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Old 1st December 2012, 07:45 PM   #7731
dvv is offline dvv  Serbia
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Quote:
Originally Posted by mr_push_pull View Post
you have no idea how fascinating this is to me.
if there is any audio brand I'd buy before listening it's Spectral. IDK, maybe some subliminal marketing techniques are having an effect on me but...
talking about fetishism LOL
Spectral is very, very serious stuff, no doubt about it.

Even after hearing just one of their products,a power amp, that much is quite obvious.
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Old 1st December 2012, 07:52 PM   #7732
bcarso is offline bcarso  United States
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Originally Posted by dvv View Post
Spectral is very, very serious stuff, no doubt about it.

Even after hearing just one of their products,a power amp, that much is quite obvious.
And despite the high prices, how many other audio power amps can you use intentionally as an AM radio transmitter?
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Old 1st December 2012, 08:00 PM   #7733
dvv is offline dvv  Serbia
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And despite the high prices, how many other audio power amps can you use intentionally as an AM radio transmitter?
You got me there, Brad.

Although I have no idea what would I want an AM trasmitter for. Intentionally or not.

Out here, you go to jail if you own an unregistered transmitter of any significant power, and if you don't have proper permits from the local equivalent of FCC. Not hard to get, but you have to get them.
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Old 1st December 2012, 08:04 PM   #7734
DF96 is offline DF96  England
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Originally Posted by dvv
Well, it's not like you HAVE to use them, you know. You can buy real time DACs, which use 8 parallel DACs and have no oversampling and no digital brickwall filters. I won one, not at all very expensive, but sounds way better than most CD players I have heard.
The anti-aliasing filter at the record end will add ringing to a square wave, so you will see it at the DAC end whatever you do.

If, on the other hand, you are using a 'digital square wave' then you have to remember that this will never happen in real life because it would never make it through the anti-aliasing filter so it is hardly a fair test.
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Old 2nd December 2012, 01:52 AM   #7735
fas42 is offline fas42  Australia
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Keith Johnson uses some quite strange language, and concepts to describe what he's after, but the end goal is squarely where I come from:

Quote:
The faster the transient-settling time in a system, the more easily you can reach in and pick out tiny details in an otherwise very big sound. For some reason - and I don't know exactly why - the staging usually appears wider when the speed and the settling is better. That seems to give a bigger perceptual window to reach in and hear fine detail. In other words, if the stage is small, then everything sounds cluttered in a small space.
The other factor you get with speed is lightness. The music can have a tremendous amount of high frequency energy, and yet you don't feel assaulted by the energy. It can be very bright, yet not at all harsh or hard to listen to - exactly the way a live instrument is. If you tried to reproduce a trumpet at a live volume, you couldn't stand to be in the room with the loudspeaker unless you get the speed issues right. With high-speed circuits, the harshness goes away and the bloated character is gone. It sounds lighter.
That's precisely what I look for, except the notion of "speedy" circuits makes me go, ehhh? Except, if you translate that to low distortion results; too much distortion = "heaviness", blahhness of sound ...

Frank
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Old 2nd December 2012, 08:26 AM   #7736
dvv is offline dvv  Serbia
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Originally Posted by fas42 View Post
Keith Johnson uses some quite strange language, and concepts to describe what he's after, but the end goal is squarely where I come from:

That's precisely what I look for, except the notion of "speedy" circuits makes me go, ehhh? Except, if you translate that to low distortion results; too much distortion = "heaviness", blahhness of sound ...

Frank
With all respect, Frank, but I don't find anything strage in what Keith said, I think I understand excatly what he's saying. And obviously, I agree with him, at least in good part.

I also believe in wide bandwidth, which is probably obvious from the fact that I pay much attention to what Harman/Kardon does, and the late Bernard Kardon was THE wide bandwidth proponent.

What is missing from Keith's comment is how was this wide bandwidth achieved. Was is through inhrenetly wide bandwidth design, with an open loop full power bandwidth of say 100 kHz, then aided by relatively low global NFB of say 20-26 dB, a mix of more modest open loop bandwidth and more global NFB, or the traditional way, with lots of global NFB?

