Flamma FC03 delay - too boosty?!

[razabri]

Hey guys, just thought I could ask what would you do, if anything can be done - have this delay, cheap stuff but ok, but it's acting as a boost, amplifying the signal or compressing it, so that it's own "natural" noise is also amplified so you can't have really clean tone with it. All controls down, but no unity with clean signal. There are no trim pots inside to bias this, but maybe there is a way? Thanks.

[ElectricDruid]

So the signal when the effect is on is significantly louder than the bypassed signal? Have I got that right?

[idy]

The issue you describe is not a bias issue, but a level issue. When engaged your "dry" signal is boosted?
Is that big chip a PT2399?
I don't see any other ICs, so its internal opamps must be doing any boosting.
It is surface mount, and a circuit unlikely to be traced, so that makes it harder.]
There are things you can try:
That HFD4 is a relay used for bypass switching. Your effect out signal goes there. So does your guitar input (and the output jack, and the effect in.) You could figure out which pin is which and then put a resistor or trimmer to ground, and if you are lucky you would reduce either the signal into the circuit (which would reduce any distortion you are hearing) or the signal out.
If you are willing/able to "cut a trace' or other wise get deeper you could add a trimmer pot to one of those places that would act as a volume control. This is more of a sure thing, as the other way you are depending on a resistor in series nearby to create the "voltage divider."

[razabri]

Thanks for the replies - yes, its output signal level is higher than in bypass, with no signal there's hiss.

Not the bias, sorry, and thanks for the explanation on how this could possibly be moded to work better (as it should). Sending some more pics from the deeper insides, and that black chip from the last one says - 3PEAK, TPF632C, BDKw. I haven't done anything yet with the surface mounted devices, so if the mod would require some special tools than magnifying glass and solder iron, I probably wouldn't be able to do it...

[razabri]

Here's some more pics when the two boards are separated.

Also, I've managed to trace the four pins to the jacks - when the put jack is in the four middle pins from each side are connected to both signal and ground, and when the in jack is in the signal goes to the same pins and this time only to the output signal line.

[idy]

Doing it and getting rid of there noise... that is trickier. Or at least deeper. Cutting the output would be the blunt force approach.

[ElectricDruid]

Crikey, it's a complicated little thing! I bet it cost peanuts too. The amount of tech the Chinese can stuff on a board for pennies never fails to amaze me. It's possible they re-use the processor board or the IO board or both in other pedals to help keep the cost down (I bet other stuff in the range has the same layout of controls).

If that 14-pin chip on the lower board (the one with the jacks and relay on it) was a quad op-amp, we might stand a chance. It's going to be very difficult to find your way around such a device without a schematic though, and I doubt they're sharing.

Not an easy fix, unfortunately. As IDY says cutting the output and patching in some sort of trimmer for volume would be a blunt force approach but might work. If the noise issues are bad, it'll help a bit but not much - after all, you're not removing any noise, just turning it down.

[antonis]

So, you guys presume it's better to attenuate the amplified noise that to amplify the attenuated noise..

[ElectricDruid]

That's the problem, isn't it? If you're just going to turn it back up again when it gets to the amp, it'll still be offensive. Ultimately, there's no improvement to the S/N, just a drop in the volume of the noise and the signal.

Ironically, feeding the pedal with a hotter signal might actually help (more signal gives better signal/noise ratio). Stick a boost in front of it, and then you can still hear yourself with it turned down enough that the noise is quieter. It won't fix the different levels between bypass and effect though.

[razabri]

I just don't get it why would they crank it that way, as with the volume drop I could do (if it wasn't too much), but this... Found more reports on this issue with the same pedal - hissing, or "breathe", as a result of it being set too high with the output, I believe. Still, I'm not sure if this is the fault in the design, as some of the promo videos out there are without this issue. Could it be that, somewhere in the circuit, they repeatedly fail to make a connection, a loose resistor maybe, so its level stays all the way up all the time?

I don't know, perhaps the least intrusive thing would be to tie the resistor to one of the lugs of the relay and to the ground, but which?

Also, you're right I think, they are probably using same boards for the series - makes me wonder about those posts that are not used - four holes with some marks, one of which is 3.3v... I know there's not much chance, but maybe they forgot to put in there something that would regulate the level?

[razabri]

I've measured voltages at pins of the relay - what I have is 3.3v shown at the image and the value changes on the upper pin when it's on to something like 0.47v. Nothing relevant on the other pins, just 0.1v at two of them. I've randomly tried to connect a resistor to ground with one of the pins, trying different values. 1k at the place shown on the image did lower the hiss which was great, but that messed up clean signal, cutting the guitar signal as soon as you roll the volume knob down a bit, so that mod is not helpful. I have no other idea as what could be done to push it down a bit on the effect signal, without touching the clean one...