Permanent Hiss from Spectravox

[Achim]

When in Filter Bank mode, the Spectravox generates a faint but audible and disturbing hiss in the output signal. It seems to be some kind of crosstalk from the noise generator, which is of course set to minimum / all the way left. Has this been observed also by othe users and is there a way to overcome the hiss?

[Ph111p]

Yes, I am also experiencing this. It's pretty audible and basically makes the filter bank mode unusable. If you turn the resonance up you can hear very clear sweeps as the lfo changes, even with no carrier signal.

Edit: I can also hear the VCO bleeding through, especially at high frequencies.
Of course it's silent when the VCA is at zero, but that doesn't really help.

Edit2: I am beginning to suspect this is a direct result of the carrier input being only +/- 1.7v (line voltage, I think). When using the built-in oscillator, it's plenty loud, so I can turn down the master volume and get a decent signal to noise ratio (although the noise is still there). If I amplify the carrier input using the program input + gain knob (as the manual suggests) I can't make it nearly as loud without extreme clipping, so I have to turn the master volume up to about half, at which point the background hiss is pretty obvious.

EDIT3: The issue may be related to a low quality / incorrectly rated power supply. I got mine in a trade and it seems like the DC adapter might have gotten mixed up with one from a different product.

Edit4: The hiss is still present with the factory power supply. I also tried a brand new unit from my local dealer. Same hiss. One workaround I found was to use a 9 volt power supply instead of 12 volt but you lose your white noise generator pretty much if you run it that way. Probably other side effects of doing that too.

Gonna return it.

[Kirneh Ness]

I hear it too. I'm old (thus losing some ability to hear upper frequencies), but still it is there. Not destructive for me to the point of returning the unit. But I'm a bit concerned that the problem is bigger than I think, based on the posts here.

[Ph111p]

Yeah for me it's pretty destructive because it's loud enough to be pretty clearly audible when I am using the unit as a filter - the carrier signal only being +/- 1.7 volts means you can't drown it out, and the silence will always have it if your gate is open.

I reached out to Moog last saturday to see if they would consider warranty support but they haven't responded yet. Kind of discouraged about that.

This is from my oscilloscope. Top line is an A-440 sine wave fred into the carrier input, bottom line is what comes out of the spectravox.

[andybutler]

The filters are noisy.
Apart from that, have a listen to how the distortion starts up, it's very sudden, and harsh sounding.
Very different in that respect to the filters on the Murf, that pedal has a smooth onset into distortion.

I've got some really good results out of the Spectravox, but Moog aren't really Moog any more and it's not really a high quality device as such.

[zaphod betamax]

As I run mine as an abstract effect and not as a foreground sound
I do not notice the noise.
Also, always run all output levels at 70% and not 100%.
I guess they lost the book on gainstaging in the last little while.