Spyder PS Doubt

[QSQCaito]

Hi, me again. I know all aspects of this supply have been covered. I searched but couldnt find answer to my question. Hum can be avoided by using isolated  and bla bla bla.. all things know and discussed at R.G.s web page.

But if i have the case below, in which i have separated transformers, but series of pedals connected one to each other, at the end, the ground of the power supplies are all together. Will this produce any noise??
Or something that might bother? and if i put the spyder PS in a metal enclosure, touching the enclosure of an fx which is grounded to the box, will this cause any noise??





Thanks a lot, any comment,help, addition, is thanked in advanced and welcomed.


Bye bye!

DAC

[Primus]

Yes, it will most definitely cause lots of unpleasent noise and ground loops. The point of the spyder power supply is that it gives you transformer isolated grounds. If you connect all of the grounds together, you might as well run all your pedals off of a single 9 V bus.

[QSQCaito]

So, is there anyway of putting fx in series without generating ground loops and unpleasant noise?? BTW all this will be in rack enclosure, with no jacks, soldered directly.. that could improve a bit.. but don't know how much.

[Primus]

Yes! You can definitely put effects in series without forming a ground loop. The only question is how those effects are powered. If you have several effects whose grounds are connected by cables through the chassis and also with a power supply that share a common ground, that will form a loop. In order to prevent this, you need to break the loop. One option is to cut the ground in your cables. This can cause problems with having a floating ground, as I understand it. The best option is to isolate each ground w/ a transformer. That way there is no physical common ground. The point of the spyder is to have an individual transformer for each effect to break ground loops. If you build a spyder, you do NOT want to connect all the grounds otherwise it will defeat the purpose of isolating the grounds with transformers. I may have some spyder parts left over. If you are intersted, private message me.

[QSQCaito]

Ok i see. I couldn't get well enough how it should be. Could you please tell me if i'm oriented correctly??

What I'd do would be the following.All transformers are isolated from each other. In the racks the only Jacks connected to the enclosure will be from guitar and to the amp, will be the only 2 jacks i'll use.. probably a send and return, but not sure yet. All the effects will be connected one directly to the other soldered. So the only ground to chassis will be the IN from guitar and OUT to amp, but i could isolate them if necessary. If i did not understood wrong, there will be only one ground, which goes from one effect to the following, grounds will not be connected through chassis i think, just with the wires shown in the drawing above.

Bonus question:P How can i isolate each ground w/ a transformer? Grounds must be connected anyway, if not the guitar signal won't travel from one effect to the other, right?


Thanks a lot Primus, i hope im oriented correctly, but hopefully i haven't started so i still have time to correct, i just wanted to have everything planned before starting.

Bye bye

DAC

[Primus]

First let me emphasize, as is customary on this board, that the voltages used in the Spyder can be lethal. Do not attempt to build a Spyder unless you are absolutely confident that you can do it safely.

I am trying to be as clear as posssible, so I will state as simply as I can what you are aiming for.

Each effect will have an input jack and an output jack. You want both of these jacks to be grounded to the chassis of the effect.

Each effect will also have a power input jack. You want the ground to be grounded to the circuit board.

Transformers isolate the ground because they work by inductance. Alternating current flows through the primary side and causes an electromagnetic field. That field induces a current in the secondary coil. Since there is no physical connection there, it acts to break the circuit formed by a ground loop. The diode bridge in the Spyder converts that AC from the transformer to a DC current. The ground coming off of the diode bridge is isolated from the ground of every other diode bridge by the transformer. Keep these grounds separate. Do not connect them to the chassis of the Spyder.

[QSQCaito]

First of all thanks a lot once again.

Each effect will have an input jack and an output jack. You want both of these jacks to be grounded to the chassis of the effect.

Each effect will also have a power input jack. You want the ground to be grounded to the circuit board.

I wanted to avoid jacks. So im not going to put each fx an input and output jack. Effects will be connected directly to each other. If you want each effect to be grounded to the enclosure there's no problem with that.