Harking back to the German LAS amp I posted some time ago, it's open loop bandwidth is just 4 kHz or so, the rest is about 49 dB of global NFB to make it hit the 1 MHz point, after which it was christened "Mega 1". No matter the fact that this particular model manages to pull this stunt off very succesfully and to sound good in the end, this is an exception rather than the rule.

On the other side of the scale, we have Matti Otala's 25/50W into 8/4 Ohms amp from 1978 (I think? Not sure about the year), which had an open loop bandwidth of 100 kHz and used only 20 dB of gobal NFB to get it to the same 1 MHz point. My own H/K 680 integrated, their top model in 1999, goes down the same route, as its 12 dB of global NFB allows it to hit 300 kHz (less bandwidth, true, but also less global NFB with less overall THD than Otala's model).

It's a question one always has to ask oneself when faced with a very wide bandwidth amp.
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Old 2nd December 2012, 08:35 AM   #7737
dvv is offline dvv  Serbia
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Originally Posted by DF96 View Post
The anti-aliasing filter at the record end will add ringing to a square wave, so you will see it at the DAC end whatever you do.

If, on the other hand, you are using a 'digital square wave' then you have to remember that this will never happen in real life because it would never make it through the anti-aliasing filter so it is hardly a fair test.
Frankly, I never bothered to test the outboard DAC. Never felt the need to do it because right out of the box, as is, it provided me with very high quality sound, even if its output stage is a lowly AD 847 op amp.

In other restepcts, I find it has been done by the book - separate power supplies, from the rectifiers onward power regulated power supplies (using 7815/7915 3 point regulators and some good quality Sanyo capacitors of no small value, 3,300 uF each I think), etc.

In esence, it manages to convey a feeling of freedom of the music, so to speak, an unforced quality where it almost literally flows. I expect my hearing has adjusted to it over the years, and I have become hard to please CD player wise, ever since then. It does what it does with flying colours, I think.

I bought it on line (my first ever) from a crew from Australia, and I believe it's the best spent audio money I ever did. $250 has sure bought me one hell of a lot of audio quality. Or so I feel.

Because I feel that way, frankly, I have left all the arguing, testing and figure bashing to others less fortunate.
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Old 2nd December 2012, 09:43 AM   #7738
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I found this an interesting read on slew rates .

DF96 might not agree about distortion due to feedback at the end of the discussion ?

Slew Rate etc.

Last night I went to a BBC recording of Beethoven , Britten , Mahler ( arr Britten ) and Poulenc the Gloria last night . The Beethoven was more like 78's or the 1944 German recordings I posted . Stunningly beautiful . Not lacking in treble , just endlessly soft . It will be interesting to hear the recordings . The Poulenc was in surround sound almost as the choir was very large . Spaced pair on strings ( about 8 feet above the conductors head ) , 4 ribbons ( ? ) for the choir . About 8 fill in mics .

Very interesting that John has measured the Quad 405 in the past , I was a little surprised how fast it was . My friend has one . I must do the without CD output filter test if satisfied no tweeter destroying nasties are coming out . It is an inverting amp , the friend who owns it refuses to try it in correct phase .
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Old 2nd December 2012, 09:59 AM   #7739
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he refuses to switch the banana plugs? why?
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Old 2nd December 2012, 10:27 AM   #7740
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It beats me ! I did notice in some set ups it sounds boomy if in wrong phase .

If anyone reads the Slew PDF I would be interested if anyone supports using Complimentary Feedback Pairs for the LTP input . The writer of the PDF uses a single input CmfbP if my memory is correct . The design I like is 90% the original Hitachi amp , 10 % me . I like the fact it gives 100 W and near op amp distortion at 50 kHz with only 7 transistor devices ( Hitachi , mine 10 ) . The pair I probably will use are 2SA1085 and 2N2504 . I recently tried a cascode VAS . It was no better and no worse .That is important as suitable transistors are now rare . 2 x 2SD756 + 2 x 2sB716 replaced by 2 x BC550C+ 2 x MPSA 42 + 2 x MPSA 92 . If was fantastically stable .
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