Kingslayer crazy Squeal

[gblekas]

Took a look into the squealing Kingslayer issue and believe I found the solution.  The issue comes from the charge pump. Pins 1 & 8 are connected in this design.
A 10uf connected to pins 1 & 2 stops the squeal for sure but I didn't get to fully test this out.
What this did prove, to me at least, is that it is definitely coming from the charge pump.

I would try seating the charge pump but lifting pin 1 (?) from the socket to see if that removes the squeal.
In any case I convinced the circuit is not quite right as is.

[madbean]

Squeal can happen for a couple of reasons in the Kingslayer and its not so much the KS circuit design vs. the Klon but rather the type of active tone circuit the Klon uses. It adds a substantial amount of high frequency boost after the gain stage so when you are running lots of gain and volume and then add lots of treble boost on top of that, the opamp pretty much rails. This is why I point out that its more of a "two up one down" kinda effect. IOW - if you are running two knobs all the way up the other knob is going to have to be pretty far down.

One thing that can make the problem worse is the type of diodes you use for the alternate clipping. Personally, I like the way LEDs sound, but they clip far less than germaniums, which means more output which exacerbates the problem. So, you can use something with a lower voltage drop like 1n914 or a different kind of germanium diode. Alternatively, you can can use a larger value cap for C15 or reduce R21. But at that point, you are starting to get pretty far away from the "Klon-ness" of the thing.

Not sure about the 10uF between pins 1 and 2 of the voltage inverter...haven't seen that before and AFAIK it's not in the application notes for the chip so it's not something I would advise doing. You don't want to lift pin1 because that is boosting the internal oscillator frequency of the inverter out of the audio range.

[gblekas]

Different power schemes between the Sunking and the Kingslayer.

Not digging the Kingslayer and while I haven't completely figured it out I am certain it's more of a power supply issue with changing the gain in the tone section being an easier fix or perhaps a pulldown resistor in parallel to the clipping diodes.

Will keep at it because that is how I am wired....lol

fwiw, the Klon does not have these issues and while a dimed Klon won't sound good I never saw one with oscillation issues like this.

[midwayfair]

Before I address your solution ...

Different power schemes between the Sunking and the Kingslayer.

The difference is that the Kingslayer does not use the ultrasonic oscillator in the chip to generate a DC-DC pump (this is how the chip works: It's an AC voltage, which gets stored on a 10uF capacitor and then rectified. Because the cap can store the voltage in the system, you are able to trade current for a voltage increase, subject, of course, to the laws of physics!). The 1054 has a higher clock frequency, and the only rail whose output is taken from it is the negative. The KS also produces more gain in higher frequencies in part from the higher supply voltage of the first gain stage, so it's important to make sure it's as clean as possible.

You could easily test the klon power supply in the kingslayer on a daughterboard. Stick three blue LEDs after the +18V power supply and you have a +9V supply. OR you could power it off a battery and see what happens. If you think it's the power supply causing the problem, then a battery should be cleaner on the KS than a Klon.

Check your wire dressing (use shielded wire if you have to), power supply caps (did you grab just any old electrolytic, or are you using low ESR caps?), etc.

As far as your solution, here's the datasheet:

http://www.ti.com/lit/ds/symlink/lt1054.pdf

Any time you start adding components on a fairly sensitive circuit, you need to ask what it's doing. So. What's it doing? Your adds a capacitor from the oscillator output to the + voltage. There are a limited number of things that can happen here, because you don't have the diodes required for a voltage doubler. There aren't too many other things a cap can do in this position. One thing that is certainly happening, however, is that it filters the DC from your high voltage to a lower voltage.

If you put the same capacitor to a ground point, does it lose this effect? What about if you put it from the + rail to the - rail? (Which would be a more conventional setup -- see any number of split rail and AC supplies).

Why bother changing it if it's working? Well, I'd always be nervous about doing something that doesn't appear in the datasheet. Usually the datasheet examples are overengineered, not the other way around.

[m-Kresol]

are you running the KS alone or is there something else in the chain? I experienced heterodyning noise when I had a KS and a lectric-fx celeste chorus in chain, because they were both running on charge pumps and they somehow managed to produce an audible squeal. No problems when they were on there own.

and one more thing: I'm not trying to step on your toes here, but please don't come in with a first post and say things like

In any case I convinced the circuit is not quite right as is.

especially without hard evidence. No problem with you pointing out a problem as such, just be polite about it please. there are tons of people who have built the kingslayer who didn't have any issues, myself included. Brian always checks his designs over and over again to make sure they work as advertised.

[gblekas]

I really am not looking for an argument as much as a solution.
The basic circuit of the SunKing & KS are the same.
Zero complaints with the Sunking but a bunch with the KS so what is the difference?
Bypass & chargepump/power voltages to ICs being the two differences.

You mention lead dressing possibly being an issue but there are 4 short wiresthere from the board to the switch and they are nowhere near the charge pump so could that really be the issue?

Fwiw, I think the pcbs offered are great and not trying to create a problem that doesn't exist but there is an issue.

To attribute the issue to the tone section kinda makes sense in that it was running at 27 V before and now at 16, give or take?

Going to check to verify voltages again.

[gblekas]

Ok since it's not all pcbs with an issue I am now leaning towards a trace whisker close to a through hole pad. Or a manufacturer issue which I have seen on pcbs that I had made.
Weird how that happens.
Unfortunately I don't have the time at present to figure out where it is exactly but if I get to it I will report back.