This Week on the Breadboard: Phase 90
- Thread starter Chuck D. Bones
- Start date
finebyfine
Well-known member
Ooph and I was hoping you hadn’t hidden the ground ratlines. That’s a doozie
Chuck D. Bones
Circuit Wizard
Good catch. Schematic in post #72 corrected.
Fingolfen
Well-known member
I really need to get this one breadboarded, but I was looking at the schematic and comparing it to the vanilla Phase 90, and noticed something.
Tracing from the audio signal in through to IC1A - it's going into pin 2 (-) on this schematic, but on the standard Phase 90 it goes into pin 3 (+)... granted, going through all of the ICs both the "A" and "B" pin attachments seem to be similarly reversed. Was this intentional?
Tracing from the audio signal in through to IC1A - it's going into pin 2 (-) on this schematic, but on the standard Phase 90 it goes into pin 3 (+)... granted, going through all of the ICs both the "A" and "B" pin attachments seem to be similarly reversed. Was this intentional?
Chuck D. Bones
Circuit Wizard
Schematics in posts #72 and #83 have errors.
I just now corrected post #72. IC2A & IC3A were drawn upside down in the previous version.
I just now corrected post #72. IC2A & IC3A were drawn upside down in the previous version.
Chuck D. Bones
Circuit Wizard
Not any more. Thanks again for pointing it out.
MBFX
Well-known member
@Chuck D. Bones Just coming by to say how impressive it is that you know how to do this stuff. I feel like a wizard knowing how to read basic boost schematics and breadboard them, but this is the kind of stuff I really want to learn and be doing. Thanks for all the help so far! I would have quit this hobby if you and @BuddytheReow and @Feral Feline hadn't taken the time to answer my questions.
cooder
Well-known member
Well I think we all win then...
While I originally thought my build report might be in January 2024 or 2025 it turns out somewhere in the golden middle...
Here's the "Phases of the Moon", sounds and works excellent and the footswitch juuuust fitted in there, geeeez it's a bit tight, she said, but fun and all worth it
Great soundz and variety, love having a Depth control and the Colour has great shades of phaseygoodiness.
Great circuit work and Chuck held my hand getting the J113 jfets to work in there and what to watch for when selecting a quad with the fab jfet tester from here:
https://forum.pedalpcb.com/threads/why-are-jfets-such-a-pain-in-the-ass.4878/post-219671
(note: there's a wee mistake in the schematic of that tester, I can post an update if someone wants it, easy enough to spot anyway).
So it's great to know that we can get this working with still readily available in production jfets. I tested about 80 pieces of J113 sourced from Mouser and found a bunch of tightly matched quads.
Anyway, enough fluffing around, here's the swirly goods:
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Chuck D. Bones
Circuit Wizard
Great job Cooder!
cooder
Well-known member
Nah nah; great job on the shematic and circuit tweaking Sir @Chuck D. Bones !
Chuck D. Bones
Circuit Wizard
Sweet!
I found that I could get a decent UniVibe throb with the standard cap values and the right COLOUR & DEPTH settings.
I found that I could get a decent UniVibe throb with the standard cap values and the right COLOUR & DEPTH settings.
thunderaxe
Member
could you clarify what the COLOUR (appreciate the non-americanized spelling on that one btw) control does? it seems like it replaced the RANGE trimmer, which from the name makes me think it shifts the sweep toward the treble or bass end? am i right?
thunderaxe
Member
and another question: as i understand it it's standard best practice so isolate the power supply for the LFO from the rest of the circuit so as to avoid crossover "tick", and yet in the phase 90 and PH-1R that isn't the case, nor have you felt the need to do so in your pretty extensive redesign of the circuit. is it that the single-op-amp LFO doesn't produce a tick, or is there another reason why that isn't a concern here?
Chuck D. Bones
Circuit Wizard
You are correct.
There are degrees of isolation from putting the LFO in one corner of the board to creating separate power and ground planes for the LFO. We seem to be getting away with doing the minimum. IC3B is a Schmitt Trigger, which normally switches rapidly between OFF & ON. That rapid switching can introduce current spikes into the power and ground traces and those current spikes can produce ticking in the audio portions of the circuit. C7 and R23 slow down the switching so there is less noise produced by the LFO. There are three ways to combat noise in a circuit: reduce the source of unwanted noise, reduce the susceptibility to noise, and reduce the coupling. The designers of the Phase 90 chose door #1 and it was sufficiently effective that no other measures were required. Since the LFO and the 3rd phase-shifter stage share the same IC package, we have basically no isolation. The susceptibility of this circuit is low because the gain is unity throughout. It would take a pretty big disturbance to be audible.
There is a concept in engineering know as "good enough." This circuit is good enough and adding more parts, making it a 4-layer board, etc. would cost more without making the performance noticeably better.
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thunderaxe
Member
did you end up doing the PH-1? i'm working on the PH-1R right now and would love to hear your insights
thunderaxe
Member
since the "throb" LED takes its input as pin 7, the square wave output of the op amp. am i correct in assuming that it will only blink in time with the rate and not ramp up and down like the triangle wave output of the LFO? because if so i think i have something valuable to contribute and not just asking questions
Chuck D. Bones
Circuit Wizard
I did not. They are so similar that I didn't see the point. I will say that the PH-1r has less distortion than the PH-1 due to the linearizing resistors around the JFETs.
The Rate LED blinks on & off at the LFO rate, does not ramp. What is your idea?