PedalPCB Blender and reissue Fender Blender hum issue

TheGroke · Post by **TheGroke** » 08 Jul 2023, 09:41

Hi,

I have a reissue Fender Blender (corrected wiring and removed resistor to match the original per standard mods) and a PedalPCB Blender kit that both have the same issue: a constant loud hum that is masked when you hit a chord/note but which doesn't seem to actually ever go away. I just spoke to someone else with a reissue, and they said theirs also has the constant hum. But when I watch videos of the reissue online, they are seem to be silent.

I thought for sure the kit would not have the same issue, but it does.

Does anyone know whether this is just part of the design (online videos suggest not - but they could be removing noise) or if it is some issue related to the reissue and certain clones?

Any guidance would be appreciated.

Thanks - DT

CheapPedalCollector · Post by **CheapPedalCollector** » 08 Jul 2023, 10:55

It's a high gain pedal, if you have single coil pickups it will have hum.

TheGroke · Post by **TheGroke** » 08 Jul 2023, 13:54

Hi. Thanks, but I have other high gain fuzz pedals, and they don't make the same low frequency hum. I haven't tried to determine the frequency, but it sounds like it could be 50Hz (I'm in Sweden). Plus, rotating my body does not affect the hum only high frequency noise/RF.

mauman · Post by **mauman** » 09 Jul 2023, 00:14

Bump up the DC filter cap (C16 in the PedalPCB schematic) from the stock 10uF to at least 100uF and I think you'll hear a difference in 50 Hz filtering. You can go higher, but the incremental gain is pretty small above 200uF. PedalPCB schematic is attached for reference.

Blender Schematic.pdf: (159.81 KiB) Downloaded 35 times

TheGroke · Post by **TheGroke** » 09 Jul 2023, 11:10

Thank you Mauman! I will try this.

Lani · Post by **Lani** » 10 Jul 2023, 01:24

You could also try replacing D5 (PPCB schematic) with a resistor along with maumans suggestion to help filter a bit more (anywhere from 33R up to 220R) but you lose your polarity protection. You could bodge a diode across the DC barrel jack (cathode to + anode to -) if you still want some sort of polarity protection after replacing D5.

TheGroke · Post by **TheGroke** » 10 Jul 2023, 19:53

I added 200 uF filtering, and it is definitely helping tame that low hum. Both are usable now. My friend had some ferrite beads and we added them to the input as well. Not sure they are doing much in regard to the high frequency noise though.

I will try the filter idea that Lani suggested if the noise keeps bugging me.

And now I noticed that my factory Fender Blender has more volume and boost than the clone. Is this likely just a result of the two having different transistor specs? I don't even know what is in the Factory one - I think they removed the number.

Thank you both for your help!