[Sovkiller]

I got the new version of the MGHead DT/OTL and I just noticed that when I move the pot up and down there is an slight noise in the background, I think is because of the cheapo pot, is there any way of cleaning or lubricate it, or as the last option upgrading or replacing it, the problem is that all what I have seen (and I'm not an expert on that as you may noticed) have only 6 legs and are round, this one is a huge blue square cube with 8 legs, can anybody can tell me how to fix that or how to replace it, and by the way where to get an APLS or so to replace this cheapo one.....is there any special thing with this control any specific remark at the time of the replacing it, which is the value?

 

[mezzman]

I have occasionally encountered very slight scratching with certain 12ax7 or 5751 tubes, try rolling in a different tube.
It's a real pain to swap out the pot, unless the scratching doesn't go away, I'd just leave it in and maybe shunt the pot wit a pair of high quality resistors.

 

[Sovkiller]

I have a pair of JJ and a JAN Sylvania grey micas, regular stuff...but I'm waiting for a pair of Sylvanias 1964 NOS triple micas, I will try them, but with all the tubes I have in the hand is the same sh...t, I was wondering if any lubricant like Cail or so will help, but how to spray it inside in the main problem, these pots seem to be all sealed, at least I don't see any hole like the regular pots....

 

[Nick Dangerous]

The scratchyness depends upon the tube you are using. Some are quiet, and others aren't. Not sure if lubricating the pot will resolve this.

 

[Sovkiller]

It seems that the voice of the experience solve the problem again, Thanks Nick, I just replace the Sylvania with a GE and the noise goes to hell, disapears, but with all of the rest i have it makes the noise, but I have a concern now, does that means that the tube is damaged or has to be replaced? or is just the internal configuration or functioning of the tube what makes that noise shows up even with a good tube....?

 

[Nick Dangerous]

"or is just the internal configuration or functioning of the tube what makes that noise shows up even with a good tube....?"

That sounds more like it. If a tube sounds good, it doesn't really matter if the volume pot is a little bit scratchy, does it? Set the volume and forget it.

 

[wasifazim]

Quote:

Originally posted by Sovkiller I got the new version of the MGHead DT/OTL and I just noticed that when I move the pot up and down there is an slight noise in the background, I think is because of the cheapo pot, is there any way of cleaning or lubricate it, or as the last option upgrading or replacing it, the problem is that all what I have seen (and I'm not an expert on that as you may noticed) have only 6 legs and are round, this one is a huge blue square cube with 8 legs, can anybody can tell me how to fix that or how to replace it, and by the way where to get an APLS or so to replace this cheapo one.....is there any special thing with this control any specific remark at the time of the replacing it, which is the value?

The MG Head DT uses an Alps pot...don't know if the OTL does as well..

- Wasif.

 

[Sovkiller]

Hi dude, I don't know if is the same, but mine is a huge blue cube with the front and the back made of casted aluminum and one screw in each corner, and soldered to an small circuit board, has 8 legs in two rows of 4 parallel to the front panel, but I was not able to read the ALPS brand in any place so I don't know if it is or not, is a continue control, not with steps and the buttom is like the size of a nickel half an inch thick and black with a dot, I don't know if is the same model as yours, but as I posted before it seems to be the sylvania 5751 tube that I have in the center who makes the noise, as Nick suggested, I as a test replaced this one with another GE and the noise disapear so ALPS or not I'm not going to replace it for now, I prefer to get a tube without any noise instead, even when the tube is OK...

 

[markjia]

You like long sentances don't you?

just kidding...

anyways, aside from the missing label and the eight connectors, it does sound like an ALPS blue pot. Here's a picture of one so you can compare.

Alps pots are some of the best out there. I use one and don't have any problems with it (no scratching). Given your description of the build quality of MG Head, I suggest sending it for a replacement. If you change the pot yourself, you would most likely void your warrentee. Make sure there is nothing wrong with the amp before doing anything drastic.

If you really want to change the pot, Noble is another good brand. Stepped attenuators are even better (you won't get the scratching sound for sure), but they are quite a lot more expensive.

 

[Sovkiller]

It looks very much like this one, thanks man, but has 8 legs, why ??? maybe is a different kind, or maybe are disconected but are soldered to the board, by the way I think Joe Lau the manufacturer can answer that better...I will PM him, even when sometimes takes abuot a week to answer.....

 

[Joe Lau]

No ! It is not a Alps Pot but this manufacturer obtain major material from Japan but assemble in Taiwan. It is same grade as Alps 18mm type. Also not all alps pot is very high quality. Some alps pot using in Inductrial field is very chaep and noise. May be noise can eliminate or lower it by parrallel a 100K to 220K resistor from Top arm to moving arm. I will test it and may be modify it if it don't have side effect.

 

[eric343]

Joe - Try a good (Caddock?) 47K ohm resistor; a number of DIYers (Videoshielded for one) have had great results with that.

 

[Videoshielded]

I had the same problem with my MG Head DT at one point.

In my case, it was the pot, not the tube, that was the problem. However, with lower-gain tubes, the noise was somewhere between less noticeable and absent.

The wiper on one channel of the pot was mistracking slightly. I was able to manipulate the contact between the wiper and the substrate by wiggling the substrate through the connecter pin holes in the pot case, and this fixed the problem. Otherwise, I would've sent it back to Divergent for warranty repair.

Stuff like this is one of the reasons I hate pots. The MG Head is the only piece of tube gear I have that still has a pot in it. The only reason it's still there is because there's not room for anything else. The shunt mod solves many of the problems, though.

FWIW, the shunt mod won't "work around" this problem. The shunt uses the pot to shunt signal to ground, so you have to get the pot straightened out first.