Hot Rod Deluxe: Buzzing

[tvandell]

Seems like my Hot Rod Deluxe is buzzing quite a bit these days.  Any thoughts?  For reference, it as less than 5 hours played on it.

[tvandell]

Seems like my Hot Rod Deluxe is buzzing quite a bit these days.  Any thoughts?  For reference, it as less than 5 hours played on it.

I'm afraid we're going to need to know a lot more than this. 

-is it 120 hz "buzz" or 60 hz "hum?"
-does it do it with no guitar or cord plugged in?
-does your room have fluorescent or neon lights?
-have you tried it in another room?
-how is the power in your room, grounded 3-prong?
-any dimmer switches in your house anywhere?
-if only buzzes with guitar plugged in, which guitar?  Did you try another guitar? Another cable?
-do any controls (volume, tone controls, reverb) reduce the hum or change its character? (this helps locate where in the amp the hum is originating)

etc etc etc.

Not sure about the hz.  How would I know.
Buzzes w/ or w/out guitar plugged in.
No flourescent or neon lights, but a plasma TV sits a few feet away.
I have no tried it in another room.
Grounded 3-prong.
No dimmer switches.
Buzzes a bit w/ all guitars, but the most w/ my Gibson RD.
No controls seems to have any effect on the buzzing but for the volume.

[RumorsOFsurF]

  120 Hz buzz sounds more like "EEEEEEEERH" while 60 Hz hum sounds more like "BUUUUUUUUH."  That probably tells you nothing. 

BTW, when I received my Hot Rod Deluxe new it had a bad microphonic preamp tube.  On the drive settings it would feedback uncontrollably even without anything plugged in.

[øøøøøøø]

Here is an example of 60 Hz hum.  Note that you can hear harmonics (120 hz, 240 hz, etc) which can make 60 Hz hum easily confusable with 120 Hz buzz if your speaker(s) have a hard time reproducing 60 cycles:

http://upload.wikimedia.org/wikipedia/c ... _60_Hz.ogg

I can't find a good example of 120 Hz buzz, but it sounds much like the above with the lowest fundamental (the bassiest bit) removed.  I'll keep looking for an example.

[tvandell]

Wow.  You guys are amazing w/ your advice.  Thanks so, so much.  I'll try any and all of your recommendations and report back.

[øøøøøøø]

Wow.  You guys are amazing w/ your advice.  Thanks so, so much.  I'll try any and all of your recommendations and report back.

Glad to (hopefully) help!  Let us know how it turns out.

[ollenorin]

i had the hrd.....rattled...way too icepicky treble.....it sucked.

great on low volumes which u cant gig with.

[øøøøøøø]

i had the hrd.....rattled...way too icepicky treble.....it sucked.

great on low volumes which u cant gig with.

Replace tubes and speakers and both those problems are solved

[tvandell]

i had the hrd.....rattled...way too icepicky treble.....it sucked.

great on low volumes which u cant gig with.

Replace tubes and speakers and both those problems are solved

Uh... might as well buy a new amp at that point.

[øøøøøøø]

i had the hrd.....rattled...way too icepicky treble.....it sucked.

great on low volumes which u cant gig with.

Replace tubes and speakers and both those problems are solved

Uh... might as well buy a new amp at that point.

Maybe.  or you might not have those problems.  Many people like the HRD just fine.

At its price point, I don't think you can do substantially better with a new amp.

You can replace certain vital tubes and the speaker and still come in under what some people are charging for amps that don't sound any better than a stock HRD.  I disagree with the reverb on the HRD, and think the "more drive" is useless and cluttery, but it's an otherwise well-designed and conceived amplifier.  It is definitely built to a price point but its heart is in the right place.

[RumorsOFsurF]

As I've said lots of times before, I love my HRD.  I've gigged it, along with my Twin Reverb for over 2 years with no probs.....except a blown jewel light.  It doesn't sound ice pickey to me at all.  I usually only use the drive channel with the gain very low.  Great amp for the money...

I swapped out one of the preamp tubes (V2) for a 12AY7 to tame the overdrive channel a little, and make for a cleaner sound overall.  Sounds great to me.

[tvandell]

so the volume control affects it?  That's good to know.

