Ross phaser - Univibe mod not phasin

[DUCKFACE]

Hello there. Im building the Ross Phaser and i have a several problems

1. The LED of phase pusle lights all the time. LD1 of the LFO is not pulsing. It glows really slow. THis suppose to indicate that LFO is not working or?
2.  The sound is not phased. Probably of non working LFO. I can hear in the speakers the pulsing buzz but it not affect the sound.
3. For the vibrato mode i use a on-off pot for the intensity. - when i turn it of it suppose to act as vibrato - there is no sound.
4. For more stages i put a blender so the stages can be separated and blended. If there are no more stages added then only the 4 of the stages will work.

how to solve the problem with no phasing sound?


edit:
intensity pot is 100k rith now coz i dont have the proper 50k. resistors are calculated as follow: R38=2k2 R24=39k

[antonis]

Can't figure out how one can get 5V from 9V and 10k/10k divider, but I presume it's only me..

[DUCKFACE]

its 4.5v im just using the voltage values in the library

[antonis]

Sorry but your draw makes me dizzy..
(can't even find signal input..)

[DUCKFACE]

Sorry but your draw makes me dizzy..
(can't even find signal input..)

ok. im takeing a bottle of mastika and im going south so you can show me some deawing skills  
pin1 on IN/OUT

[Fender3D]

Did you draw PCB from the schematic posted? 'Cause, if you used KiCad (and I guess other CADs do the same), the 2 no-connection points (marked as X between ic1a and b) usually wont get connected on PCB...
I don't get what Q2 and 3 are for...
Base of IC4-2 output buffer shouldn't be shorted to its Emitter?

[DUCKFACE]

there is a switch on the two non connected points X1 and X2. With this switch you can switch between vibrato and phaser mode.
Q2 and Q3 are for split'n blend. On the schematic that is posted in tonepad it shte place of X and Y ponts where you can add more stages. So with the blender you can add more stages (or mix between stages) - im wondering how it will sound. If there are no shages jumper on EXP will keep the signal the same.
The only difference iv made on the schematic on IC4 is that on the tonepad schematic first is IC4a and then IC4b. On mine B is first - its easy for manipulating the outputs of the IC
And for the base and Emitter you are absolutley right ill short pin 9 and pin 10.

[DUCKFACE]

Problem 1 solved. After shortening pin 9 and pin 10 of IC4B the LFO led start blinking. I can control the rate and wide of the blinking pulse.
The rest of the problems are still not solved. I still can hear the LFO in the speakers. Buzzing sound that react on every flickering of the led.
Iv bypassed the blender but the problem is not form there. Iv bypassed the intensity and vibrato mode. The problem stays.
Where is Mark Hammer?  

[antonis]

Never heard of 25μA working LED..

[DUCKFACE]

is it a problem that im using + 15v and -8 to power the lm13600? Im applying +15 on the darlingtons in the LM13600 too.

[ElectricDruid]

is it a problem that im using + 15v and -8 to power the lm13600? Im applying +15 on the darlingtons in the LM13600 too.

No, it shouldn't be. The 13700 gives power supply limits of 36V (so +/-18V max, +/-15V typical). If the 13600 is similar (and I assume it is) then 23V across the power supply is no problem.

[DUCKFACE]

Im more confused about +15v on the darlington stages. They are creating the LFO? rithg ? I can hear the LFO buzz in the speakers.

[ElectricDruid]

Im more confused about +15v on the darlington stages. They are creating the LFO? rithg ? I can hear the LFO buzz in the speakers.

Ok, so where's the original schematic you're working from? The only 13600 Ross phaser schematic I know is the one at the bottom of this list that Rob Strand worked out:

http://home-wrecker.com/phaserguide.html

That doesn't use 15V or -8V, so if that was the original schematic, you're altering stuff, in which case you need to be careful!

So.. which schematic did you start with? What have you altered?

[DUCKFACE]

im using the one from tonepad
http://tonepad.com/getFile.asp?id=99

[ElectricDruid]

Ok, so that schematic is expecting 9V, as far as I can tell.

If you boost the voltage to nearly treble that (as you've done) you'd better be very careful with the OTA current limiting resistor coming from the LFO. It's currently 10K, but with the voltages you've got, it should probably be larger. I'd try 27K or 33K (reckoning on x3 like the voltage).

The 4K7 next to the LFO rate pot could also be increased to prevent excessive current.

Failure to do this might fry all the OTAs. Maximum current into the Iabc input on the 13600 is only 2mA.

[DUCKFACE]

Ok, so that schematic is expecting 9V, as far as I can tell.

If you boost the voltage to nearly treble that (as you've done) you'd better be very careful with the OTA current limiting resistor coming from the LFO. It's currently 10K, but with the voltages you've got, it should probably be larger. I'd try 27K or 33K (reckoning on x3 like the voltage).

so R32 will grow to 33k and R31 qill be 10k. Didi i got it right ?

[DUCKFACE]

the result is the same - no phasing.
just the LFO clicking on the output is gone.

[Mark Hammer]

I was using my own Ross-o-Vibe the other day.  It's the Tonepad layout and circuit, with a few mods.  One is the inclusion of a vibrato option, by a toggle switch that lifts the resistor that mixes in dry signal.  The other is a sweep width option that places a 50k variable resistance in series with the 10k "LFO" output.  Doesn't alter where the sweep "begins", but limits howwide the unit sweeps from that starting point.  Useful for faster speeds.

One of the things to understand about the circuit is that the basic Ross phaser is optimized for slow-and-wide sweeps, so it employs a "hypertriangular" LFO waveform, as well as variable feedback.  This slows down as it sweeps downward, and speeds up as it reaches the high point in the sweep.  Vibes rarely, if ever, sweep as slowly as phasers, simply because of how human perception works (wide and shallow dips require faster movement to be as detectable is deep-and-focussed notches).  Nor do they ever include feedback, since feedback of broad-shallow dips doesn't really yield anything useful. 

Ideally, vibes will use an LFO that approximates sinusoidal waveform.  The hypertriangular waveform is sinusoidal for one half of the wave, but very sharp and almost pulse-like for the other.  The Small Stone's "Color" switch changes the LFO waveform from hypertriangular to triangular, at the same time as increasing the range of speed, and reducing feedback.  While not sinusoidal, triangle LFO "mode" is much better suited to a vibe adaptation.  So is replacing the 500KC speed pot with a 200KC or even 100kC.  Either of those values gets rid of very slow speeds and distributes the faster speeds over a broader rotation of the pot.

[DUCKFACE]

I start to think that there is somethings wrong with the 13600. When i lift the 27k resistor that mix wet and dry signal there is a huge buzz pulse.