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Old 5th December 2010, 08:21 AM   #3771
markusA is offline markusA  Sweden
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I don't want to fuel the fire any more than absolutely necessary.
Imho there are issues with the sematics.
One could measure the lightspeed and based on the measurements make a statement on whether the distortion figures are good, bad, acceptable and so on.
It is however inappropriate to say that the design is bad, flawed, impossible to use in high quality applications and so forth.

It's quite clear that many people like the design very much and a lot of people rank it amongst the very best products available.

Op-amps measure good but I havn't seen a lot of op-amp desigs in the high end segment... I guess sound does matter.
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Old 5th December 2010, 08:22 AM   #3772
ondesx is offline ondesx  France
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Originally Posted by soongsc View Post
ondesx,
I did not notice any personal attacks in this thread towards you. Whether it be interpreted as such due to cultural differences, I don't know.
Your're kidding for sure...

Quote:
But the main issue is the same "what do we make decisions on, measurements or listening experience". From a consumer point of view, nobody is going to buy into something that seems to measure good but sounds terrible. One reason why consumers don't trust measurements is that the right data is not published....to get the right information based on your own listening experience.
Here there aren't "usual customers" but technicians and DIYers. Normally, these guys are interested in what is going on... Otherwise, the "normal customer", isn't interested mostly because he don't understand a freaking word of these technical data, then he goes to the store, listen to the stuff and then he'll buy what it's allowed by his wallet...

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I have suspected that the main improvement in sound is due to better impedance match over the audio spectrum, and presented some examples of what sounds better than common interface. People are welcome to explore further on their own if they so desire. Some of the minor improvements are resulting from improved continuity of signal transfer medium. The kind of distortion presented might change percieved tone a bit, but certainly not to a point that is objectable.
Impedance is obviously an important issue, but it's very well documented now. There are very simple rules to be followed which will avoid important drawbacks...

Quote:
The simple series-shunt type volume control, whether implemented using LDRs or resistors/pots basically vary in gain and impedance for different positions (Wireless World has a good article published in the 80's on this). So when you are comparing, it's necessary to take many things into consideration, which from what I can see for now, is not done proffessionally.
Again, I'm not sure to understand... Of course the "gain" will vary : it's an attenuator !!! And yes the impedance will also vary : the bridge is constantly changing from one attenuation value to another... All things are equal between the MkI and MkII measurements, and of course the results are perfectly comparable and moreover done by a professional electrician !... But don't take my word, please do the measurements by yourself, you can do it with a good soundboard and a FREE software !... What do you want more ?
Remember that Mr Pass already found at least part of these results and that George also knew all this, as he recalled somewhere above. If you find different results (again, it'll be a very improbable eventuality...) please, let it know to all and we'll have a new, very interesting reason to investigate !
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Old 5th December 2010, 11:26 AM   #3773
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ondexs,

Please take your behavior elsewhere. This used to be a good thread, now it seems to be all about you and your personal attacks on everyone here who answers you.

A had a good afternoon yesterday. Went to a mini-meet and brought my LDR attenuator with me. Posted pictures much earlier in the thread. We substituted it for an Aesthetix Calypso line stage. Power amps are custom 845SE amps, Gallo speakers and an Aesthetix Rhea phono stage. The Gallos use a 2nd voice coil in the woofers, driven by a SS power amp, signal from the line stage. Turntable was a custom Lenco with a huge plinth, JMW arm and Shure VMxR with the Jico SAS upgrade stylus (a very pleasant surpirse to this MC guy).

When we first tried it, there was mixed opinion in the room as to which was better, the Calypso or the LDR preamp (which is George's design with a different power supply and a set of three relay selectable inputs). The bass was deemed a bit flabby. Then we realized we hadn't connected the SS amp to the attenuator. Once connected the bass tightened up very nicely and the LDR stage was clearly better. The system owner thought it was close though.
Next step we inserted a buffer stage, a DC coupled cathode follower, servo controlled between the Rhea and the LDR preamp. I really didn't expect any improvement here, since the output tube of the Rhea is a 6922, and presumably a cathode follower which should have pretty low output impedance. Oh was I wrong. The buffer made a huge improvement: better dynamics, powerful bass, resolution of much finer detail (which in turn led to a bigger, wider, deeper sound field). Better top to bottom.
The system's owner now conceded the superiority of the LDR stage, but he asked about the power cord. I replied that I hadn't experimented with them on the buffer stage. We replaced a home made power cord (using Home Depot extension cord wiring) with an affordable Pangea AC14SE 2 meter cord feeding the buffer stage. Instantly, much finer resolution. I have no idea why this may be, but we all heard it clearly.

