EHX Linear Power Booster clone buzzing problems

trebbooster · Post by **trebbooster** » 09 Jan 2018, 08:02

Hello I built a Electro Harmonix LPB1 clone ( see diagram below)Having a problem with excessive hum/buzz, can anyone maybe give me an idea what I might need to do to fix it? It works fine other than the loud buzz. I compared it to a store bought LPB (that one was dead quiet in comparison) I was planning on putting it in circuit with a small 2 watt cigar box amp. On a breadboard plugged into that or a small fender champ, it has the same problem. Any help would be appreciated. Thanks

poiureza · Post by **poiureza** » 09 Jan 2018, 15:57

This circuit is so simple, not much to go wrong. My guess would be a ground issue.

How clean is the solder job ? no bridging ? Did you use solder flux ?

Did you build it on vero ? and is it boxed ?
You sure the vero isn't touching the metal chassis ?

How did you connect the different grounds (input jack, output jack, vero ground, battery return path or PS socket, vol pot ground) ?
Did you use plastic or metal jacks ?
Do you hear something when you touch the pedal with your finger ?

Did you socket the transistor ? or solder it directly ?

trebbooster · Post by **trebbooster** » 10 Jan 2018, 07:43

[/b]ANSWERS IN BOLD IN QUOTED REPLY[/b]

poiureza wrote:This circuit is so simple, not much to go wrong. My guess would be a ground issue.

How clean is the solder job ?MMMM COULD BE BETTER no bridging ? SEMI SURE NO BRIDGING, I DID CHECK WITH A MAGNIFYING GLASS Did you use solder flux ?NO

Did you build it on vero ?YES and is it boxed ? NO
You sure the vero isn't touching the metal chassis ? ON BREADBOARD

How did you connect the different grounds (input jack,COMMON GROUND output jackCOMMON GROUND, vero groundCOMMON GROUND, battery return path or PS socketCOMMON GROUND ON BATTERY, vol pot groundNOT GROUNDED, TRIED TO TOUCH TO COMMON GROUND SEEMED TO BUZZ MORE?) ?
Did you use plastic or metal jacks METAL?
Do you hear something when you touch the pedal with your finger NO?

Did you socket the transistor ? or solder it directly ?SOCKET

Any ideas other than starting all over with a new vero board( ugg)
THANKS

Manfred · Post by **Manfred** » 10 Jan 2018, 11:32

Did you test the boards using a battery or a power supply.
I had a similar problem with a booster pedal in the past, it work was working fine using a batterie,
but it had a lot of hum using the power supply.
Finally the power supply what defective and the hum voltage componet was too high.

deltafred · Post by **deltafred** » 10 Jan 2018, 11:35

Are you powering it with a battery or a power supply?

If power supply try a battery because there is no psu decoupling capacitors on your circuit (capacitors across the 9v supply to suppress noise). Any noise on the DC is going to be superimposed upon your transistor bias voltage and will be amplified. This means you will need a really smooth supply to power it.

If it is noisy on a battery then it may be that some of the wires on your breadboard are picking up Radio Frequency Interference (RFI) from any radiating devices (e.g. switched mode PSUs in PCs, LED lighting, etc, or fluorescent lights, radio transmitters). You could try putting your breadboard in a plastic bag then put that inside a large metal box if you have one (old biscuit tin etc) or wrap the whole thing in aluminium (baking) foil, which must be grounded.