Whistling amp

[Tom]

When I turn up the volume past 10 o clock on my ultra module the amp starts making a high pitched whistle similar to feedback but not. Anyone else experienced this, and what can be done to stop it. I have tried changing the valves in module.

 

[goldwing68nv]

hey buddy! i have the reg Ultra module and i've experienced the same problem.for me,it happens as i'm right in front of the amp turning up the volume to a higher setting.at that moment,i get that "whistle",just for a second,then its gone.i can reproduce it again,after that,if i walk right up to the amp/speaker cab with my guitar really close,but that's about it.i guess that it's just some kind of little feedback deal...no biggie for me,though!!!

 

[MetalMajik]

I had a very similar problem with my ultra module and as it turns out it was not the module. The tube that supports the imput preamp had gone microphonic. It wasn't a problem with my Plexi or Clean modules I guess because they didn't have enough gain. Try turning the volume up when you don't even have your guitar pluged in, and if it does it then it could be your imput preamp tube.

 

[Scott]

Definately a preamp tube gone microphonic

 

[johnmfer]

Definately a preamp tube gone microphonic

Seconded, er.. thirded? I have heard this before with another amp, replace the preamp tubes and it'll go away.

 

[roodyrocker]

At band practice I ran into a similar whistling noise issue when using the higher gain modules. This was more pronounced when I turned on the chorus pedal. Anyway, on my pedalboard I use a Radial Engineering Switchbone to switch to my SWR acoustic amp when needed and one of the features on the Switchbone is a Ground Lift Switch as well as a Polarity Switch. Flipping the Ground Lift Switch completely eliminated the whistling noise for me.
just something else to consider if preamp tubes aren't the culprit.

 

[fulltruth]

I had a whistling issue with my Plexi module, and when I looked closely at the module I saw that a lead wire from one of the components on the board was sticking down really far and was almost touching the metal plate on the bottom of the module. I figured that when I inserted the module into its slot, the bottom was getting pushed up, touching the lead wire and causing a short. I took the module apart, clipped the wire, and when I put it back together the problem was gone.

In my case, the whistling happened when I shoved the module all the way into its slot. It wanted to stick out a tiny bit, and I had to give it a little extra shove to get it in compared to the other modules. I hope you're able to get your problem fixed!

 

[Tom]

OK Lots of ideas and thanks to all of you who replied. So far I took Metalmajiks advice and changed the input preamp tube.

This seems to have done the trick. But alas, when I cranked it up some other problems reared their ugly little heads.

This was a low frequancy oscillation then a loud thump which stopped the noise, but frightened the s**t out of me.

Anyway I've spoke to the shop and they have said they will send it to be checked over. But I will try it for another week before I send my baby off, as it's still seems to be working at lower volumes. This is a real shame, but Randall don't answer their E mails, so can't tell you what they thoguht.

I had a Marshall TSL and had 4 years of grief with it. I hope the same will not be true of the MTS combo. :?

 

[MetalMajik]

I must have missed the fact you have a combo. Well let me tell you from one combo owner to another that you are going to find yourself changing out that imput preamp tube pretty frequently. I've been told that combos are notorious for being "Torture chambers for tubes" especially if you gig a lot or play at high volumes. I run an Electro-Harmonix 12ax7EH in that position and I've had 2 of them go microphonic on me in about 6 months or so. It always seems to be that one tube in the imput preamp that goes for some reason. Here are some tips

Stick with tubes that have a short plate. Avoid tubes that have long plates like the Sovtek 12ax7LPS and the JJ EC0803 (My favorite in the Recto module)

You can swap microphonic tubes from your imput preamp over to the paralel FX loop. I never run my paralel FX much past 11 O'clock and this doesn't seem to be a problem.

I;ve found that the Sovtek 12ax7WA is a very durable tube. I got this one on the recomendation from a tube guru who says that "you can wack this one with a stick and not even phase it". Its not the best sounding tube though. It has a kind of neak-pickup warmness to it that I'm not too fond of, but it might work for you.

