C-lator hum

[ynor]

I tried the C-lator on another amp. Same problem here. Also ran it straight into a solid state power amp and guitar speaker. Same hum appears when powering on the C-lator.

[erwin_ve]

Your wall socket has a ground tab?

[ynor]

Your wall socket has a ground tab?

Yes. Also tried in another part of the house. Same problem.

[bepone]

Sorry to say nothing changed. The hum is still there.

connect c-lator to the amp, and download on the phone some free spectrum analyser app and let us know what is the frequency of humm? 50Hz? or 100 Hz?
If is 100Hz it is from rectification (not enough). If is 50 then we can discuss how to proceed.

It is very difficult to blind shoot your problem, need to be some instrument present to repair it.

[martin manning]

The heater circuit will either have a heater winding center tap connected to ground, or 2x ~100 ohm resistors, one from each side of the heater winding, connected to the chassis. Make sure that those connections are good by measuring from the tube heater pins to ground. You should see a very low resistance or 100 ohms, depending upon which type of ground reference it has. If the hum is present with the tube removed, i doubt that this is the cause.

Resistance between pin 4 and signal ground: 50 ohm. Between pin 5 and ground: 50 ohm. Pin 9 and ground: 50 ohm.

Also 50 ohm between each of the two heater taps on the PT to safety ground

All that seems good. Do the recover controls affect the hum level at all?

I recommend getting an auto-ranging meter if you are going to be working with electronics.

[ynor]

Do the recover controls affect the hum level at all?

I recommend getting an auto-ranging meter if you are going to be working with electronics.

No, hum is present with all knobs on the C-lator turned down. But it is increased when turning up the out knob.

I have ordered a new DMM with integrated oscilloscope and auto range earlier this weekend. Hope it works for this purpose.

I have sampled and recorded the hum on phone and in Protools. Will post the results later. Here’s a short video demonstrating the problem. The only things that are connected here are the power mains, speaker cable, and C-lator in amps fx loop. No guitar. Nothing in the C-lators loop. All volume turned down, except the C-lators out to have the hum amplified to a level that is suitable for the phone to record properly.

https://youtube.com/shorts/n5PR3_xa3aA? ... XDphboRh4Z

[ynor]

Here I have sampled the noise into ProTools. The C-lator is not connected to anything other than mains power and the "out" is connected to my interfaces input with a standard jack cable. So what is shown is the spectrum of the floor noise of the C-lator on its own. As previously stated, the 150 Hz is the most prominent hum.

Skjermbilde 2024-03-17 kl. 13.28.17.png

[ynor]

Here is my phones spectral analyser while recording the hum from the cabinet using my phones mic.

First is with C-lator turned off:

Screenshot_20240316_131742_Spectroid.jpg

And here is with the C-lator powered on:

Screenshot_20240316_131813_Spectroid.jpg

There’s a 13 dB boost at 150 Hz when turning on the C-lator.

From the youtube video you can also observe two other annoying noise problems that I have not adressed here yet. The PT on both the C-lator and OTS makes mechanical vibrations noise, probably laminations. I realize that this is common and expected, but I think they are vibrating more than I am used to comparing to my Matchless and Friedman.

Another annoying thing is that the OTS produses a low volume AC hum in the speakers also in standby. Removing the speaker cable of course silences the speakers, but when plugged in there's this hum also in standby. I've tried removing the power tubes but still there's hum, leading me to think that it is induction fields from the PT to the OT. Although these hums are annoying and more than I would expect, they are nothing compared to the C-lators hum.

[martin manning]

Do the recover controls affect the hum level at all?

I recommend getting an auto-ranging meter if you are going to be working with electronics.

No, hum is present with all knobs on the C-lator turned down. But it is increased when turning up the out knob.

If you ground the return tip is the hum still there? (trying to positively isolate the recover stage). You could plug a patch cable in to the FX return and touch the tip to chassis ground to test this. A missing or poor ground in that stage might cause this. You have tried changing the tube, correct?

