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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
mapman's avatar
mapman
22,199 posts
 
In this case with those speakers, having never heard either combo, I'd probably try the lower power Class A amp first under the assumption that good Class A > good Class A/B and that either amp is capable of driving the speakers to suitable volume well in the target listening room.

Not to say the Class A/B amp might not sound better, especially if the room is larger and listening levels higher in general, but if I have to start somewhere....
jesusa0
155 posts
 
I´m using a First Watt F5 clone with Zu Druid Mk IV and I don´t miss my Leben CS-300 at all.

Daniel
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islandmandan
1,260 posts
 
I've recently gone from a 35 Wpc push-pull VAC, to a First Watt M2, to drive my 12" Tannoy HPD's. The M2 is 25 Wpc, Class A, and sounds extremely good driving the HPD's.

The M2 serves as a back-up and change-of-pace amp, from my SET 300B amp.

Talk to Mark at Reno HiFi, he will send you an amp you can try at home for 10 days, if you don't like it, send it back. You have to pay for shipping there and back if you don't keep it. Shipping is free if you keep it.

Regards,
Dan
atmasphere's avatar
atmasphere
11,800 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...).
guf's avatar
guf
22 posts
 
In the past few months I've had a pass x150.5 , xa30.5 and a first watt SIT2. 150 a/b watts, 30 a watts, and 10 a watts. I had a pair of 87db speakers that both pass amps easily powered to loud listening levels. I believe the pass amps perform above their ratings. I now use the first watt SIT2 with 95db speakers and that easily powers my speakers in a room larger than yours. My experience has also been the lower powered amps sounded better.
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