 

[Tom]

Mmm its squealing like a pig at the moment,regardless of volume. i'll try one more preamp valve change then it's back to the shop. It seems a shame that this valve keeps going if I had of known this I probably wouldn't have bought an MTS. Oh well such is life,anybody got sharres in a valve company, I might be looking to by in, especially 12ax7s :?

 

[MetalMajik]

Its not so much an MTS thing. If my amp tech is correct, all tube combo amps are hard on tubes and go through them fairly quickly because the tubes have a hard time handeling the vibration from the speaker. I was a little suspicious of this though seeing as how most head people set their heads right on top of their cabinets?!?

As for your other problems, I'm suspecting that there might be something funkey going on with either your module or your amp.

OHH by the way...I almost forgot. Did you check your speaker impeedance? Mine came set from the factory at 8 ohms and the manual even says that its supposed to be 8 ohms. But as I was changing out my power tubes I noticed a sticker on the very bottom of the magnet that said (were you could hardly see it) "16 ohms". So I set my impeedance swich to 16 onms and that helped a lot ot reduce squealing. you can test your speaker with a cheap multimeter (Mine reads at 14 ohms)

See if that helps

 

[Tom]

Must admit not had any trouble with 12ax7's before, on any amp, always been the output tubes or electronics.

The last Marshall (piece of s**t) was leaking across two pins on a valve socket. Marshall couldn't even find the fault, it took a private tech three months to find. Cost a packet as well thats why I got the MTS. Might stand a chance doing it myself. I love the amp just hate the grief Im having at mo. Still it still under warranty, thats a blessing.

I've got the 100 watt combo and two 16 ohm speakers wired in parallel giving 8 ohms, measures 7.

I've got one spare valve left at the mo, so i'll give that a try if no joy back to Randall Im afraid. But thanks for all the help i've learnt a fair bit more.

Still want to do the mod to the rectified mod but can't get hold of a poly carbonate cappy of the right value, also not sure what working voltage it should be.

 

[MetalMajik]

**** your luck :!:

 

[roodyrocker]

On Saturday night my band played out and I used my RM100. I had no noise issues at all whereas in our practice room always had something going on. In the practice room I had to use the Switchbone AB box I mentioned before as well as flip the polarity switch. In addition, the pedal board is plugged into the same powerstrip as the head. I also have a Hush pedal in the effects loop. This all worked good there. At the gig Saturday night my RM100 was quit enough that I didn't even need to turn the Hush pedal on at all. It performed and sounded great all night long!
You might want to make sure your pedals are plugged into the same powerstrip as your amp if you are using any, and perhaps plug the head into a power socket in another part of the house to see is something ekse is perhaps interfering with it?

 

[Tom]

Mmm I shall try that as the room Im in is quite small. But heres an update I changed the pre amp valve again, this stopped the horrible feedback.

But, the ultra module has started whistling again albeit at an higher volume.

Right, I cranked the little bugger last night, sounded great especially with the tube screamer. After about 5 min there was a horrible hot type sort of smell. I really don't know where I stand with this at the moment. Is it knackered or not, I just don't know.

 

[metalmm785]

Are you still under warranty from where u bought it?
I would get it replaced just to make sure if such was possible....or at least get it checked out to see if something may be going on
Mike

 

[Tom]

Here in the UK after a month they will only offer a repair, our consumer rights suck, and it's still under guarantee. The shop are sending me two more valves to try out. If this doesn't work and it still smells funny I think I willl get it checked out. Thanks again, you guys have been great. I''l let you know what happens.

 

[Tom]

Latest news - changed the valves in the module and the one in the amp. thats sorted the whistle out (seems to have, still there when cranked). The Randall repair centre here in the UK seem to think the smell is the viynal getting hot? This might be a blag so we'll have to see. :?

 

[model1]

i also had a quite noisy Ultra
i changed the EH tubes in the module for JJ ones wich sorted it out
sounds better now too
andy