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 powering paia pedals with 9770 series power supplies: 
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Joined: Sun May 12, 2013 7:45 am
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Post powering paia pedals with 9770 series power supplies:
Hello Scott!
Well, it's time to put a pedal board together.
I know you can power the ca9 ring mow with a 9770 series power supply, providing you change the power resistor out for a 680 ohm one, but what about the phase shifter/envelope follower? Any mods to get it to power off the 9770 supply?
thanks!


Tue Apr 14, 2015 9:48 am
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Post Re: powering paia pedals with 9770 series power supplies:
Hello!

The CA21 and CA25, Phase Shifter and Envelope Follower projects are fine on the twelve volt supplies from a 9770R-12.

Here's to success!

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Scott Lee
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Tue Apr 14, 2015 2:13 pm
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Joined: Sun May 12, 2013 7:45 am
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Post Re: powering paia pedals with 9770 series power supplies:
thanks Scott!
is there a benefit to using 12v instead of 18v?
The other pedals are your standard 9v and I plan on building/buying a powerbrick.(the only other exception is the BYOC ping-pongdelay can be run on 18v for more 'headroom")


Fri Apr 17, 2015 8:29 am
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Post Re: powering paia pedals with 9770 series power supplies:
The 9770R-12 is a twelve volt, regulated supply, but it is dual-polarity (positive and negative DC supplies). If a measurement were to be made between the negative and positive poles of the supply, the reading would register 24V.

The CA9 Ring Modulator project uses an IC (565) that has a limit of 6V supplies so this is why the resistors that connect the circuit to the power must be increased (the higher values will result in less voltage getting to the IC).

Generally, op-amps can go up to 18V supplies. And yes, the more the voltage to them, the more that can go through them, as an audio-signal amplitude. At the signal levels in an effects chain, this usually isn't a concern as the most would be 3-4 volts p-p (however, this is getting close to the end of the range when a single polarity 9V supply is divided/split for dual, positive and negative 4.5V supplies.

Using the 9770R-12 on your EPFM projects will allow up to about 20V p-p signals to pass. The unregulated 18V version, 9770U wouldn't be such a benefit and it being unregulated and with more ripple voltage on the DC than with a regulated could result in hum with some devices connected.

Thanks!

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Fri Apr 17, 2015 5:27 pm
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Joined: Sun May 12, 2013 7:45 am
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Post Re: powering paia pedals with 9770 series power supplies:
Thanks again. I will order one ASAP!


Sat Apr 18, 2015 6:14 pm
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Joined: Sun May 12, 2013 7:45 am
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Post Re: powering paia pedals with 9770 series power supplies:
got 'er all boxed up and the volt meter is reading right, as far as I can tell.
12 0n one side and 24 om the other.

However, in the earlier post you said "The CA9 Ring Modulator project uses an IC (565) that has a limit of 6V supplies so this is why the resistors that connect the circuit to the power must be increased (the higher values will result in less voltage getting to the IC).
Do you mean i need to increase the actual resistor on the ring mods circuit
to keep from damaging the circuit?
Just being extra careful,as not to get the dreaded blue puff o' smoke and that burnt smell from frying the IC!
Thanks again


Sat Jun 06, 2015 4:28 pm
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Post Re: powering paia pedals with 9770 series power supplies:
First, just to be clear on the power supply voltages, your mention of readings of twelve and twenty-four volts will have been the positive DC measurements with the red and black test probes on any of the J1 - J6 wiring / connector points as detailed below:

Black (-) minus -- to the 9770 (-) negative DC output node.

Red (+) plus -- to the 9770 G/SG, ground/signal-ground/circuit-common/0VDC node.

a positive 12V indication of the 9770's actual negative twelve volt DC output voltage

Then:

Black (-) minus -- to the 9770 (-) negative DC output node.

Red (+) plus -- to the 9770 (+) positive DC output node.


for a positive 24V indication of the 9770's actual positive twelve volt DC output voltage


Right?

If so, and there is really not a 24VDC potential between the ground and voltage terminals of the CA-9 Ring Modulator board, but the intended positive and negative 12V supplies, then yes, it is correct that the resistors coupling the input voltages to the main circuitry on the board would need to be substituted with ones having greater resistance values.

These resistors will drop an amount of voltage according to the current flow associated with each supply voltage.

For the CA-9 these are about positive and negative 12mA and when the project is connected on the intended 9V supplies, the voltages through the PAiA kit 330 ohm power supply input resistors drop by about 4 volts and the 565 IC "sees" only dual 5V supplies (330 ohms x 0.012 amps = 3.96 volts).

On the dual twelve volt supplies from a 9770R-12, substituting 470 ohm resistors for the 330 ohm resistors will result in the voltage dropping 5.6 V (470 ohms x 0.012 amps = 5.64 volts).

The 565 IC would "see" +6.4 and -6.4 volt supply voltages when connected to a 9770R-12 when 470 ohm resistors are substituted for the 330 ohm resistors at R1 and R2 on the PAiA kit for the CA-9 Ring Modulator -- close enough to the rated maximum 6 volt supplies for the 565 IC in the kit.

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Scott Lee
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Wed Jun 10, 2015 2:08 am
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