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Townsend Isolda cable
- Thread starter Purité Audio
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Also, how does the rise-time of the transient affect the prorogation velocity?
Again you are avoiding the question. I'm sure you realise the answer.
To be audible a reflection would need to be extremely high in level and or sufficiently moved in time from the stimulus. Otherwise it will be masked.
https://en.m.wikipedia.org/wiki/Auditory_masking
https://ccrma.stanford.edu/~bosse/proj/node21.html
Without actually doing the calc, in typical installations the reflection could be delayed as little as 40nS. To put this into context the rise time of a 20kHz signal is about 17uS.
Run your spice simulation with a 20khz sine and a low impedance (maybe 10mOhms) source.
To be audible a reflection would need to be extremely high in level and or sufficiently moved in time from the stimulus. Otherwise it will be masked.
https://en.m.wikipedia.org/wiki/Auditory_masking
https://ccrma.stanford.edu/~bosse/proj/node21.html
Without actually doing the calc, in typical installations the reflection could be delayed as little as 40nS. To put this into context the rise time of a 20kHz signal is about 17uS.
Run your spice simulation with a 20khz sine and a low impedance (maybe 10mOhms) source.
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It's not even a matter of masking. With a 10-metre cable, the round-trip delay is typically 100 ns. At 20 kHz, this is a phase shift of merely 0.72 degrees. This is utterly insignificant.
Indeed its buried within the original signal. Also 10 m is probably on the long side in domestic situations. IME less than 5m is more typical.
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But he had a video!!!!
solderdude
Grand Contributor
He even has several videos but expect him to feel vindicated by now.
Even though he is correct about the impedance matching thing he is wrong about the audibility of it.
Also the way his data is presented (the video) is kind of misleading unless you dive into it and understand the implications of his method.
His 'terrible sound' ends up as 'as near as imperceivable roll-off' but granted ... the Isolda cable is better at conducting the highest frequencies.
The sound on the video is actually the sound that is lost in the cable and in reality is factors 100 lower in the speaker.
I can even bet my wife too would here the (amplified) sound measured across the cable in the kitchen with the doors closed but am certain she can't hear any differences between the 2 cables from the loudspeakers.
Those using filterless NOS DACs may well be best of with a regular cable though and let the cable lower the stairstep transients and save 2000.- Euros on cables (3-4 meter)
Even though he is correct about the impedance matching thing he is wrong about the audibility of it.
Also the way his data is presented (the video) is kind of misleading unless you dive into it and understand the implications of his method.
His 'terrible sound' ends up as 'as near as imperceivable roll-off' but granted ... the Isolda cable is better at conducting the highest frequencies.
The sound on the video is actually the sound that is lost in the cable and in reality is factors 100 lower in the speaker.
I can even bet my wife too would here the (amplified) sound measured across the cable in the kitchen with the doors closed but am certain she can't hear any differences between the 2 cables from the loudspeakers.
Those using filterless NOS DACs may well be best of with a regular cable though and let the cable lower the stairstep transients and save 2000.- Euros on cables (3-4 meter)
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The terrible sound IS NOT a roll-off. It is an increase brash sound that is clearly audible. In the last 30 years we have sold thousands of sets of cables to many fussy audiophiles who can hear this distortion and choose to stick with these cables. I can see that you are not prepared to believe there can be such an audible difference.
There are many audiophiles who have good sound as their passion and are easily prepared to pay for the hard work necessary to produce first class cables and their systems are good enough to resolve this. It is no accident that we get awards see http://www.townshendaudio.com/the-ear-the-best-of-2013-townshend-isolda-speaker-cable/ http://www.the-ear.net/review-hardware/townshend-f1-fractal-loudspeaker-cable https://www.hifiplus.com/articles/townshend-f1-fractal-loudspeaker-cable/
There are many audiophiles who have good sound as their passion and are easily prepared to pay for the hard work necessary to produce first class cables and their systems are good enough to resolve this. It is no accident that we get awards see http://www.townshendaudio.com/the-ear-the-best-of-2013-townshend-isolda-speaker-cable/ http://www.the-ear.net/review-hardware/townshend-f1-fractal-loudspeaker-cable https://www.hifiplus.com/articles/townshend-f1-fractal-loudspeaker-cable/
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solderdude
Grand Contributor
I have witnessed audiophiles stating they can hear improvements in cables when I merely suggest the cable has been changed when in reality I did not change the cable (not Isolda but Dynaudio) and reported the 'bad' sound returned when I then had the Dynaudio cable inserted while telling them the old cable was back in the system. This was done at their home.
Of course I never told them the truth so as far as they know the differences were real.
