Jfet matching for phase 45 build

[Locrian99]

Tiny little solder bridge where the 15u cap was connecting to ground was grounding out pin 6 and the LFO.   Works great now, now to to play with the bias and resistors feeding that diode.   Tomorrow I've got some coming which will have a 5.6v 1w I'll try.   Had to get the 5.1 1/2 watt from eBay so hopefully sometime next week.   Will wait to box this up and call done until then.  Now to remember the chords to lightning crashes lol.

Good one!

I've screwed up enough of these vero builds now I'm starting to know what to look for lol. 

[Locrian99]

Couple things of note.

Using the 10k resistor despite the voltage loss is a better way to go IMO, and this could I imagine have to do with the jfets as well?   It took me all the way down to 3.58, but the effect was much more pronounced than when I went with a smaller resistor.   

Using the 1n4148 in series while using the 10k was the best choice given what I have.   That got me up to 4.14 and I could get a more pronounced phase than without and not get distortion (seems like the most pronounced phase on the bias adds distortion to my ears)

Will have to see just for experimenting sake what if anything would bump it up by a 1V see how that sounds.   Does make me think the 5.6v zener at 1w isn't going to do it.   

I also realized I bought some 5952s and put them in with my other transistors I am going to go through those and see if I have a set that matches and compare, also I have a bunch of 4558's with no real project in mind for them.  Think I'll try those in here as well. 

[Rob Strand]

I've screwed up enough of these vero builds now I'm starting to know what to look for lol. 

All part of the deal with electronics.

Using the 10k resistor despite the voltage loss is a better way to go IMO, and this could I imagine have to do with the jfets as well?   It took me all the way down to 3.58, but the effect was much more pronounced than when I went with a smaller resistor.   

Not 100% sure what's going on there.   What happens when the Vref is low the on an off times for the LFO become unequal.   Maybe that's the sound you want/like?

There a tweak where you can reduce the 3M9/3M3 resistor to get a wider sweep.   There's nothing stopping you playing around with that.

[Phend]

1N914 shims are perfectly valid.

Sounds like shimming is the best plan since my builds are "open air" (no board).
Another thought, I have parts for the Rebote 2.5.
How about using a 78L05 ?
Either way saves postage to buy a 22 cent item unless I order stock, which we all like to have hanging around.

[Locrian99]

[

Using the 10k resistor despite the voltage loss is a better way to go IMO, and this could I imagine have to do with the jfets as well?   It took me all the way down to 3.58, but the effect was much more pronounced than when I went with a smaller resistor.   

Not 100% sure what's going on there.   What happens when the Vref is low the on an off times for the LFO become unequal.   Maybe that's the sound you want/like?

There a tweak where you can reduce the 3M9/3M3 resistor to get a wider sweep.   There's nothing stopping you playing around with that.

[/quote]

Interesting I'll check that out.   I'm not sure I just played around with the different resistors and diodes until I found which gave me the sound I thought was best and that's where I ended up.   Right now I've got it so the 10k resistor and diode are socketed with jumpers leading to a breadboard so I can play around with them.   I'll try the 5.6v 1 watt tonight As well as a 6.2, from what I'm seeing i think the 6.2 will end up in that 4.5 range.  Plenty to tweak with before I box it up.   

[Locrian99]

1N914 shims are perfectly valid.

Sounds like shimming is the best plan since my builds are "open air" (no board).
Another thought, I have parts for the Rebote 2.5.
How about using a 78L05 ?
Either way saves postage to buy a 22 cent item unless I order stock, which we all like to have hanging around.

I thought the same thing with the 78L05.   Rob touched on that earlier in this thread.   

[Phend]

Well, shimmed it up 3 x 914 and getting 5.07 v.
Sounds quite a bit better.

[Locrian99]

My continued tinkering I think I ended up about using the same idea.   A 1n4733a in series with two parallel 1n4148 I get 4.97, and good results.  Now to tweak that 3.9M. 

[Phend]

Been searching on how to increase the depth control now. Will continue..

[pacealot]

The best way to increase the depth of a Phase 45 is to build a Phase 90... 

(sorry, couldn't help it — proceed...)

[Phend]

So it isn't as simple as changing a pot. (Probably not)
I'm only 23 from 90.

[Locrian99]

In principle the 78L05 would work.  You might need to add a small dummy load because in-circuit the LFO can feed current *back into* the regulator.    The main reason the zener is used is because the MXR circuit originate back in the days before 3-terminal regulators were common and they weren't that cheap.    The 78L05's actually draw more current than the zener circuit.  So for battery operation it's a consideration but not so much when using external supplies.   The regulation of the 78L05 is much better than the zener.



This intrigues me for future use more than anything.   What would the small dummy load need be?

[Rob Strand]

This intrigues me for future use more than anything.   What would the small dummy load need be?

For this circuit, 10k should do it.

What happens when the Vref is low the on an off times for the LFO become unequal.   Maybe that's the sound you want/like?

FWIW, that trick/effect doesn't apply to the phase 45, only the phase 90.   If you look at the LFO circuit the phase 45 has a voltage divider (2x150k) to the + input on the opamp.   There's a few ways you can change the on/off ratio on those LFO's.

