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 ?
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....
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.
I´m using a First Watt F5 clone with Zu Druid Mk IV and I don´t miss my Leben CS-300 at all.

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.

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...).
I think 93 db sensitivity would be considered on the mid to high side. My speakers are 82 db (Harbeths) and my room is about 300 sq ft. I use 50 watt tube amps and never had any problem. I think any amp you choose would be fine driving your speakers.
I would think the 25 watt First Watt amplifier is a very good match with your speakers.I doubt that you'd be disappointed given your listening preferences.
I would think the 25 watt First Watt amplifier is a very good match with your speakers.I doubt that you'd be disappointed given your listening preferences.

Yes Charles, considering that at the moment I use a Wavac 300B amp which I love to the core, except for its 10 watts power rating, I guess the F5 would be a more suitable transition for me. On the other hand, some have suggested that I go with one of the big McIntosh amps, like the MC452. With 450 watts on tap, probably it will be a experience in itself. But then Wavac - First Watt - Naim - McIntosh seems to be too wide a palate. I have to narrow it down.
Of the two you mention I'd choose the PASS F5 any day.

Good Listening

As we both know, listening to all the choices is the only way to get a
definitive answer (easier said than done).Depending on the type of sound
you're after I can understand the 450 watt amplifier recommendation. From
your list the First Watt is the most appealing choice by a considerable
margin.Pure class A simple circuit design created by an audio icon. The
McIntosh and First Watt move in very different directions philosophically
and in execution. It seems they would attract quite different listeners and
cater to contrasting priorities.
While I have no doubt that in many setups the F5 would provide great sound (within its power range), the facts that it has a very wide specified 3db bandwidth of 1 MHz, a high input impedance of 100K, and uses feedback, raise some caution flags in my mind.

You've probably already seen it, but just to be sure I'll quote this paragraph from the manual:
A caveat is in order here – this is a very wide band amplifier with a high input impedance. In order to prevent the output voltage from bleeding back to the input at very high frequencies (thus making a fine power oscillator), keep the input and output cables separate, and don’t externally connect the speaker ground to the input ground. Good ground shielding on the input cables is important, and caution is called for in using Litz and other specially low inductance / high capacitance cables. I have not seen a specific example of a problem, but historically it is to be expected when an amplifier’s bandwidth exceeds 200 KHz. If the amp makes funny noises, runs extra hot, or blows fuses, this might be an indicator of such an issue.
Also, I would be particularly cautious if the F5 would have to be placed close to a component containing significant amounts of digital circuitry, or if there is reason to suspect that you may be in a high RFI area (e.g., nearby radio stations), or if there is reason to suspect that your AC power is particularly noisy (e.g., nearby industrial plants).

Also, keeping speaker cables as short as possible would seem to be desirable, both to minimize capacitance and to minimize RFI pickup that may be injected into the amp's feedback loop.

Not sure how critical any of this is, but these kinds of things strike me as being potential sonic issues (or worse) with any very wide band high input impedance amp that uses feedback.

-- Al
While others might disagree, Naim amps function best with Naim preamps. The 300 is a wonderful amplifier, but I don't know if you'll be getting the best out of it without at least a Naim 282 preamp or better. IMO, Class A, Class B or whatever doesn't really mean anything in and of itself. The design has to be taken as a whole and judged on sonics, not specs.
from my experience it is not correct to think that just because a speaker is of high(er) efficiency that a low(er) power amplifier will do the job.
I have a Tannoy studio monitor that is 94dB SPL/W/m & I use it with a 120W/ch class-AB amp with very good effect. This studio monitor is, well..........., used in studios where the power amplifiers are of 100s of watts & often even 1000s of watts. The max wattage handling capacity of my speakers is 350W/speaker even tho' it's rated a 94dB SPL/W/m. To me this in itself is a huge hint from Tannoy to me that my speaker will do very well with a high power amp despite its high efficiency.
A higher power amp with a Tannoy will give you more control over the music & a lot more dynamic headroom. You music will sound alive as there will be plenty of wattage on-tap for dynamics.
I would try to find an excellent 100W/ch power amp for this Turnberry SE speaker. Maybe Pass' own offerings or some well regarded 100W tube amp.....

I tend to agree with Chayro - NAIM gear seems to sounds its very best with associated NAIM components. The magic falls off the cliff once you put a NAIM component with some other brand. IMHO. YMMV. Have you heard NAIM gear mixed-matched with other non-NAIM gear? If yes, did it have the same magic as with all-NAIM gear?

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?
Obviously the Pass has a lot of upside if it is up to the task in your specific setup and room. So there is some risk with this option, possibly worth taking.

The Naim is a safer bet, and will still likely sound very good!

