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25 watts Class A or 70 watts Class A/B ?

I understand these days there are many good examples of both Class A and Class A/B amps. To the point that a well designed Class A/B can beat a similar pedigree Class A amp. However my question is in particular related to these two amps:

1. First Watt F5 (Pass Labs)
2. Naim NAP 300

The speaker to be driven is a Tannoy dual concentric Turnberry SE. It is a 93 db sensitive 8 ohm load and in general considered to go well with both high powered and low powered amps.

F5 is a highly purist class A 25 watts design with a robust power supply. It is a push-pull design so it can generally drive difficult loads better than typical single ended first watt models (F3, F4 etc). I have heard the F5 on an Altec horn system and I loved its pure and direct sound.

Naim amps in general has always appealed to me, again because of their very direct presentation. Music has a certain excitement and bounce through them. The NAP 300 is one of their top models and I am sure it will be a very refined amp.

However I will only buy one. Both these amps must be having few fundamental differences in the way they present music considering they are coming from very different designers. Even the topology is different here.

The first question here is, can a 25 watts F5 drive the Tannoys well ? My room size is 200 sqft and I listen to music at reasonably medium to loud levels. I dont play very loud though. I listen to all kinds of music from Mozart to Metallica.

Qualitatively, sound per sound, how do these two amps compare ?
pani

Showing 3 responses by atmasphere

atmasphere's avatar
atmasphere
12,099 posts
 
If the speaker is only 93 db, a lot is going to depend on how lively your room is and your personal listening habits. My room is slightly larger but has some damping (carpets, LPs in shelves, couch and armchair) so 25 watts simply would not be enough power. I suspect 75 watts would not be either.

My speakers are 98 db, meaning that I need maybe about 1/3rd the power that you do; in my room 25 watts on those speaker is marginal.

So you will want to consider this in your choice- a clean 25 watts won't do you a lot of good if you clip the amp a lot (and of course being a Tannoy I think I would prefer to put a tube amp on there as well...).
atmasphere's avatar
atmasphere
12,099 posts
 
Just a FWIW: 93 db is not considered high efficiency. It is a moderate efficiency. You are transitioning from moderate to high efficiency about 97 or 98 db.

If the room is small enough or lively enough, I would go with the F5 in a heartbeat- it is one of the best transistor amps made and by that I mean best-sounding. But if you keep running it out of gas it will be frustrating in the long run. Any chance to do an audition?
atmasphere's avatar
atmasphere
12,099 posts
 
If you are open to tubes, our M-60 can drive that Tannoy with 60 watts...
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