You are confusing PIM with PIM. RF folks refer to passive intermodulation distortion, caused by things like a bit of corrosion on the connectors, as PIM.
A real concern where you just might have a transmitter close to a receiver like in a cell phone tower.
The argument here is Phase Intermodulation Distortion. The theory is that as Vce changes across the bipolar transistor in a gain stage the Ft changes resulting in a difference in the phase shift of that stage.
Neither is to be confused with PIM a condition caused by some contributors here. That of course stands for P'd in mine (text... Contribution, etc.)
Well how do you know then, if you don't measure it? Ohh wait, you have specially tuned golden ears that pick up PIM with uncanny accuracy?
Jan
Well done John. One day one of these people will say ears are not the prime use of op amps and with a little thought we will have to say that's right. We could have a world with no people where the self driving cars live on. Aliens would detect that a primitive type of organic engineering had struggled against the inevitable in a brief past. Perhaps the machines would doubt we ever existed. Unlike some I don't really bother much about this except to say if it happens we wanted it.
Don't you wish Michael Gerzon had lived? He would have told me me off and I would have been educated into the bargain ( usually I'm just told off ). I wish I had tape recorded Michael on digital when to be honest it wasn't very good ( 1985 ? ). Like a flower opening he showed me the future. It wasn't what he said. It was the 100 % honestly and belief he had. As someone who lived better in print the internet would have been so good for him. Hey Ho.
Don't you wish Michael Gerzon had lived? He would have told me me off and I would have been educated into the bargain ( usually I'm just told off ). I wish I had tape recorded Michael on digital when to be honest it wasn't very good ( 1985 ? ). Like a flower opening he showed me the future. It wasn't what he said. It was the 100 % honestly and belief he had. As someone who lived better in print the internet would have been so good for him. Hey Ho.
My girlfriend and I had an arguement about bath verses shower last night. I said a bath is cleaner as I knew that would be opposite to how she had been " trained " to think. To take away any chance of her being right I said we should do hair last and shower as a 100 % way to do it. Most baths can offer that.
I was very surprised no one on forums said that. Most polarised around one is better. All I can say is my better ideas were either walking up the canal in Oxford to where the car was parked or in the bath. Never in the shower. Maybe the -ve ions do matter? Or am I imagining it.
She and I met by her starting an arguement. I knew she liked me.
She now wants a kitchen as big as the ground floor and says" people mostly live in the kitchen these day". I don't.
I was very surprised no one on forums said that. Most polarised around one is better. All I can say is my better ideas were either walking up the canal in Oxford to where the car was parked or in the bath. Never in the shower. Maybe the -ve ions do matter? Or am I imagining it.
She and I met by her starting an arguement. I knew she liked me.
She now wants a kitchen as big as the ground floor and says" people mostly live in the kitchen these day". I don't.
John said "We generally don't even MEASURE PIM....", the use of 'generally' implies that some do.Well how do you know then, if you don't measure it? Ohh wait, you have specially tuned golden ears that pick up PIM with uncanny accuracy?
Jan
PIM is another signal dependent noise/error that does not belong and is readily discriminated by the ear.
It manifests as time shifted non harmonic noise products (IM in nature) appearing in the soundfield.
The result is noisiness/imprecision of depth information for mono signal, for stereo the result is same depth obscuring plus LR positional accuracy noise/imprecision due to phantom sound sources appearing in the soundfield.
These phantom sound sources are constantly and unnaturally moving and this is the clue to the ear.
These unnatural sounds in the soundscape are strong source of unintelligibilty and listening fatigue due to the brain having to filter out these unnatural sounds and positions.
Once you have identified this distortion source you will realise you have heard it a thousand times.
Low gain and open loop systems reduce these noisey distortion products, and sound 'open and free' despite typically higher levels of thd and linear distortions.
Dan.
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I think he said quadrature, not vector. There are no vectors in a scalar signal. The 'j' notation and complex exponential function is a mathematical trick to keep track of phase. Anyway, you admit that PIM is measured as just another component of IMD or harmonic distortion. It perhaps is not distinguished from IMD due to other sources of nonlinearity but why should it be?john curl said:
Time shifted? By how much? As PIM comes from voltage dependent junction parasitic capacitances I would expect that it occurs at exactly the same time as the signal provoking it, like other distortions.Max Headroom said:
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Perhaps the time shift idea comes from a certain listening experience.
