I bought that particular Lundahl transformer because it has 4 primary and 2 secondary windings. That way it is very flexible. Step up ratio can be 1:5, 1:10 and 1:20 and impedance can vary over a wide range. I though that was very handy because i could experiment with a variety of arangements. I also consulted with the late Allen Wright and he recommended amorfous core. I also had a chat with Brian Sowter and he is more conviced about mu-metal as core material. I have reported that here before. So sound quality per se was not the only reason i bought this transformers. Sorry if i cunfused anybody here.
I want to thank everyone for getting me off my duff and searching the internet to put some more input here. I ran across an analog tape recorder app note by Dale Manquen dated 2001, more than 30 years after I left Ampex.
They CHANGED the transformers and the heads to 2mil laminations in subsequent models of the MM1000 and the AG-440 of BOTH the heads and THE TRANSFORMERS, just like I asked them to, in 1968, and they virtually laughed at me then. Of course, I went and PROVED my contention with both Q meter and noise with frequency measurements, and rubbed their nose in it, as I am prone to do.
Years later, they upgraded. Nice to see people catching up, even if they could have gained a small advantage on the competition, years before, IF they would had only given a darn.
Now, if I were a betting man, I would BET that Sowter uses 4 mil lams. Ampex perhaps 35 years ago, went to 2 mil lams, which will measure better AND contribute less noise at frequencies between 10K and 20KHz. If you are over 50, maybe you don't care, but if you are 18-35, you might certainly care. This is an ADDED hiss from the eddy current losses, due to thick laminations. 6 mils used to be standard, perhaps in 1950. 2 mils was possible, and commercially made in 1968. 1 mil was also possible, just more expensive and delicate to work with.
Now what are the lamination thicknesses of the audio input transformers talked about here? Sowter, Jensen, Lundhal, etc. Anybody know? If not, why not?
They CHANGED the transformers and the heads to 2mil laminations in subsequent models of the MM1000 and the AG-440 of BOTH the heads and THE TRANSFORMERS, just like I asked them to, in 1968, and they virtually laughed at me then. Of course, I went and PROVED my contention with both Q meter and noise with frequency measurements, and rubbed their nose in it, as I am prone to do.
Years later, they upgraded. Nice to see people catching up, even if they could have gained a small advantage on the competition, years before, IF they would had only given a darn.
Now, if I were a betting man, I would BET that Sowter uses 4 mil lams. Ampex perhaps 35 years ago, went to 2 mil lams, which will measure better AND contribute less noise at frequencies between 10K and 20KHz. If you are over 50, maybe you don't care, but if you are 18-35, you might certainly care. This is an ADDED hiss from the eddy current losses, due to thick laminations. 6 mils used to be standard, perhaps in 1950. 2 mils was possible, and commercially made in 1968. 1 mil was also possible, just more expensive and delicate to work with.
Now what are the lamination thicknesses of the audio input transformers talked about here? Sowter, Jensen, Lundhal, etc. Anybody know? If not, why not?
Hi John, all
I had observed something once which may be worth tossing in as a ‘for what it’s worth”
About 15 years ago I was hired to work on improving an output transformer for a 250 Watt tube amplifier. One of the things I did was to casually explore the distortion the transformer added.
Using an HP-3562a network analyzer and the two port vector subtraction approach (where the distortion from the source is excluded) I found a consistent thing.
If one viewed the spectrum with the same start / stop points, the “shape” of the distortion envelope (the shape set by the peaks of all the harmonics) stayed more or less constant regardless of the input frequency.
If I remember right, the top of the hump for that envelope was in the 200-300 Hz neighborhood and this being a 25 lb transformer, an E/I stack, M-6 I think with a very small signal low corner F.
What I saw was all the other transformers I tested have a similar general hump shape.
To be clear, this is not caused by the normal inductive corner but (I think) due to the sort of incremental nature of the magnetic material at a very low level.
Since you guys are getting serious about transformers, I thought this might be applicable.
Best,
Tom Danley
Danley Sound Labs
I had observed something once which may be worth tossing in as a ‘for what it’s worth”
About 15 years ago I was hired to work on improving an output transformer for a 250 Watt tube amplifier. One of the things I did was to casually explore the distortion the transformer added.
Using an HP-3562a network analyzer and the two port vector subtraction approach (where the distortion from the source is excluded) I found a consistent thing.
If one viewed the spectrum with the same start / stop points, the “shape” of the distortion envelope (the shape set by the peaks of all the harmonics) stayed more or less constant regardless of the input frequency.
