which amp would suit these speakers?

[bk856er]

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.

BK

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

 

[Floric]

Hi,

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.

Regards

Flo

 

[6L6]

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]

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.

BK

 

[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.

 

[bk856er]

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.

BK

An externally hosted image should be here but it was not working when we last tested it.

 

[6L6]

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]

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.

BK

 

[Zen Mod]

yup

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

 

[6L6]

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?

 

[bk856er]

Zen Mod and 6L6 - just to verify, both of you are recommending a mild F5T suitable for a 4U chassis, correct?

Any special PSU or trafo considerations to maintain interchangeability across those other designs (rail voltage, VA, etc.)?

Yes - very cool and I do plan to experiment!

BK

 

[AudioSan]

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.

BK

hmmm. without having read this tread,
a F5 with higher bias. f.ex 32V rails and 3.5A bias will drive this speakers to nirvana and then some

 

[AudioSan]

yup

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

seams i agree with the myghty ZM this time too
i see that 6L5 agree also

BTW: i have speakers that performe like this.
and i use a F5 with high bias and normal voltage. this gives me about 35W class A at 6ohm. and about 50W class A/B at 4ohm.

 

[AudioSan]

Zen Mod and 6L6 - just to verify, both of you are recommending a mild F5T suitable for a 4U chassis, correct?

Any special PSU or trafo considerations to maintain interchangeability across those other designs (rail voltage, VA, etc.)?

Yes - very cool and I do plan to experiment!

BK

+/-32V rails. (24VAC) 300+VA pr ch.
that will do the job

 

[6L6]

If you want interchangeability as I was hinting at, you will want +/- 24v rails. (which requires a 18v+18v transformer.)

However, there really is no wrong answer here is you are wanting to make a one-off amp. A F5C or T with slightly hotter rails will be really nice with your speakers.

 

[bk856er]

So this is the current build plan:

- store deluxe 4U chassis
- 1x Tea-Bag PS board with 8x 27kuF caps
- 2x Tea-Bag F5T convertible boards
- 2-pair Fairchild FQA output devices/channel + diodes + cascode
- SumR 800VA 2x24V transformer - 32V rails
- bias to 4U heatsink abilities (move to 5U as last resort)

Chassis and boards are already on hand!

Any additional feedback is welcome.

BK