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Old 29th August 2012, 11:13 PM   #2861
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by DIGORA View Post
Hello Jay,

I pasted this site link to illustrate my request about the SLC

I would like to make a very fast and linear amplifier with lateral mosfet output 2SK1058.

The speaker : http://www.hometheaterhifi.com/image...ance-phase.gif
There is no proof yet that SUPER fast amplifier is better (than "sufficiently" fast one). The SLC is fast but less fast than Esperado's SSA Crescendo. To increase the speed is difficult because faster means more prone to oscillation. I think the high voltage of the SSA crescendo also contribute to the speed (SLC uses very low voltage rail, may be 1/3 of the SSA Crescendo).

The SSA crescendo is probably the fastest amp here, but I don't think it is capable of driving some electrostatics. But to my surprise, your planar speaker is not really that difficult? I'm not sure if it is 100% planar or not. EDIT: Eww! I was looking at the purple chart. The impedance chart is the orange one, which is a difficult load. Esperado will explain if the SSA crescendo will be suitable, but I think it is not.

What do you think of a Moskido? Too slow? EDIT: I think the nature of a planar strings is slow, so Moskido might suit the speaker better.

Last edited by Jay; 29th August 2012 at 11:21 PM.
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Old 30th August 2012, 01:14 AM   #2862
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Originally Posted by Jay View Post
but I don't think it is capable of driving some electrostatics Esperado will explain if the SSA crescendo will be suitable, but I think it is not.
I don't think too, would need more than 4 paralleled power fets at least (i think 6) for each branch, so driver modification to increase the power, and no idea about the stability.
If i remember well, here, in this thread, L.C had proposed a special SSA for very low impedance devices :Simple Symetrical Amplifier and Simple Symetrical Amplifier
I think (i have no experience with electrostatic drivers) bipolar power transistors will manage better the capacitive loads.
Thoughts ?
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Last edited by Esperado; 30th August 2012 at 01:34 AM.
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Old 30th August 2012, 02:27 AM   #2863
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Thinking about electrostatic loudspeakers and fast amp, my first thoughts where those ones:
The transients and flat phase curve advantages of a very fast amp has no sense, here, because the amp will deliver his hf components in a near short circuit. PSU will not be able to deliver this fast changing current and the fastest amp will be... slow.

If we consider that the current feedback quality is on the TIM side, and this, because the CR is fast enough to make his correction in time (no pole limitation), we can go for CR. But the balance between voltage and current will be nonsense at hf and we can worry again about TIM here where global speed (and slew rate) will only present inconveniences..

So, no need to look for the fastest amp ever. On the contrary, i think the main objective would be to go for current capability and stability, and try to reduce as much as possible the bandwidth, on the hf side, before the input, to avoid any fast signal to introduce TIM by lack of current during transients. A lowpass filter need to be tuned with care before the input.
To summarize, looking for a superfast amp to power an electrostatic loudspeaker is like finding a Ferrari to plow a field, might not be the best tool.

For all the other aspects, damping factor influence, advantages between FETs and BJTs in the output, i will try to explore what's happens in the cr loop using simulation to make my mind, the subject is interesting.
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Last edited by Esperado; 30th August 2012 at 02:33 AM.
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Old 30th August 2012, 03:17 AM   #2864
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Hi every body!
Is my schema correct?
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Old 30th August 2012, 01:15 PM   #2865
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Originally Posted by Esperado View Post
PSU will not be able to deliver this fast changing current and the fastest amp will be... slow..
I have made a quick simulation of the Crescendo with 5µf paralleled with the charge. Stability looks ok (but sim is not real world).

As expected, the bandwidth is reduced from 7mhz to 2Mhz (-3db). Slew rate is not fantastic anymore and square waves shows an overshoot: I'm sure the current monster SSA will perform better in a more healthy way..
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Old 30th August 2012, 01:27 PM   #2866
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Originally Posted by nalimko33 View Post
Hi every body!
Is my schema correct?
Hi nalimko33

Yes it will work, since it is SSA (DC coupled input & feedback), be careful that R2, R6 are not less than 100 ohm and input BJT pair are face coupled for thermal stability. Otherwise I will just say, go for it
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Old 30th August 2012, 05:45 PM   #2867
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Originally Posted by Lazy Cat View Post
it will work, since it is SSA
No need for a Director of Marketing.;-)
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Originally Posted by Lazy Cat View Post
... go for it
nor advertising agency.
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Old 30th August 2012, 06:03 PM   #2868
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LC: thanks… I will finish my schema and I post it there…
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Old 30th August 2012, 09:02 PM   #2869
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There is one 1k2 resistor missing. I tried to draw, but Alex will do it better. His work is always exellent.
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Old 30th August 2012, 09:41 PM   #2870
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Quote:
Originally Posted by Esperado View Post
No need for a Director of Marketing.;-)

nor advertising agency.
hehehe Esperado I'm glad you're in funny mood, so many new info from you lately, really appreciated your support.

Regarding your quote, I meant that presented sch will work if nalimko33 will follow some rules, not that it will work just because it is SSA. My bad english use I suppose. Sometimes I hardly explain what I would like to, but eventually after few posts I usually manage to be understood.

As "go for it" matters, I meant that nalimko33 has talent because he presented his own version of SSA sch, so I meant, yes, go for it, experiment, measure, enjoy DIY work and end result, not just follow some cook book recipe.

Uff that was I meant, not marketing really
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