Pad circuit question!!!!

[dukasound]

Hi
I found difference in pad circuits. On upper pic (like on G9, etc) in normal mode all of three resistora are in parallel with input. If we used –20db pad then we have 2 x 619ohm + 169ohm=1K4.
On Jensen type pad we have open circuit when is pad off.

Can we use both or what is right connections?
Thanks
Duka

 

[tmbg]

that looks to me like two different ways of expressing the same circuit path.

Well not exactly the same, but functionally equivalent.

With the switch in the non-padded position, the first one doesnt have the series resistors in, whereas in the second one, the resistors are there, but since they're shorted they're inconsequential.

 

[dukasound]

[quote author="tmbg"]that looks to me like two different ways of expressing the same circuit path.

Well not exactly the same, but functionally equivalent.

With the switch in the non-padded position, the first one doesnt have the series resistors in, whereas in the second one, the resistors are there, but since they're shorted they're inconsequential.[/quote]
I told that, but what happened when resistors are connected on input signal in the non-padded position.

 

[tmbg]

In the G9 circuit, looks like the series combo of the three resistors will set the maximum input impedance, whereas the jensen one doesnt have any resistors causing any shenanigans at all...

 

[mkruger]

It's functioning the same. But i would go with the Jensen because leaving those series resistors in the path will probably reduce the risk of any popping sound when you flip the switch, or relay if you use one.
I guess it would be like using a diode like you usually would across a relay...

 

[alk509]

[quote author="mkruger"]i would go with the Jensen because leaving those series resistors in the path will probably reduce the risk of any popping sound when you flip the switch[/quote]

I think you mean the G9 one, not the Jensen.

Peace,
Al.

 

[mkruger]

I think you mean the G9 one, not the Jensen.

yep

 

[mkruger]

if you use a relay, would it be wise to just use a diode across it? like you would in power supply...

 

[tmbg]

across the coil, yes definitely. That wont affect the audio, because the coil isnt part of the audio path.

 

[dukasound]

Main question didnt answer :?
I found these two pad circuit.
What is right connection?
Thanks
Duka

 

[Peter Simonsen]

[quote author="dukasound"]Main question didnt answer :?
I found these two pad circuit.
What is right connection?
Thanks
Duka[/quote]

I´m sorry, but what is right..???..from a "purist" point of view..I´d choose the jensen..no need to have anything in parralel/series if not needed..other than that..!!! I mean who´s to say what is right or wrong other than the one who is in charge of the design..if it works for you..use it..hell half of my "designs" would be laughed at on the paper..but clients seem to love them..soo who is wright or wrong..???

Kind regards

Peter

 

[gyraf]

Hi Duka.

Re-read the G9 schematic and description.

Look at the component values in the G9 pad.

It is not only a pad, it also raises input impedance to 10K when padded - in order to accept standard line inputs.

Jakob E.

 

[tmbg]

It could raise input impedance when padded, but so would the Jensen style one.

The difference that I'm seeing is that the G9 version LOWERS input impedance when unpadded.

 

[dukasound]

[quote author="gyraf"]Hi Duka.

Re-read the G9 schematic and description.

Look at the component values in the G9 pad.

It is not only a pad, it also raises input impedance to 10K when padded - in order to accept standard line inputs.

Jakob E.[/quote]
OK. That would be a part of answer :grin:
In real pad impedance wouldnt be changed?
But on G9 in mic position there are all of three resistors in circuit :?

 

[gyraf]

Yes, but they are too high impedance to matter.

Think of them as a primary transformer termination.

 

[NewYorkDave]

You guys are getting "wrapped around the axle" as my boss likes to say. The Jensen pad and the Gyraf pad serve different functions and each works well for its intended function.

The Jensen pad is meant to drop the level from a "hot" mic while maintaining roughly the same impedances seen in the circuit when there is no pad. It must be switched out completely when no attenuation is desired, since the resistance values are low enough to cause undue loading on the source if left connected across the input.

The Gyraf pad is meant to drop line-level down to mic level while increasing the impedance seen by the signal source. Since the resistances in this pad are fairly high, it has little shunting effect on the input in "bypass" mode even though one side of the pad is left connected.

Contrary to what someone said earlier, the U-pad does not necessarily increase input impedance when switched in; it can be designed to maintain more-or-less the same input and output impedances as the circuit without the pad.

My friend Rick Chinn has a good webpage about mic pads here.

 

[dukasound]

[quote author="NewYorkDave"]You guys are getting "wrapped around the axle" as my boss likes to say. The Jensen pad and the Gyraf pad serve different functions and each works well for its intended function.

The Jensen pad is meant to drop the level from a "hot" mic while maintaining roughly the same impedances seen in the circuit when there is no pad. It must be switched out completely when no attenuation is desired, since the resistance values are low enough to cause undue loading on the source if left connected across the input.

The Gyraf pad is meant to drop line-level down to mic level while increasing the impedance seen by the signal source. Since the resistances in this pad are fairly high, it has little shunting effect on the input in "bypass" mode even though one side of the pad is left connected.

Contrary to what someone said earlier, the U-pad does not necessarily increase input impedance when switched in; it can be designed to maintain more-or-less the same input and output impedances as the circuit without the pad.

My friend Rick Chinn has a good webpage about mic pads here.[/quote]
Clear :thumb:
One more question
If we have typical -20db with two 619ohm and 169 and if we make circuit like on G9 pad (line switch) , how would this correspodent with impedance and signal?
Thanks
Duka