SOLVED Waving the white flag - XC Phase (several issues)

[mkstewartesq]

My issues with the XC Phase are numerous and have me stumped.

Photos of the board attached, along with a schematic. The reason there are no jacks or 3PDT attached is because I have been testing it using the auditorium platform - same for why the LED is just inserted into the board rather than soldered (I plan to wire it off board later).

I’ve checked the values on my components visually – for whatever reason, perhaps they are sold her to the board, I’m getting all kinds of fluctuating readings when trying to test with a multimeter. Continuity seems to be fine between the various points.

The JFETs are a matched quad, purchased from Banzai.

My issues:

1. Ticking in Block mode. This when I can hold off on a bit as it may resolve itself when I get this in an enclosure. But the ticking is odd, almost like a breath – tick followed by a second of silence like an exhale, then the phasing cycle begins again until the next tick.
2. Very weak phasing. Furthermore, to my inexperienced ears, the phasing seems irregular and asymmetrical - instead of a steady cycle, it’s more like a heartbeat. My best impression: “wow……....wow-wow….…wow……..wow-wow”.
3. I can bias to get Script mode and 4 stage (90 mode) working fairly well (although weak and with a little distortion). But 2 stage (45 mode) is ALWAYS heavily distorted no matter how I bias. As noted, Block mode ticks.

So basically I’ve got Script 90 working with very weak and seemingly irregular phasing and a little distortion. But Block mode is ticking and 45 mode is always distorted. I tried switching out the TLO72s (all bought from Stompbox Parts, not Tayda or eBay) and these three sound the best out of all of them.

Just a bit of additional information if it sparks a thought – as I mentioned in another thread, the area on the trim pot where you can actually get phasing is very very tiny on mine – maybe a millimeter. Everything before that and after is no phasing so I have a very very tiny area in which to attempt to bias.

Any help appreciated – I’m really hoping to be able to save this one because my daughter designed a beautiful enclosure for it that we have already had drilled and printed. So there’s a lot of sentimental value there and because of the very unique layout of this pedal's controls, I’m not gonna be able to find another phaser that’s going to fit in that enclosure.

Thanks for reading my book-length post and for any assistance.

Mike

 

[carlinb17]

Have you reflowed every joint? Cold joints can give everyone a headache. Some of your joints look like they could use a little more solder. Does the ticking continue if you remove the led and what is your power situation/ground when it comes to powering this with auditorium. Sometimes placement of wires can create interference and noise.

 

[mkstewartesq]

Have you reflowed every joint? Cold joints can give everyone a headache. Some of your joints look like they could use a little more solder. Does the ticking continue if you remove the led and what is your power situation/ground when it comes to powering this with auditorium. Sometimes placement of wires can create interference and noise.

Thanks, let me take your questions in order and also provide a bit of an update.

1. I have not reflowed every joint. Looking at them, they all look good to me but, nonetheless, your suggestion is sound so I will reflow them all tomorrow and report back.

2. The ticking does continue when the LED is removed. I have a bit of an update on the ticking below.

3. If I’m understanding your question correctly, I have the auditorium hooked up to an isolated power supply on my 1Spot CS-12.

As far as an update – the ticking might go away once I put it in a grounded enclosure (another member here reported that stopping the ticking). However, I was able to bias the trimmer to just below the point where the ticking stopped without going so far as to lose the phasing. Though it took me about 1 million tries (and if I ever lose the setting again, I’m screwed) I was able to hit on a spot where, although the phasing is not as great as I would like, Block Mode is not ticking and is phasing a bit, Script Mode is phasing, as is 90 mode - all have a bit of distortion but maybe I can live with that since JFET phasers are known to be a little crunchy anyhow. This also got the phasing to be symmetrical as expected rather than the uneven rhythm I had before. This gives me hope that if a grounded enclosure will remove the ticking, I might have a broader range of the trim pot to play with to perhaps get even more of the effect.

45 mode however is still distorting, no matter how I set the trimmer. Also, block mode is incredibly noisy while script is dead silent – but I am a phaser newbie, so maybe that noisy block mode is just the nature of the beast.

It seems to be a bit of a constant trade-off – get one mode to have a reasonably good sound and at least two out of the remaining three are out of whack. I guess I should consider myself lucky for the moment that I got three out of the four modes to sound at least passable, and would appreciate any additional thoughts to improve the performance here.

