EQ (GGG version) Noise help.

[RonaldB]

I'm busy building an equalizer by the schematic found on http://www.generalguitargadgets.com/pdf/ggg_eq6b_sc.pdf <- here.

The problem  have is that i have Hiss/Noise issues. I allready asked things on the forum see
http://www.diystompboxes.com/smfforum/index.php?topic=74912.0 But that's was an other desgin.

Now i'm trying to make it by the GGG schematic, and i think more people made this variant.

The Hiss/Noise is best described as:
A sound you here out of an old tapedeck just before a song starts.
You here that constant noise or hiss (not loud).

Well that's what i here when i build this EQ. It gets louder when i add all 6 stages. Witch makes sence because there are more amplifiers.

What have I tried to solve this:

• I have tried differant types of caps.
• I use all metal resistors
• I use 2 TL074
• Changed the input from an Inverting type to an Non-inverting type(no change)

When I detach the EQ stage the hiss/noise is gone.

But where is the problem here. Could someone point me in the right direction. Ore are EQ's allways noisy?

Best regards
Ronald

[RonaldB]

Anyone please

[jefe]

I don't think it's uncommon for eq's to hiss. I have an 80's Ibanez eq that hisses.

Also, did you see this thread? I don't think this ever got resolved:
http://www.diystompboxes.com/smfforum/index.php?topic=59332.0

[kvb]

that thing just likes to hiss.

there's a cap in the feedback loop of the input stage that most say should not be there

you say you changed the input stage with no change in noise

If I build another EQ it will be a bipolar version of RG's
Or I'll just buy one (most likely)

[RonaldB]

Thanks for the reply's.

I now EQ's do hiss some more than others.
But this is a little to much.

I read the topic through and there where some good tips there. Thanks for that link.
I will try them, but i'm not expecting that it will reduce the hiss that much.

I think it is a current problem, because the hiss is there even when the guitar is unplugged.

ROnald

[jefe]

Just a few stray thoughts: How is it w/ battery vs. power supply? Also, how is it with different amps?

[RonaldB]

I run it on a 12V regulated power supply that is really silent.
Didn't tried other OP-AMPS. but I now the problem lies i think at the INPUT or on the OUTPUT.
I tried differant EQ stages from OP-AMP stage to Transistor Stages and they all hiss.

I'm now going to do something completly differant.
I orderd some BA3812L EQ chips(same as in the BYOC design) and i'm going to try those.

[jefe]

I run it on a 12V regulated power supply that is really silent.
Didn't tried other OP-AMPS. but I now the problem lies i think at the INPUT or on the OUTPUT.
I tried differant EQ stages from OP-AMP stage to Transistor Stages and they all hiss.

I'm now going to do something completly differant.
I orderd some BA3812L EQ chips(same as in the BYOC design) and i'm going to try those.

12V? Isn't this a 9V circuit? Not sure if running it at 12 is the right thing to do. Have you tried it at 9v? Maybe the hiss will go down.... or maybe it will go up, I don't know... just thought it was worth mentioning. I'd still be curious how it reacts to power supply vs. battery. Your 12V ps may be "really silent" with other pedals, but not this one? Again, just a thought - try it with a fresh 9v battery, and not a power supply, just to see what happens.

Also, I was wondering if you had tried the effect plugged in to different guitar amplifiers, not with different op-amps in the circuit. How does it sound plugged into a solid state amp vs. a tube amp? How does it sound plugged in to a little practice amp vs. plugged in to a full-sized amp?

[RonaldB]

I allready tried a 9V regulated power supply and a 9v battery. No luck there.

I have tried differant options in amplifing. I have a lexicon rack unit with headphones out and i tested it there and the hiss was there.

Hopefully i get my BA3812L soon to test them.

Thanks for your help so far.