We (the hifi shop I worked at in that time) also had a month trial period for every cable. If they could not hear the difference they could return it.
Nobody ever returned ANY cable (be it interlink or speaker cable of any brand).
I believe this says something about audiophiles.
NOT saying your cables aren't great products that deliver what they promise. They seem to do... just questioning the true abilities of audiophiles
Of course I never told them the truth so as far as they know the differences were real.
We (the hifi shop I worked at in that time) also had a month trial period for every cable. If they could not hear the difference they could return it.
Nobody ever returned ANY cable (be it interlink or speaker cable of any brand).
I believe this says something about audiophiles.
NOT saying your cables aren't great products that deliver what they promise. They seem to do... just questioning the true abilities of audiophiles
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It's only correct when cable length is a significant fraction of wavelength. Which has been repeated enough times (and was examined decades ago by Davis and Greiner) for anyone honest to understand what bill of goods is being sold here.
There's cheaper and better ways of hooking up shortwave transmitters, if that's the goal. And far cheaper and better ways to hook up speakers for audio frequencies, where lumped LRC describes things perfectly well.
Audiophiles hear all sorts of things that simply aren't there. When put under controlled conditions they fail.
It's simply the bias of sighted comparisons, an issue they always refuse to recognise.
restorer-john
Grand Contributor
So Dr Murray is still alive is he? How old is he now, surely he must be 100+ years old?
I recently (a few years ago) restored and tested one his creations (a Murray integrated amplifier K106) for my (85yo) audiophile father, as he likes to buy odd and rare pieces from the 1970s to play with (and get me to 'look at' i.e. fix if they need it...) This amp is a classic 1970s design. All Philips semis, classic BC549C (ooh, low noise) TO92s, motorola T03s, a beautiful flux strapped Aussie made transformer, heaps of tantalums and a PA amplifier type construction. That said, the chassis is aluminium, countersunk flush screws and clearly utilized considerable thought in design. All the PCBs are fibreglass and stacked, edge connected and nicely hand routed.
Issues are numerous and the frequency response plot has to be seen to be believed. It is the worst I have ever seen in any commercial product.
I kid you not. (if you want to see it, just ask)
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restorer-john
Grand Contributor
So, I picked up an LFD linestage and matching power amplifier several years back at a bargain price. One of Bews' and Hawksford's early efforts with a mosfet TO3P output stage, Corian front panels and an instability that made it impossible to actually test the unit without partially vaporizing parts. There was a small, sub board, that looked like a modified prototype and it was soldered by someone with a plumber's iron or simply no idea whatsoever. I sent Dr Bews some pictures and asked for an explanation . The reply was nasty, dismissive and that was the end of it.
I sold the units at a vast profit (north of 4 figures), after I had replaced a bank of resistors that were cooking the PCBs because they were mounted too close and promised never to touch Low Fuzzy Distortion (LFD) gear again.
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I am asking
Of course there is, the frequency dependence only drops out for the simplifying assumption of lossless lines, which doesn't remotely apply here. https://en.wikipedia.org/wiki/Telegrapher's_equations
Me too.
^^^ So the good news is the amplifier no longer really matters; most of the time the speaker load will dictate the frequency response no matter the output impedance of your amplifier.
restorer-john
Grand Contributor
Me too.
Well, here you go gentlemen, I dug out the images from 2016.
The purple and red is before I tweaked the balance control to balance the channels. The green and white is a best case 'flat' frequency response of the integrated amplifier at (1W/1KHz/8ohm (2.83V) preset before sweep). Eeek! -13.5dB at 20Hz and -3dB @20KHz It was so bad I ran a loop-back to make sure my gear wasn't broken.
Was it the preamplifier or the power amplifier or both? I investigated this further by feeding direct into the power stage internally and got this (1W/1KHz/8ohm (2.83V) preset before sweep):
Around -3.5dB @20Hz and -0.7dB @20KHz- slightly better. So, it was a combination of the preamp stage and power amp stage. Basically it tested and sounded like a PA amplifier (Murray also made PA amplifiers under the Auditec brand). It does have a 'softness' control which when activated gave the response below, not unlike a typical loudness, except it is not linked to volume position. It does however, make the amplifier partially listenable.
These are screenshots from my trusty old AudioLab hardware.
Murray's basic construction and component quality was excellent for the mid 70s era. A few glaring (and dangerous) mistakes in design, but I didn't reverse-engineer the unit to work out where all the issues lay as it was bought just for curiosity and designed by a 'legendary' Australian. Judicious use of the tone controls could partially flatten the response, but the extreme adjustments required to do so were ridiculous. I was tempted to unscrew the knob screws and re-position the zero point, but just left it, as it really wasn't flat in any case.
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