Hi,
as bolserst said modern toroids are capable of low enough leakage inductance that bandwidth limits >20kHz are possible. With 80VA-cores (pairs of 230/6V) I achieved >20kHz with 1nF load and with 120VA core-pairs I achieved ~19kHz using a 2nF panel. The specialized Amplimo toroid gave ~3-4kHz higher cutoff frequency. Any EI-core I tried sucked, hardly surpassing 10kHz.
jauu
Calvin
as bolserst said modern toroids are capable of low enough leakage inductance that bandwidth limits >20kHz are possible. With 80VA-cores (pairs of 230/6V) I achieved >20kHz with 1nF load and with 120VA core-pairs I achieved ~19kHz using a 2nF panel. The specialized Amplimo toroid gave ~3-4kHz higher cutoff frequency. Any EI-core I tried sucked, hardly surpassing 10kHz.
jauu
Calvin
Yes. You can stack two cores and wind a new LV winding thru both cores with the same number of turns as the 12V winding. The result will be that you have increased your saturation capability be a factor of 2 because of doubling the core area(as you noted). But, you will have reduced your step ratio by a factor of 2 as well since only half of the flux in the LV winding will flow in each of the HV windings. So, if one transformer has a step up ratio of 20:1. After you stack two transformers, put the 240V windings in series and wind a new 12V winding thru both cores you will have a step-up ratio of 20:1, but twice the saturation capability.
A simpler alternative for bass panel use:
Simply wire the 240V windings in series AND the 12V windings in series. You will get the same step up ratio(20:1) as a single transformer, but with only half the input voltage across each 12V winding you will have doubled your saturation capability. Leakage inductance is increased, but this won't matter for driving your bass panels.
Not sure if you read my last post on the other thread where I had explained what was just stated.
But thanks, Steve,as I couldn't remember if the saturation frequency was reduced by 1 octave or 2 octaves.
Carry on. jer
http://www.diyaudio.com/forums/planars-exotics/181041-my-2-nd-esl-attempt-2.html#post2520508
But thanks, Steve,as I couldn't remember if the saturation frequency was reduced by 1 octave or 2 octaves.
Carry on. jer
http://www.diyaudio.com/forums/planars-exotics/181041-my-2-nd-esl-attempt-2.html#post2520508
I read that thread, and it was almost like you wound your toroids that I had in mind - but not quite!
I planed to make a small airgap between the cores and make turn one on the lower core followed by the on on top - going back to the lower one - and so on.
Anyway it was a "mind loop" as my N turns per core only handles half the voltage, the ratio stays the same => easier to connect the LV in series as bolserts says!
Roger
I planed to make a small airgap between the cores and make turn one on the lower core followed by the on on top - going back to the lower one - and so on.
Anyway it was a "mind loop" as my N turns per core only handles half the voltage, the ratio stays the same => easier to connect the LV in series as bolserts says!
Roger
I did find that the stacking method worked great for bass but not at the highend or full range due to the extra added capacitance from the extra cores and their associated windings.
I was able to drive my little panel very powerfully and cleanly that it vibrated like a foot massager.
And when I got down below 20hz I could actualy see the diagphram moving in and out using the qaud stacked cores. jer
I was able to drive my little panel very powerfully and cleanly that it vibrated like a foot massager.
And when I got down below 20hz I could actualy see the diagphram moving in and out using the qaud stacked cores. jer
I did test a Double stack with that method and it is the same result as just tying the windings in series and being seperated.
I did try seperating them a bit thinking it would help to reduce the extra added capacitance caused by stacking them, and, to reduce the arcing potentiel between the two cores.
Only the latter made a difference (arcing stopped).
However, It is my beliefe that by stacking the cores ,rather than keeping them seperate, keeps the magnetic fields in the cores uniform to one another.
Possibly reducing any distrotions that may be caused from them not being perfectly equal to one another when the magnetic field is reversed. jer
I did try seperating them a bit thinking it would help to reduce the extra added capacitance caused by stacking them, and, to reduce the arcing potentiel between the two cores.
Only the latter made a difference (arcing stopped).
However, It is my beliefe that by stacking the cores ,rather than keeping them seperate, keeps the magnetic fields in the cores uniform to one another.
Possibly reducing any distrotions that may be caused from them not being perfectly equal to one another when the magnetic field is reversed. jer
I can play bass with the amps volume maxed! 
I got four oil burner ignition trafos from the scap yard today!
220V=>2x5kV, two trafos with primary in paralell and secondary in series for abt. 1:90.
Here is my self wound 1:100 trafo (2500 turns sec and 25 turns prim).
The ingition trafos work alot better, so I will use them for the bass section.
Roger
I got four oil burner ignition trafos from the scap yard today!
220V=>2x5kV, two trafos with primary in paralell and secondary in series for abt. 1:90.
Here is my self wound 1:100 trafo (2500 turns sec and 25 turns prim).
The ingition trafos work alot better, so I will use them for the bass section.
Roger
I believe oil burner transformers come in 3 different types.
1) the heaviest/oldest ones are not current limited.
2) but, some models are current limited with a magnetic shunt, (20mA - 40mA usually).
3) the most recent/cheapest models are solid state(transformer replacements) and are not usable for ESL step-up transformers.
My guess would be if they say "intermittent use" they are probable not current limited.
But since you will only be applying at most 30Vrms - 40Vrms to the 220V winding you shouldn't run into any overheating problems.
With their high leakage inductance and primary winding resistance they should provide a nicely damped low pass filter for bass panels without needing any additional parts
Last edited:
Thanks for the information Bolserst.
As I feared... Microwave oven transformers are going the same direction. (Not that they're much use for audio anyway.)
Kenneth
As I feared... Microwave oven transformers are going the same direction. (Not that they're much use for audio anyway.)
Kenneth
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.