distortion From ESL at low level

[geraldfryjr]

Do you have any earth grounds on the esl side?
If so try removing it or try switching the polarity of the signal feeding you final bias supply transformer as i am thinking that there may be there still is a ground loop somewhere.

I did have a situation once where my amp was having a similar issue and it was all because of a ground loop that was caused by my scope ground being connected as well.
It caused the amp output to shift causing it to become unstable.
Putting a 1 ohm resistor in series made it not oscillate but the current was so great that it fried the resistor.

I schematic of your setup would help greatly.

jer

[geraldfryjr]

Originally Posted by geraldfryjr

Do you have any earth grounds on the esl side?
If so try removing it or try switching the polarity of the signal feeding you final bias supply transformer as i am thinking that there may be there still is a ground loop somewhere.

I did have a situation once where my amp was having a similar issue and it was all because of a ground loop that was caused by my scope ground being connected as well.
It caused the amp output to shift causing it to become unstable.
Putting a 1 ohm resistor in series made it not oscillate but the current was so great that it fried the resistor.

I schematic of your setup would help greatly.

jer

Sorry about the typo's I was in a hurry !!

[bolserst]

Originally Posted by WrineX

weird thing is even without cap and series resistor of 18 ohm distortion s heard in the lower regions

Distortion that increases as impedance in series with transformer primary increases, is usually core related. The series impedance can be resistive, inductive or capacitive. Looking at the attachment, if you examine the voltage before(V1) and after(V2) the series impedance you can determine if the distortion is core or amplifier related. I show a resistance, but you could use a capacitor as well(Impedance for 15uF at 100Hz = 100ohm). Whichever you use, select a component value for which you get noticeable distortion.

Since the distortion occurs at low volume level, you can use a line-input from another stereo setup to listen to (V1) and (V2).
Alternatively you could use the computer line-input to analyze with HOLM.
Just be sure to keep level < 2Vrms

If V2 is distorted, but V1 isn't, the distortion is most likely transformer(core) related.
If both V2 and V1 are distorted, the distortion is amplifier related.


Also, as geraldfryjr mentioned, a few specifics on your setup would be helpful.
In particular, what transformer you are using and a schematic of the circuit.
Also, it would be helpful to have a 100Hz sine wave recorded with and without the series resistor or capacitor to look at.
It might provide more insight into the distortion than the music sample did.

[WrineX]

Originally Posted by geraldfryjr

Did you take an odd number of steps back on the cascade or or an even number?

If it is an Odd number you must switch your ground to the esl to the other side.

The same side the output is taken from or you will get hum.

jer

well i sticked to one side. , but im gone try this tomorow with the panel that hums Thx for the advice i will report back!

[geraldfryjr]

Very good analogy I too was thinking that it could be core saturations as the distorted sounds seem to be only at the lowest of the frequency's mostly.

However without knowing about the transformer and the driving voltages it is a tough call.
It did cross my mind though as either caused the situation.

This would definitely happen if it was a rather smaller core below at about 200hz even with a 6Vpeak signal into it.

This is one of those things that make passive crossovers for ESL a real PIA !!!


jer

[WrineX]

ok i tried inceasing the resistor on the bias.
same result

i tried to switch to the other side of the row caps ont he bias.
same result.

still at low volume it sounds restrained. and distorted at low level at the crossover freq of the cap. i even switched my 2 ohm stable pioneer reference to a rotel 980BX.
same result.

Added a resistor,
same result.,

Switched bias suply to another one i had laing around, its the same but with new caps.
same result.

the setup explained by bolserst may need some more explanation for me
if i change the resistor for a cap of 15uF i should measure before and after the cap. and see what the distortion is ? so like the loop i use to calibrate the line out of the soundcard ? but then trough the amplifier trough the cap and back into line in ? and ofc first calibrate the output of max 2 volt RMS?
or listen to v1 and v2.

gone try this, only one thing i really cant believe its the amp. he never had any problems and the core would be weird to there pretty huge for a not full range.

i also tried 3 other transformers. one pair of really small ones from a 100volt line ... distortion at low freq, wich is ofc prety normal seen the size. then i tried some bigger 220-4 volt trannies, with 2 110 volt inputs and a zero to connect to bias. same story.

then i used a second pair of tranformers from the same brand as the first. one is older then the other but they measure almost the same. and dimensions of the core are the same to. one is doing slightly better and the other still has distortion at low level as the first 2.