I have ordered a new DMM with integrated oscilloscope and auto range earlier this weekend. Hope it works for this purpose.

You'll have to report back on how well that scopemeter works!

I have sampled and recorded the hum on phone and in Protools. Will post the results later. Here’s a short video demonstrating the problem. The only things that are connected here are the power mains, speaker cable, and C-lator in amps fx loop. No guitar. Nothing in the C-lators loop. All volume turned down, except the C-lators out to have the hum amplified to a level that is suitable for the phone to record properly

Sounds just like it looks, 50 Hz plus harmonics.

[Dr d]

"You have tried changing the tube, correct?"

This was my issue. I spent days trying to solve what i thought was a ground loop issue. Changed the valve and everything went quiet.

[ynor]

If you ground the return tip is the hum still there? (trying to positively isolate the recover stage). You could plug a patch cable in to the FX return and touch the tip to chassis ground to test this. A missing or poor ground in that stage might cause this. You have tried changing the tube, correct?

I tried changing tube. No improvement.

Grounding the return tip by using a patch cable in the return of the C-lator and touching tip to chassis ground doesn't change the hum.

You'll have to report back on how well that scopemeter works!

Sure will! It's a cheap $80 meter, but still loaded with functions that I don't have today with my current DMMs.

Screenshot_20240317_144719_Chrome.jpg

I cannot tell you guys enough how much I appreciate your efforts in helping me sorting this out

I wonder if I'm struck by PT transformer sickness, as I'm starting to doubt the XTs in both the OTS and C-lator

[sluckey]

I would completely remove the PT from the chassis. Then use some gator clip leads to connect the PT to the chassis. This should tell you if the location of the PT is the source of hum.

[bepone]

Here is my phones spectral analyser while recording the hum from the cabinet using my phones mic.

In spectrum analysis i see 100Hz component which is coming from rectification! So power supply is not ok like i suspected before.. CRCRC chain has some weak points. Maybe elcos are not connected properly or bad solder joint, or just bad design.. people usually doesnt know too much when designing something.

Then component od 150Hz is comming from 100+50Hz which is modulation of 2 frequencies- 100 and 50 Hz! All frequencies multiplication are seen in spectrum, k*50Hz , k is 1,2,3,4,5 are there and summs and deductionsfrom 100Hz basic frequency signal.

So both components (all is comming form 50 and 100Hz) need specific cures. 100 Hz is easy, it is from the supply and this need to be cured there via better filtering, or adding RC elements.

50 Hz components are coming from bad grounding and transformer magnetic coupling (residual magnetic flux around the transformer what other components are collecting and amplifying).
Cure no1. is move transformer to the max right position, i think i allready suggest that before. Then for the grounding we can discuss, we need to see in detail what is grounded where in this preamp. Now all the people will have million suggestions, and is difficult to follow million ideas. I know what i will do, but lets put this for the end.

Solve first major issues before, then we can discuss.

[ynor]

50 Hz components are coming from bad grounding and transformer magnetic coupling (residual magnetic flux around the transformer what other components are collecting and amplifying).
Cure no1. is move transformer to the max right position, i think i allready suggest that before. Then for the grounding we can discuss, we need to see in detail what is grounded where in this preamp. Now all the people will have million suggestions, and is difficult to follow million ideas. I know what i will do, but lets put this for the end.

Solve first major issues before, then we can discuss.

Thanks. Yes I also suspect the close proximity of the PT to the rectifier/filter circuit might be part of the problem. I'll try moving the PT further away as the next step.

[bepone]

Thanks. Yes I also suspect the close proximity of the PT to the rectifier/filter circuit might be part of the problem. I'll try moving the PT further away as the next step.

yes, to avoid the unnecessary drilling , you can extend all the wires frot he test and just drag PT around find the lowest noise point and fix it there.. (of course you will switch off the unit before some action every time because PT has exposed wires)