So if it were me, I would only buy the Pass if I knew I could change afterwards without taking a financial hit. You could buy used, not overpay and resell if needed, or buy from a source with a good return policy. Then if does not work out, you still have good options and little downside other than extra work to change and perhaps a small financial hit, depending.
Don't know where your located, if here in the US you could try one of these out.

Liberty B2B-100

Theres a few reviews out

Good Sound Review

Don't forget to click on the measurement tab, Bascom King performed the technical test of the B2B-100

Positive Feedback Review

And yes I do make them

Good Listening

So, Peter, what's the deal here (just trying to understand this for myself) - you have PBN Audio manuf loudspeakers & also several amplifiers & then you have Liberty Audio also manuf some power amps??
How does Liberty Audio compare to PBN Audio? Is Liberty Audio the down-market brand?
You have received some thoughtful replies with the inevitable varying opinions. I agree that speaker sensitivity isn't the only consideration, the load in ohms probably is more relevant. Pani my room is noticeably larger than yours and my speakers are 94 db and a 14 ohm load.

I have a 100 watt and a 40 watt push pull amplifiers class AB. Both of these fine amps have been in a 5 year hibernation since the arrival of my 8 watt 300b SET amplifier. It just sounds better and is superior overall (not close).It's very possible that the Tannoy may be more difficult to drive than my Coincident , I don't really know. It's also possible you may simply prefer the presentation of a high power amplifier (I believe that low power amps sound better with an appropriate speaker choice). Lower power may not be what you need to meet your specific goals.
Good Luck,
Pani, you might consider making a speaker change. With your Wavac, which you seem quite attached to, a move to a higher sensitivity speaker would seem to be in order.

My custom Tannoy HPD's, at 94db, with either the 300B SET (9 Wpc), or the First Watt M2 (25 Wpc) give all the dynamics and slam necessary in my large (16.5 X 34' w/ cathedral ceilings) listening room.

Obviously, you can't have it both ways, if low powered SET amps is what you want, a high sensitivity speaker is in order. A Wavac 300B amp is a fine thing, a more suitable speaker match for that amp is, perhaps, what you should consider.

Dan makes an excellent point.You say you love your Wavac to its core,
If that's true I'd keep this terrific SET and get more compatible speakers. Dan's Tannoys are apparently easier driven than your specific model. Tannoy models must vary in ease/difficulty of their speaker load.Option 2, sell the Wavac and get a higher power amplifier. If this were my dilemma, I'd keep the Wavac.

Liberty is our direct to the consumer brand which focus more on the entry level to high end. We currently have two products a Phono Preamp the B2B-1 which have received praise form many reviewers and consumers, theres even a few reviews of it here on Audiogon.

The other product is the Power amp I mentioned above the B2B-100 which has also been very well received. Currently working on a fully balanced line amplifier hoping to have that ready for the Newport Show where Liberty Audio will have a display room, right next to PBN Audio.

Good Listening

Lots of interesting suggestions. Few points worth mentioning:

1. I already have a Naim NAC 52 preamp. So adding a NAP 300 would not be an issue from the matching stand point.

2. Bombaywalla, thanks for your suggestions. Somewhere within, I know a high powered is always desirable for this speaker. But I am at a stage where I am unable to find an amp with a good balance of quality - quantity - cost. The tube vs SS battle is also on. After listening to the Wavac for the past few months, I am getting too critical of less than stellar sound from an SS amp. But then finding a neutral, high-resolution tube amp isnt easy either.

3. Charles1dad, you are really fortunate to own a 14ohm speaker. That is a cake walk for these 300B SETs. I auditioned the Wavac on a pair of WHT speakers which were 11ohms nominal impedance. The wavac could drive it to rock concert levels. So, in a way you are pampered :-).

4. Islandman, your suggestion of changing the speaker has already been on my mind since last couple of months. I have been weighing all options. After a lot of research and introspection I came down to this:
The Wavac remains among the most accurate sounding amps I have ever heard. Near flawless, I would say. However it is like a tool, a very high precision one. Tannoy prestige speakers on the other hand are a work of art. They might have flaws but to me they remain one of the most satisfying/fulfilling speakers to listen to music on. Since the time I acquired it I stopped bothering about better speakers! I mean even when I hear a better speaker I do not care because this Tannoy doesnt let me worry. When I auditioned it, it was being driven by $1k chinese amp and even with that I was floored. This speaker remains the best purchase of all time in my audio journey. I just do not know what to replace this speaker with (except the higher Tannoys). Till that time I will keep it.