.. im kind of asking myself if the panels are at fault here, or maybe there coating. can they have a to high capacitance?? because of there rather low resistance coating? i think it whas in the region of serveral hundred K or less.


funny thing is in there advertisment from the 70's they said high resistance coating so less prone to arcing and les distortion hehe well nowadays the used resistance of a coating is Way way higher

[WrineX]

Oh i just noticed something in the old (1970) brochure.... there crossover of the type i used the panels from is active.... maybe they kewn the problem and got around it by going active ??? i know there smaller models with just 4 elements instead of the 7 i use now is crossed passive as well as active. maybe theres a reason why they did not go passive, (distortion)

i also have to use like really small cap values to let it roll of at 500 hertz, 10uF.

wich implies that the resistance is already around 30 Ohm at 500 hertz.

[geraldfryjr]

Hmmmm....Interesting !!!

When I get my new panel finished I will look more into this.

The reason I had stopped was due to HV breakdown of the stator coating's and this stopped me from my transformer testing many times and permanently when the panels finally met their demise earlier this year.

So stay tuned as I will be testing the Antek AS-1206 power transformor for ESL use.
I will then be able to add a capacitor in my setup as well and see if I get the same results as you do.

It had been almost three years now since I was trying to make a passive crossover for it.
Then I had to set it down for a while to re-arrange things due to ground loops in my system and to finish building my Variable HV power supply.
Plus a trip to FLa. to get the rest of my equipment and set it all up again.

So right now I am just getting to the point were I had left off again!!!



jer

[WrineX]

ok i tried only one panel with a cap to compare with one panel wil high resisting coating.

funny enough both had no distortion....... hmmm. i then though i desolder 4 of the panels in my setup to see if i lose the distortion then.. well no. still distorted.

i do think it might have to do with the capacitance of a few of these panels and a cap in series with the primairy. i really should get me a few panels with high resistance coating to check if this helps. getting sick of this crap. cant believe al 6 tranies i tried have core saturation when playing on low volume. as capacity said. it should be more noticable when playing louder.

i just noticed capacity said this in a really old thread of mine wich exact same problem. my mind forgot ewhat the solutions was back then or if i even had one in the end or just thought id live with it. the setup i used back then was same brand and type of tranies, with same kind of panels. i used six back then and 7 right now.

[bolserst]

Originally Posted by WrineX

i do think it might have to do with the capacitance of a few of these panels and a cap in series with the primary... cant believe al 6 tranies i tried have core saturation when playing on low volume. as capacity said. it should be more noticeable when playing louder.

I agree it is not likely to be core/transformer related saturation as these type of problems almost always get worse as volume is increased. That was why I had suggested a test to prove whether the distortion is coming from the amplifier or transformer/ESL. I will try to clarify/simplify the explanation of the test.

Figure (A) is the setup you described that gives you distortion.
Measure or listen to the voltage at "V1" and "V2"...you can simply hook up headphones at these two points and listen.

If only V2 sounds distorted, the distortion is coming from the transformer or ESL.
If both "V1" & "V2" sound distorted, the distortion is coming from the amplifier.

If the amplifier is distorting it is most likely due to an impedance dip from series resonance between the 15uF capacitor and the transformer primary. I believe this is the case based on the +15dB peak in the response from your post #1. To get this size of peak, the impedance will have dropped to the DC resistance of the transformer primary(probably < 1ohm) and impedance phase will swing from +80deg to -80deg either side of the dip. This can upset the best of amplifiers.

To test this hypothesis, you can apply damping to the resonance with a resistor "R" as shown in Figure (B) or Figure (C). A resistance of 15ohm - 30ohm will work fine. With the panel producing distorted sound, connect the damping resistor and see if the distortion is reduced or eliminated. Figure (C) is the preferred setup as this placement of the damping resistor swamps variations in the transformer impedance and helps to stabilize the crossover operation.

i just noticed capacity said this in a really old thread of mine wich exact same problem.

Can you post a link to this old thread? I wasn't able to locate it.
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