hello
we are testing the firsts examples of s.e. output trafo with Litz on primary (10 wire for 0,30 mmq total )and secondary (50 wires for 1 mmQ total).
Double C core laminated 0,1 mm; the power is about 10 watt at 20 hz
At this link:
http://www.multitask.it/Litz Trafo/Foto1a.JPG
on right side there is a proto of trafo, on left a normal EI core
The ratio is 1:20, single secondary set at 6 ohm.
At Audioreview magazine (AudioReview - Il sito ufficiale della rivista) , in the lab Fabrizio Montanucci ( tec. director) done some interstring tests; I have made a s.e. proto of s.e. amp with KT120/150, just to tets the new trafo compared with a old one.
Fabrizio test both trafos and at this link:
http://www.multitask.it/Litz Trafo/Fig2.tif
there are the results of freq. answers for three different power output with non bias, 28 mA of bias and 71 mA; left side the normal trafo and right the Litz type.
The Litz show a wider freq. answer on high frequency; on low freq. it seems good but non perfect.
This is a proto and we are waiting a new one with more inductance and same geometry.
At this link:
http://www.multitask.it/Litz Trafo/Fig5.tif
there is an interesting test made with a new program developped by Fabrizio (now is in beta test) where is possible to measure the passive components ( this as general description).
On left hand the test on primary of normal trafo; on upper tabs is possible to read the real impedeance for different frequency; under this tabs the diagram of the impedance/frequency curve and the point of resonance ; after this point the shape of curve shift from inductive to capcitive and is possible to see that the value of Litz is lower than normal trafo at 40 khz, 187 pF for Litz and 296 for the normal; this is the reason for a wider freq. answer of Litz type.
More info comes in nex future, we are waiting also a push-pull Litz trafo.
Walter
we are testing the firsts examples of s.e. output trafo with Litz on primary (10 wire for 0,30 mmq total )and secondary (50 wires for 1 mmQ total).
Double C core laminated 0,1 mm; the power is about 10 watt at 20 hz
At this link:
http://www.multitask.it/Litz Trafo/Foto1a.JPG
on right side there is a proto of trafo, on left a normal EI core
The ratio is 1:20, single secondary set at 6 ohm.
At Audioreview magazine (AudioReview - Il sito ufficiale della rivista) , in the lab Fabrizio Montanucci ( tec. director) done some interstring tests; I have made a s.e. proto of s.e. amp with KT120/150, just to tets the new trafo compared with a old one.
Fabrizio test both trafos and at this link:
http://www.multitask.it/Litz Trafo/Fig2.tif
there are the results of freq. answers for three different power output with non bias, 28 mA of bias and 71 mA; left side the normal trafo and right the Litz type.
The Litz show a wider freq. answer on high frequency; on low freq. it seems good but non perfect.
This is a proto and we are waiting a new one with more inductance and same geometry.
At this link:
http://www.multitask.it/Litz Trafo/Fig5.tif
there is an interesting test made with a new program developped by Fabrizio (now is in beta test) where is possible to measure the passive components ( this as general description).
On left hand the test on primary of normal trafo; on upper tabs is possible to read the real impedeance for different frequency; under this tabs the diagram of the impedance/frequency curve and the point of resonance ; after this point the shape of curve shift from inductive to capcitive and is possible to see that the value of Litz is lower than normal trafo at 40 khz, 187 pF for Litz and 296 for the normal; this is the reason for a wider freq. answer of Litz type.
More info comes in nex future, we are waiting also a push-pull Litz trafo.
Walter
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Litz does not have any advantage over regular magnet wire at audio frequencies. The lower parasitic capacitance that you observe is the result of thicker insulation (a layer of nylon thread) of Litz wire. Using solid magnet wire with an extra layer of silk or cotton (for example Russian ПЭЛШО) will produce the same effect.
Walter, it would help if you could identify the test circuit and operating conditions when presenting results. Also, can you identify the similarity, or difference, between the non-litz and litz - the photo appears to show two very different physical constructions with no details of how similar they are for core area-length-winding window, turns, dc wire resistance, winding layer structure.
Hi
after a long time I am back with other info.
This is a brief description of the tests.
The trafos, Litz and normal, under test are 2500 ohm primary and 6 ohm secondary
The test set made by Fabrizio is in attached. Fig. 1
There is a power supply with 4.9 KV used for a old ( and advanced ) project developped by Fabrizio; it is acting as current generator that drive the primary by the R (>> of 2500 ohm); there is also a attenuator where we can pick the signal test : 200 uF+2470 +25 ohm , ratio of 100:1 just to avoid the saturation of the analyzer.
Two value of bias current are used: 28 and 71 mA. Just to have check what happen.
The first value is obtained with a resistor of R of 160 kohm and 71 mA with 57k, big enough to have a right tests.
Also the test was made without bias current.
The signal come from secondary driven by a good ss amplifier, through a 6 ohm resistor .
Every trafo is a bi-directional device so in this case the test is correct.
Fig .2 Here the frequency answer; the Litz is always better
Fig. 3 the THD vs frequency ; where the normal trafo has a better thd figure but the Litz has a uniformity of shape for different currents and power.
On Fig. 4 there is a test of freq. response on the 6 ohm resistors, no bias; we can see that the Litz trafo has a resonance 105 e 160 KHz; the normal trafo at 60 KHz and 120 KHz.
This is the first prototype we made but is coming soon a new one with more L; I think it is a good start to get an interesting trafo, also for push-pul ( it is coming)
Ciao
Walter
after a long time I am back with other info.
This is a brief description of the tests.
