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Old 22nd May 2012, 03:50 AM   #5701
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I used to make shock absorbers for 6F32P tubes from mouse pads. Then glued a nut on nuvistors, nuvistors glued to circles made of mouse pads. Then used 6S17K-V missile tubes and found that they are dead silent without any pads.
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Old 22nd May 2012, 08:20 AM   #5702
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Wow!

Shock absorbers? Oil or gas? Regular or shortened and hardened?

How about the rubber? Tubeless or not? Slicks or not?

Will we need a summer and a winter thread? Hey, this sounds like a great after market sales idea - chnage your damping for just $999.99.

Low sprung chassis, adaptable so people can adjust for their hearing.

What? This is NOT the car thread? Sorry, I got my bearings wrong.

I mean look folks, I agree vibration can be a major problem, especially with high to very high gain devices such as TTs and microphones, and its elimination can be beneficial to practically all equipment. However, my experience shows that the benefits with MOST equipment are low.

Upon installing the SoundCare (from Norway) anti resonant feet on most of my equipment, I could not hear any difference, except in case of the CD player (Yamaha CDX 993), where this yielded a very slight but still audible improvement in the bass range, which became a little better defined, and more firm. The main beneficiary was the TT, of course, and I use MM; I expect that with MC, this benefit would have been even greater. I don't use mics, so I can't comment on that.

Knowing that everything vibrates anyway, I did take some precautions - the gear is on a hard, massive surface, with very good coupling to the floor. The TT is shielded from the outside world on all except the front side, which surely can't hurt. Lastly, the sound levels present in my room rarely go from semi-quiet to thundering (on occasion I do succumb to my Dark Side), typical range being 85...90 dB SPL.

On my own gear, I always put silicon paste around any larger cap's bottom, where "larger" means 100 uF and above. Power transformers are always put on rubber rings on all points, which is usually the one point, as they are mostly of the toroidal type.

How much further should I go?
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Old 22nd May 2012, 08:49 AM   #5703
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Default UA 709 and 741

Click the image to open in full size.

Just though these worth a look . Reading up on 741 was something I enjoyed when I did it .


As far as I can see adding a 220 R output resistor to uA 709 was the only big deal difference ( current limiting ) . I am sure at the time it seemed different . uA 709 has a respectable performance on paper considering it's antiquity .

About 20 nV noise if memory is correct with 1 MHz GBP for 741 . A pull down resistor to give a class A output if small signals ( 4K7 ) . I would imagine if using a passive ( 75 uS ) followed by active ( 318 / 3180 uS ) a moderately good phono stage for MM could still be made with it even today if using the pull down resistor on the 75 uS . Gain of active stage 16 at 1 kHz if so ( 4 x uA 741 ) . Total gain 100 . Use polystyrene for 75 uS ( 10 nF + 7K5 ) and film for the rest . It is always good to build something like this just to be certain real progress is happening . If using an IC socket the history of op amps can be listened to . Much more fun than watching soccer . I would elect Grado as a good modern PU . I like Shure 44/7,one day I intend to re-tip one with a very high quality diamond ( Expert PU in UK ) . 9.5 mV is not to be sniffed at . Shure's like 1 M ohms loading . Then adjust 75 uS to get a good 20 kHz ( do the other EQ if you like ) . That would be the PU to me with the maximum dynamic range and far less costly than my Lyra . If you have never heard a modern 44/7 in a good pick up arm you have missed something . Better than Decca London to my ears and better for the records . Stereo separation is about 15 dB down on my Lyra . Not certain it matters too much .
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Old 22nd May 2012, 09:16 AM   #5704
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Default Vibration

Some RAF guy gave a talk at the Whittlebury hi fi show about measuring effects of vibration and other mysterious things .

He used a time domain before and after encoding of the information and seemed to show big differences . Talking to Richard Black afterwards he seemed skeptical . Tim de Paravacini also . He said he had tried it years ago and was not satisfied it was reality ( sorry Tim if that's not exactly true , that's how is seemed to me ) .

The RAF guy was certain it worked as it was a tool of his trade and not hi fi .

I strongly opposed this a Nordost were sponsoring it and it seemed a new expensive diversion . Very unusually for me I said no way to this . If it is provable it will grow it's own ability to prove itself . I doesn't need me . I was silenced in the meeting as I got on too well with the RAF guy who was starting to do the maths with me . The comment was approximately " for people who don't know Nigel he has very long conversations which we don't have time for " . My conversation was to be about 1 minute . It was how did we get from A to B , show me the machine so that I can build a primitive one . As far as I can see they were just doing A to D encoding and doing statistical analysis with the original . That is assuming a lot I feel .

I should add the people I work with would benefit greatly if this could be proved to be correct . I still opposed it . I much prefer we listen and decide . If not how can one be a romantic fool in this world ? I am one if asking .

