amp generating loud humm and hiss

[tambek]

hi guys

i just got myself a guitar amp. Hughes & Kettner EDITION BLUE 30R to be exact. anyway, one thing got ne questioning tho... i have wired my diy stompox (shaka 5 distortion) before the amp like this; gtr-stompbox-amp. this great amp has a really cool built in distortion channel that you can switch with a stompswitch. i like to use both of these great distortions, but for some odd reason, when i switch on the distorion channel on my amp, theres a lot of noise - humm or hiss (dont know exactly how to call it in english) and its so loud its very disturbing. Besides that, when my guitar volume is at max, and i use the 2 pickups near the end of the strings, that are the rightmost, you know, the one which is bigger and the other one next to it, - i get a loud and instant whistle. doesnt matter if im facing the amp or im far away. When i turn the volume down, tho, it wont whistle, but theres still a lot of noise. Whenever i use my own stompbox, it wont generate noise (well it does, but its very quiet, and doesnt disturb me). And it wont whistle... I also changed my guitar pickups.. and they are a little better (wont generate as uch noise as before, but still too much, the change in a ten point scale was only 1 point. ) im sorry if im too confusing, but i hope to get some help...

I have a gig in 3 days and need to solve this problem quickly cause i want to use both effects!

[Paul Marossy]

If I understand what you have written, it sounds like you have way too much gain, causing oscillation and greatly exaggerated hum that you wouldn't normally hear with just the amp's distortion.

[tambek]

anyone? :?:

[Paul Marossy]

Are you using a stompbox distortion and the amp distortion, or is it one or the other?

[tambek]

one or another.

If i turn the volume on my guitar down, the hiss levels etc are quite acceptable, but i'm losing a lot of tone. Since i need to have as much output from the guitar as possible, i would like to find a solution for this.

Could it be there's something wired wrong in the amp or in the stompswitch? Or is it my guitar?

[Paul Marossy]

Well, after re-reading the previous posts, it sounds like it's your guitar. Microphonic pickups and/or poor shielding and/or grounding would cause symptoms like yours. What kind of guitar do you have? One simple temporary fix would be to put a treble bleed cap on the volume control, if one is not already installed. All you have to do is get a 0.001uF film cap an solder it across the wiper of the volume pot (middle lug) and the outer lug that is not connected to ground. That's all there is to it. What this does is allows some of the higher frequencies to get through directly to the output when the volume control is turned down. If the 0.001uF cap doesn't have enough of an effect for your taste, then try a 0.002uF or even a 0.005uF cap.

It also sounds like your amp uses a higher gain circuit than your stompbox, so it will really bring out any flaws in the wiring or pickups.

Hope that helps.

[tambek]

thanks, i'll try that out!

i also went to a guitar shop and they gave me some ideas to play around with the knobs and see if that would work.

[Paul Marossy]

Keep us posted.  

[ryanscissorhands]

Describe EVERY electrical device plugged in in the room that you play in. That's a huge start.

[tambek]

Describe EVERY electrical device plugged in in the room that you play in. That's a huge start.

Cause they might cause interference?

[David]

Describe EVERY electrical device plugged in in the room that you play in. That's a huge start.

Cause they might cause interference?

Correct.  Famous culprits for noise problems are fluorescent lights and halogen torchiere-type lamps.

[Paul Marossy]

Also, wall warts can sometimes radiate nasty EMI, too. Add to that computer power supply fans and computer monitors.

[tambek]

Well, after re-reading the previous posts, it sounds like it's your guitar. Microphonic pickups and/or poor shielding and/or grounding would cause symptoms like yours. What kind of guitar do you have?

/.../

It also sounds like your amp uses a higher gain circuit than your stompbox, so it will really bring out any flaws in the wiring or pickups.

Hope that helps.

You mention poor shielding. Do You mean the guitar is poorly shielded or the cable from the guitar to the stompbox/amp? What can I do about it?

[Paul Marossy]

I mean the guitar may be poorly shielded and/or grounded. You may notice some improvement by shielding the pickup cavities and by thoroughly checking the grounding and doing any improvements possible to the quality of the grounding.

What kind of guitar is this that we are talking about anyway?

