# Circulator - Unity Volume



## chongmagic (Oct 15, 2019)

I just finished the circulator yesterday and I have found that unity is somewhat lower when the effect is active. Has anyone else come across this?


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## reubenreub (Oct 15, 2019)

I was thinking of putting in a trim pot on R6 to control the overall volume. I always try and add those in for effects without a volume control. I think that's where you'd do it on this one. Other uses correct me if I'm wrong.


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## Jovi Bon Kenobi (Oct 15, 2019)

chongmagic said:


> I just finished the circulator yesterday and I have found that unity is somewhat lower when the effect is active. Has anyone else come across this?


No on mine. If anything, it's almost imperceptibly louder when active, depending on the LFO frequency.


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## Chuck D. Bones (Oct 15, 2019)

With DEPTH at zero and MODE set to Phase, you should get nothing but clean signal and it should be dead on unity.  If it isn't, then one of the components on the board is wrong.

R6 is a good place to put a volume control, either a front panel pot or a trimmer.  If all you're after is some fine tuning, then a 10K trimmer with 6.8K in series would do it. The other way to insert a volume control is to increase R6, say to 15K or 22K, and connect the VOLUME control between the board OUT terminal and the stomp switch.  Anything from B10K to B100K will work.


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## chongmagic (Oct 15, 2019)

If Depth is full and mode is at Phase I get unity. If depth is at zero on phase it is barely audible. Note that vibrato is not that way. The effect does work in phase mode if the depth is turned up. I wonder if one of my opamps is bad.


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## chongmagic (Oct 15, 2019)

If depth is full on phase and all other knobs are zero I have unity.


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## Chuck D. Bones (Oct 15, 2019)

Maybe we're not talking the same language.  To me, Phase mode is when the phase-shifted and dry signal are mixed.  Vibrato mode is when there is only phase-shifted signal, no dry.  DEPTH controls how much phase-shifted signal is present.  If you set DEPTH to zero in Phase mode, you get only dry signal.  If you set DEPTH to zero in Vibrato mode, you get nothing.


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## dearthworm (Dec 9, 2019)

chongmagic said:


> If Depth is full and mode is at Phase I get unity. If depth is at zero on phase it is barely audible. Note that vibrato is not that way. The effect does work in phase mode if the depth is turned up. I wonder if one of my opamps is bad.


i'm having unity problems too. did you solve it, if so, how? i'm thinking one of the LM13700s is crud.


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## Chuck D. Bones (Dec 9, 2019)

Your Circulator is working exactly as it is supposed to work, although I would not have designed it that way.  
In PHASE mode, the wet & dry signals are combined.  The DEPTH control sets how much wet signal you get.  When DEPTH is at zero, you get only dry signal.  When DEPTH is at max, you get more-or-less equal amounts of wet & dry signal and the phasing effect is the strongest.
In VIBRATO mode, the dry signal is switched off; you get only wet signal at the output.  Since the DEPTH control determines how much wet signal gets thru, turning DEPTH down reduces the volume.  In other words, the DEPTH control is a volume control in VIBRATO mode.  If you want unity gain in VIBRATO mode, then set DEPTH to max.

Look at the schematic if you don't believe me.


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