I was thinking if the trimpot requires very fine adjustments then it's not hard to make small changes and hear an effect, when in reality if you could adjust the trim more finely you would end-up with a similar result.

[Locrian99]

I'm really happy now with how mine is sounding with the 3.3M (had 3.9 in) and the vref sitting at 4.97.   I'm not sure why but when using the smaller resistor and just the 5.1 1w I felt like the depth was lowered.   It might have just been my perception.   Anyways, I'm curious to see where I end up with the 5.6 or 6.2.   Looking at the graphs prr posted I think the 5.6 will be too low and the 6.2 too high.   We'll see though. 

[Rob Strand]

I'm really happy now with how mine is sounding with the 3.3M (had 3.9 in) and the vref sitting at 4.97.   I'm not sure why but when using the smaller resistor and just the 5.1 1w I felt like the depth was lowered.   It might have just been my perception.   Anyways, I'm curious to see where I end up with the 5.6 or 6.2.   Looking at the graphs prr posted I think the 5.6 will be too low and the 6.2 too high.   We'll see though. 

The 3M3 change will increase the depth "by design" so to speak.   Small tweaks to the voltage are likely to produce indirect and subtle changes.

If you want to try something  you can add a second fine adjustment pot to the JFET bias trimmer.
- Lift the ground leg of the 220k/250k trimpot, now place a smaller value trimpot between ground and the now hanging lead on the 220k trimpot.    You need to use the wiper and one of the other leads of the trimpot.    Use say 20k, although 50k might do.
- Set the added pot to the center.
- Adjust the 220k pot as best as possible sound.
- Use the added pot for fine adjustment.

There's many ways to do this but this method has minimal parts and gives you an idea of what finer adjustments can do.    (It's also possible add fixed resistors in place of the main trimpot for coarse adjustment and only have a fine trimpot.  OK for a one-off build.)

[Locrian99]

If you want to try something  you can add a second fine adjustment pot to the JFET bias trimmer.
- Lift the ground leg of the 220k/250k trimpot, now place a smaller value trimpot between ground and the now hanging lead on the 220k trimpot.    You need to use the wiper and one of the other leads of the trimpot.    Use say 20k, although 50k might do.
- Set the added pot to the center.
- Adjust the 220k pot as best as possible sound.
- Use the added pot for fine adjustment.

There's many ways to do this but this method has minimal parts and gives you an idea of what finer adjustments can do.    (It's also possible add fixed resistors in place of the main trimpot for coarse adjustment and only have a fine trimpot.  OK for a one-off build.)

Funny I was thinking of toying around with the idea of making an actual bias pot was thinking 10k would be good but I would have to play around with it.  My only thought on this was much like my first vero build a four knob fuzz face I found one of the knobs to be quite unnecessary, I won't go so far as to say useless but pretty close.   But I constantly second guess where is the sweet spot or think if I could just get it a little better this might be the answer.   Only other trim  I have at the moment is 10k though. 

[Rob Strand]

Funny I was thinking of toying around with the idea of making an actual bias pot was thinking 10k would be good but I would have to play around with it.  My only thought on this was much like my first vero build a four knob fuzz face I found one of the knobs to be quite unnecessary, I won't go so far as to say useless but pretty close.   But I constantly second guess where is the sweet spot or think if I could just get it a little better this might be the answer.   Only other trim  I have at the moment is 10k though. 

The idea of the added pot is only do a more accurate set-up and get around the coarseness of the single trimpot - not really a front panel pot.   However, I did see a phaser recently that had some sort of bias pot on the front panel - it was one of those boutique type units.

[Locrian99]

The idea of the added pot is only do a more accurate set-up and get around the coarseness of the single trimpot - not really a front panel pot.   However, I did see a phaser recently that had some sort of bias pot on the front panel - it was one of those boutique type units.

Yea, there was talk of it on the the thread for this build if I remember correctly.  The fine tuning I think could be huge as barely turning the pot can go from phasing pretty good to nothing.   I'll probably mess around with it some, I'm inclinded to find the coarse setting and hopefully its near a typical value resistor that I have on hand (wouldn't that be phenomenal) and wire it in series (I somehow picture myself trying to get to 163.3k with a 150k, 12k, 1.2k, and 100 ohm in series lol, I realize it wouldn't need to be that exact) with the fine tuning trim pot.
 
Something tells me this might be sitting on the bench for awhile getting poked, prodded and fine tuned before it hits a box.  But I do have a couple LDR based projects I'm itching to try as well.

[Locrian99]

So the diodes I got in from Amazon today, was a pack of a bunch of different values.   The 5.1 actually sits at 5.12, 2nd one I tried 5.18.   I feel like I get some minor clipping both at the 4.97 and 5.12v settings.   Does this make sense (silly question I know).   Would there be any drawback to upping that resistor to get the voltage down a bit.   I don't hear any by upping it to 22k which gets me down around 4.9 but I've never claimed to have golden ears either. 

[Phend]

Just settled on using a 4M1 (as measured) in the place of 3M9. I tried down to 3M and everything in-between. This is a 45 with Modifications for Vibrato and Univibe. Like it. Maybe the Depth isn't as deep but it is there. I'm good.