1976 Cornwalls - 2A3 or 300B Configuration?

[acasanis]

Hi All,

Just wondering if there is anyone with an opinion on which to choose - the 2A3 or 300B configuration?

I am in the process of building up Bottlehead Paramount monoblocks and have the choice between either config.

I currently have a Scott 299D amp. I will be running the Paramounts with a Bottlehead Foreplay III (Preamp) into my 1976 Cornwalls.

Will the Cornwalls be sensitive enough for the lower WPC with the 2A3's...?

Cheers!

[tromprof]

The 2A3 and 300B sound different so it is like asking which flavor is better; it depends on your taste. That said, it is my experience (admittedly somewhat limited with 2A3 amps), that the bass response is usually not as strong with the 2A3. I prefer the 300B for that reason (I also found the 300B sounded more filled out?), but if someone were to give me a nice 2A3 amp to try and prove me wrong I wouldn't refuse.

[Marvel]

You double the wattage with the 300B, so depending on the design and the output tranny, I could see the 300B having a bit more mass. I would loan you my 2A3 Moondogs, but alas, theywill not leave my house.

Bruce

[mikebse2a3]

Will the Cornwalls be sensitive enough for the lower WPC with the 2A3's...?

Part of what wattage amplifier you need will depend on the size of the listening space, listening distance from the cornwalls and the maximum spl you enjoy playing your music.

All things being equal in the amp designs(which shouldn't be taken for granted) then the 300b should give you about 3db to 4.5db more headroom.

The problem with asking others will it play loud enough is what you might call loud enough might be different than what I call loud enough.

Here as a very simplified example of what one could expect; If a cornwall will produce 101db @ 1meter @1watt and behaves in a linear manner for the power levels I'm listing then at 1 meter listening distance..

1watt = 101db Edit chart for Cornwall sensitivity of 98.5db @ 1w/1meter thus: 1watt= 98.5db

2watt = 104db 2watt = 101.5db

4watt = 107db 4watt = 104.5db

8watt = 110db 8watt = 107.5db

16watt = 113db 16watt = 110.5db

32watt = 116db 32watt = 113.5db

Now if you factor in a more typical listening distance in a typical home listening room then I think it would be reasonable to expect peak spl at the listening position would be reduced by maybe -4db to -6db. So a 4watt amp will give us approx. (101db to 103db peak spl) and 8watt amp will give us approx. (104db to 106db peak spl). Edit: based on BobG post if you listen about 3 meters(approx.10ft) from the system then subtract about -9db for a ball park estimation of peak spl at the listening position.

So if you know what peak levels you like your music reproduced at then maybe this will help.

miketn

Edit: Did a little research and if you look at the discontinued products page the :

Cornwall is listed as: 98.5db @ 1w/1meter

Cornwall ll listed as: 101db @ 1w/1meter

Cornwall lll listed as: 102db @ 1w/1meter

so please adjust my previous numbers accordingly.

Please not this is just an attempt to give the OP an idea of what to expect and because of many variables such as amplifiers peak power capabilities and room acoustics variables that we don't know it really can't be anymore than a ballpark figure.

[mikebse2a3]

When it comes to a 2A3se versus 300bse comparison using Khorns I will say speaking for myself the closest comparison I was able to do was between a Cary 2A3se design versus a Cary 300bse design and in that case I felt the 2A3 was very slightly better in the low end and equal in all other parts compared to the 300b.

But....and it's a big Butttttt

The problem is (as I'm sure you all know) its not just the tubes we are comparing but the total amp design and bottom line I would have been very happy with either of these amps when used with Khorns. Also it should be pointed out that because an amp is of a single ended design or uses a 2A3 or 300b or whatever tube type doesn't guarantee quality performance if proper attention to other areas of the design wasn't taken. Each amp design must stand on it's own when compared to others.

miketn

[Guest " "]

1watt = 101db

after playing around with a few SPL calculators I come to realize we often start off on unverified assumptions......I'm not clear or sure I understand what room conditions result in 1 watt=101db, considering distance from drivers, furniture, curtains, etc. And, do I really need 101db?

