Well, no, no measurements taken, but I have to say I really liked what I heard....I sold them to a gentleman hereon this site when I got hold of the Acoustat interfaces, and regretted selling the ones with the Anteks....kicking myself now, as I cannot even build new ones (they are still out of stock)
Hi,
No, not at all 😛 The major problem beeing to source devices. There don´t seem to be no transistors around allowing for enough voltage and current to not rely on advanced and complex circuitry like cascoding, etc. At the time the highest voltage capability of MOSFETs and bipolars seems around 1700V. IXYS has even higher voltage parts in its portfolio, but those seem to be made from unobtanium and they are certainly not intended for linear amplification. The upcoming SIC and GaN-technology might bring a solution.
How will You intend to reach >5kVpp (which is not even 2kVrms) signal level then? The only way at the time to reach such signal voltage levels is to use Trannies, special Tubes or cascading transistors.
As soon as You need to cascade transistors, difficulties arise to keep things stable, fast and reliable. For sure to get a similar sonic result to a SOTA lowvoltage amplifier driving a good tranny is a difficult task, not to talk about the terrible inefficiency and the huge effort required.
Its limiting in both regards, voltage levels and current levels. The 2.2kV might just be sufficient for high-efficiency lowvoltage stator designs similar to e.g MLs. It´s not enough for highvoltage FR panels like Audiostatics or Acoustats. Running on just 25mA Bias current the bandwidth limit will be well within the audible range, even for those segmented low-capacitance panels. With high capacitive panels it will run into current clipping.
Its complex because it is build with multiple feedback loops and compensation.
Its inefficient, because running in tubed SE class A (probabely <10% overall efficiency).
Now imagine replacing the output tubes by cascoded transistor stages 🙄
jauu
Calvin
ps. I don´t know R.Sanders reasons to not build and offer DD amps nowadays, but lowvoltage amps instead ... but he surely has his reasons doing so 😉
No, not at all 😛 The major problem beeing to source devices. There don´t seem to be no transistors around allowing for enough voltage and current to not rely on advanced and complex circuitry like cascoding, etc. At the time the highest voltage capability of MOSFETs and bipolars seems around 1700V. IXYS has even higher voltage parts in its portfolio, but those seem to be made from unobtanium and they are certainly not intended for linear amplification. The upcoming SIC and GaN-technology might bring a solution.
How will You intend to reach >5kVpp (which is not even 2kVrms) signal level then? The only way at the time to reach such signal voltage levels is to use Trannies, special Tubes or cascading transistors.
As soon as You need to cascade transistors, difficulties arise to keep things stable, fast and reliable. For sure to get a similar sonic result to a SOTA lowvoltage amplifier driving a good tranny is a difficult task, not to talk about the terrible inefficiency and the huge effort required.
Now that´s a somehow amusing statement, because of the Sanders amp beeing a prime example of a limiting, complex and inefficient amp design for which the connected ESL-panel must matter.
Its limiting in both regards, voltage levels and current levels. The 2.2kV might just be sufficient for high-efficiency lowvoltage stator designs similar to e.g MLs. It´s not enough for highvoltage FR panels like Audiostatics or Acoustats. Running on just 25mA Bias current the bandwidth limit will be well within the audible range, even for those segmented low-capacitance panels. With high capacitive panels it will run into current clipping.
Its complex because it is build with multiple feedback loops and compensation.
Its inefficient, because running in tubed SE class A (probabely <10% overall efficiency).
Now imagine replacing the output tubes by cascoded transistor stages 🙄
jauu
Calvin
ps. I don´t know R.Sanders reasons to not build and offer DD amps nowadays, but lowvoltage amps instead ... but he surely has his reasons doing so 😉
No question that Calvin is absolutely right about that an amp which drives a hot bunch of resistors is inefficient: yes. I bet I used to waste on electricity costs EVERY month at least 10-cents.
Yes, Sanders, businesses, and everybody (me too) need a great deal of fortitude to persevere with HV amps for homes. Likewise for that other fabulous improvement called motional feedback for subs. Hard to imagine these systems being feasible commercially, wonderful as they are. On the other hand, let's not confuse our own commercial agendas with providing objective advice on this forum.
I can't say if there are good solid-state devices. All I've ever seen is HV amps with tubes at the output.
My B+ was 2400 volts but, being big gap Dayton-Wrights panels (in individual panels in air and later, whole gas-filled speakers), thousands more volts of negative bias adding to that.
