The Audiophoolery Thread.

[Beobloke]

Originally Posted by Sergeauckland

There is none in the A500. It's an artefact of the measurement method. If the input and output measuring instruments share a ground connection, there is a small amount of crossover distortion in the residual. However, if the measuring instrument has a differential input without a ground connection, there is no crossover distortion.

In normal use into loudspeakers, loudspeakers do not share a ground connection with the input, so there is no crossover distortion.

It did take me a while to work that out, but the three I have here all behave in exactly the same way.

S.

Well the Rodhe & Schwarz UPV it was tested on definitely has balanced inputs. What test frequency were you using?

[Radio Wrangler]

Is this a case of something giving decent linearity in the differential signal while there might be all manner of unwanted products on the common-mode signal?

What you think you're getting depends on the CMRR of whatever is receiving the signal.

A two-wire differential connection has two dimensions of freedom.

David

[Sergeauckland]

Originally Posted by Beobloke

Well the Rodhe & Schwarz UPV it was tested on definitely has balanced inputs. What test frequency were you using?

1kHz, 8ohms
If you look at the distortion residual using a floating balanced input on the Distortion meter, there is no sign of crossover distortion. If you connect the loudspeaker -ve terminal to ground, a small spike at the zero crossing, i.e. crossover distortion, is visible. I put this down to some coupling between the input ground and the output, but don't know where this coupling occurs.
In normal use into loudspeakers there's no issue, as loudspeakers are normally floating, but with a distortion measuring set where the signal generator and measuring instrument share a ground, it shows up.

S.

[knobtwiddler]

Here is a fun article: https://www.theaudioinsights.com/bac...ritic_20_r.pdf

The letters pages are quite prescient in my mind, as the mag's from 1993, and some of the submissions are questioning the validity of various tweaks. 30 years on, we're still having many of the same arguments. At least 2 of the letters are submitted by people with engineering qualifications who've developed products (E Barbour and John Hardy). Plus ca change!

Serge - I have a UPV at the workshop. I don't have a Deadringer amp to try, but I can possibly simulate a test if that's of interest (the I/O is floated / grounded via relays). I have 200W dummy loads, but do not have a reactive load.

[Beobloke]

Originally Posted by Sergeauckland

1kHz, 8ohms
If you look at the distortion residual using a floating balanced input on the Distortion meter, there is no sign of crossover distortion. If you connect the loudspeaker -ve terminal to ground, a small spike at the zero crossing, i.e. crossover distortion, is visible. I put this down to some coupling between the input ground and the output, but don't know where this coupling occurs.
In normal use into loudspeakers there's no issue, as loudspeakers are normally floating, but with a distortion measuring set where the signal generator and measuring instrument share a ground, it shows up.

S.

1kHz is indeed the standard value for testing crossover distortion and at this frequency, I absolutely agree that the A500 turns in a very good result.

However, we silly audiophools couldn't tally its good measured performance across the standard suite of amplifier tests with the terrible sound it produced when we had it in for review at Hi-Fi World magazine, so Noel Keywood did some further digging and......well, lets just say, try running your crossover distortion test again at 10kHz...

[Sergeauckland]

Originally Posted by knobtwiddler

Here is a fun article: https://www.theaudioinsights.com/bac...ritic_20_r.pdf

The letters pages are quite prescient in my mind, as the mag's from 1993, and some of the submissions are questioning the validity of various tweaks. 30 years on, we're still having many of the same arguments. At least 2 of the letters are submitted by people with engineering qualifications who've developed products (E Barbour and John Hardy). Plus ca change!

Serge - I have a UPV at the workshop. I don't have a Deadringer amp to try, but I can possibly simulate a test if that's of interest (the I/O is floated / grounded via relays). I have 200W dummy loads, but do not have a reactive load.

I suspect it's something peculiar to the Behringer amplifier, as no other amplifier I've tested has ever done this. My normal distortion measuring set (Ferrograph RTS 2) has unbalanced in and out, with the ground common to them both. If I use this with any amp except the Behringer, it doesn't show any sign of crossover distortion.

If I use my PC-based distortion measuring set, which has balanced I/O, I don't get any crossover distortion. Using a transformer to balance the Ferrograph input so the amplifier output -ve is not grounded, that too shows no crossover distortion, so my conclusion is that there's some interaction between the Behringer input and output grounding that's causes crossover distortion when they're connected together, something that doesn't happen when the amplifier is driving loudspeakers.

S.

[fetteler]

Again, the discussion is getting far to rational and measurement based!

