Easy Phaser Project.

[lightningfingers]

I've been working on the easy phaser project for some time now, (about 6 months in fact) and i'm happy to say its finally finished.
I didn't have room on the page itself for acknowledgements, so here they are: R.G, for his technology of phasers and flangers, article, my main source of information, MXR for ispiring me to make a simpler phaser that did the same job, and J.D Sleep for his schematic templates and discrete buffer PDF.
If anyone is actually interested i'll draw up my perf layout.

Let me know what ya think.

[mikeb]

Looks nice .... is there really a volume boost using the 4559 rather than another dual op-amp?

I know it adds another two parts, but placing resistors in parallel with the LDRs (say 100k -> 200k) might help increase the phasing effect by making them 'track' a little more closely. Worth a try?

Cheers

Mike

[Marcos - Munky]

Looks cool and simple. Could you record some soundclips?

[gez]

I only see a vibrato circuit.  Where's the wet/dry mix at the output?

Edit: unless the 'feedback' connection is doing the honors?

[gez]

PS  It would be an idea to show the pin 8 connection for the ICL7611.   It's not a good idea to leave it 'floating'.

Well done for getting it going though, 'bout bleedin time!!!  

[Hal]

what type of wave does the LFO output?  If you're going for simplicity, it seems like you could have used a much simpler LFO, if im not missing something...

looks awesome, though.  I'll get it on breadboard as soon as i get some free space (I have 4 projects on now)

[lightningfingers]

what type of wave does the LFO output? If you're going for simplicity, it seems like you could have used a much simpler LFO, if im not missing something...

still kind of a sawtooth, but tis much more triangular now (cheers gez )

Edit: unless the 'feedback' connection is doing the honors?

you got it! its weird but it doesn't actully pitch shift that much at all even without the feedback loop, the ridiculously big version (16 stages) has a proper output mixer. I was going to include it (honest ) in the small one but like i said i was going for simplicity. I'll put the output mixer on the page any way though...

Looks cool and simple. Could you record some soundclips?

I wish i could, but my computers mic is broken (soundcards crap anyway) next time i'm in the studio i'll see what i can do.

Thanks for your input guys :mrgreen:

[strungout]

grats man!

I got a P45 working this week. This project looks like something I need to try. Any specification for the LDRs?

[lightningfingers]

Any specification for the LDRs?

the ones i used go from about 10R to 1k. Its not real picky about LDRs, you can adjust the LEDs brightness to accomodate a wide range.

I know it adds another two parts, but placing resistors in parallel with the LDRs (say 100k -> 200k) might help increase the phasing effect by making them 'track' a little more closely. Worth a try?

Probably, if you are using something like the ORP12, which has a typical dark resistance of 10M.

[Boofhead]

There's nothing wrong with the basic idea but it won't work as shown.

The opamps aren't biased properly.  The LDRs should go to a Vcc/2 divider+cap, and with that in the input buffer could be biased from the same divider.  So you will need to add a biasing network.

[gez]

Well spotted Boof!  Perhaps it would be easier to use an op-amp for the input buffer?  Use a dual and the other half could be used for mixing at the output.

[lightningfingers]

well its only a few more parts,

[gez]

well its only a few more parts

And it could be a few less if you get rid of the trannie plus associated circuitry and use an opamp for the input buffer (now that you have that second divider that is).  

Alternatively you could have used 'noiseless' biasing for the trannie (resistor from its base to centre of divider using smaller values - signal couples directly through to base) and this would have allowed you to make use of its divider to bias the op-amps too.

The 100k from output of last op-amp to V ref seems superfluous.

[gez]

PS lower 220k resistor in the divider and the 4k7 emitter resistor should go to earth and not V ref.

[gez]

If you get rid of the upper 220k resistor in the divider (leave the lower one connected to Vref) and ground the 4k7 emitter resistor this will give you the 'noisless biasing' I mentioned.  Though it would be wise to make the resistor values smaller for the divider used to bias the op-amps (and now the trannie).

[lightningfingers]

Yes, yes the emitter resistor should be grounded, this is what happens when you sub coffee for sleep  

Hold on a second, i DID ground that resistor (why did i put it like that on the schematic?) :?

I will try the noisless biasing thing, but the background noise isn't all that prominent now, could you explain why this arrangment results in less noise?

It sounds better now, i'm hearing more o' that pitch shift

[gez]

I will try the noisless biasing thing, but the background noise isn't all that prominent now, could you explain why this arrangment results in less noise?

It's just a term to describe a type of biasing which can result in less noise if done a certain way.  The reason I mentioned it is because your revised circuit has two dividers, one of which is superfluous - the trannie can be biased from the same divider used for the opamps or vice-versa.

The noiseless arrangement rusults in slightly higher imput impedance - one 220k in parallel with the trannies input impedance rather than 110k in parallel with it (I think that's right I can't see the schematic while I type) - and one less component (but it would still be less if you used a bloody op-amp!)  

The method is only 'noiseless' if you use smaller value resistors for the divider.  For an explanation search for RG's post on the subject (the term is his I believe) it'll be a lot better than anything I can cobble together!  

[lightningfingers]

Okay gez, you win  :lol:  the next version will have an opamp input buffer.

A word about soundclips, I have MS sound recorder ( :oops: ) installed but I press record, and the bloody mic wont pick up anything. It says something about no mic being detected, but its a working mic, and its  plugged into the socket with with "MIC" written on it..  Can anyone help me out with this, as I would like to put  some clips on the page.