Noise with My Dumbleator Clone (Ceriatone)

[rane008]

Hey Guys,

This is my first topic post here, so please forgive any noob-ish-ness.

I've just received a 100w Bluesmaster and a C-lator from Ceriatone. Hooked them up, running George L cables between amp and 'lator, and I am getting a significant amount of hum on the amp. I'm pretty sure it's related to the power as I have tried this. Amp on, C-lator in loop, C-lator switched off = hum. Same scenario, but C-lator is unplugged = no hum.

Anyone have any thoughts on this? Checked the PT, it's tagged @ 120v, running it through a 3-prong chord supplied by Ceriatone.

Thanks in advance, guys.

[erwin_ve]

Hey Guys,

This is my first topic post here, so please forgive any noob-ish-ness.

I've just received a 100w Bluesmaster and a C-lator from Ceriatone. Hooked them up, running George L cables between amp and 'lator, and I am getting a significant amount of hum on the amp. I'm pretty sure it's related to the power as I have tried this. Amp on, C-lator in loop, C-lator switched off = hum. Same scenario, but C-lator is unplugged = no hum.

Anyone have any thoughts on this? Checked the PT, it's tagged @ 120v, running it through a 3-prong chord supplied by Ceriatone.

Thanks in advance, guys.

The clator is better known around here as a dumblelator.
Why do you switch off the Clator when in the loop? It should be on always.
Can you describe exactly the way you wired it?(maybe with pics?)

[rane008]

I was running the dumbleator off in order to test where the hum was coming from. Since I still got it when the unit was off, I assumed it was a problem with the cables or with the power.

The unit was ordered pre-built from Nik, so I don't have it wired any strange way. I've attached the layout from the Ceriatone website though.

[leleduke]

Before you try anything else chage the 12AX7 in your clator

[Structo]

If changing the tube doesn't help, try lifting the ground on the C'lator.
If that doesn't help you may have a ground loop.
Buy a three prong adapter and plug the loop into it.

But, since Ceria built them both, there should not be a ground loop.

Email Nik.

[paulster]

There is a ground loop with these by default since they are both Class 1 devices, so they are connected via signal ground and also via mains ground.

It is electrically unsafe to lift the ground on the loop with a 3-prong adaptor (which, incidentally, were designed to actually add a ground to ungrounded outlets) but it can safely be done with a few changes to the loop, using a pair of back to back diodes in parallel with a fusible resistor between the audio and chassis (mains) ground, and changing to insulated jacks so the audio and mains grounds are separated. See the schematic/service manual for the Fender standalone reverb reissue unit for a good implementation example.

One thing you can do without any change though is to minimise the length of the audio leads between amp and loop, and of the power leads between both of the units and the (common) power outlet they are plugged into.

That will minimise the possible potential difference between the two grounds which will go some way to helping the hum.

It's a surprise that more of these type of units don't suffer the same problem unless a lot of people are lifting the grounds.

[Structo]

I had a bad hum in my D'lator when I first built it.
I ended up snipping one of the shield wires on the recovery pot.
I can't remember which it was but I know I wired mine the same as everybody else according to the schematic.
Once I snipped the shield, no hum.

['67_Plexi]

There is a ground loop with these by default since they are both Class 1 devices, so they are connected via signal ground and also via mains ground.

It is electrically unsafe to lift the ground on the loop with a 3-prong adaptor (which, incidentally, were designed to actually add a ground to ungrounded outlets) but it can safely be done with a few changes to the loop, using a pair of back to back diodes in parallel with a fusible resistor between the audio and chassis (mains) ground, and changing to insulated jacks so the audio and mains grounds are separated. See the schematic/service manual for the Fender standalone reverb reissue unit for a good implementation example.

One thing you can do without any change though is to minimise the length of the audio leads between amp and loop, and of the power leads between both of the units and the (common) power outlet they are plugged into.

That will minimise the possible potential difference between the two grounds which will go some way to helping the hum.

It's a surprise that more of these type of units don't suffer the same problem unless a lot of people are lifting the grounds.

A ground loop is broken by breaking the loop....

Usually nothing more complex than sleeving back the ground of any signal cable that completes the loop is needed. I've never had to go beyond that method to break even the most complex loops in very large stage systems. You did mention the same thing by way of isolating jacks.
If you use Cliff jack sockets then these are isolated from ground by design (plus kids can't poke things inside the amp/unit either because they are encased). I can't think of one reason to ever use a Switchcraft style jack.....With the Cliff jacks it is possible to easily implement ground lift switches right there in the buffer unit to deal with all potential ground loop situations.

I concur with the 'never us a 3 to 2 pin mains adapter'.
The screen (shield) of a signal cable is not designed to deal with fault currents....plus the safety earth should always be seperate and bonded to the chassis. Using a jack plug is hardly bonding anything.


The earth bond from the mains input should always be bonded to the chassis as close as possible to the mains input using it's own seperate wire and ground point. In some countries it is required to mark that point as the electrical safety ground with the appropriate symbol next to it. There are also certain color requirements for earth cables in most countries. Green/Yellow and solid green being the most common.
It should never be bonded with power supply or signal grounds like it is shown on the Ceriatone drawings....thats just wrong.

Amp building 101...Signal grounds, power grounds and safety grounds are three seperate entities and the more you think about them being seperate and knowing where the various currents flow through the amplifier/unit, the more quiet and safe your build will be.

Alan P.

[UltraHookedOnPhonix]

A ground loop is broken by breaking the loop....

Usually nothing more complex than sleeving back the ground of any signal cable that completes the loop is needed. I've never had to go beyond that method to break even the most complex loops in very large stage systems. You did mention the same thing by way of isolating jacks.

I’ve always wondered why Alexander didn’t solder the coax shield on the signal wire leading to the Recovery Input pot wiper but did on the other two pots. Maybe this is relevant to what you’re referring to?

Take a look at the middle pot in the picture:

[IMG:840:630]http://i205.photobucket.com/albums/bb17 ... putPot.jpg[/img]

[Structo]

That's probably the cable I snipped the shield on.

[rane008]

Wow, guys, thanks for the info. You guys are pros (unlike me, hehe).

I will probably end up taking it to my tech, but if there is something I can do that doesn't require too much technical knowledge (I do have ample common sense). I'd like to know that. For instance, which wire was it that you snipped Structo, if you can remember? That may be something I can take care of on my end.

Thanks, again, guys,


Stephen

[Structo]

Try snipping the braided shield on the cable that goes from the middle pot to the board.
If you have a soldering iron it would be better to un-solder it in case you need to hook it back up.
I'm 90% sure that was the one I clipped.

I am a bit surprised this hasn't come up more with the guys building their own.
It may also be why several including Gil Ayan used isolated jacks.

[rane008]

Thanks, again guys. I'll let you know how it goes.

Stephen

[Stromgitarrenspieler]

Thanks, again guys. I'll let you know how it goes.

Stephen

One thing you might try, too: Check all the ground points inside the clator.
Got mine from Nik 3 weeks ago and the new guy, who build the clator did not scrap off the paint at the ground points inside chassis.
I did that and the hum was gone

[rane008]

Hey Strom, I did exactly that, and it was definitely the problem. Thanks for the suggestion, though!