# Tyrian distortion squeeling



## ferdinandstrat

Well, built it, sounds ok but it squeals like crazy. Maybe I should increase one of the 100pF caps?


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## zgrav

If it squeals all the time there is a problem somewhere in the build.  So please provide a bit more detail about when it squeals, whether it is only when the gain is above half, etc.


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## ferdinandstrat

zgrav said:


> If it squeals all the time there is a problem somewhere in the build.  So please provide a bit more detail about when it squeals, whether it is only when the gain is above half, etc.



It is when the gain is above half, and when the volume is at unity


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## zgrav

How hot is the signal going into your effect?  Does it stop if you back off the guitar volume instead of turning down the gain on the pedal?  I don't know the pedal so others may know if this is way out of bounds for the way it is supposed to work.


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## music6000

zgrav said:


> How hot is the signal going into your effect?  Does it stop if you back off the guitar volume instead of turning down the gain on the pedal?  I don't know the pedal so others may know if this is way out of bounds for the way it is supposed to work.


What happens if your Guitar is facing away from Amplifier, This is a High Gain pedal & are prone to Feedback if you are facing the Speaker.


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## Robert

Can you post a pic of your build?    A couple other folks have mentioned a similar problem, but quite a few people have built them with no issues. 
(I have personally built two of these with no oscillations whatsoever)

I'm wondering if it might be a particular component construction type that is causing the issue....


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## temol

Did you use shielded IN/OUT wires for your build? For many hi-gain circuits it's a must. 

T.


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## ferdinandstrat

temol said:


> Did you use shielded IN/OUT wires for your build? For many hi-gain circuits it's a must.
> 
> T.



Here's the deal, the Brown Betty I built also squealed but after increasing one of the ceramic caps, the 47pF one I think, it was far more controllable. I thought that maybe increasing one of the 100pF caps here might help.


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## temol

I'd start with new wires 

IN jack -> 3pdt -> board IN
board OUT -> 3pdt -> OUT jack

But wait..try this - bypass 3pdt completley. Connect input jack directly to the board, same with the output jack. 
Use shielded wire, at least for the input jack. 

T.


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## ferdinandstrat

Well sadly I dont have any. I do have some copper tape though.


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## temol

So bypass 3pdt with the wire you have.  
Don't you have any broken headphones, microphone, old audio patch cables?

T.


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## ferdinandstrat

I am fairly certain I have some headphones lying around. As for the bypass, I am using a effect tester type thing from Delyk with a 3PDT switch.


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## temol

Connect jacks directly to the pcb. Do not cross  in/out wires.


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## ferdinandstrat

temol said:


> Connect jacks directly to the pcb. Do not cross  in/out wires.



Does a buffer help?


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## ferdinandstrat




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## music6000

ferdinandstrat said:


>


As pictured, Which side of the LED's does the Flat at the Base of the LED's Face


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## temol

ferdinandstrat said:


> Does a buffer help?



I'm not sure. It probably depend on the nature of the oscillation. 
But seeing picture of your pcb - long, naked wires..  you know my opinion.

T.


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## ferdinandstrat

My LEDs dont have a flat side but from what I understand the flat side is the kathode, I put both of them through the square holes.


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## Robert

I didn't use shielded wires either (it's certainly not a bad idea), but I would definitely try separating those In/Out wires as far apart as possible so they aren't overlapping each other.   

Everything else looks fairly standard (although I didn't use green mylars for the 4n7 caps)...   It may not have any relevance, but some of the pins of your TL074s are awfully close to the adjacent socket contacts because of how they are shifted.       Did I ship you dual/quad adapters with this?   It might be worth giving them a shot.

Does lowering the Volume make it stop oscillating?


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## ferdinandstrat

Robert said:


> I didn't use shielded wires either (it's certainly not a bad idea), but I would definitely try separating those In/Out wires as far apart as possible so they aren't overlapping each other.
> 
> Everything else looks fairly standard (although I didn't use green mylars for the 4n7 caps)...   It may not have any relevance, but some of the pins of your TL074s are awfully close to the adjacent socket contacts because of how they are shifted.       Did I ship you dual/quad adapters with this?   It might be worth giving them a shot.
> 
> Does lowering the Volume make it stop oscillating?



You didnt bet never mind that, besides from what I read on forums it doesnt help. If anything I should try to solder one TL074. 

Lowering the far below unity works.


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## ferdinandstrat

Well, built it, sounds ok but it squeals like crazy. Maybe I should increase one of the 100pF caps?


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## music6000

ferdinandstrat said:


> My LEDs dont have a flat side but from what I understand the flat side is the kathode, I put both of them through the square holes.



