Diagnosis madness

[Demanic]

Or maybe it should say "Diagnosis, madness".
I've been trying to diagnose a problem for the last several months, to no avail. Two separate amps, one a solid state Randall and the other a tube Jet City, seem to be suffering from the same problem: a volume drop off/swell. It almost sounds like a slow tremolo effect. When I start playing, the signal sounds fine, loud and clear. Then, as I continue to play, it gradually becomes more muted. If I stop playing and start again, it goes back to full strength only to gradually mute again. I've tried different guitars, different effect setups, played directly into the amps with no effects, used different cords. I started to think that it might be the power coming out of the outlet, so I ran both the amps and the power supply for the pedals through my Furman power conditioner. Still the same problem.
Any thoughts as to what else I can check?

 

[ehdwuld]

Re: Diagnosis madness

my buddys amp did that when the speaker was under sized
amp wanted 16 ohm
he put in 8 ohm

 

[Mincer]

Re: Diagnosis madness

I don't know the solution, but I have experienced 2 different amps with the same issue. One was a friend's, and the other was provided backline. I don't know what the outcome turned out to be. But you're not crazy.

 

[Demanic]

Re: Diagnosis madness

I'm fairly certain that the impedence is properly matched with both of the amps.
And I know that I'm not crazy (at least in respect to this issue) but trying to diagnose something like this is maddening, given all the variables that need to be eliminated.

Sent from my Alcatel_5044C using Tapatalk

 

[ehdwuld]

Re: Diagnosis madness

heat related with the one of the transformers overheating

starts fine
as you play it heats up
resistance increases
signal fades
stop
cools

check speaker connections and maybe the cable

are these heads and cabs or combos?

if head and cab, same cab?

 

[NegativeEase]

Re: Diagnosis madness

Since, you have isolated each variable to both amps producing this issue independently, I'm going to skip the gear conjecture and go for the wild stuff -power

You running a washer/dryer in the house around these times? are you near an industrial area? do you generally do these tests around the same time each day?

have you measured the voltage at the socket? if it wanders heavily between 110V and 120V, it can cause the amp to draw more current when the voltage drops and less current when voltage rises... Or if it is dipping below 110V is can really start to pull hard and have dramatic tone changes.

How does the step down transformer to your house look/sound? maybe it's at it's last breath and when you plug in an amp it

also, long shot, but it could be your ears -human brain starts to dull the senses once incoming information is recognized, maybe with as long and as much as you play it's happening much faster.

 

[Gtrjunior]

Diagnosis madness

Very strange. If it was just the tube amp I’d say the power tubes are on the way out. But since you’re getting the same issue with the Randall, I’m not so sure.

I also think you may have a power issue somewhere. Either in the house or as part of the amp circuit. More likely the house, I’d think.

Try the amps on a different household circuit and see what happens.
Also, I’m sure you already did but unplug all fx and plug straight into the amps. If you have fx plugged in and the power to the fix is suspect it may cause the issue you’re describing.

Good luck.

 

[dr.barlo]

Re: Diagnosis madness

Are you getting this issue with the same cab? If so, maybe it's the speaker?

Or... Could you measure the voltage in the power line when that happens? You'd need a multimeter and some knowledge. It's easy, but still you are gonna tap in into the main power line. If you were to see a consistent drop in Voltage, then the issue has to do with the main power in your place.

B

 

[Demanic]

Re: Diagnosis madness

Two different amplifier heads into two different cabs. As I said, I believe that the impedence is properly matched for each, 1x12 cab with a 16 ohm speaker into the 16 ohm output of the Picovalve, 2x12 cab with 2 16ohm speakers wired in parallel into the 8ohm output of the Randall.
The problem appears whether I am running through pedals or going directly into the amp. However, it only seems to occur when I'm running distortion, either with a pedal into the clean channel or in the case of the Randall the distortion channel straight in. I should mention that I use bridge pickups that are considered high output in conjunction with distortion. And it sounds normal for the first second or two of a fast palm muted run, then seems to lose volume and clarity. Then as soon as I stop and restart, the volume comes back up and then fades out. I'm starting to think that maybe the front end of the amps are compressing the signal, but it seems like this was not always the case.
I've also considered that the power coming out of the outlet is dirty, which is why I've tried running everything through my power conditioner. A power conditioner suppose to clean up the current regardless of what comes from the outlet?
I also considered ear fatigue, but I've been testing in short bursts of only a few minutes and my wife in a different room is able to hear the fluctuation.
I have a third amp in the room that I'm going to try running through to see if there's any difference in response.