Finally, like a lot of things, if you don't like challenges and big risks to life, you can find other interests in HiFi that are easier to get into. I'd say committed ESL people should make the effort, if they know how to manage the risk.
I sold my amp maybe 10 years ago, for a lot more than the parts. I am not a good source of tech information today, if ever.
Ben
Hi,
And I´d also fully agree if the claim of superiority of DD were limited to headphones and small ESL-panels, which require much lower signal voltages and currents. A sensitive supply voltage limit for transistorized non-cascaded circuitry is at the time around 1200-1300V, far below the needs of larger ESL panels. The requirements of larger Speaker panels can´t be fulfilled as easy and simple as those of HP-cells. These raised requirements inevitably cost on important amplifier parameters such as bandwidth, dynamic range, complexity, efficiency and eventually sonic quality.
The limitations are so severe that a DD amp is no longer superior to transformer-coupling but most parameters are in fact worse.
Tubes would allow for higher voltages, but sourceability may be an issue.
I sure don´t mix my own commercial agenda, that´s a silly statement, but as soon as one thinks of sharing and starting a project, he needs to think at least a bit in commercial terms, such as sourceability and price of parts -especially of obsolete parts- as this may become serious issue. See for example those project threads where obsolete Toshiba JFETs are required.
Or the 6HB5 Tube used in the Acoustat-X amp. Besides beeing far from optimal a tube for an ESL-DD amp it is hard to find nowadays and nearly costs a fortune.
jauu
Calvin
I fully agree 😀
And I´d also fully agree if the claim of superiority of DD were limited to headphones and small ESL-panels, which require much lower signal voltages and currents. A sensitive supply voltage limit for transistorized non-cascaded circuitry is at the time around 1200-1300V, far below the needs of larger ESL panels. The requirements of larger Speaker panels can´t be fulfilled as easy and simple as those of HP-cells. These raised requirements inevitably cost on important amplifier parameters such as bandwidth, dynamic range, complexity, efficiency and eventually sonic quality.
The limitations are so severe that a DD amp is no longer superior to transformer-coupling but most parameters are in fact worse.
Tubes would allow for higher voltages, but sourceability may be an issue.
I sure don´t mix my own commercial agenda, that´s a silly statement, but as soon as one thinks of sharing and starting a project, he needs to think at least a bit in commercial terms, such as sourceability and price of parts -especially of obsolete parts- as this may become serious issue. See for example those project threads where obsolete Toshiba JFETs are required.
Or the 6HB5 Tube used in the Acoustat-X amp. Besides beeing far from optimal a tube for an ESL-DD amp it is hard to find nowadays and nearly costs a fortune.
jauu
Calvin
I would like to revitalize this thread by suggesting the use of a stepup autoformer (say 1:2 or 1:4) rather than a stepup transformer this would hopefully remove some of the saturation design constraints,
Would this work better? Assume we put DC decoupling caps 50-100n in the push pull lines before the autoformer.
Regards,
Ron
Would this work better? Assume we put DC decoupling caps 50-100n in the push pull lines before the autoformer.
Regards,
Ron
This would increase the problems!!
A higher input voltage on the primary means that more total amount of turns would be required.
This increases the transformers self capacitance and it also increases the losses due to the DC resistance's of the winding's.
In order to make something that may work with this method one would have to select a very very very large core in order to keep the initial amount of Primary Turns to a minimum!!
jer 🙂
A higher input voltage on the primary means that more total amount of turns would be required.
This increases the transformers self capacitance and it also increases the losses due to the DC resistance's of the winding's.
In order to make something that may work with this method one would have to select a very very very large core in order to keep the initial amount of Primary Turns to a minimum!!
jer 🙂
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Wrong. In case of autoformer total number of windings will be reduced for the same output voltage, because part of voltage is shared with the source. However a benefit of doing so IMO is highly questionable, since transformer is still not avoided while adding big complexity of a high voltage amplifier.
BTW the linearity of high quality step-up trafos driven by low impedance source is usually about an order better than that of ESL element. A question if complex HV amp is more linear that a good quality common setup amp+step-up trafo.
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An Autotransformer is just a type of configuration for a transformer.
The same rules still apply to the Driven part of the winding that is called the primary section.
If the primary (driven bottom section) is run at a higher voltage swing then it requires more turns to keep the core from saturating for any given core size compared to a winding that is operated at a lower voltage swing.
