Impedance matching

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Playing around with various configurations of kit here. Question of impedance matching between kit....

If I use an eq between pre and power anps, is the imoedance that the power amp input sees just the output impedance of the eq or is it actually the output impedance of the pre-amp AND the eq added together?

Ta...
 
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Playing around with various configurations of kit here. Question of impedance matching between kit....

If I use an eq between pre and power anps, is the imoedance that the power amp input sees just the output impedance of the eq or is it actually the output impedance of the pre-amp AND the eq added together?

Ta...
It’ll just be the impedance of the equaliser, as its output will be buffered, thus ‘hiding’ the output impedance of the preamp.

That is obviously presuming the equaliser isn’t a completely passive device, of course.
 
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It’ll just be the impedance of the equaliser, as its output will be buffered, thus ‘hiding’ the output impedance of the preamp.

That is obviously presuming the equaliser isn’t a completely passive device, of course.
Thank you. I don't think it is completely passive as it has a power supply, is that right?

Following on, would a Pro-ject switch box (again has a power supply) between the pre and power amps (instead of the eq) work int he same way i.e. the power amps will see the output impedance of the switch box and not the pre-amp?
 

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Thank you. I don't think it is completely passive as it has a power supply, is that right?

Following on, would a Pro-ject switch box (again has a power supply) between the pre and power amps (instead of the eq) work int he same way i.e. the power amps will see the output impedance of the switch box and not the pre-amp?
No, the switch box is different as all it does is pass the signal straight through, so it has no output impedance of its own to speak of. The Pro-Ject one has a PSU as it does the switching electronically, but this has no effect on the connections passing through.
 

rabski

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As above, it depends on the eq device. If it's purely a passive filter, then the output impedance of the preamp may (partly) affect the output impedance of the eq device. If the eq device is active/buffer, then only its output impedance will matter.

The switch box AFAIK is effectively a passive device. The power is for relay switching or indicators, and it should 'pass through' in terms of impedance, so the output impedance will be the output impedance of whichever device is switched through it.

About 10 times is a good shout, though as always 'it depends'. Much less and there's a possibility of low-end frequency roll off or issues with enough 'drive'. I've seen (and had) combinations with much worse, however, that never suffered at all.
 

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No, the switch box is different as all it does is pass the signal straight through, so it has no output impedance of its own to speak of. The Pro-Ject one has a PSU as it does the switching electronically, but this has no effect on the connections passing through.
Ah yes that makes sense, for some reason I was working to the Switch Box having 100ohms output impedance, but can't find any info. on that now - I guess I was looking at the phono box or similar by mistake (Pro-ject have so many devices!).
 

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As above, it depends on the eq device. If it's purely a passive filter, then the output impedance of the preamp may (partly) affect the output impedance of the eq device. If the eq device is active/buffer, then only its output impedance will matter.

The switch box AFAIK is effectively a passive device. The power is for relay switching or indicators, and it should 'pass through' in terms of impedance, so the output impedance will be the output impedance of whichever device is switched through it.

About 10 times is a good shout, though as always 'it depends'. Much less and there's a possibility of low-end frequency roll off or issues with enough 'drive'. I've seen (and had) combinations with much worse, however, that never suffered at all.
I think the Schiit Loki and Lokius are active/buffers unless passthrough is enabled.... ?

So difficult to tell if there is any roll off / lack of drive... once the seed is planted my mind hears it whether it is there or not 😂

Darn OTL valve headphone / pre-amp.

To say I am currently in a pickle is an understatement, too many amps and too many ways of configuring it all... listening outside on the iPod classic direct to headphones is so much easier!

I will get there though, thanks for the replies all.
 

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About 10 times is a good shout, though as always 'it depends'. Much less and there's a possibility of low-end frequency roll off or issues with enough 'drive'. I've seen (and had) combinations with much worse, however, that never suffered at all.
fanx, man. Am I right in thinking that a bad mismatch will just result in a crap sound rather than damage?
 

rabski

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Yes.

It's a voltage output, so you want to try to not load it excessively. Also, less than the 1:10 ratio could give issues with longer cables, as the capacitance of the cables can work to then act as an unintentional filter.

No preamps will be harmed in this process though. The absolute worst case is a 'flat' and lifeless sort of sound and possible some rolled off top or bottom end.
 

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It should be very easy to change the input impedance on the eq, probable two resistor changes per chanel
In this instance the change in output impedance from the eq was very much wanted as the OTL amp (used as a pre) outputs too high an impedance for the power amp; the eq lowers it substantially i.e. 2.5 kOhms down to 100 ohm. And I wouldn't have clue how to add resistors to a channel! 😂👍
 

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You could potentially change the input of something, but we are talking about impedance here, not resistance. You cannot lower the output impedance of something by putting a resistor across it.
 

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