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camshaft 11th November 2012 10:03 PM

Cheapest/simplest way to connect computer to F5?
Hi all,
I've decided to embark on an F5T V2 as my first major power amp build. It'll be driving a pair of Zaph SR71's (85db efficiency). Although I have a turntable and CD players, the truth is that the majority of my music listening will be from 256-320kps MP3's on my macbook pro laptop. I'm looking for not necessarily the best way to connect the laptop to the F5, but the simplest/cheapest way to hold me over for awhile without committing some egregious error in sampling/gain structure/impedance that would degrade the sound quality even further than the MP3 already has.

I can't find exact info regarding the analog 3.5mm jack output of the 2009 13" macbook pro, other than a post regarding a different 2008 model stating 1.4V rms and 24ohm impedance. It does however also do optical digital out via the same plug.

1. So firstly, if I connect my 3.5mm headphone out from the comp directly to the F5, just 'how bad' would it sound?

2. A B-1 preamp is inexpensive and easy to build, and I don't need to worry about loss of bit depth from volume control via the computer, but I'm still relying on the laptop's built in DAC, and low gain.

3. A mini-dsp + mini-digi combo would give me an external DAC, appropriate gain, and impedance matching. This seems to me like the best cost/benefit option. Plus if I decide to add subs later I can use it as the crossover for them. My only concern is that I've read subjective reports stating the mini-dsp/mini-digi stuff isn't up to par sound-quality wise with equipment of the Pass level. I don't however know if that loss of sound quality is at the level a 10awg-power-cable-believer thinks they hear, or the level at which your grandmother would definitely hear.

Thoughts comments, concerns at my evident lack of understanding?

Thanks for your time!

Danger Mouse 11th November 2012 10:23 PM

2. A is the way i`ve also done

works well for a cheap onboard soundcard with 3,5mm headphone out to cinch connection with normal copressed mp3`s

But with mx CD Player as source its much better

Andersonix 12th November 2012 12:25 AM

You could get an idea of your headphone output's SQ relative to other preamps and computer headphone outputs by listening to headphones (or try pushing other power amps), but that's probably only a temporary solution, as it's not going to be loud enough for an F5.

In the miniDSP product brief it says the max output level is 0.9Vrms, which I don't think is going to be enough to push an F5. This is also my own long term upgrade path (miniDSP and F5T), although I expect to need a gain stage before an F5 (or maybe bypass/improve the miniDSP's analog outputs).

One can also build the F5 with more gain/less feedback...

Nelson Pass 12th November 2012 12:54 AM

There are those with good ears who think the F5 with more gain (less
feedback) sounds fine. Easy enough to do.


camshaft 13th November 2012 12:26 AM

Thanks everyone. I'm leaning towards using the minidsp for connection options and versatility, and may just increase the gain a bit on the F5 if it ends up being an issue, which it sounds like it won't.

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