The problem at hand is to maximize the sound for the money. I have written to Reno hifi for the F5, lets see if I could get a demo. I am at Singapore btw, so the typical demo policy probably wont hold for me.
As much as you like the Wavac it is apparent you admire/adore the Tannoys even more.This being the case, your amplifier search makes sense. You're right, a 14 ohm speaker load is ideal for my situation.The 8 watt SET provides effortless drive and ease of musical flow{same as Dan described with his system}.
If you are open to tubes, our M-60 can drive that Tannoy with 60 watts...
Pani, from what little I delved into the design of your Turnberry's, and from listening to a pair of them at a friend's home, I gleaned they are a more difficult load than Monitor Gold's or HPD Tannoy drivers.

I am in the position where I just couldn't afford one of the top of the line Prestige speakers. Being in Singapore, a hotbed of vintage audio enthusiasts, you should have access to many vintage Tannoy drivers.

I know in recent years, prices for older Tannoy drivers has risen to near ridiculous levels, but where you are located, you may be able to find a bargain.

I spent a max of $4500 US to build my custom HPD's, which includes reconing the woofers with Hard Edge surrounds, custom crossovers using Mundorf SIO caps, Dueland reisitors, and Alpha Core inductors. The cabinets I had built of a total of 1 7/8" MDF @ 150 liters, and weigh 192lbs. bare weight.

They haven't disappointed in any way yet, no matter what amplification I've thrown at them. My point in all this is, especially in Singapore, having some custom built Tannoys should be very doable. I wish you luck.

Best regards,
Are the older Tannoys an easier load than the current models in general or is your speaker an isolated case?
Charles, from what little info I could find on the subject, the Turnberry's seem to benefit from a bit more power than that available from the typical 8-9 Wpc produced by SET 300B amps.

There was reference made to phase irregularities stemming from the Tulip Wave Guide/crossover interaction.

The Turnberry's seem to perform better with a bit more power, as a result.

Thanks Dan. I was curious because Tannoy Westminster owners often report very good results with their 300b SET amplifiers. The Westminster may be an easier load for these amps{I'm guessing}.
Atmasphere, I have never heard any of your amps before. I have only heard one OTL by Graaf and for some unknown reason I found it too coloured and bloated. However, I am trying to audition your amp here. Will report here if I get to hear them.

Charles1dad, I find it amusing that some westminister owners have complained repeatedly about their push-pull amps unable to control the bass of that speaker and then there are some who are ecstatic about them with puny SETs. I dont know that speaker well I guess.

Another amp that I may be considering is Ayon Crossfire III. It is a 30 watt SET built around AA62 tubes which are again derieved from 300B tubes. 30 watts of SET feels like a great proposal. Has anyone heard the Crossfire ?
The Ayon Crossfire from your description could be an ideal match with your Tannoy. I hope you're able to listen to it and the Atma-sphere OTL as well. I've heard the M 60 and MA-1 numerous times and they're very good amplifiers. I just personally prefer what a good SET uniquely offers. Horses for courses.Once you compare them, one or the other will move you more. It just depends on what type of sound you want.
Pass labs watts need to be X 5. when you go from A to B.

Naim and Pass Labs are so differently. Pass Labs is superior in depth and wide.

At shows with very extreme Naim stuff the stage was fully 2 dimensional. I had my music with me.

I played; light my fire from Jacintha. The cross flute in the beginning of the song was on the same line as her voice. In real it is about 3-4 metres behind her voice.

In my opinion depth and wide are essential parts for the absolute sound.

When you go back to a 2 dimensional stage you miss a lot of the exitement.

When I confronted the Naim people with these information. They did not know what to say.

An amp of 100 dollar also can give a 2 dimensional stage.

That is why I call 2 dimensional audio standard audio.

In 7 years of time I have done many comparisson between 2 and 3 dimensional sound.

All people prefered 3 dimensional sound far over 2 dimensional sound. Audio can sometimes be very simple and convincing.
Got in touch with Reno hifi and Srajan Eaben (6moons). Both of them highly recommended the upcoming F6 over the F5. The F6 is more powerful but it supposedly sounds more like a SIT too. So it is like the best of both worlds, power, transparency and finesse.

Anyone has heard about the F6 ?

I would certainly not pass up on a chance to audition the Ayon Crossfire should you have a chance. If its 30 wpc is enough for your needs, based on my experience with the brand I am confident you would find it to be an excellent component in your system.

Hi Pani, as you can see from the impedance graph (linked), these 93db speakers are easy to drive with an impedance from 8ohm up, I myself with my taste in music would go for the FW F5, your Metallica discs may tax the F5 if you want to fill a bigger room than yours at very loud level.

Remember though, you will need a source or preamp that has higher than usual voltage output as the F5 only has 15db of gain, it has a very passive preamp friendly 100kohm input impedance, but you will need a higher than normal output source.


Cheers George