Phaser "clock" bleed?

[m_charles]

Hi,

I just bought a boss ph-1r phaser (from 1981). It sounds great, I have the proper ACA adapter, but I'm getting this low "da, da, da, da" sound that the pedal bleeds off into my signal even when the pedal is in bypass. The speed of the sound is directly linked to the "rate" knob on the pedal even when in bypass.

Is this "clock" noise, or am I using the term wrong?

Anyways, my reason for posting is: Does anyone here know how I could fix it?

thank you!

chuck

[gez]

If it's a phaser, then the sound you're hearing is more likely the LFO.  If it's a Boss pedal, it's pretty safe to assume that there was no tick when it was manufactured, so your best bet is to replace the electrolytics (even though it's probably only one that is causing the problem, it's indicative that the others are dodgy, or about to go).

[StephenGiles]

If it's a phaser, then the sound you're hearing is more likely the LFO.  If it's a Boss pedal, it's pretty safe to assume that there was no tick when it was manufactured, so your best bet is to replace the electrolytics (even though it's probably only one that is causing the problem, it's indicative that the others are dodgy, or about to go).

Couldn't agree more.

[rhdwave]

Would that work as well for the neovibe (replacing the electrolytics?)?

[m_charles]

thanks guys.

any other possible causes? is this a common thing?

chuck

[Mark Hammer]

Would that work as well for the neovibe (replacing the electrolytics?)?

If your Neovibe is 25 years old, maybe, but I doubt it's that old.  The cap recommendation was because of the tendency for electrolytic caps of a certain type to dry out and go off spec over time.

thanks guys.

any other possible causes? is this a common thing?
chuck

Common?  I'd say there are at least 1,000 or more posts on this forum's archives concerning the elimination of what has come to be called LFO clock tick.  The simple cure is decoupling the LFO circuit from the power lines supplying the rest of the circuit.

[m_charles]

Common?  I'd say there are at least 1,000 or more posts on this forum's archives concerning the elimination of what has come to be called LFO clock tick.  The simple cure is decoupling the LFO circuit from the power lines supplying the rest of the circuit.

I couldn't think of what words to search, but now I'll try "LFO clock tick". Mark, would you care to short-cut me to instructions for decoupling the LFO?

thanks again!
chuck

[Mark Hammer]

Here's the short version.

The LFO circuit first produces a square wave, and then smooths that down to a triangle wave output.  When the signal swings suddenly in either direction to produce a square wave, it draws current from the supply in a sudden manner.  By analogy, if your partner got out of bed very slowly to use the bathroom in the middle of the night, the bed would not shake and you would not wake up.  If they jumped out of bed suddenly, the bed would shake and you would be awoken.  If your cat slept with you on top of the bed and jumped off the bed in the middle of the night, you probably would not be awoken.  So, it is the suddenness of the departure and the force of the departure that results in a detectable bed-shake and awakening.  Similarly, with an LFO, it is the smoothness or suddenness of the current draw, and the amount of current draw that produces a detectable "tick".

The TL022 and LM358 are often used for LFO circuits, because they draw much less current, so that's one part of the overall strategy.  The other is to smooth out the current draw via "decoupling".  Here, additional filtering is inserted between the supply (9v battery or wallwart).  That could be in the form of something like a 100R resistor betwen V+ and the V+ pin on the dual-opamp that forms the LFO, with a 10-47uf cap from that point to ground.