If I remember right, the top of the hump for that envelope was in the 200-300 Hz neighborhood and this being a 25 lb transformer, an E/I stack, M-6 I think with a very small signal low corner F.
What I saw was all the other transformers I tested have a similar general hump shape.
To be clear, this is not caused by the normal inductive corner but (I think) due to the sort of incremental nature of the magnetic material at a very low level.
Since you guys are getting serious about transformers, I thought this might be applicable.
Best,
Tom Danley
Danley Sound Labs
Given the high efficiency, and therefore low attenuation, of a transformer its thermal noise will be low. I can appreciate that thermal noise is not just due to winding resistance but also core losses - any loss mechanism will contribute thermal noise.
Excess noise normally means noise over and above thermal noise. What are the sources of excess noise in a transformer? Perhaps leakage inductance contributes indirectly by allowing coupling between the transformer and its EM environment? In that case, noise will depend on the environment so perhaps should be treated as 'EM soup rejection ratio'.
Excess noise normally means noise over and above thermal noise. What are the sources of excess noise in a transformer? Perhaps leakage inductance contributes indirectly by allowing coupling between the transformer and its EM environment? In that case, noise will depend on the environment so perhaps should be treated as 'EM soup rejection ratio'.
Yeah, it's fine for experimentation, but it's one of the things that have turned me off on the Lundahls.
Most of their transformers are of the "Swiss Army knife" variety, forcing you to strap them externally from their shields which can make them more susceptible to noise pickup.
I'm with Sowter on this one. Perhaps because I never cared much for freeze dried coffee.
se
Eh?
Would you care to explain how eddy current losses in the core produces added hiss?
se
Tom,
Are you aware of Menno Vanderveen's AES paper on exactly this subject?
jan didden
I'm having trouble picturing what you are describing. If the B-H curve had steps I would expect sudden changes in distortion components. And as we discussed before a step at 0 would mean below a certain input there would be no output.
Jan could you send a copy? That might make it clear.
Joachim, please continue to contribute, I get all kinds of new ideas from you. For example, has ANYBODY compared the sound difference between Metglas and Mumetal transformers of almost identical construction? Has anyone MEASURED the difference at low frequencies of the HARMONIC DISTORTION between two otherwise identical transformers except for core material, as I have?
Joachim, YOU are using a Metglas transformer, SY is using a mumetal core. I predict that SY's transformer will measure much better at low frequencies such as 20 Hz. I also predict that your transformer will have a better mid-range quality.
Identical transformers, my aunt Fanny! '-) We are comparing apples to oranges!
Joachim, YOU are using a Metglas transformer, SY is using a mumetal core. I predict that SY's transformer will measure much better at low frequencies such as 20 Hz. I also predict that your transformer will have a better mid-range quality.
Identical transformers, my aunt Fanny! '-) We are comparing apples to oranges!
John your using the term excess noise wrongly. It has been accepted since probably before the 50's to mean noise that is roughly proportional to the square of the stimulous and inversely proportional to frequency. Eddy current loss models as heat or simply an extra resistance. Jensen has a free chapter on line, covers it well. Even my cheap input transformers are dead flat in spectrum (noise) down to 10Hz.
I thought this might be of interest and I would like to find out if its still possible to be off topic in this thread
Super sense of smell not innate
rgds
james
"Quote:
Over time, the study also showed, activity in the brain shifts from the area that governs conscious effort to a region in which actions are performed automatically, like breathing or swallowing.
This makes it possible to graduate from technical competence to artistry, the researchers argue.
In the same way that musicians can be more creative once they no longer need to concentrate on technical virtuosity, great perfumers can conjure new scents just by imagining -- and mentally mixing -- the smell of individual ingredients."
Ever compare tasting notes for the same wine by two of the most respected wine critics in the world, Robert Parker and James Suckling? Or Parker and James Laube? Not only can their ratings differ wildly but from the subjective descriptions they offer you'd often hardly know they were talking about the same product.
There are people who are "super tasters." Scientist now know that some people just have many more taste buds in their mouths than others. But experience and training are also a necessary ingredient to become a top notch critic of food and wine and it ultimately boils down to a matter of opinion.
