Questions about recent build.

ignition · Post by **ignition** » Wed Jul 22, 2009 11:42 pm

I know it's kind of hard to quantify with words, but I finished up a 100w Metro Plexi build and was wondering how much noise is normal. If all the controls are turned up all the way, will it squeal? Mine does. Not too bothersome, because it isn't played like that.

It also has a vibrating kind of hum to it. Not audible through the speakers. Just being powered on, you can hear the transformers and feel it buzzing a bit through the chassis. (not electrocution!!!) I imagine this is normal, but want to be sure.

Also, is the Volume 1 channel supposed to be extremely bright? I found that I don't mind Volume 2, but prefer to jumper the two.

Cabbagebreeze · Post by **Cabbagebreeze** » Wed Jul 22, 2009 11:55 pm

If you are cascading it can easily squeal. Do a little chopsticking. Also, just double check your bias, perhaps a high current is making your pt vibrate a little too much.

neikeel · Post by **neikeel** » Sat Jul 25, 2009 10:43 am

ignition wrote:I know it's kind of hard to quantify with words, but I finished up a 100w Metro Plexi build and was wondering how much noise is normal. If all the controls are turned up all the way, will it squeal? Mine does. Not too bothersome, because it isn't played like that.

It also has a vibrating kind of hum to it. Not audible through the speakers. Just being powered on, you can hear the transformers and feel it buzzing a bit through the chassis. (not electrocution!!!) I imagine this is normal, but want to be sure.

Also, is the Volume 1 channel supposed to be extremely bright? I found that I don't mind Volume 2, but prefer to jumper the two.

If you are testing it out of the cab and cranking it (particularly the presence) it will squeal as the chassis bottom needs to be covered with an aluminium sheet (most headboxes come with these already fitted). Make sure the transformers are sitting squarely and are fully clamped and bolted down to the chassis. You may also find squealing if the presence wires are not routed away from other wires and throughout the amp check that signal wires do not touch or cross unless they are at 90 degrees to each other. Check the bit at the end of the build instructions (often the bit that gets passed over as people get impatient to test

)

Hum is one of those things that as you do more builds and have neater wiring and proper grounding schemes does not usually give a problem.

Flames1950 · Post by **Flames1950** » Sat Jul 25, 2009 10:48 am

To clarify Neil's post above, if you run the purple wire from the turret board to the presence pot right to the front of the chassis and under the other tone controls you often get squealing at high settings. Instead, push it back under the board and then bring it straight out to the presence pot, and usually the squeal is gone. Unless, as stated above, the chassis is out of the head cab, where it isn't shielded anymore.

ignition · Post by **ignition** » Sat Jul 25, 2009 11:00 am

No, the testing that I'm doing is always in the headcase, and it does have that shielding in tact. I'm pretty sure that I have everything already squared away that was mentioned in this post. Let me know if I'm wrong.

Take a look at some pictures of my build. I'd be curious to hear what you think of the quality. Is there anything that I should change or work to improve? I can post more pics if needed.

Chassis Shot.

Chassis Shot at an angle.

neikeel · Post by **neikeel** » Sat Jul 25, 2009 11:56 am

It all looks all there to me. All those looped and tied wires form the PT could do with pushing across into the far end of the chassis and one or two wires could do with shortening to take out the loops without tension but otherwise it should be fine. Also if you can try to gently work your heater wires so that they lie right in the corner of the chassis away form the signal wires. Your presence wire (to the selector has the usual and virtually unavoidable problem of running with the other wires) and can give rise to cross talk and as suggested above the chopstick method may help find a non-squealing position.

novosibir · Post by **novosibir** » Mon Jul 27, 2009 3:02 pm

neikeel wrote:Your presence wire (to the selector has the usual and virtually unavoidable problem of running with the other wires) and can give rise to cross talk and as suggested above the chopstick method may help find a non-squealing position.

Agree!

That's (as far as I can see) the only point, from where crosstalk/coupling/squealing might occur.

Larry

Mcewen4444 · Post by **Mcewen4444** » Tue Jul 28, 2009 10:37 pm

ignition wrote:
It also has a vibrating kind of hum to it. Not audible through the speakers. Just being powered on, you can hear the transformers and feel it buzzing a bit through the chassis. (not electrocution!!!) I imagine this is normal, but want to be sure.

I just built my second 100w kit, and this one has this buzzing as well. My first one does not do this nearly as loud. With the amp in the headcase sitting on a 4x12, with the first amp I built powered up sitting on another 4x12, one hand on each, I can easily hear and feel the difference. This is with both amps on standby. The new build doesnt sound as beefy as the first one, with some kind of added noise I find hard to describe, am still troubleshooting that. I did notice that the PT on the new amp is narrower. Not including the bell ends, first amp PT is 2 1/8 inch, while the new one is 1 7/8 inch wide. Not sure if that is significant.

I'll start a thread on my amp after I go through it again and check voltages, check grounds, and take pictures. It is quite possible that I screwed something up, but when you mentioned the buzzing with your amp I had to put my 2c in.

neikeel · Post by **neikeel** » Wed Jul 29, 2009 4:09 am

Mcewen4444 wrote:
I'll start a thread on my amp after I go through it again and check voltages, check grounds, and take pictures. It is quite possible that I screwed something up, but when you mentioned the buzzing with your amp I had to put my 2c in.

Good idea

dtdionne · Post by **dtdionne** » Fri Aug 07, 2009 4:37 pm

I noticed that my 12xxx series hummed a fair bit (just like your describing) more then any of my other marshalls...oddly it also squeals which im working on so I'll be sure to watch this thread.

ignition · Post by **ignition** » Sun Aug 09, 2009 10:49 pm

Finally had a chance to go through the amp again and found a few things. The bias was running a bit hot. I forgot to recheck after a few hours and it was high. Seemed to reduce the buzzing sensation.

I tried a bit of poking around with the chopstick, and it didn't seem to make too much of a difference. I went ahead and retied the excess transformer wires off to the corner and pushed the heaters into the corner.

I also replaced the feet on the amplifier. They were really small and hard. Just swapped them with a practice amp that I had laying around.

All told, seems that the issues have resolved themselves. Thanks for the tips!!!

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