People sometimes refer to a the mental experience of listening to a sound as including some small distortion factor that may be described as "smeared." Not clear if anyone has actually identified what type of distortion produces or is associated with that particular mental experience.
People sometimes refer to a the mental experience of listening to a sound as including some small distortion factor that may be described as "smeared." Not clear if anyone has actually identified what type of distortion produces or is associated with that particular mental experience.
D'oh. It was late and I had drunk half a bottle of port. Yes. RealPIM(tm) was a bane of my life for many years. When you get it badly wrong its embarrassing, esp when its in a filter in space.
One distortion type I don't understand is valve verses op amp active phono stages. The valve for all the evidence against it seems less distorted. There is colouration which I suspect is less than the LP. This often seems to be that the designers didn't have ideal measuring devices when choosing the curve compromise ( loop gain problems ). The sound for all that can be very open and pleasing to the ear. Most active RIAA stages of the sensible modern type sound a bit as if a good digital copy. Not the simple one made by Clear Audio I have to say.
Could it be the way a valve works still is that step simpler and is free of some mechanisms. Perhaps less complex at the point when an electron is influenced on it's journey. I really like pentodes for these designs, alas the best were mostly from the past. A cascode being the modern choice ( ECC82 perhaps ).
This is a bit of stimulation.
https://www.researchgate.net/post/I...ments_Is_it_possible_to_amplify_energy_at_all
Could it be the way a valve works still is that step simpler and is free of some mechanisms. Perhaps less complex at the point when an electron is influenced on it's journey. I really like pentodes for these designs, alas the best were mostly from the past. A cascode being the modern choice ( ECC82 perhaps ).
This is a bit of stimulation.
https://www.researchgate.net/post/I...ments_Is_it_possible_to_amplify_energy_at_all
Stimulating yes. Unfortunately the guy goes off on the wrong foot, thinking that if we talk about amplifying devices we mean amplifying power. Which is an error only extreme newbies would make. We speak of amplifying voltage, current, and that a transistor does.
So getting this wrong at the start, he goes downhill from there into an absolutely irrelevant discussion. Didn't he have a good friend that could have stopped him?
Jan
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Nigel, I think that a decent tube phono stage vs a single op amp 'equivalent' makes a poor comparison. The tube phono stage will have more peak output swing, and the op amp will suffer heavy loading at high frequencies.
A better comparison is a 2 op amp design, where the EQ is either split or stuck in-between two op amps. This appears to work much better. Still, the tube phono stage can sound better most of the time. PS I miss Michael Gerzon too!
A better comparison is a 2 op amp design, where the EQ is either split or stuck in-between two op amps. This appears to work much better. Still, the tube phono stage can sound better most of the time. PS I miss Michael Gerzon too!
Words of wisdom and ones I am causing trouble with elsewhere.
Michael reminded me of Star Trek when McCoy ( the real man claimed some link to Lee de Forest ). Breifly " Bones " can reinstall Spooks brain whilst having been on an educator ( like Forbidden Planet story ). He made me think I understood things when in fact he made me see.
Did I tell you John I made my friendship with Sid Smith by arguing pentodes better than triodes ? Sid in the end saw my arguement and said EL34 the best triode he knew of. After years of trying EL34 is the best triode I know of. I have suggested it to two valve companies ( JJ and Kron ) a TR34 simplified EL34 with a slightly improved g1 possition. It would be like an indirectly heated PX25 if I get my numbers right. One can get a low Mu triode with EL34 also. It is a wonderful design.
I said to Sid " inside every good triode a better pentode is trying to get out ". He nearly crashed the car. It was exactly as he pointed out the Twin Towers. We went to a diner to draw graphs and load lines.
I hope, for your sake, eventually that peace and quiet comes back. Okay, for my sake too, but mostly for you.
Well firstly DeForest was one of his first names, and although named in honor of Lee de Forest there is no relationship.
Secondly 'Spook'. Come on Nigel...
Another analog designer that I really respect is Sid Smith. I only met him once over dinner, but I am sorry that I did not know him better. It was his Marantz 9 in triode, his earlier 50's triode design that I directly compared my first solid state design efforts (and failed) and even now, the circuits that he did for the Marantz 10 (that I am listening to now) that kept me struggling to make better and better audio circuits. Through a process of elimination, did I find what was different between his designs and mine. Also, I have some of those German EL34's that he liked in some Dyna MK 4's that I keep around for reference.
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