Vibrational effects on vintage hifi components

To sum up this rambling (interesting and daft) thread, "The vibrational effects on vintage (and new) hifi components is... near as damn it... ****** all"

[G8HQP Dave]

Actually there is, just, a valid reason for using a valve after a DAC. A valve may cope better with the HF transitions than an opamp, unless the circuit is carefully designed. In most cases, though, CD player valve circuits are designed by people who know less than those who design CD player opamp circuits.

[barrymagrec]

I think in most cases a valve output stage is fitted so that the DAC / CD player can be marketed as "Valve sound" and the price suitably enhanced.

Actually there is, just, a valid reason for using a valve after a DAC. A valve may cope better with the HF transitions than an opamp

And just what is the output stage of an audio DAC, an op amp!

[G8HQP Dave]

Not necessarily. Some DACs output a current, from some sort of programmable or switchable constant-current-source. The standard design then sends this current straight into the virtual ground of an inverting opamp, but this relies on the opamp having enough HF loop gain to cope with the sharp transitions. The obvious solution is a passive lowpass filter before the opamp but this is omitted in many designs.

[Radio Wrangler]

Most C players now use single-bit delta-sigma DAC stages where a fast logic driver switches between two voltages. The art comes in randomising the switching so that within the audio range the mean value carries the signal, and the inevitably huge amount of noise is pushed up to far higher frequencies, making the filtering easy.

It's oversampling carried to the extreme.

There are still some CD players with multi-bit switched current sources and an R-2R ladder, but the one-bit jobs are in the vast majority.

David

[julie_m]

There is another way. Silicon is fine with digital signals, hard ones and zeros that it can't get wrong. You only have to eliminate the use of semiconductors as linear amplifiers.

What if you had a speaker with 16 separate sections of voice coil, binary-weighted and energised via simple on/off switching transistors from the corresponding bits of the digital signal? The speaker itself would be doing the digital to analogue conversion .....

[TonyDuell]

Originally Posted by julie_m

What if you had a speaker with 16 separate sections of voice coil, binary-weighted and energised via simple on/off switching transistors from the corresponding bits of the digital signal? The speaker itself would be doing the digital to analogue conversion .....

I knew somebody who tried to make an '8 bit electrostatic speaker' (8 regions of electrode of the appropriate areas) like that. From what I recall it did not work that well.

[Radio Wrangler]

You'd still need a lowpass filter somewhere in the air between the 'digital' speaker and your ears. Your dog would start howling.

David

[mark2collection]

I know valves can suffer the effects of vibration/microphony, it explains why some vintage radios have their chassis or sub-chassis mounted on rubber blockes/pads et al.

I've had my Leak Stereo 20, Point-One Stereo & Troughline II for a good few years now, the cheapest 'mod' for them in the late 90's early 00's HiFi days of 'must-have isolation platforms' ...(?) Whilst being 'dragged' around the supermarket (Tesco - just a happy customer) they had a variety of granite place-mats going cheap, so I grabbed the ones which looked about the size of the Point One & Troughline II, & a larger 'cutting board' also granite, about the size of the Stereo 20. The stone is in black, all about 10mm thick.

Has it made a difference? Probably not, at least I can now see the wonderful/symmetrical work under the Stereo 20 in the reflection of the polished stone!

Mark