Here is how your Clipping LED's should be mounted.
 Check with Robert (PedalPCB), If yours are both reversed, It may still Clip the same?
 From all the different Led's I have purchased, They all have a Flat machined at the base of the Plastic, That is the Cathode - Side.


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## Robert

Yes, as long as both clipping LEDs were installed using the same method it won't matter if they're both backwards.

Is what you're hearing _electronic_ oscillation, or acoustic feedback?     Does your guitar tone control / pickup switch have any effect on the squealing?
What about the direction you're facing with your guitar?

I just dimed the gain and volume direct into my audio interface (it gave my interface hell at that level, but no oscillation).... 

Then I tried it into my Twin.... Realistically I can't crank the Twin up all the way because... well...  it's a Twin...  but no oscillation.   My guitar does want to naturally feedback at higher volumes, but not in a _bad_ way.


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## ferdinandstrat

Robert said:


> Yes, as long as both clipping LEDs were installed using the same method it won't matter if they're both backwards.
> 
> Is what you're hearing _electronic_ oscillation, or acoustic feedback?     Does your guitar tone control / pickup switch have any effect on the squealing?
> What about the direction you're facing with your guitar?
> 
> I just dimed the gain and volume direct into my audio interface (it gave my interface hell at that level, but no oscillation)....
> 
> Then I tried it into my Twin.... Realistically I can't crank the Twin up all the way because... well...  it's a Twin...  but no oscillation.   My guitar does want to naturally feedback at higher volumes, but not in a _bad_ way.



Its the same type of squealing that happened on the Brown Betty, I was capable of somewhat remedying it by increasing the 47pF(I think cap) in the feedback loop(compensation cap? Like in the RAT?). Its definitely electronic oscillation because adjusting certain parameters and the volume knob on my guitar increases or decreases the pitch, much like a Fuzz Factory, but it happens when I try to add volume or gain.


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## temol

I've build couple of Thermionic Distortion pedals, Brown Betty, Tyrian on a breadboard  - no squealing at all, even of highest gain setting. 
Is it inside the enclosure?

If you suspect that replacing the cap should fix the oscillation, then go for it.
Just add another 47p in paralell.
T.


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## ferdinandstrat

OK can someone please explain this phenomenon to me? I put an OD I built before the Tyrian to act as a clean boost/buffer and THE SQUEALING IS GONE. I heard that putting a buffer before such a pedal mends the situation and it DID, how?


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## zgrav

Does the squealing come back if you turn down the level of the signal going into your board, or if you turn down your guitar level?

And is the squealing gone using the OD even when you turn up the gain on your new pedal?


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## Robert

One possible explanation is that the input is picking up a stray signal (output signal, or some other internal signal path).

A buffer acts as a voltage follower and ensures that it's output (and in turn the input to your Tyrian circuit) closely matches its input, so whatever interference is being induced back into your Tyrian input is subdued by the buffering.

Fire up the Tyrian, set it so it's oscillating nice and loudly, and see if touching the input wires has any effect on the oscillation.

Also two questions:

What kind of guitar / pickups are you using?
What overdrive did you use in front of the Tyrian?


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## ferdinandstrat

Robert said:


> One possible explanation is that the input is picking up a stray signal (output signal, or some other internal signal path).
> 
> A buffer acts as a voltage follower and ensures that it's output (and in turn the input to your Tyrian circuit) closely matches its input, so whatever interference is being induced back into your Tyrian input is subdued by the buffering.
> 
> Fire up the Tyrian, set it so it's oscillating nice and loudly, and see if touching the input wires has any effect on the oscillation.
> 
> Also two questions:
> 
> What kind of guitar / pickups are you using?
> What overdrive did you use in front of the Tyrian?



I use an Ibanez SA960QM with Dimazio/Ibanez pickups, the overdrive was a Zendrive but the signal was even before by a spillter/mixer and the Zendrive.


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## music6000

Q. If someone asks me '' What value Resistor is this''?.
 A. I'll just grab my DMM (Digital Multi Meter).
 I have never bothered to try & learn the Coloured Bands (Try reading 1/8W Resistors).
 Simply because I measure *every* Resistor I put in a Circuit, ie 10r = 10r, not 10k.
 I measure *every* Capacitor, the Pots - Diodes, Transistors & LED's (Peak DCA55).
 I always Print out an Enlarged picture of the PCB photo to confirm what I see on the actual PCB matches.
 I highlight the component with a Marker Pen on the PCB photo as I load the PCB.
 I believe this is a Good Practice so when it comes to Firing it up it minimizes a Faulty component.

 Happy Soldering!
 Cheers, music6000


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