Phase II and the Circulator

kristopher

Well-known member
I'm asking for your opinions of these two Phasers. I have recently built a Phase II. And it's a fine Phaser. But I'm finding that the Circulator I built a few months back is more "Present". Maybe the term is "Cleaner"...?
Based on the reviews of the Phase II, I thought it would Wow me away from the Circulator.
I'm wondering if I chose incorrect LDR's or something. Their peak wave length is 570nm. I used these: https://www.mouser.ca/ProductDetail/Advanced-Photonix/PDV-P9004?qs=Znm5pLBrcAKsmy65LwnluA==
I've tested it with a covered LED and uncovered. In both a well lit room, and the dark, and in an enclosure. The trim pots act as they should.
I wired the pots on the Phase II off board, in case I decide to pair it with another pcb in the same inclosure.
I like my Phasers set to full blend, and slow. But not all the way slow. And at the end of the signal chain. After OD's and Fuzz, before Reverb, which is last. Just saying.
And here are some guts. out of the box.
 

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I’m not familiar with the Circulator, so may not be of much help. I don’t think that the choice of LDR or LED will affect anything other than the amount of phase, and you are talking about presence and clean sounding — so I think it must be another aspect of the two pedals. Either the circuit design, or a build / parts issue.

I run my mods after gain also, almost always at a slower throb, but do vary the blend, from just adding a bit of movement to full on.

What I’d like you to try is comparing them with very little boost before them. I wonder if the Circulator has a higher headroom, and so sounds cleaner when fed a higher level signal. This may help point to the part of the circuit that is the problem. On the other hand, it may not be a problem. It’s possible that the Phaser II just distorts more easily. I’ve come to realize that overloaded mod pedals are the “clipping diodes” of my pedal board. I tend to play lower gain, and pretty clean. But many of the mod pedals really have lovely overdriven sounds to them, and this is where I get my distortion.

I’ll be curious what people familiar with both pedals suggest. If the less “stressed” sound is still “unclean” I wonder if swapping out some of the op amps would be worth a try?
 
Does the Phase II sound "stressed" with the frequency control at Min? The Circulator was on my board for a few years before being kicked off by the Phase II. The Circulator is a fine circuit, and does what it does very well. I never had any issue with it locking up like some. For me, the Phase II is meatier. Kinda like the difference between a digital replication of a Phaser (the Circulator) and an actual Phaser (Phase II). The Frequency control takes the Phase II into places the Circulator can't touch. Other than adjusting the trim pots, the only other thing I could think of that might be causing the big difference is the extra stages of the Phase II (the frequency control)...

...or maybe try swapping the IC's. Sometimes some are more behaved than others...
 
Thanks for the suggestions. I'll give the IC's a swap tonight. And I'll do a side by side comparison for headroom.
And I'll give the Phase II a stress test.
Man, I got a lot to do. I guess the four other finished builds I have on the bench will have to wait another day for enclosures.
 
The Circulator is pure analog, just like the Phase II. The circulator uses variable-gain amplifiers to make variable phase shift. The Phase II uses LDRs to make variable phase shift. The Phase 90 uses JFETs to make variable phase shift. Each one will sound different. The matching (or lack thereof) of JFETs or LDRs will significantly affect the tone. They're all good phase shifters and each has strengths and weaknesses. The weakness of the Circulator is it is the noisiest of the three. The weakness of the Phase 90 is if you drive it too hard, the JFETs will distort. The weakness of the Phase II is the relative difficulty in matching LDRs.

The FV-1 provides a digital solution for phase shifting. There's no matching required and it has good headroom.

It's up to the player to decide which one makes the best tone for them.

One more thing: don't obsess over LED color. LDRs are very sensitive and require very little light to do their thing. Any color LED will make more than enough light at full brightness. It's silly to use super-bright or white LEDs because they make so much light you may not be able to dial the trimmer down far enough. Testing must be done with a light-tight cover over the LDRs/LED, a closed box or in total darkness.
 
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All my futzing with the guts outside of a box has lead me to further problems. The LED has no pulse. I must've bumped something loose while pulling and swapping IC's.
Looks like I have tomorrow's project. Dang it.
Thank you for your patience.
 
Well I got it going again. I wiggled some TL072 around. The yellow defused LED pulses again. But it never goes fully dark. no matter the trim pot settings. The circuit does phase.
I tested the IC voltages and got similar numbers to what Coda posted back in April when he was trouble shooting:

"I found some measurements for Q1 in another thread. It should read C: 8.8, B: 4.2, E: 3.6. I am reading C: 8.8, B: 7ish, E: 6ish.

Here is what I'm seeing at IC5:
1) 7.2
2) .50
3) .51
4) -7.73
5) 0
6) 0
7) 0
8) 8.7

IC's 1, 2, 3, and 4 read as follows:
1) 0
2) 0
3) 0
4) -7.73
5) 0
6) 0
7) 0
8) 8.77

IC6
1) -6.33
2) 0
3) goes from 4v down to -4v, and then back
4) -7.71
5) 0
6) 0
7) goes from 4v down to -4v, and then back
8) 8.11
...."

My numbers are similar, just a bit higher. I hit 9.3 on the 8's, and 8ish on the 4's.

I'm going to box it up and see if it grows on me. And I'll let a few friends try it out. But I am willing to admit that it may be a matter of taste. The Circulator, to my ears, has what I'm after in a phase.
Also, on my last purchase, I grabbed a second Phase II board, so I'll have to build another one to compare. Maybe this one got a hex on it, cause I was finishing it around Halloween.
Thanks for listening.
 
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