Wierd noises coming from 6505 combo (Need help ASAP!)

[broj15]

So over the past couple weeks my 2x12 6505 has been acting up. It sounds just as good as it always has when I'm actually playing, but sometimes when I'm not playing I'll notice a weird kinda rhythmic tapping/clicking, almost like someone was winding a clock, coming through the speakers.

Sometimes it's fast and almost kinda sounds like a fart with a tiny bit of reverb (not trying to be funny... this .... is really pissing me off) and sometimes it's slow. When it happens I can play quietly and the sound is still there, but everything else sounds like it always has. When I play loud with my OD on it's still there, but the sound of the actual guitar is enough to drown it out. Once again, with the OD on everything sounds normal except for the mysterious clicking. And it only happens intermittently, and flicking the amp to stand by for about 10 seconds and then turning it back on again fixes the problem but after about 10 minutes of playing it comes back.

I've done some research online and all I can think of is that it could be a bad preamp tube, however I can't find anyone else who's had the exact same problem so I'm afraid it could be something less simple and more costly.

If it helps the only thing I have going into the 6505 is a fulltone OCD out front used as a boost and a Boss GE-7 in the effects loop. I have 3 shows over the next 10 days and need to get this sorted out ASAP so any (fast) responses are GREATLY appreciated.

 

[TedEH]

a weird kinda rhythmic tapping/clicking, almost like someone was winding a clock

Maybe a dumb suggestion, but is it possibly interference from a cell phone? I've got one combination of guitar/amp/phone that causes all kinds of noise, and I have to keep my phone in another pocket while I'm using that setup.

Otherwise, I can't offer much else since I don't know the amp very well. Sounds like you have the right idea though- troubleshoot/eliminate possible suspects, maybe it's pre tubes, maybe it's power tubes, maybe the power coming in from the wall is an issue, etc.

 

[glpg80]

Tube amplifier? Number one rule - always check tubes. Half of it sounds like a microphonic tube picking up sensitive EMI.

Check tubes always - especially if you're hitting the front end hard with OD's and hitting the phase inverter stage hard with stuff in the effects loop.

I don't doubt it might also be guitar wiring/grounding problems. I think you need to check your cables/try other cables, and also try other guitars.

 

[broj15]

Maybe a dumb suggestion, but is it possibly interference from a cell phone? I've got one combination of guitar/amp/phone that causes all kinds of noise, and I have to keep my phone in another pocket while I'm using that setup.

Otherwise, I can't offer much else since I don't know the amp very well. Sounds like you have the right idea though- troubleshoot/eliminate possible suspects, maybe it's pre tubes, maybe it's power tubes, maybe the power coming in from the wall is an issue, etc.

That's something that never occurred to me but I'll give it a try. I'm willing to try anything at this point honestly. If I had thought to do so I would've filmed it at practice last night, but I just didn't have time.

Tube amplifier? Number one rule - always check tubes. Half of it sounds like a microphonic tube picking up sensitive EMI.

Check tubes always - especially if you're hitting the front end hard with OD's and hitting the phase inverter stage hard with stuff in the effects loop.

I don't doubt it might also be guitar wiring/grounding problems. I think you need to check your cables/try other cables, and also try other guitars.

I'm almost 90% sure it's the amp. I've played 3 different guitars through it and have let my bassist use a few of my cables and pedals when he recorded his noise/ambient demos with his amp this weekend and he didn't notice any issues. Looks like I'll be buying a new set of tubes. The only thing is I've never replaced the tubes on my Fender HRD and I know for a fact they've had more hours put on them than the 6505.

 

[TedEH]

Looks like I'll be buying a new set of tubes.

It's maybe not a terrible idea to just swap one at a time out with a tube you know is good, and if it doesn't solve the problem, just put the old ones back, since you know at that point that they're still good. Saves you money on a whole set of tubes, and there's less risk that the whole new set of tubes will have a dud in them that introduces a new problem.

 

[NinjaRaf]

Tubes would be the first thing I would check. After that, try unplugging the reverb tank and see if that fixes it. For a while with one of the ones that I had, the reverb tank was ....ing .... up pretty good. Unplugged it and VOILA. Worked perfectly.

 

[broj15]

^^^ how would one go about doing that? If that's the case that would be great as i never use the built in reverb on the amp.

