zaph sr71 good match for f5

[anonomouse]

I'm researching my future setup and I'd like to do it right the first time and build a b1 preamp and an F5. I've been looking at building the zaph sr71s. From what I've read the F5 requires sensitive speakers. Are th sr71s a bad match for this amp setup?

[d to the g]

The F5 puts out 25 watts in class A, and 50 in AB. It will have plenty of power for a pair of the SR71s.

In my experience, the F5 is the best I've heard for driving my Proac clones, which are not exactly high efficiency.

[juma]

Originally Posted by anonomouse

... b1 preamp and an F5. ...

F5 needs about 4V peak at its input to produce 25W@8Ohms and most sources will give you 2.8V peak. Since B1 has zero gain you better go for the preamp with some gain (6-10dB) instead of searching for very sensitive speakers.

Search the forum for adequate preamps for F5 - there's plenty of them...

[anonomouse]

Yup noticed that after the edit window had closed that the B1 won't work as a preamp. Is there any way to build a preamp into the same case as the F5 and have it run off the same power supply without having to redesign things?

[Zen Mod]

Juma made few of these

just search for his posts

[Melon Head]

Yes Juma made a very nice preamp for driving the F5 to full power.

However I don't entirely agree that you can't use a B1. How many of us listen to music using the full power of the F5.
I connected my cd player direct to F5 to show my wife and she freaked out because it was too loud for her. So I actually need to attenuate the signal (not add gain to it).
My speakers are 89dB

It looks like those Zaph speakers are 85dB. I think it would be worthwhile having a look around at other speakers of higher efficincy that you also like.
I am not saying you can't use those Zaph speakers, they're just not ideal.

If you don't mind waiting and like open baffle speakers then Nelson's BOB might be worth considering.

[anonomouse]

Does having lower sensitivity deaden the sound or does it simply mean that I have a more lilmited gain? I live in a very small apartment 18 sq meters, so I can't really crank it up, i sit roughly 3 meters from the speakers. The sr71 are ideal for me in that I can purchase the baffles and crossovers assembled and avoid the expense of purchasing numerous woodworking tools. I intend on running all audio into the f5 via an arcam rdac connected via usb to a mac mini, do i even need a preamp in this case?

[Zen Mod]

in my experience lower speaker sensitivity leads to more "deaden" sound , even with more powerful amps

to my ears - gain is in speaker's gain

[juma]

Originally Posted by Zen Mod

...lower speaker sensitivity leads to more "deaden" sound ...

Not necessarily so, try BBC/Rogers LS3/5A (83dB/W) - extremely alive...

[Russellc]

It may partly turn on the particular speaker, amp and room. One thing I noticed when using B-1 with F-5 with the Karma Indignia speaker, a small 2 way with about 85 db efficiency, is that when I switched out to the Mcintosh MC225 power amp, it suddenly sounded like a heavy hitter, way more toe tapping sound. When I equalized the volume between the F-5 and the MC225, the F-5 ate its lunch. With a preamp with gain, the F-5 sounded a bit more in the heavy hitter catagory. (By heavy hitter, I mean ability to get louder than you need)

Moving the speakers and the F-5 to an upstairs bedroom, (much smaller) and listening more near field, the B-1 really provides enough volume. While it is quite adequate, I still enjoy that setup better with a little gain on the pre's part.

With the Large E'waves, approx. 93 dB, they get rock and roll loud with the B-1.

I'd build the B-1 regardless. Very inexpensive, board is available from Pass Labs with matched fets, and sounds dynamite. With other amps, the B-1 had plenty of gain to drive them to maximum volume.

Russellc