Sorry RGA, I didn't read your post earlier. What you said about the amp scenario is not exactly correct. Let's see, we have an amp rated 100 watts @ 8 ohms. Now what you need to know is whether the manufacturer designed this amp for a lower impedance. If it can go lower, you would get an inversely proportional increase in power with change in the impedance IF AND ONLY IF it is a perfect amp. Unfortunately class A and AB amps are fairly innefficient If it were than at 4 ohms, you would get 200 watts, which translates into a 3dB gain which is TWICE the volume unless the speakers are getting into powe compression territory. The amp might fry if you connect 4 (8 ohm) speakers to it in parallel if it isn't rated for 2 ohm output. I PROMISE you, though, that you will NEVER, EVER, EVER fry an amp or destroy a speaker if it is a higher impedance than rated output. It might not get loud at all, BUT it will not be destroyed unless your amp has nasty clipping and the harmonics of the subsequent square waves produced decide to burn the voice coils on your mids or highs.....person clipping amps... Again, I hope this helped...at least more than my last post... Happy listening to all and to all a goodnight!

Brett

Domer:

Just a quick point on db. 10db is perceived as a doubling of volume. if a a 10 watt amp produced 90db you would need a 100 watt to get 100db. a 20 watt amp is double the power and generates a 3db increase which is mildly audible.

You are right that a 100 watt amp can theoretically provide 200 watts because it is the resistence being lowered...but as you noted no amp truly doubles perfectly...and as you also noted not all are stable at lower impedences...this is why I used a pioneer receiver because they don't have the big or even decent power transformers...and man that pioneer elite was smoking with those MLs...playing very quitly is ok but turn it up and there was nothing left in the amps reserves...again luck the MLs didn't fry from the clipping.

CHECK THIS OUT

http://www.soundstage.com/systems/systems200006.htm

That's a great review. What I found most interesting was the comment about the berating of the product because it's chinese. I read a similar review of the ASL AQ 1003 integrated selling for $1000.00 Canadian.

Very Subtley the UHF review noted that the parts would not look out of place compared with $10,000.00 Tube amps from the NAME companies...indeed they also likened the designes to those NAME companies. UHF also said that they (Chinese amps)get away with it because their are no restrictions...anyone can build the designs no patents left on the classics. And they cand build this gear for 1/10 of what a North American company could build it for...and probably not as Greedy in the profit margins because they realise if they sell 10 times the units the profit margins will be take care of themselves.

And Of coarse sight and price bias is prevelant...so it would be interesting to see if Cary and that Ilk really would score better in a blind test...not different here...better? After hearing the 1k Jolida VS the 8k NuVista...I wonder...and I shouldn't wonder for that kind of price disparity. But Hey the Rich have to delude themselves because what's the point of killing yourself in a high paying job with no reward if you can't say you bought a better amp? LOL...even if it is not....Of course they could donate the difference to some charity...perish the thought.

How does one go about getting a Mod done after the fact...I have little electrical experience and don't want to mess things up?

Recently I had a chance to listen to the Head (with upgraded JJ tubes and wire cage listing at $329) and to my ears I found the bass slow and weak when using Senn 600s. I agree with earlier comments that the impedance switch had little effect.

My question for all you tube rollers out there are suggestions for alternative tubes that will firm up the bass on this otherwise very fine amp.

Yep I've heard before that MG Head's impedance switch had little effect. I think Chych found that when he built his own adapter there WAS an effect. So is the MG Head's impedance switch just decoration? Is it implemented correctly or to specs.

Because impedance matching DOES have a big impact on sound.

RGA, you are DAMN lucky you didn't destroy those Logans... You're a lucky, lucky man if those are yours. ANYWAY, I have't gone to check myself yet, but I still hold that a 3dB increase is double the "loudness". Remember that dB's are logarithmic, meaning that you're looking at what power of 10 is double. If you get a calculator, plug in 10^(.3). You will get ~2, meaning that a 3dB increase is twice the amount of sound......basically. If you have any more questions about this, feel free to PM me, and I will try to answer any questions about dB's and such.

Brett

Domer:

No The Logans were just in a store...I asked them to connect the Elite...they figured since it was the flagship it would be fine...Doh!

Actually I've seen that log calculation before...and it is not right...not the math just the application.

That calculation does work for instance when talking about power...you typed in 10(watts) to get a (.3)3db increase which requires 2(times the power). The 2 does not signify a doubling of volume level however as watts are also associated with a log scale - you need 10 times the power to get a doubling of volume.

What I suggest is that you go to www.audioasylum.com and ask the question there...they have many amp designers and Electrical Engineers to explain to you, as they did me, that you need a 10db increase to get a PERCEIVED doubling of volume. The word 'perceived' may be at issue here.

This is also why amps in the early 80s at 25watts were considered beasts...you'd need a 250Watt amp to DOUBLE the volume...which could also be done by purchasing a speaker with 10db more sensitivity.

