question to all SmallClone builders

[edd101]

hi there,

is it normal for SmallClone to have some background hiss? it's not that bad, but this question buthers me, cannot get to sleep at night.
decreasing 150pf cap also decreases some hiss, but for me 150cap sounds the best are there any other solutions or it's just the nature of bucket-brigade type chorus?

Ed

[PRR]

> some background hiss? ..., cannot get to sleep at night.

Un-plug when you go to bed.

Yes, BBD systems DO hisss.

[Mark Hammer]

It is a traditional battle, where BBD-based effects are concerned, between the desire to get more bandwidth and the desire to get less noise.

Because there is a clock and sampling involved, there is the eternal risk of aliasing effects, stemming from that teeny-tiny stairstep between each successive analog sample.  You CAN make it go away by imposing severe lowpass filtering on the BBD output, but that sacrifices bandwidth in the delay signal.  And obviously filtering out all the notches in the upper mids and treble robs the effects of any soul.

By making the 150pf cap value lower, you raise the clock frequency, such that the sampling is occurring at a faster rate, and the aliasing is then moved upwards in the spectrum, presumably where you don't hear it as much (most guitar speakers roll off above 6khz or so).

If you wish to go back to the stock value, getting rid of the resulting hiss increase will involve increasing some of the lowpass filtering.  The simplest thing would be to increase the value of the .0047uf cap on the output of the BBD by adding a 1000pf cap in parallel with it to bring the value up to 5700pf.  Consider increasing the value of the 180pf cap in the transistor filter stage to 220pf.  That should quiet things down.

[asatbluesboy]

Have you tried feeding it off something else?