Cherrybomb help...trailing sizzle noise

[salty]

Hi there. I am kind of new to building pedals and the Cherrybomb was my almost my first Madbean build and now trying to complete my second attempt at my first.

If any one could help me out, it would be greatly appreciated. I am at wits end with this build.

So, I bought a Cherrybomb board and populated it, got it all wired up and connected to my test board and it sounded great, except for this trailing kind of static/sizzle noise at the end of notes. It seemed to happen more so on some notes than others. I started swapping parts out thinking I must have something wrong...I ended up lifting a couple of traces and decided to start fresh with a new board.

I ordered the board and it arrive. I populated it with a total different set of components... the only thins I tried to use were the transistors.

I am having the same sizzle sound and this time it is worse than before.

I have tried all of the BC109 and other compatible trannies I have and all get the same result, that leads me to believe it is not my transistors causing the problem.

I read somewhere that the ceramic cap could possible be related and I saw that another layout for the circuit showed a 500pf, so I swapped in a 470pf that I had on hand. The problem still exist.

On my first build I ended up swapping out R6 and R13 for 2.2K instead of the stock 1.8K. The swap I made lowered the collector for Q2 and Q3 to around 5v, they had been almost 6 before.

On the current board I socketed those two transistors and currently have the 2.2k in the sockets.

My current transistors readings are:

Q1: BC169
E: .46
B: 1.01
C: 1.68

Q2: BC109B (I had another BC169 here and from all the putting in and out, one of the legs broke off)
E: 1.03
B: 1.67
C: 4.7

Q3: BC183
E: .92
B: 1.55
C: 5.1

Like I said, it sounds great, but that trailing noise makes it unusable.

Here are some shots of the board....I had to break the bottom shots into sections because I piggy backed my pots on the back with short leads.

[wgc]

There's a few solder joints that look a bit cold, especially from the top side. Ideally, the solder will wick through both sides of the hole, but it's not required. Just more likely that you created a good metal to metal bond that way. Connections to ground may need a little more time.  Flux helps. You can also try reflowing from the top.

Also double check the polarities on your electrolytic caps.

[twin1965]

I get the same type of sound. It happens as the note(s) decay. There's a few discussions on the Colorsound Overdriver describing the same issue.

I think the conclusion was that this effect does that normally. I could be wrong though! Anyone else has/built one of these?

I tend to use it for chunky/dirty rhythm as opposed to lead, so not too bothered.

If your problem is more severe then follow wgc's advice as a start.

Sent from my GT-I9100 using Tapatalk 2

[G.G.]

Mine sounds like that too, after listening to a few YouTubes it seems like that's what most of them sound like. I put a MP38a in Q3 (IIRC) and it lessened the sizzle on the decay a little. On mine it's most apparent in mid-gain settings and is less noticeable with the gain up more.

[salty]

Thanks for the replies!

I can reflow everything, my soldering skills are still being developed...so it is fair to not rule that out as the cause. I would be surprised though if I had a problem in the same area on both builds that led to the behavior I am experiencing. It could be possible though. I did check continuity between the components, is that a safe way to discover cold joints? Maybe there could be some wiggle room that is not detected that way? I am still learning all of this and really appreciate the help and advice.

I did verify that all the electrolytic caps are oriented to match the pcb layout...I thought that could be the problem on the first board.

I have a friend that built this circuit on tagboard from the tagboard site's layout. He is going to let me borrow it to see if I hear the same thing on his circuit that I am hearing on mine.

I did notice last night that the madbean layout has different electrolytic values than the other schematics I have found...could that be related?

Are the electrolytic caps like C5 and C9 important value wise? I notice on the madbean layout they are 10uF and on the other schematics I have looked at they are 4.7uF. Also C2 on the Madbean layout is 22uF where it appears to be 10uF on others. Is it possible that these play into what  am experiencing? I am wondering about swapping those values out jsut to see, unless you guys think it is a waste of time and that they would not have an effect.

It has a great sound for that chunky rhythm stuff for sure, but I also really like what it does EQ wise with a lower gain setting and would love to have the ability to use it for that. If you guys have not tried it with the BC169's and BC183/184, I would highly recommend that you do. In my opinion, those transistor really make this circuit sound great! To me the 109's were more punchy and out front, but not near as smooth sounding.

Thanks so much for the replies.

[salty]

Mine sounds like that too, after listening to a few YouTubes it seems like that's what most of them sound like. I put a MP38a in Q3 (IIRC) and it lessened the sizzle on the decay a little. On mine it's most apparent in mid-gain settings and is less noticeable with the gain up more.

Lol...well I guess I need to pull my first attempt out of the junk drawer then, as it seems it may be performing as expected.