To make things easier i made this drawing, lets see if it correct:



A new question appears, is this ok? Should the wires from gnd to gnd of each FX be taken out, because it's already grounded throught the chassis...

Hope im correct this time, if not it's only a matter of keep trying.. I wish english was my native language.. it'd make things much more easier

Thanks a lot once again

bye bye

DAC

[Primus]

Oh, I understand now that you want to put multiple effects PCBs inside one enclosure.

You wrote: "A new question appears, is this ok? Should the wires from gnd to gnd of each FX be taken out, because it's already grounded throught the chassis..."

Yes, it is better to take those wires out since each board is already grounded to the chassis through both the input and output jacks. That way you will have clean power with no ground loops. Good luck!  A lot of people on the forum have experimented with multiple effects in a single enclosure. I encourage you to use the search function to find out more detailed information and build reports : )

[QSQCaito]

Ok, thank you a lot. So finally i'll have effect inputs and outputs connected directly to each other. 9V supplies will be connected directly to the pcb, and for the (don't know if this terminology is correct) negative of the signal, i'll solder a wire to the chassis.

Just one tiny little doubt, would it be better to take all wires from GND of the PCB to the chassis and put them in one spot, all together, or it's not necessary?

Thanks you a lot lot lot


Bye bye

DAC

PS forgot to add that wires from input and amp out to the effects GND should be also removed right? because that is already grounded to the chassis.
Sorry for being so bothering but, how can grounds of each transformer be isolated if they meet each other throught the chassis?

thanks
bye
DAc

[Primus]

DAC,

Each circuit board should be grounded to the chassis through both the input and output jacks. So, your input jack will have three ground wires each going to 1 circuit board as will your output jack. You do not need to make a separate ground to the chassis.

Regards,

John

[brett]

Hi
Why do you want a spyder when you've only got one ground (shared by all effects)?
Can't you use one transformer to power all, and use a star ground to ground all of the effects?  That should be as quiet as a mouse.
cheers
PS Don't forget to use bypass caps near each effect, especially if they use op-amps.

[QSQCaito]

Ok, excuse my ugly drawings, but if i'm not wrong it should end up somewhat like these:



This should be correct now one tiny question again, if i want to add a send and return, jacks should be isolated from chassis??


Thanks a lot lot lot

Bye bye

DAC

[QSQCaito]

Hi
Why do you want a spyder when you've only got one ground (shared by all effects)?
Can't you use one transformer to power all, and use a star ground to ground all of the effects?  That should be as quiet as a mouse.
cheers
PS Don't forget to use bypass caps near each effect, especially if they use op-amps.

I really exactly don't know. But all my effects will end up altogether in one big rack.. i'll add a rack every now and then when i complete couple more FX. I know that a big transformer wont fit. And i might also add external voltage outputs.. I believe a spyder has more uses, maybe not in this specific case.. i could use it for something else..

thanks a lot

byebye

DAC

PS: what are bypass caps more exactly?

[brett]

Hi
If it's any consolation, I run about 12 pedals together from 1 good power supply (2 x 4700uF caps and LM317) and have no noise or hum problems.

RE: bypass caps.
Because the supply lines often contain lots of noise, some way of disposing it to ground is required.  It is wise for each effect to use a large electrolytic cap (e.g. 100uF) to AC-couple the +ve line to ground for low frequencies, and a small film cap (greencap or MKT) (e.g. 0.1uF) to AC-couple high frequencies to ground.  Usually, the electro is "upstream" of the film cap.  And for each op-amp in an effect, another small cap is required as close as possible to the op-amp. 

Also, hum and noise rejection can be improved by adding some series resistance before the electro.  100 ohms before a 470uF cap can really help clean up a power supply.  In some effects (this is rare) the voltage drop across a 100ohm resistor will be large, so the bulkier, but equally effective combination of 22ohms and 2200uF cap might be prefered.

cheers

[QSQCaito]

Oh thanks a lot. so before the 78l09 i should put a 100ohm resistance then a polarized cap(the larger the ebtter right??) and a small film cap right after?

One more question, this should be done either using spyder or only one supply??


thanks a lot

bye bye