You cannot become a true musical virtuoso until all of the technical problems associated with your chosen instrument have been mastered. That is not to say such people don't occasionally make technical mistakes but they are the rare exception. The great violinist Jascha Heifetz would not allow them to be edited out of his recordings the way many other musicians do. Even when all of the technical problems have been put behind them, many musicians cannot rise to the level of world class virtuosos, they lack understanding of the music they perform or can't bring that understanding to their performances. This does not mean that they are not outstanding professionals in their field but they do not rise to the top, they are not memorable, just sometimes very pleasant, often boring. One such performer who IMO falls into this category is Joshua Bell. Tragic, it seems he has most of the necessary ingredients but not quite all of them.
Can't say that I have. But I've done a lot of FR, distortion, phase, impedance and other measurements of different transformers, often of the same size and specs. Even done a good bit of blind test listening. They are all different.
Where is this leading?
extra noise != excess noise
So if my microphone transformer reflects 220 Ohms rather than 200 Ohms to the input it matters? Jensen quotes 1.2 dB total thermal noise figure, for 10 Ohms the BT at .4nV is 2.5dB NF.
Did that on my Quan-Tech sliderule still have yours?
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Well, IF they are all different, then maybe we should sort out the 'better' ones for a specific application. For example, I need a 'great' MC transformer for very LOW LEVEL phono cartridges. Nothing else. I chose, almost a random, the Lundahl LL1931 or the LL1933 transformers, but I am open to anything, that MIGHT be better sonically, measurably, or cheaper with the SAME quality performance.
To my surprise and dismay, the Metglas version of the SAME transformer measured MUCH WORSE at 10Hz, at least 20 times worse! WOW! Can I use it? Joachim uses something similar in Metglas from the same manufacturer, and he has twice as expensive a phono cartridge than I have-$5,000 worth. He is a good listener, and a professional designer, should I go with his recommendation?
SY has a cheaper transformer (mumetal) from Sowter. SY likes his transformer and it is cheaper than either the mumetal or Metglas transformers from Lundahl. Should I change over to that transformer? We are still at the prototype stage, so it would be possible. Anybody COMPARE Lundahl with Sowter, subjectively? Nobody here has contributed anything here so far. In fact, nobody here has COMPARED mumetal with Metglas either, subjectively. What to do? I guess that I will just have to muddle on with what I have in front of me. '-)
To my surprise and dismay, the Metglas version of the SAME transformer measured MUCH WORSE at 10Hz, at least 20 times worse! WOW! Can I use it? Joachim uses something similar in Metglas from the same manufacturer, and he has twice as expensive a phono cartridge than I have-$5,000 worth. He is a good listener, and a professional designer, should I go with his recommendation?
SY has a cheaper transformer (mumetal) from Sowter. SY likes his transformer and it is cheaper than either the mumetal or Metglas transformers from Lundahl. Should I change over to that transformer? We are still at the prototype stage, so it would be possible. Anybody COMPARE Lundahl with Sowter, subjectively? Nobody here has contributed anything here so far. In fact, nobody here has COMPARED mumetal with Metglas either, subjectively. What to do? I guess that I will just have to muddle on with what I have in front of me. '-)
Let's see 'em.
What transformers? What core materials?
Which Metglass material? M4? M6? 50% nickel? 80% nickel? Cobalt? What?
Are you saying that an M4 Metglass core will give you lower distortion than an 80% nickel laminated core?
And by the time you get to midrange frequencies, the distortion of a transformer made with an 80% nickel laminated core is so low I don't know why anyone would lose any sleep over it, unless it's all nothing but a numbers game.
Nice straw man. Who said otherwise, John?
se
Yes, Sowter told me that Mu-Metal has lower distortion in the bass. Allen on the other hand told me that he likes the sound better from amorfous because of detail resolution.
I bought the Lundahl after i heard Allen Wrights KT88 poweramp in my system. It is stuffed with amorphous Lundahls and the sound we got in my system was mesmerising. After that i simply trusted him. Stupid me.
I use my transformer coupled phono stage rarely anyway because with the cartridge i use my phono stages are low enough in noise.
What i can tell is that this particular Lundahl has enough treble extention to make me happy. I had several commercial transformers in my house before that had a drop in resolution and extention in the treble. Not this Lundahl or maybe i am getting old.
I bought the Lundahl after i heard Allen Wrights KT88 poweramp in my system. It is stuffed with amorphous Lundahls and the sound we got in my system was mesmerising. After that i simply trusted him. Stupid me.
I use my transformer coupled phono stage rarely anyway because with the cartridge i use my phono stages are low enough in noise.
What i can tell is that this particular Lundahl has enough treble extention to make me happy. I had several commercial transformers in my house before that had a drop in resolution and extention in the treble. Not this Lundahl or maybe i am getting old.
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