The trafos, Litz and normal, under test are 2500 ohm primary and 6 ohm secondary
The test set made by Fabrizio is in attached. Fig. 1
There is a power supply with 4.9 KV used for a old ( and advanced ) project developped by Fabrizio; it is acting as current generator that drive the primary by the R (>> of 2500 ohm); there is also a attenuator where we can pick the signal test : 200 uF+2470 +25 ohm , ratio of 100:1 just to avoid the saturation of the analyzer.
Two value of bias current are used: 28 and 71 mA. Just to have check what happen.
The first value is obtained with a resistor of R of 160 kohm and 71 mA with 57k, big enough to have a right tests.
Also the test was made without bias current.
The signal come from secondary driven by a good ss amplifier, through a 6 ohm resistor .
Every trafo is a bi-directional device so in this case the test is correct.
Fig .2 Here the frequency answer; the Litz is always better
Fig. 3 the THD vs frequency ; where the normal trafo has a better thd figure but the Litz has a uniformity of shape for different currents and power.
On Fig. 4 there is a test of freq. response on the 6 ohm resistors, no bias; we can see that the Litz trafo has a resonance 105 e 160 KHz; the normal trafo at 60 KHz and 120 KHz.
This is the first prototype we made but is coming soon a new one with more L; I think it is a good start to get an interesting trafo, also for push-pul ( it is coming)
Ciao
Walter
Attachments
I deal only in PP outptus, so a means to apply idle current is of little interest. Have learned a bit by driving the OPT's backwards, across the various secondary taps, with source impedance a variable. Say put 4R I series with the 8 R tap, then 8, then 16, while the primary is loaded resistively( 2500R for a 2500R reflected impedance vs the tap being driven ). Applying a bit of capacitance is of use too.
A SS amp with very low output Z is employed as the driver...🙂 All sorts of interesting things fall out of this sort of measurement. It is a good place to start, and test complexity can increase from there.
cheers,
Douglas
A SS amp with very low output Z is employed as the driver...🙂 All sorts of interesting things fall out of this sort of measurement. It is a good place to start, and test complexity can increase from there.
cheers,
Douglas
To get the right nominal specs of the trafo I must use the right R for a different taps connected by the ss amp.
Of course other test will show you how the trafo works
For p-p trafo this test is more simple, you have to use always a 40 dB attenuator to monitor the signal
Walter
Of course other test will show you how the trafo works
For p-p trafo this test is more simple, you have to use always a 40 dB attenuator to monitor the signal
Walter
Walter - good stuff. Can you indicate the DCRs of the secondary windings?
Do you have any comment on why the mid-band distortion levels would be significantly more for the litz versions.
Do you have any comment on why the mid-band distortion levels would be significantly more for the litz versions.
x Wavebourn
your info is general.
It is interesting to understand if the amp is a s.e. or pp and if it has a feedback; the 120 kHz at what attenuation respect at 0dB?
Which power you mean?
bye
Walter
your info is general.
It is interesting to understand if the amp is a s.e. or pp and if it has a feedback; the 120 kHz at what attenuation respect at 0dB?
Which power you mean?
bye
Walter
At that moment was the only way to have a current generator with the right specs to do the job.
Fabrizio is developping a circuti that can do the same job with different topology.
Walter
Fabrizio is developping a circuti that can do the same job with different topology.
Walter
Another question: why to compare Double C core vs EI core? That's the main matter you get different behaviour, I think.
Why did you not used same cores for your tests with same winding geometry? Is seems a little bit odd experiment.
The bobbin is the same; the core has a major impact on low frequencies where the inductance goes down.
On high frequencies the parasitic became important; you can check this with different level of signals because the parasitic aren't linear so you can see different shape of curves.
In every case is ready a two new prototypes one same core normal wire and another with a bigger core that will be a test for a my next schema with 2A3/300B
Walter
On high frequencies the parasitic became important; you can check this with different level of signals because the parasitic aren't linear so you can see different shape of curves.
In every case is ready a two new prototypes one same core normal wire and another with a bigger core that will be a test for a my next schema with 2A3/300B
Walter
look here from post 1:
At this link:
http://www.multitask.it/Litz Trafo/Fig5.tif
there is an interesting test made with a new program developped by Fabrizio (now is in beta test) where is possible to measure the passive components ( this as general description).
On left hand the test on primary of normal trafo; on upper tabs is possible to read the real impedeance for different frequency; under this tabs the diagram of the impedance/frequency curve and the point of resonance ; after this point the shape of curve shift from inductive to capcitive and is possible to see that the value of Litz is lower than normal trafo at 40 khz, 187 pF for Litz and 296 for the normal; this is the reason for a wider freq. answer of Litz type.
walter
At this link:
http://www.multitask.it/Litz Trafo/Fig5.tif
there is an interesting test made with a new program developped by Fabrizio (now is in beta test) where is possible to measure the passive components ( this as general description).
On left hand the test on primary of normal trafo; on upper tabs is possible to read the real impedeance for different frequency; under this tabs the diagram of the impedance/frequency curve and the point of resonance ; after this point the shape of curve shift from inductive to capcitive and is possible to see that the value of Litz is lower than normal trafo at 40 khz, 187 pF for Litz and 296 for the normal; this is the reason for a wider freq. answer of Litz type.
walter
SE, pentode, with nested feedbacks, -3 dB from full 5W power from 20 Hz.
https://www.youtube.com/watch?v=IWcLxpUbPW0
Here are pictures, 1/10 probe. Sweep times on the screen.
Attachments
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Given 99.999...% of tube amps don't use litz, then presenting data on any one of them doesn't progress the topic, and is more likely to get everyone posting results about their own particular 'normal' amp.
Of course if you were going to swap out the OT in your amp for one with litz wiring, and post comparison results in the next day or two then
Of course if you were going to swap out the OT in your amp for one with litz wiring, and post comparison results in the next day or two then
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