[mikebse2a3]

speakerfritz maybe this will clear up how Klipsch did it at least in 2002 and I'll see if I can find any more current info.

http://forums.klipsch.com/forums/p/8860/63961.aspx

BobG post in the above thread:

" Klipsch measures sensitivity on home loudspeakers in the following manner:
1. We place the speaker to be tested in our anechoic chamber and do a free space measurement (no boundary gain or room gain) at a distance of 3 meters. This distance is chosen in order to be in the far field of the speaker. The test signal used is wide band pink noise.
2. Starting with this result in dB, we add 9 dB to obtain a one-meter equivalency, as the industry standard for expressing sensitivity is one meter. The 9 dB difference is all inverse-square gain. Move half as far away and gain 6 dB etc.
3. To this we add 4 dB for room gain and boundary gain to translate the measurement to a typical listening environment. Speakers are not operated in free space in any normal application. An increase in sound pressure comes from proximity to nearby walls, floor and ceiling. Theoretically, a maximum of 18 dB increase is available through corner placement but that is rarely the position chosen for full range loudspeakers; and the increase is also frequency dependent, being prominent at low frequencies. Additional measurable increase comes from room gain wherein the room is pressurized by low frequency information. Again, this is frequency dependent impacting only the low end of the spectrum. We have verified the 4 dB figure we use in numerous empirical measurements and believe it to be quite accurate.

Our KPT-904 professional theater speaker was mentioned above. It should be noted that the KPT-904 is a model designed to be placed behind the screen at a movie theater and as such does not benefit from as much boundary reinforcement as in a typical home installation. The 4 dB room gain figure is not applied to the sensitivity measurement for such models.

BobG "

[mikebse2a3]

I believe I have a much easier and more relatable way for the OP to see if a 2A3 amp puting out worst case 3.5watts would work for him spl wise anyway.

Your Scott 299D is rated at 34watts and the 2A3 is worst case 3.5watt.

If we convert this difference to db then: the ratio of 34watts down to 3.5watts = -9.87db

Now this perception isn't exact and is frequency and spl level dependent also and many times you will read that +/-10db changes will be perceived as twice or half as loud but some indicate maybe +/-6db. See this for good information http://www.sengpielaudio.com/calculator-levelchange.htm

Anyway here is something you can try;

If you find yourself cranking the scott to full power often when listening to music then the 2A3 might not be for you but if you find that if you crank it to full power (stay below amplifier distortion of course) and then reduce it down to what sounds like 1/2 as loud and it is still louder than you would normally listen at then the 2A3 amp might be a good option for you.

miketn

[Guest " "]

yeah....maybe I have less than spl /1 watt of 101db....but in any case....4 watts seems to be enough.

[JBryan]

Either config will work but not without compromises. My favorite 'common' triode is the 45, followed by the 2A3, then 300B but If you're new to SET, I would suggest the 300B. If I had to assign characteristics to each, I would say that the 45 has a pace and silky quality and really displays the best in SET 'magic' while the 2A3 is detailed and accurate if a bit edgy and the 300B is full-sounding, smooth though slightly 'wooly' and slow. The obvious compromise you'll face moving from a +30w P/P amp to SET is power and though each triode will offer a very good taste of SET - accuracy, detail, presence, etc., the 300B will pump those 15" woofers with more authority and make for a better comparison with your Scott. >P>

As you move to lower power triodes, you'll face more compromises and it becomes more difficult to match components - the speaks being the most difficult. In an average room, a 45 amp simply will not drive CW's beyond 90dB w/o considerable compression and distortion. At 90dB or so, a 2A3 amp can comfortably drive CW's but soon thereafter, its 'edgier' qualities will become noticeable. The 300B has enough power to drive the CW's close to 100dB before displaying any compromises and thus is a great way to introduce yourself to the world of SET. Have fun.