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  #16 (permalink)  
Old 15th September 2008 , 12:22 PM
Round The Horn
 
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Now here's an idea....
If I did want to use a ready made PCB that has been designed for IC op-amps, wouldn't it be nice to have plug-in alternative high quality discrete op-amps.
Burson Discrete Opamp
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  #17 (permalink)  
Old 15th September 2008 , 06:44 PM
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Hmm...read some of the Burson article, and found myself thinking of "The Emperor's New Clothes"! There's a lot of exageration in it, and statements which are factual, but irrelevant! It's obviously aimed at people who have no knowledge whatsoever about component fabrication, and does read very convincingly - but I'll not be rushing out to buy a load of them! The "The considerations when choosing an audio op amp" article is much more professionally written, and takes a reasonable approach to using op-amps.

Lets face it, you can be pretty sure that virtualy everything you listen to nowadays has gone through op-amps somewhere, or equally miniaturised circuitry at some point. Replacing output drivers (which generally have little or no gain, and therefore few noise related problems) is not going to make a huge difference. I'd love to put some of the "reviewers" through blind A/B tests to see whether or not the improvements are as marked as they claim, and whether or not the Emperor really does have new clothes!

When it comes to the sort of gear you are using, pure power is a pretty useless measure - lets face it, no-one, even with the most inefficient hi-fi speakers, is putting out anywhere near 100's of watts rms - the spl would be incredible, and you'd be deaf. The real purpose of having these powerful amps is all about headroom, and the ability to faithfully reproduce peaks in the music, rather than having awesome, ear-shattering volume. It's possible for example, that a 100W per side stereo amp will sound better than a 200W per side, at a given volume, because (for example) the 100W amp has seperate psu's for left and right channels. There are so many factors involved that power is a very poor indicator of what your system will sound like.

The ultimate measure when it comes to "super hi-fi" like yours, is what the two measuring instruments either side of your head tell you!
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  #18 (permalink)  
Old 15th September 2008 , 09:51 PM
Round The Horn
 
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Quote:
Originally Posted by Stagesound View Post
The ultimate measure when it comes to "super hi-fi" like yours, is what the two measuring instruments either side of your head tell you!
Very true. I think this could be a fun DIY project if based on a not too expensive design. I would have fun building something and trying it and would be happy to say "oh well, nice idea but it sounded better before". That is, of course, as long as I had not spent too much building the crossover. The Burson op-amps would be adding six or seven hundred pounds to the build
I will put together a parts list and start pricing a DIY unit based on the Elliott Sound Products design and based on the idea that I can source very good quality low noise op-amp ICs at a fraction of the cost of one Burson op-amp!
However, the project will a be a non-starter if I can not find out the current crossover points of the passive crossovers in the speakers. I have contacted Wilmslow Audio and asked them but they may not want to tell me. I suppose I could deduce the crossover points one of two ways;
1. Open the speakers and study the passive crossover PCBs and components. Deduce the circuit and calculate the crossover frequencies.
2. Use my RPlusD software to produce graphs of the frequency response from each driver in turn. This should be quite easy to do by having one power amp connected in turn. I would hope that it would be obvious from the graphs as to where the crossover points are set.
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  #19 (permalink)  
Old 18th September 2008 , 12:41 AM
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The nice people at Wilmslow Audio have confirmed that the crossover points are 380Hz and 3800Hz. So now I have all the info I need to start calculating the components needed and work out the cost of building an electronic crossover.
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  #20 (permalink)  
Old 7th October 2008 , 07:15 PM
Round The Horn
 
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Sorry Khazul, it seems I overlooked your post last month.

Quote:
Originally Posted by Khazul View Post
If your really picky about your filter network wouldnt you perhaps want to chain in some all pass filters as well to correct for the phase shifts induced by the other filters?
I have decided to build the 3-way version of the Linkwitz-Riley Electronic Crossover I am using high quality IC opamps and I will be taking great care to match resistor and capacitor values. ESP have high hopes:
Quote:
This unit will provide a completely flat frequency response across the crossover frequency, with the signal from both filters remaining in phase at all times.......It is important with both versions that the filters are properly matched, both within the individual filters, and between channels. While small variations between channels will not be audible, if the high and low pass sections are not accurately matched, then phase and amplitude errors will result.
Quote:
Originally Posted by Khazul View Post
Back to the original question - do you know what amp power you actually need to acheive the listening levels you want for those particular speakers? And what kind of music are you mostly listening to?
I mostly listen to jazz and I reckon my amps have enough power.

Quote:
Originally Posted by Khazul View Post
With your speakers - you would would probbaly want to go closer to 600W combined to leave plenty of head room. In the end it depends what levels you listen at normally and whether this is just hi-fi use or whather you do sometimes review production material at high levels (if thats your thing).
Well, my amps are rated at 140WRMS in to 8ohms, 250WRMS (4ohms). Given a bigger room and a bigger house I could see that higher power amps could be useful. However, I don't think my amps or speakers are anywhere close to straining at the kind of volume that is comfortable. ie, I feel I could 'safely' push my current setup quite a bit louder but not be able to stay in the same room
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