Impedence Matching Help Needed

Ditto
B

I would advise against any schiit preamps. I have not had success with them in my systems.

To add to the previous responses, from a technical standpoint the main concern I would have with the proposed configuration is not related to impedance compatibility, but rather that it may not provide you with enough gain for the phono source.

Your reference to the Mani phono stage providing an output of 5 volts appears to be incorrect. Assuming you would be using it with a moving magnet cartridge, from a sonic standpoint its 42 db gain setting is likely to be the optimal choice among the four gain settings it provides. That setting is correctly stated at the Schiit website to boost a 2.3 mv cartridge output to 300 mv. Moving magnet cartridges usually provide somewhat more output than that, under the standard test conditions their output voltage ratings are based on. Let’s optimistically assume the cartridge can provide 5 mv under the standard test conditions. 42 db of gain would boost that to 630 mv.

Assuming the specs on your Classic 125 amp are similar to the currently produced NewClassic 2125 v.2, the amp requires an input of a bit more than 1.1 volts to be driven to full power, or roughly twice as much as the combination of a 5 mv cartridge and the 42 db gain setting of the Mani would provide under the standard cartridge test conditions. While some recordings can have dynamic peaks which significantly exceed the standard cartridge test conditions, and while you might never need to drive the amp to its maximum power capability if your speakers have relatively high efficiency, at best you would probably find yourself using the volume control close to its max position on many recordings. And that would be with the rear panel level control on the amp at max.

Also, btw, I would definitely not count on cranking up the settings of all of the gain controls on the equalizer to be a good way of addressing that issue, as I suspect doing so would degrade sonics significantly.

But to answer your question about impedance, I suspect there would not be any significant issues with the proposed configuration. Although I can’t say that with certainty, in part because the specified output impedances are undoubtedly based on a mid-range frequency such as 1 kHz, and do not reflect the highest output impedances at any audible frequency. And in part because I suspect that the 2 ohm output impedance specified for the Audioengine DAC is for its headphone output, and the output impedance of its line-level output is probably a good deal higher. The Audioengine website does not make that clear.

Regards,
-- Al

Went the passive way once with a pre-amp. Thought it sounded fair until we added a buffer circuit. Not passive anymore, and sounded exceptional compared to the weak sound that the passive produced. Maybe if the math all worked out, the story could be better.

Thank you for the great answers, especially Al for the phono cartridge info. My phono carts (pickering xv-15, shure m91ed, and AT95e...@ 5.5, 5.0, and 3.5mV respectively). So, they probably wouldn't drive the amp well enough after passing through the mani.

I'm leaning away from passive after reading your comments.

I have a yaqin ms-12b I can use as a tube buffer that should simplify this whole idea for now. With this I could bypass the schiit mani altogether since it has a phono section. I'll get an active preamp down the road, I'm just paranoid that they try to 'do too much' and arent neutral. I'm on a budget so a used NAD or new Onkyo might suffice. My goal is clean refined sound that doesn't have the harsh highs or bass bloat associated with cheap gear. Speakers are dynaudio and are great. It feels like a good preamp is the last piece of the puzzle.