The biggest factor (besides voltage swing) that determines the amount of starting turns required is the lowest frequency of operation.
The secondary will always be more since it is a step up transformer.
So, it is best to keep the primary turns as low as you can to keep the rest of the losses low and core size down as well!
This has been discussed before in great detail in another thread already.
jer 🙂
The same rules still apply to the Driven part of the winding that is called the primary section.
If the primary (driven bottom section) is run at a higher voltage swing then it requires more turns to keep the core from saturating for any given core size compared to a winding that is operated at a lower voltage swing.
The biggest factor (besides voltage swing) that determines the amount of starting turns required is the lowest frequency of operation.
The secondary will always be more since it is a step up transformer.
So, it is best to keep the primary turns as low as you can to keep the rest of the losses low and core size down as well!
This has been discussed before in great detail in another thread already.
jer 🙂
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Sorry but I think you didn't get the point. In case of autotrafo you dont need the 'primary' section of windings. For the same output voltage and core section autotrafo will always need less windings.
One more common term that is used in Transfomer design is Volts per turn.
This is the amount of voltage that one can apply per single turn of wire around a core before you send the core into saturation.
It is a "Constant", and, it applies equally to both the primary winding and the secondary winding.
Even if the winding's are tied in series as in an Autotransformer configuration.
You can not apply more volts per turn for any of the winding's turns else you will be putting the core into saturation for a given core size.
If you do the math this stacks up to the amount of total turns required even if it is in an Autotransformer configuration and there is nothing gained.
That is best that I can explain it.
jer 🙂
This is the amount of voltage that one can apply per single turn of wire around a core before you send the core into saturation.
It is a "Constant", and, it applies equally to both the primary winding and the secondary winding.
Even if the winding's are tied in series as in an Autotransformer configuration.
You can not apply more volts per turn for any of the winding's turns else you will be putting the core into saturation for a given core size.
If you do the math this stacks up to the amount of total turns required even if it is in an Autotransformer configuration and there is nothing gained.
That is best that I can explain it.
jer 🙂
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Ok lets look at the drawing.first drawing is trafo. second version is the same physical device but connected as autoformer. as you can see in second version there are more turns connected to the load therefor the voltage will be higher. so to get back to the same voltage we could reduce number of windings for autotrafo.
Attachments
Yes, I understand now.
Sorry for the confusion.
There is some benefit but it is not much.
At higher voltage primary's this my work Okay.
But there is one main risk involved and that is isolation of the many KV's of the bias and stator voltages to the output devices their power supply.
You still have to have X amount of total turns as turns per volt on the complete winding for the HV side this does not change.
If your are trying to get to 20Hz than this is still a very large number of turns.
Also it all depends on what ESL driving voltage is required for your setup and listening requirements.
Should you happen to go over and damage the windings, is it worth the risk of a very expensive tube setup?
However Thank you for pointing this out to me!! 🙂
I will re-think this and give it another look when I start working on another amp design using some HV FET's that I finally got.
My goal is to get to 5-10Kv peaks but maybe it can be done using FET's on a 1200v supply and a 1:8 step-up ratio rather than the complicated construction method of end stacking the FET sections running at 5-6Kv or more.
This would definitely help to make for a safer setup than for the method I was thinking about in a D-Drive amp!!
But, It would still call for a custom wound transformer.
Thanks!!
jer 🙂
Sorry for the confusion.
There is some benefit but it is not much.
At higher voltage primary's this my work Okay.
But there is one main risk involved and that is isolation of the many KV's of the bias and stator voltages to the output devices their power supply.
You still have to have X amount of total turns as turns per volt on the complete winding for the HV side this does not change.
If your are trying to get to 20Hz than this is still a very large number of turns.
Also it all depends on what ESL driving voltage is required for your setup and listening requirements.
Should you happen to go over and damage the windings, is it worth the risk of a very expensive tube setup?
However Thank you for pointing this out to me!! 🙂
I will re-think this and give it another look when I start working on another amp design using some HV FET's that I finally got.
My goal is to get to 5-10Kv peaks but maybe it can be done using FET's on a 1200v supply and a 1:8 step-up ratio rather than the complicated construction method of end stacking the FET sections running at 5-6Kv or more.
This would definitely help to make for a safer setup than for the method I was thinking about in a D-Drive amp!!
But, It would still call for a custom wound transformer.
Thanks!!
jer 🙂
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