[tambek]

It's the cheapest Yamaha around   EG112

BTW, I have no idea how would I have to shield this thing. Is there a tutorial or lesson for beginnerrs about this? :roll:  :oops:

[Johnny Guitar]

this great amp has a really cool built in distortion channel that you can switch with a stompswitch. i like to use both of these great distortions, but for some odd reason, when i switch on the distorion channel on my amp, theres a lot of noise - humm or hiss (dont know exactly how to call it in english) and its so loud its very disturbing. Besides that, when my guitar volume is at max i get a loud and instant whistle. doesnt matter if im facing the amp or im far away. When i turn the volume down, tho, it wont whistle, but theres still a lot of noise. Whenever i use my own stompbox, it wont generate noise (well it does, but its very quiet, and doesnt disturb me). And it wont whistle... I also changed my guitar pickups.. and they are a little better (wont generate as uch noise as before, but still too much, the change in a ten point scale was only 1 point. )

I edited out some of the info to focus a bit more on where you are having the problem. I read it that the problem is more in the amp distortion and maybe a problem with that circuit. Since I don't know anything about the amp I can't comment on that.

Let me suggest that you do a couple of things to try and locate the trouble.

1) Try your guitar into another amp, then try with your Shakka box. Listen for the noise (hum and static) and make a note of how it is.

2) Try a different guitar into your rig (first just through the amp, then with the Shakka). Again, listen for the noise and the feedback (pickups going microphonic producing a high pitched whine) and make a note of how it is.

3) In fact see if your amp has these problems without anything plugged in. (is this a tube amp?) Preamp tubes can become microphonic and start exhibiting this behavior too.

4) You mention that you get the feedback when you are far away from your amp. How far are you away and what are the amps settings (and what is it's power rating)? If you are say eight feet away from a 100 watts RMS  amp plugged into a bright channel with volume treble presence all at max (like I used to do with a Strat  :oops:) you can expect some microphonic feedback. BTW, we used to put foam between the amp head and the speaker cabinet as the vibrations would cause the tubes to feedback too.

5) Are you only using the "distortion" channel for distortion (and so it always exhibits this problem when you are using it)? Can you verify (by say turning down a distortion control while still using that channel) that the channel is OK? (if there was some thing wrong with the electronics in that channel you won't to find out -- things only get noisier when you add distortion but that may not be where the problem lies)


BTW, when I saw the topic thread about loud hum and hiss my first thought was bad filter caps on the power supply -- you would hear that with just a guitar cable (no guitar) plugged in and turning the volume up and you will hear a lot of 60Hz hum (in the US where the AC power is at 60Hz).

[Paul Marossy]

Sure there is!  

Here's the Stewart-MacDonald page on shielding:
http://www.stewmac.com/freeinfo/I-3789.html

Here's another one:
http://www.guitarnuts.com/wiring/shielding/shield3.php

The simplest way to shield a guitar is to use that special conductive paint, which looks something like this:
http://www.guitarattack.com/fm3/shield.htm

I personally like the self adhesive metal foil. It works great as long as you make sure all the pieces have continuity and are connected to ground.

Shielding your guitar would probably make a very noticeable difference in the amount of hum and noise you hear.  

[tambek]

Is aluminium foil any good for shielding?

[Paul Marossy]

People have used it successfully for shielding guitars. I personally like this stuff called "metal repair tape" that is sold at places like Home Depot. It's a self-adhesive aluminum duct tape kida thing. It works pretty well, maybe not as good as copper, but it works.  

[bwanasonic]

Yes, heavy-duty alum. foil and rubber cement is all you really need. This really only helps with HUM and RF, not HISS from using TOO MUCH DAMN GAIN. It will not help your microphonic squealing problem either. Some sort of noise gate might be in order to help with the hiss. The other thing you need to get used to if you are using TOO MUCH DAMN GAIN is rapid control of the volume knob. You may find that the hiss is less noticeable while playing, so you can crank the volume knob while playing, just be ready to quickly turn it down the second you stop playing. A volume pedal can also be used for this purpose, as kind of a manual noise gate. As for the pickup squealing, another pickup might help, or it might just be TOO MUCH DAMN GAIN.:idea:

Kerry M