Lovetone clones - Wobulator, Doppelganger

[Tuemmueh]

Great one!

[Dirk_Hendrik]

I believe that some of the production wobulators has a tick problem as well.

You're right in that. 

Congrats with the work so far.

[Shed_FX]

The testing is going quite well, I just thought I would post an update. I originally had the circuit running on 4JRC4558 as they were the only ones I had laying around. I changed them over for TL072 and the whole thing stops working! The best I can seem to do is have 3 TL072 and retain one 4558. Seems very odd but the ticking got slightly better. Im thinking about trying a TL022 in the place of the power isolator as it is supposed to suck less juice. Maybe worth a try. I have been reading up on the old posts about ticking and tried putting a large value cap (220uF) between the Vref from the op amp and ground. This reduced the tick considerably. I will try out some more values and see how I get on. But at the moment these too options seem the best for reducing the tick without rebuilding the board! I think it will be fine for all but the fussiest of players but considering it was my first ever layout Im pretty pleased. Im getting my pignose out of storage tonight so will start testing out all of the panning and phase switch stuff to do the final tests.

Cheers for all of the support, hopefully it should be up as a project file within a few weeks

Shed

[markusw]

Thanks for the update! 

Did you try to increase the cap across the power supply pins of the LFO opamp? Maybe in combination with the 220µ you added between Vref and gnd?

Edit: Did you try to add large caps to both LFO opamps? BTW, good to know that a cap between Vref and gnd helps!!

Regards,

Markus

[StephenGiles]

Has the Lovetone Flanger been cloned?

[markusw]

Has the Lovetone Flanger been cloned?

Don't know...

[Shed_FX]

Markus:

So far ive been prodding the circuit placing a Cap at certain places to see what happens (Not very technical but eliminates possibilities!  ). Im going to go through systematically tonight and what i will do is take a not of any caps I add and then I will add them to your schematic in another colour to show that they aren't original.

Stephen:
The flanger hasn't been cloned to my knowledge. It may have been done and that person is keeping it close to their chest. Ive got my sights on the doppelganger as my next project. Ive got a couple of contacts who are going to get me some photos. The flanger is quite a complicated beast and has some components that are joined "above the board" as it were in a diode ldr configuration. The problem is finding someone with one who will take photos. I'll keep my eyes open.

[StephenGiles]

Markus:

So far ive been prodding the circuit placing a Cap at certain places to see what happens (Not very technical but eliminates possibilities!  ). Im going to go through systematically tonight and what i will do is take a not of any caps I add and then I will add them to your schematic in another colour to show that they aren't original.

Stephen:
The flanger hasn't been cloned to my knowledge. It may have been done and that person is keeping it close to their chest. Ive got my sights on the doppelganger as my next project. Ive got a couple of contacts who are going to get me some photos. The flanger is quite a complicated beast and has some components that are joined "above the board" as it were in a diode ldr configuration. The problem is finding someone with one who will take photos. I'll keep my eyes open.

Many thanks.

[markusw]

Markus:

So far ive been prodding the circuit placing a Cap at certain places to see what happens (Not very technical but eliminates possibilities!  ). Im going to go through systematically tonight and what i will do is take a not of any caps I add and then I will add them to your schematic in another colour to show that they aren't original.

Cool! 

Thanks a lot!!

No ?Flanger owner out there to share some data? 

[Shed_FX]

Just a quick update, I solved one problem. But it wasn't the ticking. I previously wrote that it wouldn't run using 4 TL072'2 as designed. This seemed very odd. Whilst trying to sort the ticking I read up about current consumption in LFO circuits, and found that the system may not have enough juice to run the op-amps efficiently. I checked the voltages on the board and found that the power to the op amps was fluctuating around 5.5-6Volts. This didn't seem good so I traced it back through checking components as I went. The voltage drop was over the polarity protection diode. I have removed this for the time being. The circuit seems to run better (still with tick) and can run 4 x TL072 chips.

Just thought I would write this down before I forgot about it as it may help others when building this circuit.

Back to the de-ticking!

