Originally Posted by
nat8808
The output stage of the source still had to be able to drive the power amp well though. Essentially there is no difference between an active line stage in a pre-amp and the output stage of a source component... other than how it is designed and what it is specifically designed to drive!
I guess the 851 isn't designed in a way that drives your Conrad-Johnson sufficiently well.
Of course, err.. opening up ALL possibilities, free thinking and all that.. perhaps you're experiencing something more neutral and your previous set up was slightly top and bottom heavy?
I remember a famous speaker designer saying that that was many people's reaction to his speakers that he'd put so much effort into being completely flat responsed and neutral. As they came from other speakers accentuating certain extremes, they were hearing lack of sparkle and bass. Sticking with that neutral goal however, over time people adjusted their ears.. and now regard the designs as being neutral.
Hi Nat,
It well known that many speaker designers deliberately engineer a rising treble characteristic or exaggerated bass response and that some people have aclimatised to that, and so a speaker with flat response curve may sound dull or bass-light at first aquaintance and that time is needed to get used to the 'non-loudness' version
My pre-amp has a pretty much ruler flat frequency response out to about 50k, so I don't think it is simple as that. The line-output impedance is 95 Ohms, which is pretty low, and will be able to drive the 100kOhm input of the power amp without any problems whatsoever. The output impedance of the 851c is <50ohms, which also suggests plenty of ability to drive a high impedance input too. I have read that this is typical in domestic audio, i.e. low output impedance/high input impedance - the load is essentially a bridging load and doens't actually load the source at all, and this maximises the voltage swing across the signal and ground of the power amp's input, with very little current flow.
One area where the specs don't guide is highlighting at what frequency the output impedance is measured - if it varied significantly with frequency and between the source and pre-amp, then that could account for differences in frequency response. To be honest I don't think that is happening here as the 100KOhm power amp input resistance is so much greater than the source output impedance.
... which is all well and good, but I am left wondering why a pre-amp with a flat response sounds so different to a directly connected source given that the interface to the power amp is 'ideal' in terms of impedance. It actually sounds 'fine', but a bit bloodless, lacking in 'oomph'. I am just curious as to why this is... this is just a temporary arrangement while my preamp is away for a service. It will certainly be interesiting to see what I think when it is back in the system - I hope I like it!.
Regards,
Alex
Technics SL1210| Jelco SA-750| Benz Micro ACE SM MC| Squeezebox Touch/MCRU linear PSU | Cambridge Audio 851C | High Resolution Music Streamer II+ / Linestreamer+ | Raspberry Pi 2/IQ-Audio DAC+ / Max2Play | Conrad-Johnson ET3 Control Amplifier| Conrad-Johnson LP125sa KT120 Power Amplifier| Avalon NP Evo 2.0 Speakers| Cardas Audio Quadlink-5C Speaker Cables and Interconnects| Finite Elemente Pagode Signature E-14 equipment support