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Alembic Club » Owning an Alembic » Troubleshooting » Archive through November 30, 2011 » Are high frequencies you can't hear a problem? « Previous Next »

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Senior Member
Username: jazzyvee

Post Number: 2559
Registered: 6-2002
Posted on Thursday, August 25, 2011 - 11:35 pm:   Edit Post

Since I've got my strat with Alembic activators back from refurbishing I've noticed that the high frequencies are much more evident and "in your face" compared to my other guitars and has a similar kind of hard attack that I hear from electro acoustic guitars

Normally when I'm practicing at home or learning new material I have the guitar at a moderate volume, loud but loud enough to get some "feel". But what I'm noticing is that my ears feel tired very quickly in a way thats the same as if I'd been to a very loud concert/gig. This i find strange since the volume is nowhere near this level.

So that got me wondering if there are any frequencies coming from the guitar that I cannot consciously hear but are much louder than the regular guitar sound that are affecting my ears in some way.

Oy the amp Ive been using lately is my Roland JC120. I also have tried the guitar in my Ashdown acoustic/electric guitar amp and do not get the same problem but don't know if this is due to the amp not being as crisp at the higher frequencies generally nor as powerful.
I hope this makes sense.
Username: adriaan

Post Number: 2851
Registered: 6-2002
Posted on Thursday, August 25, 2011 - 11:45 pm:   Edit Post

Does it have the filter but no Q-switch? Then it could have the permanent 8 dB boost which would account for harshness.

When playing through headphones, my ears really don't like it when the filter is not fully open, with or without Q boost.
Senior Member
Username: jazzyvee

Post Number: 2560
Registered: 6-2002
Posted on Friday, August 26, 2011 - 3:33 am:   Edit Post

It has orion electronics. Bass and treble boost and cut, master volume and 5 pos blade switch.
Username: stout71

Post Number: 7
Registered: 7-2011
Posted on Saturday, August 27, 2011 - 11:37 am:   Edit Post

The higher the frequency, the more directional it is. The output of those super-high frequencies that aren't audible to you would have to basically pointed directly at your ear at a relatively short distance to cause fatigue. For the most part, frequencies over 20K aren't audible to humans, although I know a few musicians who would argue. Frequencies above 20K DO offer directional cues though, even if you aren't consciously aware of them.

Anyway, the bottom line is that if you can't hear the (high) frequency, it's not really going to cause discomfort or ear fatigue, especially at the volume you describe in your listening environment.

Low frequencies, however, are omni-directional. I've seen tests where they can produce a fundamental of like 16 Hz in the lab and bump it up to like 120 db SPL. That would shatter most windows within 50 feet. Not a pleasant experience, but you'll most likely never encounter that in life. If you've ever been riding on the highway at high speed in a car with one of the windows barely cracked, that is a good example of really low frequencies at a moderately high SPL. Not comfortable either (but you can crack one of the other windows to relieve the pressure.)

Again, at the volume you're describing, this is not a likely scenario either. I think something else is at play here.
Senior Member
Username: terryc

Post Number: 1687
Registered: 11-2004
Posted on Tuesday, August 30, 2011 - 3:22 pm:   Edit Post

Audiometry for noise exposed employees(machinists, mechanics exposed to compressors, jet engine techs etc) in the UK is tested from 1KHz to 6KHz - HSE standard for noise exposed 80Db over 8 hours with hearing protection.
I don't believe anyone can hear 20KHz..that is feline/canine range, even that would be beyond them
Senior Member
Username: bigredbass

Post Number: 1764
Registered: 9-2002
Posted on Friday, September 02, 2011 - 10:44 pm:   Edit Post

The big reason the fabulous Roland JC's are typically difficult for distorted tones is that it's made to power amp specs with very low distortion relative to most any other guitar amps you can think of. It's just that clean because it's just that clean. The speakers are the limiting factor, but it would be interesting to hook these to a good small 3-way PA bin and see how it sounds.

Plus there are separate amps (2), one for each speaker. This is how the chorus sounds so convincing, and hard to replicate in other (mono) amps with a pedal or rack unit.

Without tweeters, I doubt the speakers are making freqs you can't hear. I would suspect where the amp is sitting is causing standing waves, a wierd phase shift / cancellation, or some other room-related acoustic anomaly. Try moving it to a few different spots and see if it still happens.

I'm hopless at eluding standing waves almost anywhere in my home. Stand six feet infront of the amps, it's thin. Step back another three feet, and it sounds suddenly like one of those awful Best Buy car installs where it's just unintelligible. Sheesh . . . .

J o e y
Senior Member
Username: dfung60

Post Number: 512
Registered: 5-2002
Posted on Saturday, September 03, 2011 - 9:50 am:   Edit Post

Been thinking about the original post for a few days now. What kind of refurbishment did your instrument have? Did they remove the electronics?

I'm wondering if something was removed and reinstalled incorrectly. One source of the kind of distortion you're describing might be a bad battery which is easy to fix, but if they erred in reinstalling the jack, the power switching might not be working. Or, the power delivered to the pickups and EQ might be diminished in some other way. That would cause the guitar's output to be clipped which will cause this unexpected ear fatigue.

Another part of your description is "harsh attack". That's often the sign of an impedance mismatch. If the electronics are connected up correctly and the power is OK, then it's possible that this can be caused by dirty contact surfaces on the connectors. Unplug each connector and make sure the plug contacts are bright and shiny. If you haven't got contact cleaner like Deoxit, then a pencil eraser will work fine too.

While you're checking those contacts, make sure everthing is plugged in correctly. If you have the little brown molex connectors, they're indexed so you can't plug them in backwards. If one pickup were reversed, the intermediate positions will be out of phase and sound thin. If the power connector is backward, then you migth see a reduction of power to the preamps.

One other thing that might be easy to try is to remove the output jack so it's not touching the body of the guitar, especially if your guitar is shielded. If there's an expected short that's stealing some of the power to the circuit or some of the audio, removing the output jack will take out the most likely area of the problem. You can take a look at the wiring of the pots too to make sure that nothing is touching ground that shouldn't. Activators are pretty complicated compared to most guitar electronics and fully insulated, so it's unlikely that anybody would have screwed this up by rewiring, but they have to do the output jack, so there's a window for error. A grounding problem like this can be fixed with electrical tape, shrink wrap, or thin nylon washers as needed.

Good luck!

David Fung
Senior Member
Username: jazzyvee

Post Number: 2582
Registered: 6-2002
Posted on Sunday, September 11, 2011 - 2:54 pm:   Edit Post

Hi David, thanks for your input. The refurbishment was done for my by John at Jaydee custom guitars and was for the body of the guitar only. The electronics were mounted on the original pickguard that came back from alembic when I sent it to them for a service. So would have I presume they would have been transferred directly to the new one without having to do any re-wiring apart from connecting the jack up. However when it comes to a string change, soon, I will take the opportunity to take the pickguard off and have a look inside to see if anything is out of order.


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