Also if it is a tube issue I probably won't have time to get it sorted out till the middle of next week. Do I run any risk of doing long term/expensive damage of using the amp in the mean time? The closest place that sells tubes is Guitar Center which is an hour away and I have shows tomorrow night and monday night.

 

[USMarine75]

Wiring issue... the signal chain should be E then I here. Common mistake. Only the C models are wired I then E. Easy fix.

Seriously though, sounds like line noise. Try a different outlet that is not on that same circuit, especially away from fluorescent lighting.

 

[broj15]

Well after some trouble shooting (aka "the tap test") it looks like the v1 (input gain) and v4 (effects loop) have both gone microphonic so I've decided to use this as an opportunity to try out some different preamp tubes. Considering this is the first time I've ever replaced the tubes in an amp before I'm kind of confused by all my different options. IIRC it currently has a combination of tung sols and sovteks in the preamp.

I like almost everything about my tone right now except I can't seem to strike that balance of having enough note definition in the upper register while still having a smooth / not to shrill high end. I've tried cutting the upper frequencies with my EQ pedal, however when I do that I lose the bite/attack in the low end (I like my chugs very percussive). I've decided what I'd like to achieve, but I just don't know what tubes to get to achieve it. Here's what I know I want for sure:

- tight, punchy, lows with lots of attack
- smooth, but defined highs... the tone on this album is a good example of what I'm after: https://euthgroup.bandcamp.com/
- something that will cut down noise in the effects loop. Right now my boss GE7 is causing a lot of "hiss".
-still maintain that aggressive sound the 6505 is known for

any help is much appreciated.

 

[TheWarAgainstTime]

I like to use a Tung Sol in V1 for most amps since it adds a fair bit of clarity and has a medium-high amount of gain. Maybe an EHX for a smoother high end and some extra mids, but still brighter/clearer than something like a JJ.

For the V4/effects loop slot, the brand of tube won't make a discernible difference to the tone, so I'd just go with something that's been tested for quiet operation.

 

[NinjaRaf]

For the reverb, you have to pull the chassis out and disconnect the 2 leads that go to the reverb tank from the PCBs. They're just like RCA sort of cables or whatever. Super easy. Then you just unscrew the tank from the bottom of the chassis. Another advantage, you don't have the the damn springs rattling around when you move the amp around.

 

[broj15]

so, after doing a bit of research on the various types of tubes and what positions in the preamp effect what I think I know what I wan to go with, but i thought I'd get some input.

V1-Tung Sol 12ax7
v2 - Tung Sol 12ax7
v3 - EHX 12ax7
v3 - EHX 12ax7
v5 - Tung Sol 12at7 (balanced triode)

First off I just want to confirm that I can run a 12at7 instead of a 12ax7 in the V5 (phase inverter) without damaging anything. Second I want to confirm my reasoning (again, after doing some reading online) for using a 12at7: 12at7's typically have less gain then 12ax7's, but allow for more current to pass through to the power tubes, thus allow for more clean headroom (due to less gain?) and will increase volume due to allowing more signal to pass through (I'm skeptical of this).

Also if anyone can recommend the best place to buy tubes online (preferably somewhere that tests the tubes before sending them out) that would be much appreciated.

 

[DarthV]

Try eurotubes or dougstubes? Give them an email and see what they recommend?

Another trick for the high end, turn highs down and presence up? Or the usual 5150/6505 solution, a 10 band eq in the loop

 

[USMarine75]

First off I just want to confirm that I can run a 12at7 instead of a 12ax7 in the V5 (phase inverter) without damaging anything. Second I want to confirm my reasoning (again, after doing some reading online) for using a 12at7: 12at7's typically have less gain then 12ax7's, but allow for more current to pass through to the power tubes, thus allow for more clean headroom (due to less gain?) and will increase volume due to allowing more signal to pass through (I'm skeptical of this).

Also if anyone can recommend the best place to buy tubes online (preferably somewhere that tests the tubes before sending them out) that would be much appreciated.

This works on any preamp tube distortion style amp. It will drop the cascading distortion that slams the power tube section down to 60%, making your preamp gain/volume much more usable. You won't have more overall volume as that is controlled by the power tube section.

I've bought from Tube Depot, Eurotubes, and Musiciansfriend, and I haven't had any (real) problems. One tube from Musiciansfriend was microphonic, but they exchanged it for free.