Comparing LME49810, 49830 and 49811 - Page 3 - diyAudio
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Old 4th May 2009, 09:49 AM   #21
AndrewT is offline AndrewT  Scotland
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what happened to the requirement for linearity.
The gain @ 7.5Apk is excellent @ >10000.
but at 25mA (~bias current) it is ~160.
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Old 4th May 2009, 10:34 PM   #22
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Quote:
Originally posted by AndrewT
what happened to the requirement for linearity.
Very good point! Current gain of NJL3281D output and MJE15030 driver are "nearly" flat.
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Old 5th May 2009, 07:11 AM   #23
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I don't see the reason why mess with Darlingtons, gain curve tells you all. I really do not like to impose but please try my output stage schematic and you'll hear the difference compare to all classical outputs. Besides you won't have any problem with too large output currents of LME49811.
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Old 6th May 2009, 01:13 AM   #24
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Here is LME49810 (the chip itself) clipping property.

Click the image to open in full size.

When there is not external load, except 100 k input impedance of the AP S1, the chip has symmetrical clipping.

Click the image to open in full size.

When a 500R resistor is added as load, the positive cycle clips earlier.

Click the image to open in full size.

Here you can see how the waveform changes during chipping (slope to flat top).
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Old 6th May 2009, 01:23 AM   #25
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Quote:
Originally posted by Lazy Cat
I don't see the reason why mess with Darlingtons, gain curve tells you all. I really do not like to impose but please try my output stage schematic and you'll hear the difference compare to all classical outputs. Besides you won't have any problem with too large output currents of LME49811.

Dear Lazy Cat,

The only valid reason I can give you is that the STD03's (darlingtons) sounds exceptional good. Fast, totally holographic and deep.

I am a very spoiled listener, I owned Bryston 7B's Krell KMA200's Mark levinson NO 23.5 before and I am very critical. I build many power amps myself from mosfet to BJT to passlabs design. And the STD03's just blowed me away in combination with the LME49810. This is just a judgement by my ears and not any technical reasons.

With best regards,
Bas
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Old 6th May 2009, 01:42 AM   #26
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Is it analogous to vacuum tube? They don't have "good curves". But there are good sounding tube amps. Although we can do many measurements to collect technical data, the final judgment is still sonic performance. We are making audio equipment for complex human auditory system.
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Old 6th May 2009, 02:05 AM   #27
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Originally posted by panson_hk
Is it analogous to vacuum tube? They don't have "good curves". But there are good sounding tube amps. Although we can do many measurements to collect technical data, the final judgment is still sonic performance. We are making audio equipment for complex human auditory system.

Exactly Panson.

I will admit as first that I was myself often blinded by pre judgements and "ideals"

The STD03 darlingtons's are a good example of that. Trust me I disliked them.. and I could never understood why brands as Musical Fidelity or Arcam used those Sanken darlingtons. Then I got a project where I needed to design a very very compact amplifier that can be as small as class D. So a logical step was a driver chip alla LME49810 and STD03 darlingtons. This way we safe a lot of space. No need for VBE multiplier circuit, no driver transistors. Very compact, mission accomplished. The whole project felt as a huge compromise and I didn't expected to much. Till it was all done and built and we start to listen... And then we got floored by the incredible holographic 3D stage, the speed and the bass tideness. Since then those STD03's became an obsession for me since I get totally hooked to this sound.

My point is, we should really try things out, even though we don't expect anything from it.

That is why I feel it is a good thing you test out all 3 driver chips. With actually built and listen to it, it all become clear. No specsheet or measurement can really tell you which of the three driver IC's wil sound best. Now you are able to actually listen to them. A second nice (listening) test would be, the drive IC with various output devices. From mosfet's to the ON thermal traks' and for sure give the STD03's also a try.

I believe by doing this, actually listen step by step to various parts of a circuit and combine them, this is the way to truly create an amplifier that fits your sound ideal and philosophy of how music reproduction should be. Measurements don't lie, but our ears don't lie either. Measurements can be manipulated or implemented differently. Our ears can cheat us and fool us as well. As often the truth lies somewhere in the middle

With best regards,
Bas
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Old 6th May 2009, 09:26 AM   #28
Dxvideo is offline Dxvideo  Turkey
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A (may be stupid ) question ,

Does, driving SAP15 (or STD03) devices directly with LME49811 cause any problem do you think?
Because as I see in Panson_HK's distortion analysis when you drive lower loads (like 1K) with 49811 then THD levels increases just after 2V RMS output! And we have a 200R bias trimmer between SAPs (or STD) bases...
So I am not sure that 200R trimpot seems a load or not from the LME side????
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Old 6th May 2009, 02:03 PM   #29
michahn is offline michahn  France
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Dear Bas,
Interesting comments. Would you be so kind to tell us how you managed the BIAS business in your LME49810/STD03 project?
Thanks in advance,
Michael
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Old 6th May 2009, 02:10 PM   #30
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Quote:
Originally posted by Dxvideo
A (may be stupid ) question ,

Does, driving SAP15 (or STD03) devices directly with LME49811 cause any problem do you think?
Because as I see in Panson_HK's distortion analysis when you drive lower loads (like 1K) with 49811 then THD levels increases just after 2V RMS output! And we have a 200R bias trimmer between SAPs (or STD) bases...
So I am not sure that 200R trimpot seems a load or not from the LME side????

AC (signal) current does not pass the trim pot. The voltage drop across 200R is a DC.
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