I can't figure out the source of buzzing in my Ironheart 60

[Ademsan]

Hey all. I recently started having sound issues with my Laney Ironheart 60 amp. I noticed sometimes when I use the clean channel I get a kind of crackling (random pops), but on the gain channels (rhythm and lead) there was no issue. But recently I started having a buzzing sound on these channels, but only when a guitar is plugged. I made a video to document the issue: https://www.youtube.com/watch?v=wh8kaVTZ5_w

So here's things I did to try to diagnose the issue.

1- Buzz sound:

- There's buzz only when a guitar is plugged in.
- Unplugging the guitar stops the buzz.
- The buzz is present with any of my guitars.
- Reducing the volume on the amp reduces the buzz.
- Reducing tone from the tone knob on my guitar significantly reduces the buzz.

2- Crackling/popping sound:
-On the clean channel there's crackling/popping sound.
-Plugging a guitar adds a buzz to the crackling.

Any help would be appreciated.

Thanks.

[Wonks]

Probably a failing preamp valve, and it's likely to be V1, the first one,

With no guitar plugged in, the input is grounded.

Are you happy dealing with valves?

[Ademsan]

At this point, I really hope it's just a failing valve. I didn't know they could cause buzzing. I thought the problem was worse.
Thanks man.

[Hugh Robjohns]

The buzzing is obviously coming from the guitarbecause its affected by the guitars tone knob — therefore it is being generated before the tone knob.

Guitars are basically aerials which pick up RF signals in the air. LED lights often generate RF noise that the guitar converts to buzz for example. There are lots of other possible sources.

Screening the control cavity often makes a big improvement. Search the guitar forum for specific guidance.

The popping/cracking could well be a front end valve, or a valve later in the clean channel path... or it could be a failing capacitor or even a dry-joint or dirty connection in the circuitry.

[Wonks]

There's always the risk of ground connections coming loose in any amp from vibration. So I'd first check the main power ground connection to the chassis is really tight.

The board with a lot of the pots and input jack in seems mainly to be supported by the pots, so there's a risk of solder joints cracking around the input jack. I'd remove the knobs and tighten the pot nuts.

I'd test the ground path resistance from the input jack sleeve connection to the earth pin on the IEC socket; this should ideally be as close to a dead short as you can get.

I've seen reports of the valve base soldering joints being cracked, so it's worth giving those a visual inspection.

And the FX loop return jack switch connection can oxidise if not used and provide a high resistance and allow electrical noise in, so it's always worth some contact cleaner in those jacks and insert a jack plug several times.

[Wonks]

Has the buzzing come on gradually, or did it suddenly start? If suddenly, have you introduced any new equipment into your guitar room around that time (that could be putting out a lot of noise).

Have you checked your guitar cables for good solder joints? Have you tried a different guitar cable?

Is this with the guitar plugged directly into the amp or have you got a pedalboard. If a pedalboard, have you added any new pedals or changed their arrangement? Does the power supply for it have galvanically isolated outputs?

[Ademsan]

Ok guys, I did a stupid. I use a Boss NS-2 noise pedal (only pedal I use) hooked through the FX loop which filters out the buzzing noise, so I didn't notice it for the longest time. At some point, random pops and a low-level hiss started going through even when I'm using the noise pedal. So, I removed it and connected my guitars directly to the input jack of the amp. That's when I noticed the buzz (in addition to the pops). So, first thing I did was to change the cable, and I used a cable (the one you see in the video) I was using for a monitor that I didn't use in a long time and still got the buzz, so I concluded that it's not coming from the cable.

Today, as per your suggestions, I repaired the original cable and used it to connect my guitar to make sure it's not from the cable. Lo and behold, the replacement cable was also faulty. Good news: no more buzzing sound. Bad news: pops and crackles are still there.

I guess now, the most likely explanation for these sounds is a faulty tube.

[Ademsan]

Here's a new video of the problem: https://www.youtube.com/watch?v=ykTw-gB6LgE

[ajay_m]

What does the amp do when you just short out the far end of the guitar cable? And if you put a DVM on the far end across tip and ring on a low current range eg microamps, is there any current flowing? It's been a long time since I've worked with valves but we can't rule out passive component failures either. Really I'd want a service manual and be plugging my scope in to check power supply voltages, ripple, grid bias all within tolerance, no evidence of leaky caps etc . Let me just see if I can find a schematic online, that might help.

[Wonks]

Ajay, the buzz is now gone. Just the crackles/pops which is usually down to a failing valve (or valves).

[ajay_m]

Yeah there's a service manual at electrotanya. Looks like the input feeds an tl084 opamp which then feeds an ecc83 triode. There's a bunch of those in there so one thing worth trying is to just swap the front end triode with another one eg the one on the slave input for example and see if the problem remains the same. That more or less eliminates the front end valve as the source since you'd expect a change in behaviour if it is faulty.
Caution: high voltage caps can retain potentially lethal charges with power off. Take considerable care working on valve circuitry.

[Ademsan]

Alright everybody. Problem solved. After I took the video, I turned off the amp, but I forgot to turn off the Boss-NS2. Later, when I walked past it, I noticed the leds flickering, so I figured something must be interfering with it. I started unplugging the devices I have home. It turns out the wifi router was causing the pops and cracks. I just need to move it to another room now.

Thank you all for your help.

[Eddy Deegan]

It turns out the wifi router was causing the pops and cracks. I just need to move it to another room now.

Thank you for following up with that info Ademsan

[Wonks]

I’m not sure how that is happening, unless there’s something wrong with the router or it’s feeding noise out into the mains. Maybe the PSU rather than the router itself?

I run my valve amps a few feet away from a wi-fi access point and don’t have any problems.

[adrian_k]

Some time ago I was getting buzzing when playing electric and decided it was a wifi repeater unit nearby. Moving away solved the problem. I never did a proper fault analysis. It happened with any guitar. The amp is an old Fender 25 Watt solid state.

[Ademsan]

I’m not sure how that is happening, unless there’s something wrong with the router or it’s feeding noise out into the mains. Maybe the PSU rather than the router itself?

I tried using different power sockets to power the amp and I got the same pops and cracks. But you're right, something must me wrong with router. It has been running in that place for almost 3 years without interfering with the amp.