Sent from my Alcatel_5044C using Tapatalk

 

[ehdwuld]

Re: Diagnosis madness

is there an effects loop on these amps?

jump the effects loop with a patch cable

I have this problem with all my amps

 

[chadd]

Re: Diagnosis madness

I've also considered that the power coming out of the outlet is dirty, which is why I've tried running everything through my power conditioner. A power conditioner suppose to clean up the current regardless of what comes from the outlet?

The inexpensive power conditioners are essentially glorified power strips. Even the moderately priced ones with a voltage meter on the front aren't fantastic, but they would at least show any irregularities in power.

 

[NegativeEase]

Re: Diagnosis madness

The inexpensive power conditioners are essentially glorified power strips. Even the moderately priced ones with a voltage meter on the front aren't fantastic, but they would at least show any irregularities in power.

That was my next question for Demanic... What are you using for conditioning? if it's just filtering without an isolation transformer conversion or AC/DC/AC isolation, it may not be cutting it.

 

[jeremy]

Re: Diagnosis madness

could be a power issue, but sound like both amps have a borderline failing component. you have other amps that done exhibit this behavior from the same outlets?

 

[ehdwuld]

Re: Diagnosis madness

my Laney solid state would play for a bit then just stop
there is a switch on the send jack that opens and allow the signal to re route
through the loop
this switch gets held open by the jack being in it all time
or gets gunk in it
fades away as the metal heats up
and opens the switch

my Belair Tube amp does it too

all my amps with Effects loops do this

I have all the loops bypassed with a patch cable when not in use

Jeremy or or one of ya'll told me about this 10 years ago

Try it

what could it hurt

 

[Demanic]

Re: Diagnosis madness

The power conditioner is a Furman ML-8. Don't know if it's just a glorified power strip, though it certainly may be.
It's also possible that it's a component in both of the amps getting ready to fail, and if so, I wish that it would just hurry up and get it over with.

Sent from my Alcatel_5044C using Tapatalk

 

[Aceman]

Re: Diagnosis madness

I was on board with a power problem until you said Furman. I'm out.

 

[Demanic]

Re: Diagnosis madness

Did some more investigating today. Per advise offered, I checked the loop on the Randall. I'm running a 31 band eq in it and I noticed that the send and return volumes were both maxed, so I backed them off to 1 o clock. Bumped the master on the eq slightly to compensate.
I also checked the power supply feeding my pedals. The junction where the wire meets the transformer was frayed and I could see copper. Replaced it with a new power supply. Ran the Randall through it's paces (with an X2N and a Metalzone) and it seemed to hold up just fine.
Warmed up the Picovalve and gave it a check and it seemed good too.
Hopefully it holds up. I think that the power supply was the primary issue and the fluctuation that I thought that I heard playing direct was due to the loop levels being maxed in the Randall. I'll put it down to ear fatigue playing direct into the Picovalve (no separate gain channel on that one).
So, as it's been said, so far, so good (and yes, so what).
Thanks to all for the assistance.

Sent from my Alcatel_5044C using Tapatalk

 

[ehdwuld]

Re: Diagnosis madness

so it was all of the above

sweet
hope it works out

 

[Demanic]

Re: Diagnosis madness

so it was all of the above

sweet
hope it works out

That's what makes diagnosing electrical stuff such a b#$ch. I just hope that it holds.

Sent from my Alcatel_5044C using Tapatalk

 

[NegativeEase]

Re: Diagnosis madness

The power conditioner is a Furman ML-8. Don't know if it's just a glorified power strip, though it certainly may be.
It's also possible that it's a component in both of the amps getting ready to fail, and if so, I wish that it would just hurry up and get it over with.

Sent from my Alcatel_5044C using Tapatalk

That's more a rack power strip with pull out convenience lights and basic AC filtering and something like a Metal Oxide Varistor for Surge protecting. It's good for RF and EMI interference.... but it isn't doing anything for a variable Voltage stability and true clean power

I mean it might be possible that you've worn out both amps with overdriving the pre (I'm guessing your not killing the power/post these days in your backyard.) and you got a pre amp component in both that has the same warm up/temperature issue because you've smacked both amps in the face with way way way high level from your MT2 or something like that.