One last note, because it’s hard to explain a “sound” - when I refer to “weak phasing”, I guess what I’m trying to say is that I’m used to phasers that make it sound like the note is actually phasing - on mine, it sounds more like the guitar notes are clean and there is a phasing sound in the background, rather than the notes actually going through the phasing sound themselves. That may not make sense to anyone else, but that’s the best way I can explain it.

Thanks for your help.

Mike

 

[mkstewartesq]

Have you reflowed every joint? Cold joints can give everyone a headache. Some of your joints look like they could use a little more solder.

Just following up - I reflowed all joints (so much new flux to clean!) and no change from what I reported above.

One other thought - in addition to whatever else ails my XC Phase, I'm wondering if there is an issue with the trimmer pot. A few times this morningI would just get to the point of dialing out the ticking in Block mode, test it (no tick) and switch to Script. When I switched back to Block, sometimes but not always the ticking had resumed - making me wonder if the the pot is either defective or poorly built such that even flicking a switch on the board can cause it to shift settings slightly.

This trim pot is the first time I have used this model -usually I use the Cermet but Tayda had no 250K Cermet in stock when I ordered. I do have a 200K Cermet - would that work in this circuit/is there anyway to modify it (such as with a resistor) to make it work to try that out?

Thanks again for everything,
Mike

 

[Drayve85]

I had a couple issue with this build the last couple days. Although, I built a vero board version, with script switch, and depth knob. I was going insane last night with the trimpot, until I noticed that if the pots are turned down, it’s hard to tell if there’s any phasing goin on.lol idk if your problem has anything to do with the jfets or not. I bought 20 smd 5457’s with boards, and used my el cheapo Amazon component tester to sort and match them. Using the ‘I’ and ‘Vgs’ readings were enough to match them. I had to try a couple different sets, but I think I got the right ones. I have some extra 250k trimpots, if you wanted a couple to try out.

 

[mkstewartesq]

First of all, thank you for the very kind offer of the 250 K trim pot. But I think I’m OK for now on that front. Last night I got the feeling that the Tokyo Denshi trim pot was perhaps prone to slight shifts when I moved the board (I biased it to remove the ticking and then after flipping a few switches the ticking would be back and I would need to readjust). So I just took it out this morning and replaced it with a 200 K Bourns - since all of my phasing seems to occur near the middle of the turn, I think that the 200 K works fine.

When biasing, I usually have the rate at about 12 o’clock or a little higher because, as you noticed, even if it’s phasing properly, it’s hard to hear when the rate is too slow. In addition, because I am trying to buy us to remove the tick, having it at a faster rate makes it easier to hear exactly when the ticking stops and not turn the bias any further.

So I may be about as good as I can get (although I am hopeful that once I put it in a grounded enclosure with shielded input and output wires, maybe I’ll be able to get some more improvement). I’m actually getting a somewhat acceptable level of phasing now in both Bock and Script in 90 mode (4 stage) - but 45 mode (2 stage) is still unusable. There is hardly any phasing in that mode and, as it goes toward the deeper frequency end of the sweep, everything gets really distorted.

As far as my JFETs, I checked the voltages on them again once I got to the best level of phasing I could attain and they seem to be where they should be - all of the gates are at around 2.3 V. As far as the drain, I’m not sure if they’re all supposed to be at the same voltage as well – two of mine are at 4.4 V while the other two are at around 5.5 V. But since the gate is in that “magic range“ of 2 V to 2.5 V, I’m assuming everything is as it should be since they were reported to be a matched set when I bought them.

So maybe this is as good as it gets – if so, I can live with it as a passable Block 90 and Script 90, and just pretend the 45 mode doesn’t exist.

I really appreciate you sharing your thoughts and, again, for the kind offer of the 250 K trim pot.

Mike

 

[Drayve85]

Not a problem. On mine, the voltages on the Jfets are all the same on all four. I’m getting 5.14v on drain and source, and a fluctuating around 2-3v, I think, on the gates. Idk if it’s weird or not, but my ‘magic spot’ on the trimpot is just north of 3v. I doubt any of this will help, hope it does tho!

 

[Drayve85]

If I were you, I might get a cheap component tester off the bay of E, or Amazon, and check those Jfets. Even build a JFET tester. There are vero board layouts for that. Just to make sure your Jfets aren’t the problem, ya know. Because those Jfets that are running at a lower voltage don’t seem right.

 

[mkstewartesq]

Not a problem. On mine, the voltages on the Jfets are all the same on all four. I’m getting 5.14v on drain and source, and a fluctuating around 2-3v, I think, on the gates. Idk if it’s weird or not, but my ‘magic spot’ on the trimpot is just north of 3v. I doubt any of this will help, hope it does tho!

