Maestro PS-1A layout...for your pleasure

[tomas1808]

Hmm I think the bias is OK.

I think it is a impedance thing.

When I plug a guitar into the phaser and then into a DI, I get a big difference between effect-on and true-bypass.

However when I go from my sound card to the phaser and back again to the sound card (all line level) I get pretty much no difference between effect and bypass, only some volume differences.

Maybe this unit was made for line signals?

I haven't tried this in a real guitar amp yet though.

[tomas1808]

Just found out that the 4.7uF cap is backwards on jdubs layout!

Positive lead should go to ground!

This resulted in a loss of about 1.5V to the FETs gates a few minutes after powering on. This meant the phasing would become less apparent minutes after turning it on.

Reversing the cap fixed this. Now voltages are rock steady.

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The only problem remaining is the HF attenuation on bypass which is a bit too much for my taste.

When I wired the true bypass I would get a level drop when switched on.

How can I fix this level drop?

---

Also, I hear faint clicking. Any ideas on how to remove it?

Thanks

[duck_arse]

clikking? hmmm, that's bad. you'll need to seperate all the earth connections to the oscillator from all the earths to the audio sections. the best way to do this in my opinion, is to build the osc on a seperate board (I use vero). as for the volume drop, there is 4 resistors on the OP circuit diagram at the top right corner, marked "3k" "4k7" "12k or 10k" "3k or 4k3". what of those do you have fitted?

[edit: ] and what type opamp you using for oscillator?

[jdub]

Hey Tomas, sorry about the reversed cap on the layout, meant to change it as it was in my notes, but never got around to it.  I need to learn to not keep so many versions of layouts...or, better yet, how to proofread 

I'm not sure about your volume drop, I have mine wired true bypass and don't seem to get much drop.  You could opt to place a small boost circuit after the effect, I did that for an Electric Mistress I built a few years ago and it worked well.

As for the ticking, I had that problem too, though juansolo didn't.  I cured mine by using a TL062 for the LFO opamp, as well as performing some surgery to install a 100R resistor to pin 8 of the opamp (the +12 pin), and a 22uF to ground from that pin.  It's a tight fit, I had to cut the trace going to pin 8 and install the resistor upright, then I mounted the cap over top of the 33k.  I can post a photo of the hack if you like, let me know.  It totally cured the ticking.

One other thing:  I posted (another) fixed layout in my gallery (orientation of the cap now correct); I also changed the MPF102 in the LFO circuit to a 2n5485.  I was getting a bit of a lopsided phase, and it was tough for me to get the trim set correctly.  Changing this tranny helped, TBH I'm not sure why I used an MPF in the first place.  YMMV, of course...

Cheers 

[tomas1808]

Thanks for the info guys!

Will try the TrueBypass again now that the circuit is soldered (last time it was on breadboard). Will try a boost circuit if the problem persists.

Ticking is very faint, maybe i am being a bit anal. I might try the mod anyway. Is the TL062 important? Could I just do the 100R and 22uF to ground and be done? Dont have any TL062 around.

So its +12v rail-->100R-->pin 8 right?

I used 2N3638As and PN4303s so I think I have no problems there.

duck: I used 3K, 4.7K, 10K and 3K. Anything I should be aware of?

Thanks!

[jdub]

The reason for the TL062 is that it is a low-current opamp, and using such a device in an LFO circuit can help ticking by reducing the magnitude of the current spike that causes the ticking in the first place.  I used a 62 because I happened to have one, but you could also try an LM358 or a TL022; if your ticking is very faint, just an opamp change might take care of it. 

Correct about the other mod.  You should run a 100R resistor from the +12v source (which is shared by both the LFO and audio paths) to the V+ pin of the LFO opamp, and run a 10-100uf cap to ground from that pin (22uF worked fine for me).  This will decouple the LFO and the audio paths.  Like I say, if you'd like a photo, let me know.  If I ever revise that layout, I may add some pads specifically for that, but...

[duck_arse]

are you using a fet bypass circuit? I thought of the "mix resistors" on the phase 45, for inst, which are sometimes tailored for vol drop. then I got confused as to witch ones were witch, because of the extras.

[tomas1808]

The reason for the TL062 is that it is a low-current opamp, and using such a device in an LFO circuit can help ticking by reducing the magnitude of the current spike that causes the ticking in the first place.  I used a 62 because I happened to have one, but you could also try an LM358 or a TL022; if your ticking is very faint, just an opamp change might take care of it. 