*sighs* This is getting rather lengthy. I forgot what the original title of this thread was... Anyhow, I thought about what you said, RGA, but it's still just a little bit off. dB measure electrical or acoustical energy of sound. Since they are logarithms of base 10, a 10 dB increase is a 10 times greater volume. That said, a 3dB increase is jus slightly less than double. For example, 30 dB is 10 times greater than 20 dB. 40 dB is 10 times greater than 30 dB. Therefore, 40 dB is 100 times greater than 20 dB. I know logarithmic calculations/applications can be tricky. Since it is Log base 10, ANY 10 dB increase is 10 times louder. 43 dB is 10 times greater than 33dB. It's all about reference points and such. Trust me on this RGA. If you don't believe me, though, check out Encyclopaedia Britannica (sp?). I am not trying to be mean. I am just trying to get the truth out. Maybe a PERCEIVED doubling could take more than 3dB. I don't know. I do know, however, that a 10 dB increase is VERY significant as you get into higher SPL. Again, I am just trying to explain things. Happy listening

Brett

To get further off topic, Grados (SR-60 at least) do require more power than Sennheiser HD600s to reach the same SPL. This is because they are less sensitive (94 dB at 1 mW vs. 97 dB at 1mW). This of course assumes the manufacturers provide accurate ratings. 3 dB less sensitivity means that SR-60's require approximately double the power to reach the same volume as HD600.

The equation is 10 dB more SPL for 10x the power:
log(power in mW)*10dB = x dB more SPL than the rating at 1mW

So, for example to reach 110 dB SPL for HD600:

110-97 = 13 extra SPL = 19.95 mW of power
Combine that with its rated impedance of 300 ohms to get
v = 2.45 volts
i = 8.15 mA

And for SR-60:

110-94 = 16 extra SPL = 39.8 mW of power
Combine that with its rated impedance of 32 ohms to get
v = 1.13 volts
i = 35.3 mA

2.45 volts vs. 1.13 volts is why the volume knob will be turned up further for the HD600s even though they are drawing less power. I think some of the higher Grados are more sensitive, and hence are easier to drive.

Koss KSC-50 (60 ohms, 101 dB at 1 mW) are quite easy to drive to 110 SPL:

110-101 = 9 extra SPL = 8 mW of power
v = .7 volts
i = 11.5 mA

So the volume knob would be turned up even less than for SR-60, even though they have higher impedance. It's their greatly increased sensitivity that wins the day.

All of this assumes, of course, that the headphone amp can handle the voltage swing and current draw, which is why portables have trouble with the higher impedance headphones that require more voltage.

Even easier to drive are the Sennheiser HD25 (70 ohms, 120 dB at 1mW):

110-120 = 10 fewer SPL = .1 mW of power
v = .08 volts
i = 1.2 mA

Now these are some insanely sensitive headphones, and a great way to conserve battery power!

Pretty good Scott, I didn't check all your figures, but I glanced over everything, and it looks to be in order. The moral of this story is that sensitivity does win out as far as ease of drving is concerned.

Brett

Ok Moder...I agree and I know you are not trying to be mean... hey this is just a detail and in the end nothing is gained or lost in the details in audio. As I said I agree about the Math... now please follow this from the Speaker designers from Wharfedale(and or Mission):
Quote:
"Most Loudspeakers will produce around 88db from 1 watt at 1 meter. Most people listen at a distance of about 2 meters from the speakers, so they hear 85db, not 88db from that one watt. The Smallest difference in loudness of 3db takes TWICE the power. To INCREASE the loudness TWO-FOLD takes 10 times the power."

Note the word smallest 3db difference(takes twice the power) and 10 times the power to get twice(Two-Fold) the loudness.


Further to this point:

If you are listening to "speakers rated at 87db 1 watt/1metre , that means you are drawing an AVERAGE of 4 watts to reach your desired level, seated 2 meters away. If you then want to turn it up a bit, OR MAKE IT SEEM TWICE AS LOUD, you would need 40 watts AVERAGE. if you have tone controls and you increase it to maximum(normally 10db) you would need 400 Watts"...the amp if it does not have the required power will cause "clipping."

Here is a chart:

Faint 30db - Average domestic background level....
no music playing.
40db - Very soft radio music playing in house
Moderated 50db - Average Office
60db - River or Streamside, running water
Loud 70db - Typwriter or computer print room
80db - School playground or cafeteria at break
Time.
Very Loud 90db - Noisy factory or noisy urban street with
lorries.
100db - Car Horn at 10 feet away
Deafening 110db - Accelerating motor cycle at 10 feet
Average discoteque(Night Club)
120db - Threshold of feeling - Rock Concert
130db - Threshold of Pain
140db - Near jet engine during power take-off.

Domer- RGA is correct.

LOL. I am tired of arguing about this. I know that a 3dB increase in SPL is esentially "twice" the loudness. I cannot refute what the so-called engineers from Wharfedale claimed because I do not have the full context of that explanation. But I do know that what I claimed is true. Sound is measeured logarithmically because to do otherwise would cause the measurements to go off the charts. Their are some military applications that use SPL's of over 200dB which means that, according to your chart, it would be 10000000000 times louder than a car horn at 10 feet. This is crazy!!! Sound is so incredible! Again, I challenge you to check any sort of Physics publication on the issue or consult an Encyclopaedia. That is all I have to say about the subject. You're right RGA it really doesn't matter in the end. I am just stubborn

Brett

lorries... I didn't know that term was used outside of England...