistors, or with anything else vaguely suitable.


I have same experiences that some pedals that I´ve made multiple times seem to work every time (that are Skreddy top fuel and other transistor-based stuff like muffs). Also some opamp-based builds are close but there´s enough to tell they are not perfect, like some Lovepedal tubescreamer-based stuff are very close to sound right but when testing properly you can hear some sustain lacking and also the nature of the distortion isn´t 100% right.

Maybe it´s a combination of many things. Bad quality components and that the circuit doesn´t suit to stripboard all that well, opamps biasing a little off etc. Maybe even quality of the stripboard copper, the legs of cheap components + incompatible solder would make every single solder joint only 99% perfect and then causing gating and crackling at the end of fading notes when the signal gets weaker.
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