Does anyone remember the brief exchanges in the letters pages of Wireless World sometime in the mid/late seventies when the spoof concept of Tied Electron Distortion (TED) was suggested? The so called idea was designed to excite the Audiophool reader and show them up a bit: basically the (non existant) problem was that electrons in the speaker and speaker leads would eventually become 'fatigued' and 'worn out' by constant cycling back and forth in the same bit of conductor. This, of course, results in a soggy worn out sort of sound...

The suggested cure was very simple - have a small DC offset present at all times to ensure a fresh supply of electrons in the output. Lovely!!!

I can't recall too many WW readers falling for it....


Steve.

[Radio Wrangler]

I think there's a typo. The fates dictate that such must hit the worst place. Tied, Tired?

David

[Sergeauckland]

Originally Posted by fetteler

Again, the discussion is getting far to rational and measurement based!

Does anyone remember the brief exchanges in the letters pages of Wireless World sometime in the mid/late seventies when the spoof concept of Tied Electron Distortion (TED) was suggested? The so called idea was designed to excite the Audiophool reader and show them up a bit: basically the (non existant) problem was that electrons in the speaker and speaker leads would eventually become 'fatigued' and 'worn out' by constant cycling back and forth in the same bit of conductor. This, of course, results in a soggy worn out sort of sound...

The suggested cure was very simple - have a small DC offset present at all times to ensure a fresh supply of electrons in the output. Lovely!!!

I can't recall too many WW readers falling for it....


Steve.

I remember a series of cartoons by OddBod (Geoff Jeanes) which lampooned some of these silly ideas. Quad used them in their advertising.

However, the DC offset nonsense has been taken up by one of the cable manufacturers with battery polarised cables

S.

[fetteler]

Originally Posted by Radio Wrangler

I think there's a typo. The fates dictate that such must hit the worst place. Tied, Tired?

David

It was definitely tied alluding to the fact that the electrons in the speaker circuit are 'tied' to the same average place along the conductors.

Steve.

[Radio Wrangler]

Ah, I thought the electrons were tired-out. As in the famous Monty Python phrase "....ed-out after a long squawk"

No typo then. Sorry

DAvid

[fetteler]

Well I'm sure tired electrons would give just as much - if not more - of an audible effect to the right ears!

Steve.

[Craig Sawyers]

Who can ever forget A Decade of Tuning Tips, Part Two (no one has ever found Part One!). Free with Hi-Fi Answers, May 1989.

Here are some excerpts https://hifi-writer.com/wpblog/?p=132 and https://hifi-writer.com/wpblog/?p=3216

Craig

[fetteler]

I just had a read - delightful!

Now, where's a nice sheet of plain paper?

Steve.

[G.Castle]

Originally Posted by G.Castle

OK! have we done Nordost Odin 2 speaker cables yet?

Good value at $29,999 a metre.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Once again they have excelled themselves.

https://ripcaster.co.uk/Nordost_Odin...r_Cable?v=4406

If you're having trouble with that price, it's:

Eighty four thousand, four hundred pounds.

[deliverance]

Nordust are full of it just when you thought $29.999 was pushing it to the extreme and beyond Odin pops up at $84.400 . Them that can hear things nobody else can will be pleased ? Now where are my sheets of White paper .

[Craig Sawyers]

Originally Posted by G.Castle

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Once again they have excelled themselves.

https://ripcaster.co.uk/Nordost_Odin...r_Cable?v=4406

If you're having trouble with that price, it's:

Eighty four thousand, four hundred pounds.

Say what? No wait - I clicked the link. I cannot un-see it now

[Radio Wrangler]

As the cable probably does nothing special, I expected at least £83,980 worth of beautifully-crafted prose justifying their existence in my system.

David

[ppalped]

Sometimes I wonder if the people designing and selling this kind of absurdly-expensive-cables actually believe that they can hear the difference, or if they just sit tight on their desks all day thinking how to write the next null sentence for a product description that, on one hand won't get them in trouble with any kind of law suit, but on the other hand it would make sense to some people that have nothing else better to do with the money.

Anyway... every time I wonder about this, I end up with same conclusion.

Alex

[Radio Wrangler]

These are aspirational products. They probably don't expect anyone to buy actually one but their very existence and price casts a glamour on the rest of their product range and hence helps along the sale of their 'lesser' products. They do have to make some, just for them to go out and get reviews.

When I moved to this part of the country, there was a famous restaurant several miles away. It was only famous for being expensive, not for the food or the 'atmosphere' but everyone knew of it and its prices. It did well. People took other people there when they wanted to impress them with how much they were prepared to spend on them. Human psychology moved the hifi industry firmly out of the 'Let's make a really good....' era after the 1970s.

They can fool enough of the people enough of the time.

David