That means it's somewhere before the volume control.  This makes the problem very easy to track down,. because to tell the truth, there is not much in that or any guitar amplifier before the volume control, which is in the first gain stage.

First of all, take it into another room (or even another house) away from the plasma tv and anything else suspicious, if you want.  See if that changes the problem.   If it does, then your problem is environmental.  Do you have any other devices in your signal chain plugged into the same power source (effects, etc)?  You can try using a ground lift adapter on the amp (the thing that converts 3 prong to 2 prong) to lift the ground and see if you had a 'ground loop.'  You can also try rotating your amp 90 degrees and seeing if anything changes (can help detect radiated hum).  If you try all that and no change, read on:

Take the first preamp tube (the one farthest from the power tubes) out completely and turn the amp on.  Does it buzz?  it shouldn't.  If it does, double-check that the volume control affects it.  Write back with findings if anything peculiar.  If buzzing stops with first tube (called "V1") removed, read on.

Try replacing that tube with another one.  If you don't have a spare 12AX7 sitting around, you can try swapping it with another one later in the amp to see if the problem "moves."  Did the hum go away (or 'move')? 

If so, problem solved-- replace V1.

If not, then I would check the grounds on the input jacks.  If you don't feel comfortable dropping the chassis to have a look, you can take it back to the place where you bought it (sounds like you bought it brand new from a music store).  They should be happy to test/exchange it if defective.  The thing is, (and this is the main gripe I have with this and many other moderately priced PCB amps) the input jacks are soldered directly to the printed circuit board.  If the nuts holding them to the chassis should become even slightly loose, the only thing supporting them are the solder joints.  If one of the solder joints should crack, one of two things happens: either the input jack ceases to pass signal, or there is a prominent buzz/hum introduced into the signal.  The only way to repair it is to touch up the solder joint (or better yet, replace the PCB mount jack with a panel-mount switchcraft jack and three short wires). 

The way I see it, if the noise is unchanged with a guitar plugged in (though you said some guitars made it worse?), it has to be either 1) V1 preamp tube 2) input jack solder joint 3) something in the room/wall power/ground loop, or 4) the noise level is normal and you're just not accustomed to it.  Hard to say without hearing it myself.  I guess it's remotely possible that there's a failed filter capacitor from the factory.  But I'd lay odds it's one of the other things, especially if the amp is silent with the volume turned to "zero" (which, I gather from your second post, it is... correct?)

Good luck.

Oh, and the difference between 60 Hz hum and 120 Hz buzz: 120 Hz buzz is, obviously, an octave higher than 60 hz hum.  120 Hz buzz sounds more like "EEEEEEEERH" while 60 Hz hum sounds more like "BUUUUUUUUH."  That probably tells you nothing. 

Follow-up... When I turn on the amp, it's completely silent.  No buzzing.  I can crank the volume, reverb, etc.  When I plug in the cable into jack #1, the buzzing resumes.  It's lessened, albeit present, when the cable is plugged into jack #2.  Is it a bad input jack?  Shoddy cable?

[øøøøøøø]

well obviously try a new cable first.  You want to isolate the problem as much as possible, so things that are easy to change, like the cable, are the first things you should try.  After that, I'd be looking at the input jack. 

You're getting close.  It's narrowed down to a couple of things now.  Is the buzzing the same with or without a guitar attached to the cable?

[tvandell]

well obviously try a new cable first.  You want to isolate the problem as much as possible, so things that are easy to change, like the cable, are the first things you should try.  After that, I'd be looking at the input jack. 

You're getting close.  It's narrowed down to a couple of things now.  Is the buzzing the same with or without a guitar attached to the cable?

The buzzing's the same irrespective of whether or not a guitar is connected.

A buddy of mine just asked if it was truly a buzzing or just a hum.  I'm not sure I understand the distinction (semantics?); however, as I mentioned below, the audible "noise" varies depending on the situation.

I'll swap out the cable and see what happens.  The cable is the easiest fix, I guess.  Better than a blown speaker or something.

[øøøøøøø]

It's really just semantics, but when I think of "Buzz" i think of 120Hz (i.e. bad filter caps).  When I think of "Hum" I think of 60 Hz (ground issues,  etc.)