[A.S.P.]

http://www.diystompboxes.com/smfforum/index.php?topic=35335.msg280189#msg280189

[Processaurus]

Just a quick update, I solved one problem. But it wasn't the ticking. I previously wrote that it wouldn't run using 4 TL072'2 as designed. This seemed very odd. Whilst trying to sort the ticking I read up about current consumption in LFO circuits, and found that the system may not have enough juice to run the op-amps efficiently. I checked the voltages on the board and found that the power to the op amps was fluctuating around 5.5-6Volts. This didn't seem good so I traced it back through checking components as I went. The voltage drop was over the polarity protection diode. I have removed this for the time being. The circuit seems to run better (still with tick) and can run 4 x TL072 chips.

Just thought I would write this down before I forgot about it as it may help others when building this circuit.

Back to the de-ticking!

Odd, are you sure it was the diode?  Could be a short in the circuit sucking a ton of power, or something wrong with your power supply, your opamps should be seeing near your 9v supply voltage.  Might want to measure the wob's current draw, analog circuits are funny, something can be terribly wrong and they'll still kinda work.

[Shed_FX]

I can confirm it was the diode. It seemed to have a high (100kohm) resistance. Now I've removed it it seems fine. Just without the drastic voltage drop. Seems bizare tho. Im planning to wire up and test the right hand side tonight to confirm everything else is working and try a last few ideas for reducing the ticking.

[Shed_FX]

Right entering the final stretch (I think!). Im sorry the progess has been slow on this but I nearly have it all working. The oscilators are working fine and on mono it sounds really nice and wobbly. The problem is that I get no sound out of the right hand channel. I have checked all of the components in that part of the signal path and all seems fine. It just doesnt give out any sound at all. When the right hand connection is removed and the pedal is run in mono the output distorts as if the signal from the left is being "sucked" as it were back up the right channel. I have tried everything I can think of an checked things through twice but cannot work out what it could be 

I am now going to try re-melting all of the soldering joints just incase there is a dry contact anywhere. But any suggestions would be greatly recieved.

So near yet so far!

Cheers

Shed

[markusw]

Thanks a lot for the update!!

Resoldering is probably a good idea. Maybe also check for shorts, or those "tiny solder bridges", what's their name..?

When the right hand connection is removed and the pedal is run in mono the output distorts as if the signal from the left is being "sucked" as it were back up the right channel.

What do you mean with "right hand connection"?

Markus

[Shed_FX]

Oh sorry I suppose it should be the right channel I suppose. It does seem really weird like the signal is being lost somewhere, either way I'll re-solder it and see where that take me!

[markusw]

Which connection exactly are you talking about?

[Shed_FX]

Its marked on the schematic as "Out Right". There is no output from this side of the circuit.
I have resoldered all of the joints with no joy from that. I found one mistake with the depth pot on the LFO2. But i have now isolated the problem to the E113 JFet on the schematic. The replacement I had in there (a J113) had blown and was shorting between the source and drain. I have now replaced the fet with another fresh J113 and now the circuit does not oscillate at all! 
Could this be to do with my choice of replacement fet? What exactly is the function of this component and how does the trigger input work? It seems bizarre. Any help would be gratefully recieved.

Thanks

Shed

[markusw]

As far as I understand the FET just resets the LFO upon an external trigger by discharging the integrating cap. If you leave it off the LFO should work.

Besides this, you probably may have an issue with the phase switch. I could imagine that with some settings both channels cancel each other.
Just an idea.
Maybe check with an audioprobe where you loose the signal...

[Shed_FX]

Thanks Markus, I thought the Fet would probably do some thing like that. I actually found that I had the new one connected wrongly. Its now back to where it was. I think I'm going to remove the phase switch for the time being and work back through the audio path, I haven't got an audio probe but should be able to work something out. The other thing that seems to be an issue is that on the sine wave oscillation setting LFO 1 barely appears to be oscillating. LFO 2 is nice and smooth and seems to be fine. Could it be that the 10uF cap in the feedback of LFO1 is too large? I may try changing it out just to see whether it has an effect or if the problem is further up the line.

Thanks for the on going help.

Shed