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Old 18th January 2003, 03:57 AM   #151
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Quote:
Originally posted by Peter Daniel
An old Dyna Reflex, pretty nicely built actually.
Don't think i've ever seen one of those... shouldn't you be in bed... don't you have to go on holiday tomorrow?

dave
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Old 18th January 2003, 04:35 AM   #152
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I'll get some sleep on the airplane. I hope I'll get internet access were I'm going
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Old 18th January 2003, 05:35 AM   #153
Wombat is offline Wombat  Germany
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Most interesting will be the sound of Cuba!

No place sounds like the other!
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Old 18th January 2003, 11:09 AM   #154
Bobken is offline Bobken  United Kingdom
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Quote:
Originally posted by fdegrove
Hi,



Neither copper nor alu will effectively shield against RFI.
Copper is very effective to combat EMI.

RFI can be tackled at the input of the amp by means of filtering (usually this limits the bandwith too),a small .01 mF ceramic cap across the input is quite effective or the use of a steel enclure is very effective as well.

Cheers,
I am surprised at you Frank, you naughty man! Ceramic, indeed!!! And after all we have discussed about the sound of components, too!

Another anecdote coming on, I'm afraid.

It was just this same kind of situation which first started me on 'the road to ruin', or at least to discovering that
not all similar components sound alike, and which has occupied so much of my spare time, not to mention my bank balance, ever since!

About 35 years ago, I would have said exactly the same as you just did, since, of course, ceramics are good at HF because of their quite low inductance. Also, like everyone else at that time, I had been indoctrinated by conventional wisdom into believing that *all* caps will sound the same as any other cap of exactly the same value, irrespective of type or manufacture.

However, about that time JLH sent me a prototype moving coil head amp, which he was intending to sell in small quantities
through his own cottage industry business, for a second opinion on its 'sonics' before he finalised it.

Unfortunately, I was plagued by RFI in my location when I plugged it in, and after phoning John for his suggested 'cure', it was agreed that I should try a slightly larger cap across the input (from the already existing very low value ceramic one), in the same manner as you have suggested here.

Regrettably (or fortunately, depending upon how you view it!) I didn't have a suitable value of ceramic to hand to replace the existing ceramic cap, so I tried a polystyrene, instead.

I 'knew' that it wouldn't be so good as a ceramic, because of the higher inductance and impedance at HF, but decided to try it out merely to see if this was the best route to curing the breakthrough, and to gain some idea of the value of ceramic caps I would subsequently need to order up to do a more permanent job.

Well, to say that I was amazed at the difference in the overall sound when the MC pre-preamp was plugged in again would be an understatement, and the head-amp sounded like an entirely different and much better unit throughout the audio spectrum.

Some earlier apparent harshness or grittyness had vanished, completely, and the sound was soooooooo much nicer to listen to in the mid and upper frequencies.

I simply couldn't understand this, so I spoke to JLH who was convinced I had imagined it, or (as we both concluded) he suggested I must have disturbed something else in the changeover of the caps.

I therefore retraced my steps, and the sound deteriorated, and I then did this swap many times over again, all with the same consistent results, and I also tried some other types of cap I had to hand, like polypropylenes etc.

During this time it became clear that (within reason) the actual value of the caps tried was not of much importance to the sound changes which I was clearly experiencing, and that all of these caps were showing a kind of family semblance.

In fact, the differences I heard were so obvious that I sent JLH a list of my ranking order of 'sonic goodness', which some time later I discovered agreed very well with the DA of the caps I had tried.

The rest, as they say, is history.

What I would recommend in a location like that which you have suggested, would be perhaps a stacked-foil (to keep inductance as low as possible) plastic film or maybe a silver mica, both of which should have far less adverse effect on the resultant sound than any ceramic I have ever come across. I would also experiment with different values to ensure that the minimum value possible is chosen to effect the desired 'cure', and yet avoid too much harm to the signal at HF.

Sorry to get a bit off-topic, but I hoped this might help.

Regards,
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Old 18th January 2003, 11:56 AM   #155
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Default NAUGHTY FRANK.

Hi,

Bob,

I must admit I didn't give it any further thought,the method I suggested is what is commonly done.

