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bk856er 16th February 2013 09:47 AM

which amp would suit these speakers?
Looking to build my first Pass amp to drive some 2-way speakers (Sierra-1 NrT from Ascend). Some specs below.

Any specific suggestions? Would the standard F5 have enough grunt?

Bonus points for something that the 4U Deluxe chassis could handle.


Floric 16th February 2013 08:33 PM


sorry but these speakers, the ones the impedance is measured, are 4 Ohm (or 6 Ohm) speakers. The minimum impedance defines the rating, the "average impedance" that is listetd in the specs above does not make any sence.

4 Ohm and 86.5 dB of efficency are not the typical speakers for Pass-Diy Amps, I think only one of the F5 variants would fit these.



6L6 16th February 2013 10:32 PM

Of the F5, the cascode version (F5C) with 2 outputs, or an F5Turbo would be good. The F5C would fit in the 4U.

Much of what you need is dictated by what kind of room you have, how loud you play, what music, etc...

What are you using now? Can you give us a bit more info about your setup?

bk856er 16th February 2013 11:00 PM

Thanks for the input, guys.

Room is large and open, about 12x25', but listening levels are typically low and a little bit seems to go a long way in this space. Music type is all over the map.

Current setup is a humble Onkyo TX-NR807 AVR with the 2-ways crossed at 70Hz and a 15" powered Rhythmik sub handling the low frequencies.

The AVR preamp outputs are only 0.7V, but my other sources are a Twisted Pear Buffalo-II DAC + Legato, an AMB Gamma-2 DAC and an Oppo BDP-95. I'm not really tied to any of that gear, especially the AVR, but the speakers will probably need to stay for a while.

Spent the last few years building and enjoying many headphone amps and DACs, and now I want to extend my DIY efforts to speaker amps.


6L6 17th February 2013 12:24 AM

You are biamped? That makes it easy --

Any of the amps will work well. Choose the one that seems the most interesting to you. :)

bk856er 17th February 2013 01:34 AM


Originally Posted by 6L6 (
You are biamped? That makes it easy --

Any of the amps will work well. Choose the one that seems the most interesting to you. :)

I never really thought of it that way, but I suppose I am biamped. That really simplifies everything?

I currently use the AVR for bass management (with some manual REW work and AVR-based room EQ). I could shift some of those duties to the sub if I wanted to bypass the AVR altogether.


6L6 17th February 2013 01:49 AM

Yes, even with your satellites running full-range, you don't the burden of one amp and speaker trying to make all the bass.

Plus all the signal that requires the real oomph to drive (I.E., the deep bass) will be handled by the sub.

With your descriptions, I think you will have no problems with any of the Pass Firstwatt amps. They are a great experience regardless, fun to build, very rewarding, and sound utterly fantastic. :) You can't go wrong.

bk856er 17th February 2013 03:03 AM

This is good news - thanks 6L6!

I thought I pretty much needed those 45W for my setup, which would push me to an F5T variant or similar and a large 5U case or 4U monoblocks. More than I'm up for right now. Already picked up the 4U deluxe case as a gift.

I like the idea of an F5 or mild F5Tv1 to get my feet wet.


Zen Mod 17th February 2013 03:10 AM


mild F5T is right word ...... and choice

6L6 17th February 2013 03:11 AM

Build an F5. You will love it.

When you have that done, and are thinking about another project, all you need to do is carefully take the amp PCB and replace it with an Aleph J -- the PSU and chassis will be interchangeable, and the Aleph J PCB sholud be available by then. :)

After that, you will be very curious on how the F4 works and sounds, so you can again replace the amp PCB into your case with PSU and give it a whirl.

Cool, eh?

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