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Old 19th August 2010, 07:36 PM   #1
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Default what amplifier for driving esl

Hi

today my amp quit working , the fuse is black an a part called sanken 2sa1216
is black too it was a sony 550 es amp I mean it still is I hope replacing the parts should fix it.
so this amp isn't the right one i think.now i have the sub a TL with a sls10 and a active crossover behringer and the esl panels work well but i need now a amp for driving the esl.
I also tried a resistor 1 ohm at primary winding but they get hot and smoky.

My question what amp work fine for an esl and what specs must it have.
what amps do you have?

(Ps: I accidentally unsubscribe from my last thread )

thanks hironimo
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Old 19th August 2010, 08:18 PM   #2
taotao is offline taotao  Germany
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Location: Cologne
Hi hironimo,

you didn't give some details 'bout your ESL's.
In my installation, I use a Vincent SP331. It has good control over my ML Sequel2 and doesn't sound stressed. Tight bass and silky highs.
I have also good experience with a tube amp (KT88 PP), but only with impedance correction to flaten the impedance.
Most ESL are a difficult load to amps, not because low efficiency, the reason is more the twist in phase combined with a capacitive load.

Regards
Olaf
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Old 19th August 2010, 09:12 PM   #3
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Hi Olaf

my system is:
2 toroidal transformers 1:65 ,
regulated bias supply
the tall speaker has 4 panel each 6 inch x 10 inch ( 15 x 25 cm)
the grey panel is 16 x 20 inch ( 40 x 50 cm)
a tl with a peerless sls10
coated with elvamide.
behringer crossover
behringer amp reference500

I'm experimenting how o to put all things together it sounds ok but not so good it's hard to match the tl with the esl and daming the tl more or less makes not much difference to me

my priority is now to get another amp.

thanks!

hironimo
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Old 19th August 2010, 11:32 PM   #4
EUVL is offline EUVL  Europe
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If I could presume you could read German :

FAQ

under the section "Können Sie einen geeigneten Verstärker empfehlen ?"

Naturally they are meant for Capaciti products, but most ESLs have similar impedance behaviour, so you might wish to consider what he says. He did recommend using Class D amps in one of the German HiFi forums, if I remember correctly.

PS I have no link with the company whatsoever.


Patrick
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Old 20th August 2010, 07:34 AM   #5
Calvin is offline Calvin  Germany
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Hi,

as Taotao wrote low resistance are typically not the major problem for a decent amplifier. The major problem is rather the complex load which You can read from the phase-response of the impedance plots.
Amplifiers with global feedback which is connected from their very outputs to the inputs lets the amplifier react on this complex load. The negative feedback, which under normal conditions reduces failure artefacts within the signal, can change towards a positive feedback that enhances failure artefacts and can lead to oscillation of the amp. I assume this happened to Your amp.
There are some measures against this effect, some relate to the speaker itself and some relate to the amplifier.
Toroid transformers typically are lowloss devices which means that the amplifier ´sees´ more from the ESL´s capacitive nature. The phase response shows exaggerated values which can reach values of >80°. This is alot more than many amps can handle, hence they are prone to oscillate. Transformers with different cores like EI typically present the amp with lower values of phase shift and the amps life is much easier and it might remain in a stable working condition.
Series connected resistors (they need to be power resistors rated at several W) also reduce the burden on the amplifier by reducing phase shift and increasing the resistive part of the load impedance. Because this measure also influences the amplitude response of the speaker, resistor tuning works only within tight limits.
The amplifier related measurements mean modifications of an existing amplifier -without the guarantee of success- or the choice of a capable amplifier. Tube power amps coulod be a choice. Their output transformer counters the capacitive ESL load to a degree and Tubes show a more relaxed behaviour under large signal or overdrive conditions. The copper resistance of the transformer works like a seriel resistance, so in some cases You don´t need a dedicated series resistor or a lower value (otherwise there could be a high frequency loss). With transistor amps it may be useful to choose an amp which has been tested to work stables into loads with vast levels of phaseshift. It may also be helpful to break the direct output-input connection of the negative feedback. Most amps feature sourcefollowers or emitterfollowers as power output stage. This confirguration has a gain of ~1 and a tight internal feedback. Because of this one can place the output feedback node right in front of this last stage, thereby ´isolating´ the feedback from the load. Mr. Erno Borbely had some amps on his website where You could choose between different feedback-nodes. Probabely the best would be to omit with global feedback altogether. Single Ended Triode amps wo global feedback seem to be the best solution not only from the point of stability but also from the point of sound. ESLs are very revealing and I must say that I still have to hear the globally fed back amp that doesn´t sound grainy and flat with a good panel.
Class-D amplifiers are a different class of amplifiers that may give good results with regard to stability. But this depends similar to class-A or class-AB amps on their topology. Class-D which don´t incorporate their output filter into the feedback loop (type A) are rather stable working, class-D with global feedback (type B) have their feedback loop modified by the load. Class-D amps have problems similar to classA/AB and problems of their own. In case of type A the output inductor forms a resonant circuit with the ESL. As a result a quite strong peak in the amlitude response develops (I measured up to +12dB!) which lies within the audio band (10kHz-20kHz) or the low ultrasonic range. Amplitude response above the peak frequency drops sharply. This must be countered with an equalizer that notches the peak. Still tough the bandwidth limit of the system may be as low as 10kHz. Class-D of the type B show a better amplitude response and higher bandwidth. Sonically on both types the ESL sounds very tightly controlled and high level dynamics can be truely outstanding. But the tonal character is rather technical -some may say ´cold´. With ´processed´ music this can sound awesome with natural sounds and classical music its sounds rather uninspiring. You never doubt any second that You listen to a technical reproduction of music. Sadly ESLs are very unforgiving in this quality of an amplifier which ha meade me very supspicious over the years about the use and good or bad of global feedback in audio amplification.
More unfortunately are good and powerful SE-triode amps rare and expensive. If Your budget can afford the abuse You might give such a tube amp a chance. But beware You might be affected by a music virus ;-) ....and what the heck...building a concert hall in Your garden and hiring musicians will be even more expensive in the long term

