Preamp to Amp impedance matching

thsmith
thsmith Posts: 6,082
edited January 2010 in Electronics
I need to help to make sure I understand what I am looking for in my next Tube Pre that will be connected to my Anthem AMP 1 with input impedance of 100K ohms. Also I am using MITs S3 Shotgun ICs.

I have read where a Pre Amp should not have more than 500 ohms output impedance.

Is there more to it than that?

What else should I look for?

How do the MITs come into play with its impedance selector box?

Thanks,
Speakers: SDA-1C (most all the goodies)
Preamp: Joule Electra LA-150 MKII SE
Amp: Wright WPA 50-50 EAT KT88s
Analog: Marantz TT-15S1 MBS Glider SL| Wright WPP100C Amperex BB 6er5 and 7316 & WPM-100 SUT
Digital: Mac mini 2.3GHz dual-core i5 8g RAM 1.5 TB HDD Music Server Amarra (memory play) - USB - W4S DAC 2
Cables: Mits S3 IC and Spk cables| PS Audio PCs
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Comments

  • Ricardo
    Ricardo Posts: 10,636
    edited January 2010
    With that input impedance you won't have any problem. I've used the rule of thumb that there must be a minimum of 20:1 (read it somewhere) between the amp's input and preamp's output, so you can use virtually any preamp. If your IC's have the selectable impedance, just use the highest (should match the receiving equipment).
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  • thsmith
    thsmith Posts: 6,082
    edited January 2010
    So if my Pre has output impedance of 137 ohms and my Amp input impedance is 100K ohms then I have a 740 to 1 ratio ?

    wrt the MITs I was wondering since the cables (I guess) are trying to impedance match does it even matter ?
    Speakers: SDA-1C (most all the goodies)
    Preamp: Joule Electra LA-150 MKII SE
    Amp: Wright WPA 50-50 EAT KT88s
    Analog: Marantz TT-15S1 MBS Glider SL| Wright WPP100C Amperex BB 6er5 and 7316 & WPM-100 SUT
    Digital: Mac mini 2.3GHz dual-core i5 8g RAM 1.5 TB HDD Music Server Amarra (memory play) - USB - W4S DAC 2
    Cables: Mits S3 IC and Spk cables| PS Audio PCs
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  • Ricardo
    Ricardo Posts: 10,636
    edited January 2010
    thsmith wrote: »
    So if my Pre has output impedance of 137 ohms and my Amp input impedance is 100K ohms then I have a 740 to 1 ratio ?

    Pretty much. As I said, amps with such a high input impedance are not a problem; my amp has an input of 22 kohm, so it makes it a bit more difficult to match; there are preamps that have output impedance of over 1 kohm.
    with the MITs I was wondering since the cables (I guess) are trying to impedance match does it even matter ?

    The MIT's have to be set to match the receiving piece of gear; I am not sure how it works with the sending equipment or if it even matters.
    _________________________________________________
    ***\\\\\........................... My Audio Journey ............................./////***

    2008 & 2010 Football Pool WINNER
    SOPA
    Thank God for different opinions. Imagine the world if we all wanted the same woman
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  • thsmith
    thsmith Posts: 6,082
    edited January 2010
    thanks Ricardo !
    Speakers: SDA-1C (most all the goodies)
    Preamp: Joule Electra LA-150 MKII SE
    Amp: Wright WPA 50-50 EAT KT88s
    Analog: Marantz TT-15S1 MBS Glider SL| Wright WPP100C Amperex BB 6er5 and 7316 & WPM-100 SUT
    Digital: Mac mini 2.3GHz dual-core i5 8g RAM 1.5 TB HDD Music Server Amarra (memory play) - USB - W4S DAC 2
    Cables: Mits S3 IC and Spk cables| PS Audio PCs
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  • headrott
    headrott Posts: 5,496
    edited January 2010
    My amp (Aragon 8008bb) also has an input impedence of 22Kohms. My tube pre-amp has an output of (to quote AMC specs <200 ohms). That's not very specific. So, let's assume an output of 175ohms. So my ratio would be 125:1 (approximately). I guess that's not too bad huh? I should be fine then, correct?

    Greg
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    Taken from a recent Audioholics reply regarding "Club Polk" and Polk speakers:
    "I'm yet to hear a Polk speaker that merits more than a sentence and 60 seconds discussion." :\
    My response is: If you need 60 seconds to respond in one sentence, you probably should't be evaluating Polk speakers.....

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  • heiney9
    heiney9 Posts: 25,421
    edited January 2010
    headrott wrote: »
    My amp (Aragon 8008bb) also has an input impedence of 22Kohms. My tube pre-amp has an output of (to quote AMC specs <200 ohms). That's not very specific. So, let's assume an output of 175ohms. So my ratio would be 125:1 (approximately). I guess that's not too bad huh? I should be fine then, correct?

    Greg

    I see you're still obsessing over this, YES you'll be fine :):);).

    Perhaps you should sell your seperates and get an integrated or a receiver :p.

    Let it go...........just fo' get about it!

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Puritan Audio PSM136 Pwr Condtioner & Classic PC's | Legend L600 | Roon Nucleus 1 w/LPS - Tubes add soul!
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