TL72IP or TL72CP question, and popping apostle.

[eh la bas ma]

Hello,

I am currently trying to find out what are the differences between the designations IP and CP on TL72 IC.

For exemple, which one would be more suited for an high-gain circuit ?

I tried to search the forum, but no luck so far.

Every observations and suggestions are welcome !

[GibsonGM]

Generally, that's about temp. range, compensation...things that make zero difference to us doing small signal audio.  The only ones that come to mind would be codes that tell you it's SMD...

HTH!

[FSFX]

.. the differences between the designations IP and CP ...

It is the operating temperature range.

CP is 0 to 70 degrees C
IP is -40 to 85 degrees C

BTW, it is the I and the C that indicate the temperature range, the P indicates that it is a PDIP (DIL) package in both cases.

[eh la bas ma]

Thank you for your replies !

All is clear now.

[eh la bas ma]

...I have one more question, on an other topic. Not sure if it's worth a new thread :

I used illuminated red/green 3PDT on two recent builds. I am experiencing big popping noises when switched on and off.

https://www.musikding.de/3PDT-footswitch-illuminated-red-green

I tried to add 10k resistors on each legs, three resistors in total, but I couldn't reduce the noise.

10k resistor, between 9V and the positive leg, usually fixes any popping issue with regular status led on all my builds.

Before I uninstall them, would you have any suggestion on the matter ? Anything else I could try ?

[GibsonGM]

Very common problem; a forum search should bring up more than a few discussions of this!

This might help you:  http://www.muzique.com/lab/led.htm

I believe the cap has quite a lot to do with why this works And Jack explains why on the page.

[eh la bas ma]

Thanks !

I used a 4.7K and 390R with a 10uF, then I tried 47uF.

I can reduce or totally supress the noise when switching on, but no effect on the popping noise when I switch off.

What would be the next step ?

Edit : I should mention that i am using a regular switchboard instead of the designated switchboard for illuminated 3PDT.

So I added a wire going from the 3PDT's bottom terminal of the middle row, to the middle leg of the led device. I had to do that in order to get the second color activated when switched off.

[GibsonGM]

To satisfy my curiosity, I would make sure that my output cap is good on the circuit in question.  Just measure for DC mV on input and output of switch terminals before switching to bypass.

Does the circuit have a pulldown resistor on its output....does it do the 'pop' if the volume pot is turned down?  Is it wired to have input grounded in bypass?

Since you said it's a high-gain circuit...there may not be any way to stop the pop, since any noise present will be 'greatly amplified'...if it is in fact the mechanical noise of the switch, it could be permanent.    An option may be to convert the switching to something that is more 'soft switching' such as some sort of IC switch.

Maybe someone else has a better idea (?)....the AMZ 'fixes' for this have been enough to solve my own popping issues! 

[eh la bas ma]

Thanks for your help.

That's the circuit :

https://kurtballou.com/docs/N.E.W.%20Apostle%20Build%20guide.pdf

...and that's the switchboard :

https://musikding.de/docs/musikding/3PDTwiring/3pdtwire.pdf

I managed to get the other circuit quiet with the AMZ fix.

On the Apostle, I uninstalled the illuminated 3PDT, put a standard status led, and still have popping noise with 10k resistor, or with 10k + 470R (don't have 390R)+ 47uF to ground.

No noise when volume is fully CCW.

Edit : I notice that the led flashes briefly when switching on, it quickly gets to the usual intensity, but it flashes for a short half-second. Maybe the cap is doing that ?

[GibsonGM]

Measuring the in/out terminals at the switch before you bypass it might tell you what voltages are present there.  Rapidly changing potential with a mechanical switch IS going to pop...but it could MAYBE indicate that you have a leaky output cap, or some such thing.  Chances are good that it's just amplifying a small pop A LOT and sending that to the output.  And some brands of switches are noisier than others (lower quality)   

I have yet to find a distortion that doesn't POP when it's turned on or off, tho the POP can usually be made less annoying with the addition of the R and C    Searching the internet, I've found thousands of complaints about this.

http://www.geofex.com/Article_Folders/box_pop.htm

If you added a cap to the switch as from the AMZ site, yes, it can alter the way the LED comes on...

[antonis]

That's the circuit :
https://kurtballou.com/docs/N.E.W.%20Apostle%20Build%20guide.pdf

IMHO, R1 without input cap is totally useless..
(I'd get rid of it and make R3 1M for not to worry about elevated temperature Gate leakage current..)

[eh la bas ma]

Input is grounded in bypass.

On 3PDT's Jack In, I read 0.3mV in bypass, and 0.1 mV switched on.

Jack out, I read some oscilations between 0.3 and 0.5 mV in bypass, steady 0.1 mV when activated.



I guess the output cap is the last one on schematics, C26 1uF ? I will reflow its pads right now.

[eh la bas ma]

IMHO, R1 without input cap is totally useless..
(I'd get rid of it and make R3 1M for not to worry about elevated temperature Gate leakage current..)

Thank you for taking a look at this !

This adjustment you kindly suggested is about efficiency and mainly to avoid the waste of a good resistor ? Or is it related to the popping issue ?

I have an absolute trust in your wisdom, but i'd like to avoid modifying the circuit if I can.

I'll do it without hesitation, if you think it could help the switching process and make it quieter.

I reflowed C26 1uF film cap, it has a good connection with C25 and R25, as shown on schematics.

[antonis]

No relation with popping issue..

You may keep the circuit as it is or (strongly suggested) add a cap (10n should be fine) in series with R2 (between R1 & R3..)

[eh la bas ma]

Here is a picture, just in case :

[Rob Strand]

C = Commercial (std temp range)
I = Industrial   (wide temp range)
M = Military (wider temp range)

Other specs can vary for M.

[eh la bas ma]

No relation with popping issue..

You may keep the circuit as it is or (strongly suggested) add a cap (10n should be fine) in series with R2 (between R1 & R3..)

I am not sure if the cap should be before or after R2. Do you mean like this ? Desoldering one leg of R2, one leg of R3 and soldering the 10n cap between these two resistors ?



Is it what is called an "input cap", meant to control impedance?

Is it meant to improve the circuit's interactions with various guitars, or with various effects connected to the Apostle input ?

I looked for "input capacitor" on wikipedia, and I found something about "ripple" voltage, I am afraid I can't really get the idea clearly in my head...

I would be grateful if you could clarify things a little bit. Here is a link for the schematics :

https://kurtballou.com/docs/N.E.W.%20Apostle%20Build%20guide.pdf

[FiveseveN]

I am not sure if the cap should be before or after R2.

Electrons don't know the difference. How do components in series work?

Is it what is called an "input cap", meant to control impedance?
Is it meant to improve the circuit's interactions with various guitars, or with various effects connected to the Apostle input ?

I mean—technically yes but it's much easier to say it blocks DC.

I looked for "input capacitor" on wikipedia

Try "coupling capacitor": http://www.learningaboutelectronics.com/Articles/What-is-a-coupling-capacitor

[eh la bas ma]

I tried to add a 10n film cap as described in reply #16. I desoldered the legs circled in blue, and soldered a cap on the legs, leaving the pads empty :



I have a signal in bypass, it shuts down when the effect is engaged, unfortunately no sound.

Did I do something wrong ?

[eh la bas ma]

Electrons don't know the difference. How do components in series work?

Thanks for your replies.

You mean they always work the same way, no matter their location in the chain ?