jauu
Calvin
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Old 22nd August 2010, 05:26 PM   #6
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Hi

Thank you for your replies I'm getting slowly smarter.
so a transistor amp should work with 2 ohm speaker
min 100 w and it's better it has a huge powersupply ?

and a class D amp B type should be fine Also 100 W ?

and when I want to get a tube amplifier , how much W should it have?
Can i just buy one and it will work fine with my panels (sound and quality of the amp is another topic)
(and what about "TaoTao :I have also good experience with a tube amp (KT88 PP), but only with impedance correction to flaten the impedance.")

hironimo
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Old 22nd August 2010, 06:41 PM   #7
taotao is offline taotao  Germany
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Hi hironimo,

I'll give you an example, concerning impedance correction.
If I measure the impedance over frequency at my ML Sequel2, I get the diagram as you see in the first left pic.

After adding an impedance correction, I get the curve as shown in the second pic.

Tube amps in general have lower dampening factor in comparison to solid state amps,
as a result, the peaks in impedance response produce a peak in frequency response
(in my case up to 4 dB more in the midrange with the Sequels if impedance is uncorrected).
The corrected impedance gives a nicer load for the amp,
also the phase twist is lower. All in all the sound is better.

Even SS amps can benefit from this correction
(although, with my Vincent it's not necessary/ audible).

You need only three parts (if you don't flaten the imp peak in the bass region).
This parts don't have to be high quality parts.
You need a coil, a resistor (cheap cement type, 5-10 watt) and a cap
(electrolytic is sufficient).

The values I needed were: a coil with 0,15mH (0,3ohm),
a 4ohm resistor and 47 mF cap (not milli, but micro, I can't put the right sympol in this editor :-)

This three parts have to be connected in serie from the minus to plus terminal of the amp (or at the speaker terminals).

Of course, the values are for the sequel, but may work with your combination, too
(if you should decide for a tube amp).

Concerning power: My amps have EL34 and produce around 38 watts per channel.
This is plenty enough for my needs and I can play very loud (OK, very subjective, of course)

One addition: I didn't calculate the values, I used ARTA for imp. measuring (ARTA Home)
with a measuring box and some parts I had at hand.
Luckily they fitted well.

Regards
Olaf
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Old 24th August 2010, 02:46 AM   #8
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OMAK Jewel One or Three
Hard to find but few amps handles complex impedances as thos amps, most because of the no nonsence design.
Low feedback, low distortion, high current drivability, low output impedance, and output transformers in 600VA size (pretty good for a 50W amp)
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Old 25th August 2010, 10:10 PM   #9
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Hi Hironimo,

I have been using a pair of Crown DC300A series 2 for two years (1 section for each of 4 panels) with good results.

Jeff
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Old 3rd September 2010, 07:59 AM   #10
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Default Proton D 1200

Hi
What you think about a Proton d 1200 I can have one for 300 euro it looks like it is good for esl.and by the way replacing the transistors in my sony amp worked! so I'm verry happy.

hironimo
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