Thanks – if I go above 2.2 V or 2.3 V on the gate with the trim pot, I’m back into getting ticking in Block mode. That may go away once I get this in a grounded enclosure, which will allow me to go a little higher on the trim pot. But your experience is not unique – while I’ve read here that 2V to 2.5 V is the sweet spot for phasing, I see others who have reported they were getting the strongest phasing at around 1.5 V on this circuit.

I’m also very lucky that a friend is sending me another matched set of JFETs to try out to see if they work better than the matched set that I purchased from Banzai. (Banzai’s listing for them was for a matched quad - but they didn’t specifically mention matched for phasers, which other sellers of matched quads are usually careful to point out – so the ones I have may be matched to each other but not necessarily “the right spec” for a phaser). Who knows, that might even account for the fact that my two stage mode is distorted no matter how I bias it.

Thanks, as always, for offering the insight, assistance and additional information.

Mike

 

[Drayve85]

That’s cool your friends sending ya another matched set. I think that’ll fix your issues. As for the distortion, the only way I could ‘get rid’ of it, was running it at 12v. I haven’t tried 18v yet, because of the 15uf cap. Mines only rated for 16v. But I believe they can be run at 18v so long as all components are rated for it. Good luck, and let us know how it turns out, please!

 

[mkstewartesq]

Well, I am going to update this and mark it solved (at least for me). I know that various people, including builders far more experienced and knowledgeable than me have had problems with the XC Phase and been unable to resolve them. After digging through tons of threads about phaser ticking across various forums dating back to the early aughts, I tried the suggestion of replacing the TL072 most directly tied to the LFO with a lower power TL022. I switched out IC3 and this actually cured ALL of the remaining issues I have been having with the XC Phase, namely

• Ticking in block mode (completely gone, meaning that I can dial-in a stronger phase without ticking, which previously would only go away if I dialed the phasing down to make it disappear)
• The hiss I was having in block mode (even when dialed back up, the hiss is now completely gone – all modes are dead silent)
• I can actually hear phasing in 2 stage/“45” mode (previously, dialing back the trimmer enough to get rid of the tick in block basically made 45 mode non-phasing).

Because I can take the trimmer higher without ticking, the phasing is definitely stronger than it was before.

I hope this helps someone in the future as at least another avenue to try. I’ll admit that I was stocking up this morning to build another MXR 90/45 clone (either vero or GuitarPCB) because I had basically given up on this one (which was a real bummer because none of them had the same feature set or would fit the drilled enclosure that has some very special art my daughter designed as I detailed in my build report) – then I decided to do a lot of additional last ditch research and it paid off.

Mike

 

[KR Sound]

That’s good to know and I’ll have to try that on the one I made for my friend.

 

[neiltheseal]

Did you use the matched quad from Banzai in the end?

 

[mkstewartesq]

Did you use the matched quad from Banzai in the end?

I did not. I I was lucky enough to receive matched JFETs from a member here, which definitely cured some of the phasing issues as far as distortion in certain modes, etc. But even then, the phasing was still weak and I was getting heavy ticking in Block mode, which is why I went on the lookout for another solution - the replacement of the TL072 with the TL022. If you want to know more about what issues a properly matched set fixed, and which ones it did not, my build thread is here.

Mike

edit to add– all that being said, maybe I will try the Banzai fets again sometime, just to see how they perform with the rest of the circuit working properly.

 

[neiltheseal]

I did not. I I was lucky enough to receive matched JFETs from a member here, which definitely cured some of the phasing issues as far as distortion in certain modes, etc. But even then, the phasing was still weak and I was getting heavy ticking in Block mode, which is why I went on the lookout for another solution - the replacement of the TL072 with the TL022. If you want to know more about what issues a properly matched set fixed, and which ones it did not, my build thread is here.

Mike

edit the ad – all that being said, maybe I will try the Banzai fets again sometime, just to see how they perform with the rest of the circuit working properly.

Thanks. I’ll have a look at your build thread.

I would love to hear how the banzai gets go. I have some in my cart but am hesitant to buy them for this build now.

 

[KR Sound]

I just replaced IC3 with a TL022 and it made all the difference. Both modes sound great and all issues are fixed.

Edit- oops, looks like I swapped out IC1 and not 3. Still fixed it ¯\_(ツ)_/¯ Who counts from bottom to top? Ha.