Schematic for Noise reduction pedals like HUSH?

[tambek]

Are the any available at all?

[nelson]

There is a project on http://www.tonepad.com for the MXr noise gate. Whole lot of mods available with that project. attack, decay, attenuation. It is probably your best bet.

[12afael]

the mxr is not a noise reductor is a noise gate . the hush use a SSM2000 that is obsolete. if someone have a source for that IC please pm me .

[sir_modulus]

A noise reductor(filter) actively opens and closes a high frequency filter that takes away the higher (more prominent...usually) hiss/noise from the signal. This gives a nice noise reduction without the abrupt quality normally associated with a noise gate. I personally like noise gates better, but that's just IMO...I'm sorry, I don't know where to get that part though...

Cheers,

Nish

[Maneco]

lm1894

[cd]

Unless you enjoy a challenge (sourcing schematics, obsolete parts, etc.) I would spend $60 on a used BOSS NS-2.  Believe me, it will KILL anything you could possibly build.

[Mark Hammer]

The SSM2000 datasheets show some applications, but of course they don't do you much good if you can't get the chips.

Maneco's suggestion of the LM1894 is a good one.  The LM1894 precedes the SSM2000, and was intended for single-ended noise reduction in noisy sound reproduction/reinforcement contexts.  Whent he chip arrived in the early 80's there were a bunch of magazine construction projects using the chip, though not optimized for guitars.  That's not a reason why an 1894 could NOT be adapted.

The thing about the noise fader systems, as opposed to noise gates, is that they include both downward expansion AND sliding lowpass filtering.   The SSM2166, used in the Q&D compressor Jack Orman posted at his site, offers downward expansion, but not the filtering.  HOWEVER, it does have an insertion point in between the input buffer stage and the VCA, where one could insert some sort of lowpass filter whose rolloff is influenced by the output level of the chip.

The other thing you could do, I suppose is to gang a FET or optoisolator to the same envelope follower driving a noise gate, and use the FET/LDR to form a subtle RC lowpass filter, where the resistance goes low when the input signal is louder, and high as the signal decays.  This will provide more bandwidth at max signal and less bandwidth as the signal decays.  In principle, this ought to let you set the gating action to be slower in its decay and have a much lower threshold for turning on and off.  Normally one selects a gating threshold that is a little higher than you'd want to assure no noise leaks through unless it is WELL masked by signal.  If you can roll off some of the hiss, though, you can afford to wait until the signal is much lower before gating it off.