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rick57 25th March 2005 02:18 PM

better the Pass camp?
 
I’m close to entering a great new paradigm: high efficiency speakers (100 dB) in horns, to give about 105 dB, ie + about 10 dB on so called ‘high efficiency speakers. I’ve just read remarks like this:
“FACT: The first few watts are always the juiciest. In every amplifier those first few watts, or milliwatts, are the best sounding watts, which is why it is so desirable to keep an amplifier operating in that range. This explains why, for decades, our Japanese bro’s have preferred high efficiency speakers...especially for their transistor gear.” (Harvey Gizmo)

so 15 watts is *plenty, 8 enough

* But how does the relative sound quality of amps at 0.3 watts compare with the relative sound quality at “normal levels” of say 5 watts?
* How can we assess the sound quality of amps for 105 dB speakers, auditioning with often only 90 dB speakers?

From the Pass deisns: ZEN V1/ the light bulb version/ a mini A? Aleph-X on batteries?

What tube amp?? benefits?

Thanks

Sherman 25th March 2005 04:20 PM

Re: better the Pass camp?
 
Quote:

Originally posted by rick57
... high efficiency speakers (100 dB) in horns, to give about 105 dB, ie + about 10 dB on so called ‘high efficiency speakers. ...

“FACT: ... In every amplifier those first few watts, or milliwatts, are the best sounding watts, which is why it is so desirable to keep an amplifier operating in that range...” (Harvey Gizmo)

so 15 watts is *plenty, 8 enough

...

Thanks

An interesting experiment to try is to measure the power output of your amp as delivered to the speakers at a "normal" listening level. I did this with some of my amps and found that even with relatively inefficient speakers (88dB or so) the power delivered to the speakers was well under one watt (average).

Cranking it up to louder than my normal levels still resulted in somewhere between 3/4 and 1 1/4 watts. Of course all this depends on the music content, more bass = more power required, size of your listening room, the volume you normally listen at yada yada yada. And the process isn't exact but it does give an indication of your power requirements.

In my case with 100dB efficient speakers 8 watts would be *plenty* and 4 watts would be enough, maybe even two or three watts for anything less than "party" levels.

rick57 25th March 2005 10:29 PM

Hi Sherman

How do you measure the output of your amp as delivered to the speakers? Multimeter across the back of speakers??

Sherman 25th March 2005 11:02 PM

Quote:

Originally posted by rick57
Hi Sherman

How do you measure the output of your amp as delivered to the speakers? Multimeter across the back of speakers??


That's pretty much it. You get a more accurate reading if the meter is a true RMS meter but it still isn't exact since the impedance of speakers varies with frequency.

Just measure the AC voltage across the speaker terminals and calculate the wattage based on the nominal impedance of your speakers. As I said it isn't exact but should put you in the ballpark.

Sherman 25th March 2005 11:08 PM

Oops, forgot the formula and some other advice.

If you have a dummy load you can of course measure the power output of your amp but can't tell what the output would be at a normal listening level. So you measure with speakers connected and live with the error induced by impedance changes.

Now you can compute the power using-
P = E^2/R

So if you measure 5 volts into 8 ohms you get-
P = 5^2/8 or P = 25/8 or P = 3.1

Hope this helps.

Brett 26th March 2005 02:35 AM

When talking about power levels, are you referring to to an RMS/average or a peak? To give a referent, my modified Khorns typically required < 0.5Wrms even in the huge room they were in at anything less than (very) loud levels. In the 20'x16'x12' room they'll soon be in (about 1/6th - 1/8th the cu volume of the last room), I expect they'll need even less. A 20W class A PP tube amp was VERY loud and I don't recall ever hearing any hard clipping.
Get an SPL meter, and record the voltages across the speaker terminals of your current speaks via soundcard/software to get an idea of what you're actually using now, and convert that to the higher sensitivity speakers to get a better indication of the power you'll actually NEED under all listening conditions.

rick57 26th March 2005 06:04 AM

Sherman
Thanks I’ll give this a try, though on my currents speakers I really don’t like, my tolerance of volume is low.

Brett
When I talk about power levels, I’m referring as per amp specs to RMS.

I am going to China in May, and want to get an amp there and then (very low cost). The speakers are highly unlikely to be built & XO sorted by then be done, so I’m going to best estimate the need for watts, and take advantage of the low prices. I may not be back there for 5 or 10 years.

(If I’m a little wrong, I’ll keep it; if I’m a lot wrong, I’ll sell it, and probably not lose money, in fact from what I hear about prices there, I could make a small amount, to offset the hassle).

There’s also the fact that the amp will only be driving > 250 Hz, which may halve(?) power requirements. Maybe 5-10 watts is enough, say a 300B. But I want to avoid any wooliness.

Anyone know how to avoid that in a 300B?


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