Last edited by nigel pearson; 22nd May 2012 at 09:29 AM.
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Old 22nd May 2012, 10:18 AM   #5705
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I believe in oscillation of Universe that consists of big bangs and big collapses.
I believe you need as much belief to believe in the big bang as to believe in the invisible guy in the sky as the origin of everything.
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Old 22nd May 2012, 01:13 PM   #5706
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Nigel, you surprise me. You seem to have had long and meaningful conversations with 'everybody and his brother' in audio, (I have had many of the same, with most of the same people), yet your 'conclusions' seem 'scattered', virtually random, each having merits in some situation, but generally very limited.
For example, bringing up the UA709 and the UA741. If you want two examples of perhaps the worst op amps for making a phono stage, you have hit the target. But do you know why?
First, the UA709 has a CLASS C output stage. The only way to fix it would be to put a resistor (at the very least) to the -supply from the output. A jfet would be much better, to remove the 'dead zone'. However, even if you did that, the internal phase shift characteristic of that design would limit your slew rate to less than 1V/us with unity gain compensation (external). What a mess! What a headache!
AND today, for about $1, more or less, you can buy a quieter, jfet input, faster, and more linear IC, with no need for external compensation caps, and short circuit proof.
The UA741 has different problems. It was a wonderful invention, back in 1969, when I was designing video servos for Ampex Research, but in trying to use it for audio, I found it SLOW, (0.6V/us), a true 'poster-boy' for TIM distortion', and NOISY, because the first stage active load adds additional noise to the input.
What is the point of bringing out these two 'dated' IC's that probably cost MORE to purchase than something more up to date?
Now, don't get me wrong, everyone. I LOVED these devices, when they were first introduced. Did you know that the original UA709's cost about $100 each? They were a 'Godsend' to military designers making compact circuitry. We used them as early as 1966, in the hundreds, at Friden, and I was put in charge of characterizing each and every one of them for offset, distortion, etc, over temperature. I tested 100 of them, with a custom tester, the schematic provided by Fairchild. They reduced a whole card of discrete parts into a little case, about the size of a typical transistor of the day. It was almost a miracle!
When the UA741 came out, we used them by the 100's at Ampex for servo design. They were great for this application, because they were input-output overload proof, and they did NOT require added cap compensation. I would still use them today for that application, but they were LOUSY audio IC amps, and it took us years to show everyone how bad they were, because some audio companies, even big ones, adapted them to save space and money, to the detriment of audio quality.
Even the major designer behind these products, Bob Widlar, in 1974, told me that these IC's were NOT designed for audio, and that we should make our own audio designs.
Today, there are at the very least, cheap and usable alternatives to these early, primitive IC's. Enough said, at the moment.
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Old 22nd May 2012, 02:47 PM   #5707
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@JC

Exactly. Eeverything has its time, its five minutes of glory, and is then surpassed by another device.

For example, even LF 356 or 357, with their FET inputs, were great stuff - but in 1981. Today, they look absolutely antiquated, even if they are still perfectly usable.

The TLO series is another oldie but goldie - I've seen them used literally everywhere, right or wrong.

But, today I have a stock of AD817, AD827, AD829, etc. The only oldie I still have much respect for in audio is the venerable OP37, the decompensated evil brother of OP27. It stubbornly refuses to fade away and manages to sound really good even after all these years.
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Old 22nd May 2012, 03:22 PM   #5708
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@JC

The only oldie I still have much respect for in audio is the venerable OP37, the decompensated evil brother of OP27. It stubbornly refuses to fade away and manages to sound really good even after all these years.
Designed by George Erdi a former neighbor from just north of you.
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Old 22nd May 2012, 04:06 PM   #5709
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Even the major designer behind these products, Bob Widlar, in 1974, told me that these IC's were NOT designed for audio, and that we should make our own audio designs.
It is true even today, and will be true forever, like tractor is always suboptimal to be a racing car, opamp is suboptimal for audio amplifier.

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Wow!

Shock absorbers? Oil or gas? Regular or shortened and hardened?

How about the rubber? Tubeless or not? Slicks or not?

However you can use mouse pads for cars, but do not expect it to last long enough.


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I believe you need as much belief to believe in the big bang as to believe in the invisible guy in the sky as the origin of everything.
I believe in what you said.
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Last edited by Wavebourn; 22nd May 2012 at 04:15 PM.
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Old 22nd May 2012, 04:20 PM   #5710
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I hope I have not been too 'strong' on this topic, but 'reason' must prevail, even though I am often attacked as 'unreasonable' on this website.
It kind of reminds me of a parallel situation, where enthusiasts are recommended to drive two (restored) autos across Europe. Let's say that I recommend a 2-CV, or a Renault Dauphine? Let's say that I found these autos enjoyable in my experience and they have quite a heritage. Well, car enthusiasts?
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