[salty]

Thinking about it, and mind you I really have no idea what I am talking about.  , would the place to start be replacing the  C2 value with a 10uF that appears on other schematics? I know with the gain all the way off the problem does not manifest, but as I turn the gain up it appears. Is there anything to do with that higher cap tied to the gain control on the Madbean version that could cause the sizzle trailing noise? I honestly do not understand yet what that cap does, but it is one thing I can see is different from other schematics and is located in an area of the circuit that comes into play in order to reproduce the problem. Maybe I am totally off.

[midwayfair]

It sounds like the pedals are working properly. That fizz you're hearing is "transistor sound." Basically, every transistor-based distortion pedal makes it to some degree.

C2 is a negative feedback filter and affects the AC gain of Q1. It forms a hi-pass filter with R2, setting the cutoff frequency of the boost provided by Q1 (it's probably something like 1 or 2Hz, so "everything," but you could calculate it if you want at 1/2Pi*R*C).

Decreasing it to 10uF won't make any audible change. It's probably 22uF just to make all the emitter bypass caps (C2, C3, C10) the same size. You'd have to decrease it to something like 2.2uF before you start hearing any change in the bass content, and 1uF for anything really meaningful to happen. At that point I think it's possible you'd start getting some positive feedback, though.

In either case, it has nothing to do with the sound you're hearing, and I doubt you soldering does, either. Unfortunately, you might just not like the sound of this pedal.

[salty]

Thanks for the info on what C2 does. I am trying to soak up as much information as I can along the way.

I just spent about 45 minutes listening to clips of the pedal and clones online and in some of the clips I could hear the noise I am talking about....so I think it is part of the design and certain frequencies seem to exaggerate the effect. Some of the videos it was hard to tell if the camera mic was clipping or if it was the pedal. Other videos I did not hear the sound at all. This confused me a bit, is the sound more prominent with certain setups maybe?

So by transistor noise, what exactly do you mean? I finished up a Mayo build and did not hear a similar after note effect, is that just a difference in the circuit? Does the Colorsound circuit lend itself to that artifact more than other transistor circuits? If so, is there a way to decrease it in this circuit possibly?

I think I may really like the circuit in the end, just being new to building...I was sure I had something wrong. Then when others said they had the same thing, my mind went to, "why?" I tend to be curious and try to solve things logically, but sometimes my lack of understanding the rules of physics involved get in the way. So thanks again or the explanation of the C2 cap. So, why would some schematics go out of the way to change that one value? I did find a schematic from Sola Sound that had C2 as 25uF which is in line with the Madbean build.

I want to make sure it is apparent that I am not doubting anyone at all, just curious and like to dig for answers and think through things as I go. I see differences in circuits that are reported to be the same design and I wonder why the decision was made to change such things. Your explanation of keeping all the emitter bypass caps the same makes total sense, since the difference in size has no audible effect on the circuit when going from 22 to 10.

I do really like the tone of the pedal and if nothing else, I love what it does with the gain turned all the way down, running into my princeton ar bedroom levels, it really thickens up the tone and makes it sound more full and as if the amp was actually turned up more. The problem really only manifest at lower gain stages when it can be heard clearly as notes trail off. At higher gain settings it is a cool kind of add on to the distorted sounds.

[midwayfair]

"Transistor sound" is ... that noise transistors make when they distort. Op amps, too. A sort of crackle, harsh "bladt" sound. Some people call it "fizz." You don't hear that (or notice it) in the Mayo because that's mostly diode distortion, or at least mixed diode distortion.

Schematics aren't "going out of their way to change one value." That might be the value used in any particular build. I'm saying that if it's the original value and Brian changed it, he probably did so so that you don't need to get one 10uF cap, instead of just using the same 22uF that's elsewhere in the pedal. Because both values are big enough that there's no difference between them.

[salty]

Cool. Thanks so much for the information...learning all the time!

[GrindCustoms]

That's very weird... i've built many of those and never add an issue of that type.

You likely want to use transistors with gain/hfe betweent 450 and 550, can you measure the gain of the transistors you are using, from what i know a BC109B might be too low.

On my builts i also reduce the resistor at the input simply to hit the gain section harder.

Don't know if it could have an influence on the «problem» you are facing.

[salty]

Hey Grindcustoms,

Thanks for the reply. I can verify the hFE tonight, original I was testing the circuit with BC109C's and still had the problem. No matter which ones I put in, I get the same result. I am thinking maybe I should do a quick recording with my handheld and have someone confirm that theirs does the same thing mine is doing.

[GrindCustoms]

Those i built usually sound like this:

http://www.madbeanpedals.com/forum/index.php?topic=14730.0

[salty]

Okay, so I did a quick crappy recording of it using my hand held. I tried to find a setting that accentuated the effect. When I converted it to MP3 and uploaded it to SoundCloud it lost high frequency, but the sound is still there. Now it sounds like it blends into the actual note more than it does in person, but it does show the kind of splatty sizzle I hear with the pedal.

https://soundcloud.com/shane-salty-douglas/overdriver-sizzle