Effects loop issues

Hi all,

I have attached a YouTube video link that I made showing a strange noise that is coming from my Grandmeister36

https://youtu.be/igrbI96afZs

The noise has something to do with the effects loop. I have my volume pedal along with the Strymon Timeline and Big Sky in the effects loop. Also my tuner is connected to the tuner out on the volume pedal. If I disconnect volume pedal noise remains. If I disconnect all Strymon pedals, noise remains. Disconnect everything from effect loop noise remains. Also you’ll notice in the video that the tuner goes all whacky when that noise happens. Makes it almost impossible to tune during playing at church. Strange…

If I then disable the effects loop via button on front of amp head the noise is gone. Thoughts as to what is causing this? Thanks in advance for any help you can offer.

Best Regards

Tony Vitale

Haven't a clue what it is Stugotz but I can tell you your tuner WILL go whacky when it hears that.  The tuner is looking for a constant base frequency in the signal which it recognises as the fundamental of the note.  It's getting a dropping frequency with horrific overtones and is just unable to make sense of it.  I'm sure that isn't important.  It sounds to me like there is some sort of issue in one of your pedals rather than the amp having a fault.  If the amp works without this noise without the loop engaged then it is very unlikely to be causing anything untoward.

Try putting just a normal patch or guitar cable into the loop Send and Return sockets and engage the loop.  It should play as normal and that will test the Send buffer stage and the sockets.

Is there any chance that a pedal is demanding more current than the supply can give it?  That has nothing at all to do with voltage supplied which of course must match, the supply must be capable of giving at least a minimum amount usually shown on the ID labelling of the pedal.  If it can supply more than is required that is a good thing.  Digital devices are very demanding of current and normal supplies sometimes do not give enough.  My own supply has a number of 9V/100mA outputs intended for a single analogue pedal.  My only digital pedal requires 300mA which looks similar to both your Big Sky and Timeline which need 300mA each.  I can't use my supply with that pedal.  It may be that your digital pedal is trying to draw more than the supply can cope with and the processing part shuts down temporarily as it cannot sustain its normal action.  If the supply periodically tries to come up again and collapses once more this could be the sound of it.  It's just a thought.

How are you powering the pedals?  Do they all work together with any other amp with the same power arrangement?  Does the tuner still go whacky when the pedals are not plugged into the amp loop and the guitar is just plugged into the first one direct?

Thanks for the well rounded reply!!! Wow!
I’m using a DC ISO brick from MXR. The strymon are plugged into the appropriate spots getting the power they need. The noise still exists even when I have no pedals powered on. When I turn off the effects loop via front button the noise goes away.

You said "Disconnect everything from effect loop noise remains."  If you mean that you have the pedals completely removed from both of the loop sockets then that is important and a good observation.  It means that the pedals cannot be causing this.  Apologies, I missed the significance of this in your first post.

Remember I asked you "Try putting just a normal patch or guitar cable into the loop Send and Return sockets and engage the loop.  It should play as normal and that will test the Send buffer stage and the sockets. "  That is an important test.  The only area of the amp which could be causing this is the loop send buffer stage.  That tests it.

The GM36 is not like most other amps.  It's loop is controlled by a relay in the preamp so the loop send buffer and the sockets are not in use at all when the loop is bypassed, and you have no problem when it is in bypass and they are not in use.  Most normal amps use the switching on the loop sockets to route the signal straight through when nothing is plugged into the loop.

So r u saying to take one cable and put one end in send and the other end in receive?

That's right. It will put the sockets and the loop buffer stage into the signal path when you activate the loop. With no pedals in the loop they cannot be the cause. If this happens with just a plain cable in the loop then we know it is the amp, we know it works with no loop, therefore the fault must be in that loop send buffer stage or the loop sockets.

Gotcha. I’ll try that and see. Any idea what could be wrong with it. I don’t know anything about these types of electronics

If we can prove it is the loop buffer it is a very simple stage. There are only 5 components which are all cheap so a decent tech should sort it out pretty quickly.

Awesome. Thanks so much for the insight. I’ll let u know what happens!

well i have isolated the problem. It shows up as as soon as i connect my WMI-1 adapter into the fx loop. I am running it based on the H&K diagram here. page 11

http://hughes-and-kettner.com/wp-content/uploads/2015/04/WMI-1_BDA_E_D_J_1_0.pdf

If i run the WMI direct to amp all is quiet. Once its inserted in the MIDI chain thats were things go haywire. Thoughts??

It's a shame the shaky head smileys looks evil or mad, I could do with a sad looking one. The WM-1 is not one of my personal favourite pieces of kit. I'm not averse to things being wireless particularly for only control purposes, (I use an AKG wireless system myself but that's at the front end), but I don't see creating private networks as a simple thing to do and manage reliably. But that's only me, others will love them of course and good luck to them as long as it works for them.

Do you have a Timeline AND a Big Sky in the loop and both controlled by MIDI at the same time?

Do the pedals and the WM-1 all light up and stabilise as they should? In particular is the WM-1 showing it has made a successful network connection to your controlling device (maybe iPad)?

Are you using the correct Send/Return sockets on the Timeline? From the position of the plugs in the back panel, the vid seems to show you are using the Left channel. Is it possible to use the other channel just to check that aspect out?

I would check that you have the MIDI connections between each device the right way around particularly to your Fx unit. They should all be Out/Through -> In. I know first hand how easy it is to connect two 'In's or two 'Out's together even when you are well aware that is wrong.

I have the Strymon pedals in the MIDI loop. I do not control them via MIDI. I only wired it this way so that i can have my WMI mounted under my pedal board and permanently wired with minimum setup.
I was planning to control the Strymons with the FSM foot switch but for me its not really useful. its easier to just change presets as needed.

Yes all pedals light up as they should and the WMI works as it should.

I can try the other sockets i guess. but at this point its probably easier to just connect WMI direct and call it a day! LOL