Personally I'm lucky enough never to have to resort to that.

It is quite likely that a better quality cap in that position (a shunt) will yield better sonics.
If it is just as effective at killing off RFI then, by all means, use the best possible cap,smaller values often sound better than larger ones IME.

Cheers,

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Old 31st January 2003, 12:42 PM   #156
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Hi,

I've finally made it to the las post in this thread. I'd really like to understand the subject of mechanical-engineering choices in hifi so that I can predict what tweak/ technique will work and which will not. So far I've not been been able to get a full grasp of the subject, especially since the article that I found speak against each other and all have some omissions in their proof that their product is the best to buy. I'm only getting more confused and amking my stuff more vibrations proof would be a matter of trial and error, so I'd like to have a conclusive theory rather than anecdotes.

It seems that it falls into two different discussions:
1. The choices made to reduce vibrations.
2. The choice of material for the casing (wood/aluminum/steel/mu-metal) etc

Ad 1: It seems that coneshaped spikes work, otherwise speakerbuilders would not invest money in them and people would not have paid money for them for such a long time. I'd like to think of spikes as the oposite of a stetoscope. I'm still hessitant to call it a sonic diode, but I would not know any electrical component that would be a good analogy for this.

Aircushons/ springs/ rubber bands etc can be compared to a coil. They can store energy, and the higher the frequency the higher the resistance.

A heavy stone tile as in the setup of Peter Daniel can be compared to a capacitor.

Furthermore it seems that all materials have a specific resistance to vibrations and therfore can be compared to an electrical resistance. I think that Does anybody have a table that gives an overview of this for different materials? Peter mentionod that acrylic absorbes (high resistance) a lot of vibrations.

Does the ratio mass/surface have influence? If so Peter's gainclone is a real beaty to look at but might not be the best in the vibrations department.

Furthermore I know that in in the old days the high end turntables used springs. Nowadays they don't. Why?

Ad2: Of this I know very little. I'm surprised to hear that different kind of woods/metals have different sounds. Does anybody have a theory on that ? (other than shielding from RFI/EMI)




Cheers,
Andre
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Old 31st January 2003, 02:37 PM   #157
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This is a quote from 47 Laboratory site, concerning suspention for their Flat Fish CD transport:

>Full-hard-suspention system

The platform/casing of Flatfish is a 2/3 inch thick, machined aluminum board. All the driving mechanisms, pick-up mechanisms and the circuits are directly mounted on this one piece of aluminum board.
The huge difference between the mass of the mechanisms and that of the platform (150g against 1200g) enables to cut off the vibrations caused by the slight off-centering of the disks and the tracing mechanisms returning to the bit-tracing lens itself, allowing us to minimize the amount of servo control dramatically.
This rigid and compact structure of the platform has a very small surface area to receive the vibrations, and its large mass helps to reduce the vibrations smoothly and effectively without any extra damping or suspensions.
As a result, storage of vibration energy was minimized, letting us achieve a refreshingly quick transient response. Compared to the conventional box-type chassis/casings, this platform is almost completely free from any stress of construction. Now, you can hear how much harmony and bottom-end information was obscured under those mechanical stresses.<<
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Old 15th December 2011, 11:05 PM   #158
a.wayne is offline a.wayne  United States
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Bringing back this oldie ...

I need to get moving on my amp chassis and wanted to see what are the collective thoughts on the different materials available, steel is the best for noise rejection , aluminium for heat rejection..

Anything new to add to this about the sound of different materials , i prefer to work with aluminium, and of course i will have steel on the inside to shield the transformers and the noisy bits..

Steel is more difficult to work with ... well for me ... Thoughts ..?
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Old 15th December 2011, 11:34 PM   #159
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With proper layout and grounding, aluminum will work fine for noise and it's easier to machine (my RLD gives better than -90dB unweighted S/N). If your grounding and layout aren't proper, the chassis material is the last thing to worry about.
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Old 16th December 2011, 12:40 AM   #160
a.wayne is offline a.wayne  United States
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So aluminium will work without degrading the sonics..? I know layout is important as is the gnd circuit , what is considered , best ? don't intend to reinvent the wheel, was planning on following basic stuff from others that work ..


Well after peeking in my Threshold .....
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