robot poet
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Robo Sapien NoiseMaker
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Post by robot poet on Oct 21, 2020 18:39:02 GMT -7
Update: WiFi expander in the room. Please see the last post. Just picked up a 2017 EMS head which appears to be making unusual noises. I guess what I need to know is if this is normal. It was making the noise with the original set of tubes, so I bought the recommended set from The Tube Store and just put them in. Biased for 36mA / SS rect like the good Doctor says. Here's what it sounds like: SoundcloudSettings: JCM 800 - ishP:12:00 B:12:00 M:12:00 T:12:00 V:12:00 G:2:00 Sound doesn't change on rectifier setting or touch. Unsurprisingly, it's louder on Hi but still there at Lo just quieter. 8ohm output into a Suhr RL IR (1.3 - Suhr 4x12 GB SM57) into a Focusrite 8i6 into Logic. I record all day into this with a range of different amps, and I highly doubt it's anything but the EMS. Any help, thoughts, or advice appreciated.
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Post by Jaguarguy (Mike) on Oct 21, 2020 19:02:39 GMT -7
Is there a phone near the amp?
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Post by purpletele on Oct 21, 2020 19:22:46 GMT -7
That is not a normal sound, it almost sounds like it's picking up RF. Then it continues with new tubes, ..
My first thought would be that there are some wires too close to something else on the board or near the tubes, but I can't imagine that being an issue on that amp, there is plenty of room inside the chassis and you don't hear of wire interference issues.
Have you plugged it in at other locations?
I listened again, it sounds like phone interference or something in the power source.
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robot poet
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Robo Sapien NoiseMaker
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Post by robot poet on Oct 21, 2020 20:13:05 GMT -7
Is there a phone near the amp? No, it's on weight bench with power to a voltage regulator I use with every amp and speaker cable to the Suhr RL IR a few feet away as well. I did the usual isolation stuff while troubleshooting. I've got a bunch of amps including a 50w JCM 800, 50w Barber Echelon, 50w Fargen Olde 800. None of them do this when hooked up the same way - I tried that as part of troubleshooting.
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Post by pcns on Oct 21, 2020 20:16:37 GMT -7
sounds like RF to me.
Are the chassis to cab screws tight? Ifbthebscrew are loose it could leave a small gap in the shielding and allow noise to enter the chassis.
I've also seen bad cables make noise too. They can act like an antenna.
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robot poet
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Robo Sapien NoiseMaker
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Post by robot poet on Oct 21, 2020 20:19:12 GMT -7
That is not a normal sound, it almost sounds like it's picking up RF. Then it continues with new tubes, .. My first thought would be that there are some wires too close to something else on the board or near the tubes, but I can't imagine that being an issue on that amp, there is plenty of room inside the chassis and you don't hear of wire interference issues. Have you plugged it in at other locations? I listened again, it sounds like phone interference or something in the power source. I've got it off by itself at least 4' from anything else. Two cables (power => voltage regulator, speaker cable to the Suhr RL IR). I haven't tried moving locations yet - I can try that tomorrow - but I have plugged other 50w Marshall types into the same spot and they don't do this. If figure if anything in the environment that was going to whack an amp out like this, it would be the '84 JCM800. It's got a noise floor for sure, but it doesn't do anything like what this EMS is doing.
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robot poet
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Robo Sapien NoiseMaker
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Post by robot poet on Oct 21, 2020 20:27:11 GMT -7
sounds like RF to me. Are the chassis to cab screws tight? If the screws are loose it could leave a small gap in the shielding and allow noise to enter the chassis. I've also seen bad cables make noise too. They can act like an antenna. Yep, chassis is snug. Evidence Audio Forte instrument cables, Lava speaker cable. Voltage regulator. No other amps do this, even an old JCM 800. I've turned off all the lights in the room. No other amps were on when I recorded it. Guitar unplugged from the amp. If it's RF interference, then it's RF interference but I'm playing hell figuring out why only the EMS is picking it up.
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Post by DRZ on Oct 22, 2020 1:15:41 GMT -7
First let me say that isn't a problem I have seen on any other EMS. Remember that is a used amp, so directing this question to the original owner may shed some light on it. Just like a car it is rare that someone trades one in that is in 100% perfect operating condition, usually some issue or fear of a failure causes one to trade in. Seems like a simple problem to fix once it is on a test bench. I would say send it in and let me fix it for you .
DR.Z
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robot poet
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Robo Sapien NoiseMaker
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Post by robot poet on Oct 22, 2020 3:23:19 GMT -7
First let me say that isn't a problem I have seen on any other EMS. Remember that is a used amp, so directing this question to the original owner may shed some light on it. Just like a car it is rare that someone trades one in that is in 100% perfect operating condition, usually some issue or fear of a failure causes one to trade in. Seems like a simple problem to fix once it is on a test bench. I would say send it in and let me fix it for you . DR.Z Thank you! To your point, I think it's a common experience that a used amp or instrument comes along with a surprise or two. Usually it's nothing, but rarely it's an outright misrepresentation. Who knows the history of something that's passed through other hands? I'll send the seller the link to the soundclip but I don't expect much insight from him. "Gee, it never did that before. Good luck!" More practically, I'll contact your "repairs@" service today and work out a RA. I'm confident it's a minor thing that was introduced by a previous owner diddling around inside of it. Respect, sir. Thank you.
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Post by Jaguarguy (Mike) on Oct 22, 2020 6:51:05 GMT -7
Never hurts to have Doc's guys look at it. Very reasonably priced and it will sound as good as new. Don has cleaned up several "all original" amps off Reverb/Ebay for me.
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Post by detuned on Oct 22, 2020 15:44:01 GMT -7
Reverb's been hit and miss for me. I've purchased a used Swart that arrived in perfect condition, and a '65 Fender Bandmaster that had been converted into a combo which had been described as "recently serviced" which required a full retube and rebias before the tremolo would work. Caveat freakin'-Emptor these days...
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robot poet
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Robo Sapien NoiseMaker
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Post by robot poet on Oct 22, 2020 17:26:06 GMT -7
Never hurts to have Doc's guys look at it. Very reasonably priced and it will sound as good as new. Don has cleaned up several "all original" amps off Reverb/Ebay for me. I believe I've found the offending bit of environmental electronics triggering this: I have a WiFi expander in the room. 1) When I step in between the expander and the EMS, the noise stops. My body is blocking the WiFi field. 2) When I position myself next to the expander in a way that allows the noise, then unplug it, the noise stops. NOTE: I have found that after switching the amp off of standby, it takes a few minutes for the noise to start. Maybe there's a marginal component or something that only becomes susceptible to RFI after it warms up enough.
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Post by DRZ on Oct 23, 2020 6:30:44 GMT -7
Well I'm certainly glad you found the environmental cause of your issue. As is the case many times units are sent in and without WiFi expander in the room the source of the problem I would not have been able to reproduce the problem let alone fix it.
Now regarding your "NOTE ".
All preamp tubes are Receiver Tubes , so they are susceptible to Radiant Random pickup and amplification . They will only do this when they are fully powered by proper High Voltage , Bias voltage, and Filament voltage. If you have the 5U4 rectifier selected it will be a moment or so before full Hi Voltage is fully present on each tube after Stand-By is disengaged. Hence, the slight delay in the in the noise. This is also true of the Solid State rectifier, just to a lesser degree in delay.
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Post by detuned on Oct 23, 2020 6:39:17 GMT -7
Wait? Z amps aren't wifi-enabled? :-)
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