Thermionic Deluxe background noise/hum/hiss

[ferdinandstrat]

I am experiencing quite a lot of background noise from this pedal, even while enclosed. I am using a wall wart and I am not daisy chaining anything. Several higher gain pedals produced much less background noise than the Deluxe using said wall wart and I've read quite a few times online that the F***dM*n tends to be a bit on the noisier side

Is the issue inherent to the pedals or is there a way to remedy this?

 

[zgrav]

are you getting a 60Hz hum in your noise? high pitched whine? hiss? is the noise constant regardless of where any of the pots are turned?

 

[Chuck D. Bones]

I would say it is not normal. I built a Betty, which is 1/2 of a TD and it is quiet. With all of the knobs at noon, except volume at 9 o'clock (unity), and the input grounded, there is no discernible difference in hum or hiss between engaged and disengaged. With the Gain all the way up, there is a slight hiss. High-gain pedals will have some noise, there is no way to eliminate it completely, but there are ways to minimize it. It is important to use quality parts, clean the board thoroughly after soldering and make sure that the pots, switch & jacks make electrical contact with the chassis.

 

[ferdinandstrat]

are you getting a 60Hz hum in your noise? high pitched whine? hiss? is the noise constant regardless of where any of the pots are turned?

The noise is dependent of the amount of gain, its basically white noise, not squealing.

 

[Nostradoomus]

Any build pics?

 

[Chuck D. Bones]

Is the noise the same with either channel selected and nothing plugged into the input jack?

 

[ferdinandstrat]

Is the noise the same with either channel selected and nothing plugged into the input jack?

No, its specific to when a guitar is plugged in, hand on strings and not playing. The amount of noise changes with each channel because one is lower gain than the other

Sadly I dont have any built pics

Its basically the same noise coming from cranking up the gain on almost any pedal, its not squeeling

 

[Nostradoomus]

Does adjusting the trim pots have any effect?

 

[Chuck D. Bones]

Unplug the guitar at the pedal and see if the noise goes away. If it does, then the pedal is working normally. Pickups, volume pots, even cables generate noise. Any pedal with gain (and this one has plenty of gain) will amplify the noise.

BTW, the channels have different gains if the gain trims (TRIM A & TRIM B) are set the same. You can dial in the same gain on both channels by adjusting the trims.

One more point, the wiring diagram in the build doc shows two wires going to the input connector. The connector I use (Switchcraft #12A) for the input side has a 3rd contact that connects to the tip terminal when the connector is unplugged. I wire that terminal to ground so that when nothing is plugged in, the pedal's input is grounded. Almost all production pedals are built that way.

 

[ferdinandstrat]

Does adjusting the trim pots have any effect?

Yes but it lowers overall gain which defeats the purpose of the pedals IMO.

 

[Bobbyd67]

I also find it quite noisy :/ would using shielded cable help ,

 

[Chuck D. Bones]

Once the box is closed up tight, shielded cable inside doesn't do much of anything. Read my first post; my Betty is not noisy. Here's a gut-shot. Resistors are all metal film. Caps are either film or tantalum, except the 100uF power supply filter cap. Yeah, the solder joints on the power connector look sketchy at this angle, but they are solid. No, I don't use IC sockets. One thing I should have done was clean the board one more time after installing the pots; you can see flux residue around all of the pot solder joints. Note the use of tooth washers on the I/O connectors. Makes for good grounding and they'll never come loose. Also note that the input jack has three terminals. It shorts the input to ground when the plug is disconnected.

 

[ferdinandstrat]

Here's the deal, I did build the Brown Betty and I dont recall it being as noisy

 

[Chuck D. Bones]

I just checked the schematics, the only difference between Betty & Thermionic Deluxe ch B is C8 & C9. TD has more bandwidth, but that only affects the noise above 1.5KHz. If I read your earlier post right, the noise goes away when you unplug the guitar from the input. If that's the case, then the pedal is not making the noise, it's amplifying the noise from the guitar and/or cable. It's possible that the gain is too high in the 1st or 2nd stage. Have you verified these resistors: R4, R5, R8 (both A & B)?

 

[ferdinandstrat]

I just checked the schematics, the only difference between Betty & Thermionic Deluxe ch B is C8 & C9. TD has more bandwidth, but that only affects the noise above 1.5KHz. If I read your earlier post right, the noise goes away when you unplug the guitar from the input. If that's the case, then the pedal is not making the noise, it's amplifying the noise from the guitar and/or cable. It's possible that the gain is too high in the 1st or 2nd stage. Have you verified these resistors: R4, R5, R8 (both A & B)?

No dude, you read wrong, its making the same noise plugged or not

 

[zgrav]

This part of the answer above gave the impression that the noise is only there when the guitar is plugged in

"No, its specific to when a guitar is plugged in, hand on strings and not playing. The amount of noise changes with each channel because one is lower gain than the other "

If the same noise is there even if nothing is plugged into the pedal, and when you are using a power source that is quiet on other high gain pedals, then I would check the resistor values for R4, R5, R8 as suggested above. If that does not work you should see if you can find a way to post some pictures of your build.

 

[Jiuk]

I builded both Thermonic Distortion & Dirty Betty. It was full of hum noise so I couln't use it. I felt it was wrong, so had re-soldering all and all the noises were gone.. very clean when it's full drive. Both pedals are best pedal to me now. Good luck to you.

 

[Mourguitars]

Once the box is closed up tight, shielded cable inside doesn't do much of anything. Read my first post; my Betty is not noisy. Here's a gut-shot. Resistors are all metal film. Caps are either film or tantalum, except the 100uF power supply filter cap. Yeah, the solder joints on the power connector look sketchy at this angle, but they are solid. No, I don't use IC sockets. One thing I should have done was clean the board one more time after installing the pots; you can see flux residue around all of the pot solder joints. Note the use of tooth washers on the I/O connectors. Makes for good grounding and they'll never come loose. Also note that the input jack has three terminals. It shorts the input to ground when the plug is disconnected.

View attachment 995

C.D.B you brought so good tips in your reply..

So before and after you clean the board and wipe with the isoproptl to remove flux to prevent problems correct ?

Use the tooth washers on jacks to get a better ground..

If you get a powder coated enclosure should you scrap area over spray or coating off around the pots , power jack and input / output jacks to get a better ground exposing some bare metal if using a flat washer, maybe score the area on the inside pretty good ?

Could you use copper shielding tape like you do on a Strat to help with ground , i seen someone mention the 60 cycle hum..thought i would ask

I used the tooth washers on jacks and pots on my Thermionic Distortion and its dead quite which is amazing ...didnt know if its because i used the tooth washers on the pots and jacks, used the shortest wiring possible...if any of that helped

Also you used a stereo jack on the input jack, is that for better ground ?

Mike

 

[Chuck D. Bones]

I always clean my boards after soldering, makes inspection easier and flux can attract debris, moisture and create undesirable electrical paths.

I have not had to abrade the inside of the powder coated boxes I use. I believe the tooth washers do a good job of biting thru the paint. It certainly doesn't hurt to abrade the inside.

The box is metal and makes an excellent shield. Adding copper shielding won't make it any better.

We follow best practices when building pedals so that we avoid problems. Keeping wires short and more importantly, keeping input & output away from each other is always a good idea.

That is not a stereo jack, it is a grounding jack. When nothing is plugged into the input jack, the jack automatically shorts the input to ground. Keeps the pedal from acting like a radio receiver when nothing is plugged in. Is it necessary? No. Is it a good idea? I think so.

 

[Mourguitars]

Very Cool C.D.B !

Excellent advice..you are the man !

Thanks for all your help

Mike