Correct about the other mod.  You should run a 100R resistor from the +12v source (which is shared by both the LFO and audio paths) to the V+ pin of the LFO opamp, and run a 10-100uf cap to ground from that pin (22uF worked fine for me).  This will decouple the LFO and the audio paths.  Like I say, if you'd like a photo, let me know.  If I ever revise that layout, I may add some pads specifically for that, but...

Got it! I might swap the OP amp next time I order parts. Thanks, I dont think I need a photo. Unless you want to 

are you using a fet bypass circuit? I thought of the "mix resistors" on the phase 45, for inst, which are sometimes tailored for vol drop. then I got confused as to witch ones were witch, because of the extras.

Yes, using the FET bypass ATM. I will go for True Bypass as soon as I have time.

Thanks!

[charbot]

HI,

First off, Jdub, thanks for making this thing available- this is one of the best sounding phasers ever.

I just finished my build and it seems like im in the same boat as Tomas - I have some slight volume drop with true bypass and cant seem to shake LFO ticking.  Not bothered by the level drop that much, but the ticking sucks big time.   I tried adding  a 100 ohm resistor and cap, swapped in a lm358 and rerouted the ground (of the LFO op amp) directly to the powerjack. no luck.  I guess Ill go  in again and make sure the complete lfo circuit has a separate ground path, not just near the IC.  Aside from that it's awesome.

One thing I can add:  I have photocopied original schematics of both the PS-1 and 1a, - the later lists  5457's as a replacement for all of the 2n4302's.

edit: hmm looking back, i used a .22 uf cap in place of the .33 one by the LFO IC, that wouldnt make much of a difference, would it?

[jdub]

TBH, I'm not sure, but it might...I would try swapping it out for the correct value.

You know, I saw that note about the 5457s, but I didn't have enough to match a set...

What size cap did you use from the power pin of the 358? 

[charbot]

33uf is on there now - but I also tried adding a 100uf and even threw on a .1uf for good measure.  couldn't tell much of a difference.

I also swapped the other cap for the correct value.

The ticking is not so noticeable, but it is there.  I can make it fade with the trimpots, but the point where it is totally gone, I have a really weak phase effect.  I guess its a juggling act to find the perfect balance.  The best i can get it so far, the ticks are gone when set on high, but become audible as the the phasing ramps down.  Medium is the worst, on low they are so spread out that they are almost disappear.   

Also maybe I should mention that before I went true bypass, I had a tough time adjusting the 'off' bias trim.  Would still get a 'woosh' on the low setting even w/ the pot at max.  maybe something else might be weird in mine? 

[jdub]

Hmmm, 33uF should be plenty...have you replaced the .22 with the correct .33 yet?  If the 100R resistor and cap are done correctly, plus the low-current op amp, you should be able to cure the ticking.  Any other part swaps? How are you powering it?

[charbot]

Yeah the .22 has been replaced w/ the correct value:.33uf.  
Tho' I just discovered that I used a 10 ohm resistor instead of 100-bet thatll make a difference!
edit/ nevermind- just put in a 100 ohm- still ticking.

[jdub]

Any chance for photos? How about the power supply?

[charbot]

Power supply is a regulated 12v wall adapter and an lt1054 to deliver the -12.  the LT1054 is on a second board and I had the ticking before adding it.  For testing/building I was  using a dual regulator supply and 12v tx left over from another project.
Will try to get a pic up soon.

[juansolo]

Got a cure for the high end loss. Strap an input buffer on to the front of it. We just used a Klon buffer and it sorts it out spot on.

So, in all we've done this to ours.

- Link the slow. This allows us to run true bypass.
- Replace the resistor on the output with a 220nF cap, then run a 1M resistor to ground after it. That gets rid of the DC and stops it popping.
- Add an input buffer. That addresses the loss of highs.
- Replaced the 2n5087 on the input with a BC559C. That addresses the volume drop.
- Add the anti-RFI caps. Because we got radio otherwise.
- Use the following power supply: http://juansolo.demon.co.uk/stompage/schematics/Power/12vBipolarPSU.jpg We get no issues with this, no ticking.

[jdub]

Many thanks for all your work on this, guys- you've helped make a great pedal even better!

[juansolo]

Yep just stuck a klon buffer on the front of our two and the highs pop back. It also helps with the vol drop also. Pretty much perfect now.

[Canucker]

why have I not built this yet?....note to self...build this!

[kaycee]

Thanks for the updates on this Juan. I have a board ready to be populated and this info is going to help greatly so cheers. One question though, where exactly do you put the RF blocking caps? I can read the schemo easy enough and translate to layout. Thanks