Getting back to members on passive vs active lines


I found a buffered passive linestage for really cheap for experimentation. It is a Harman Kardon AP 2500 preamplifier with a passive linestage option (switch) made between '93-95' so minimalistic that it doesn't even have a balance control. Input impedence is 33k ohms;output impedence is 300ohms. I also have Rothwell attenuators in lieu of the Endlers which are again backordered--at the preamp's inputs and at the amp's inputs. It sounds really good, a lot better than the Celeste in the same set-up which I had figured out was being driven into distortion by the amp's low input impedence. The same with the CD player to preamp. The CD player's output impedence was too high and preamp's input impedence too low. So the system likes the H/K in passive mode better than it likes the active Celeste. And I'm not getting the anamolies at the low end of volume that I expected. The Rothwell's are dull as advertised, however. But Gregm was essentially correct in saying that a passive linestage won't work for me, because I don't have enough volume on the Telarc 1812. I have enough on all other CD's I've tried. When I get stepped attenuators, mybe I can decrease the attenuation enough so that I will have enough volume. But a CD player with 10K ohms impedence is a problem. Moral of story: match components within parameters before buying. Thanks to everyone for the info and help and for challenging me. I really needed to learn all this stuff. Comments welcome. Lynne
arnettpartners

Showing 3 responses by arnettpartners

It's a Harman Kardon HD7600ll made between '90-'92. I bought it like new in the box from a member a few months ago. It was highly regarded but I couldn't afford it back then. It ran circles around my Simaudio Moon Equinox--made it sound and look like the Kling-ons made it. So I sold the Moon. I keep checking that spec but it says 10k ohms@2V. What determines output impedence? Is it the internal impedence of the amplifier section or is there a buffer at output? I know a power amp would ideally have zero output impedence. Also phono stages usually had 47K ohms at about .75-1 V.
Rodman99999, Thanks. I found the review/test results on the Cary. I haven't found a review yet on the 7600 but it would be interresting to get measurements on it. I did remove the Rothwells from the preamp's inputs and I think maybe I won't need them with the preamp's 33k ohms impedence compared with the Celeste's 12k ohms. It's hard to tell because the preamp is only starting day 2 of break-in. That would probably give me enough gain for the cannons.I don't have the vinyl disk but even the CD engaged the amp's protection circuitry at moderate-loud levels when I played it on the Sim. It doesn't with the 7600ll. But maybe then the impedence spec is conservative on the high side.
Addendum: I get it. Output impedence is a characteristic of frequency and is effected by components ie tubes or ss components. Hope I stated that correctly.