Bottom line, LDR preamp wins again, against a $4500+ preamp. But admittedly it lacks remote control, remote phase reversal switch, pretty looks, balanced in/out, etc.

And, don't be afraid to try a GOOD buffer. Relieving the load on your source's output stage can result in better sound, despite the addition of active and passive components in between.

Best of luck to all who try out this circuit. I think you'll be very happy.

Stuart
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Old 5th December 2010, 12:10 PM   #3774
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onedsx

By your own admission it sounds good ( in your early posts )
By your tests maybe the figures are not the greatest.

Soooo what ?

It's not relevant - period.

It came from nowhere....meant that until you came in all of the posts were about advice, tweaks, power supply improvements, impedance matching and how everyone was using theirs generally.
Then there's an argument generated by you about small details that everyone knew already - Mr Pass, George, Soongsc and all the others who have comprehensive understanding of electronics.
I don't have this - but I don't need to - I just rely on the advice of these people and make decisions about whether to take the plunge and try something different.
Good job I did too !!

There are lots of members like me who can solder and assemble things to make music come out of the speakers - there are perhaps not so many with the intelligence and experience of George, Nelson, AndrewT, Soongsc, Uriah and even yourself who I and others rely on for good advice and positive input.

In my short time here this place has never been about squabbling - and at the moment it is.

Andrew
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Old 5th December 2010, 12:11 PM   #3775
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well ,I'm turntable-tubes -FR boy ,distorsion is not problem for me! I use optivol ie mkI

But I never understand why the mkII sound better, two possibility for me:

-ldr resistive element is better then shinkoh or zfoil
-add distorsion (that are there all here know)


Ps

don't replay about ladder and so on please
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Last edited by nicoch58; 5th December 2010 at 12:14 PM.
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Old 5th December 2010, 12:40 PM   #3776
soongsc is offline soongsc  Taiwan
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ondesx,
Can you discribe how one can detect distortion you measured during a listening session?
You, like many others in various cases are just trying to get people mad so that they will post things that you do not know. For people being around forums long enough, this technique does not work. It is not only a disgrace to yourself, but also to the country represented by the flag. It is already clear that you have not done enough research, and it would be much better if you did some more dilligent work to really gain respect. While I have posted much data in various forums, I can only claim that those are what I have learned, but I would seldom insist that I am correct beyond doubt. As a matter of fact, I consistently seek opinions from local audiophiles and dealers to make sure that I am not missing anything. This is a very important process in development of audio products. Trying to attack other products does not show style and dignity. You have already expressed distortion is important, and others feel different. If you cannot bring any more data to support your views, I would recommend that it's best left just like that respecting the optinion of others.

Mind that opinions on impedance issues are also very diverse. Rather than having a fight in a forum, I just went and did things the way I understood and came out with data that is compliant with my listening experience, and the listening experience of many others as well. So what I can say is, if you trust your judgement, just do it rather than waste time in arguements.

As for me, well, I have a good feeling how LDRs can benefit audio reproduction, and it will get in a design when the time and product is right.
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Last edited by soongsc; 5th December 2010 at 01:08 PM.
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Old 5th December 2010, 01:14 PM   #3777
soongsc is offline soongsc  Taiwan
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Anyone with the passion for music that exceeds passion for being technically correct will always improve their designs.
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Old 5th December 2010, 06:01 PM   #3778
ondesx is offline ondesx  France
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It seems easier to admit a wrong simple concept, rather than a true one a bit harder...

Well, from now I stop any discussion with people not interested in technical data about the LDRs, since it's the major reason of the existence of this forum. I'll avoid any discussion about all subjective superiority of whatever circuit...

Then, for all guys who remain interested to understand what is going on and how to improve, if it's possible, this design, please keep posting, for any other reason don't waist your time in posting personal attacks...
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Old 5th December 2010, 06:40 PM   #3779
qusp is offline qusp  Australia
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Quote:
Originally Posted by nicoch46 View Post
well ,I'm turntable-tubes -FR boy ,distorsion is not problem for me! I use optivol ie mkI

But I never understand why the mkII sound better, two possibility for me:

-ldr resistive element is better then shinkoh or zfoil
-add distorsion (that are there all here know)
joking right?
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Old 5th December 2010, 07:00 PM   #3780
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Hey!
I know there is alot of smart,KIND and knowledgeable people here so let's all get along and see if we can get back to making better audio systems,THAT'S why I Like being a member here to learn and improve,and with ALL of you guys help I have succeeded in improvements I couldn't have done or known otherwise!!!!!!!!!!!
Maybe improve the LDR..........
Thanks for listening!
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