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Simple Symetrical Amplifier
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Old 8th November 2011, 07:15 PM   #1361
Lazy Cat is offline Lazy Cat  Slovenia
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Quote:
Originally Posted by sonnya View Post
Sorry, I can't tell you.

I am doing the job for another guy.
mhmmystery I like it
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Old 8th November 2011, 07:30 PM   #1362
sonnya is offline sonnya  Denmark
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Well the frontend is not different from your design.
This evening i have added a servo, and the circuit behaves very well. DC offset is below 1mV..

I just wanted to offer my knowledge and findings on the frontend.
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Old 8th November 2011, 07:35 PM   #1363
Salas is offline Salas  Greece
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Can you at least reveal generalities like power output, bandwidth, up to what stage the servo loop extends, and how the amp compares subjectively regarding your prior art amplifiers?
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Old 8th November 2011, 07:56 PM   #1364
sonnya is offline sonnya  Denmark
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The servo is added to the feedbackloop, notning special about.

The bandwidth is ~800khz, its output level is ~ 150watt in final version..

But right know it is running from +/-45vdc

I am going to compare it with My last AMP (CFB with ecx10) output.
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Old 8th November 2011, 07:58 PM   #1365
Salas is offline Salas  Greece
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SMT multilayer PCB like those beauties you used to do for the Mirand?
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Old 8th November 2011, 08:36 PM   #1366
sonnya is offline sonnya  Denmark
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Like this one:

http://www.diyaudio.com/forums/solid...ml#post2659204

In this stage with minor modification it performa very well. In fact it has top and midrange is better than a burmester integrated. The bottom lacks a bit compared to burmester. But it is only a 50watt design with a single 300va for both channels compared to a 100watt with a larger powersupply, also the bottom has the same signature as Many mosfet based amps.

The top and midrange is very detailed and in the same time not harsh. I Think mainly due to the 400ma bias current.

This amp is the mark for comparison. This AMP is also being updated, and will get better.

my own designs Will follow the path from the mirand A1 to get this design more purified. The AMP i am doing for another person is made on the basis from the AMP in this thread, not my mirand AMP.

I Will try to compare Them but it Will maybe be in favor of my own designs. Such comparison should not be done vy the designer himself.
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Old 8th November 2011, 08:48 PM   #1367
Salas is offline Salas  Greece
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I will put 1k trimmer for the output stage bias resistor in the one with the CCS patches I am preparing to test because I smell there will be a few Iq favorites to listen to (if the rest will go well, first things first). 100mA looks interesting in LT SPICE at least.
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Old 8th November 2011, 11:50 PM   #1368
Esperado is offline Esperado  France
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Originally Posted by mikelm View Post
Could you explain the subjective sound when you achieved 1000V / uS slew.
I would also strive for high slew rate but in practice I have found that slower can sound more pleasant and realistic in some ways.
It may seem curious, but the more noticeable improvement is in the basses. Specially kick drums. More solid, less "one note", more fast and detailed. Separation is better and treble less aggressive (you can feel you have lost some of them). Of course all depend of the source. You can discover some saturation and clipping in CDs that you never noticed before, and an aggressive recording will sound more aggressive, while a good one softer. By contrast.
You can feel you have lost some power too (less distortion at high level ?).
Of course, there is not a huge improvement in my amp, as it was quite fast before (~200V), and the incoming signals where yet kept slower than his capability. And it is difficult to say what is the part of the speed and the one of the reduced distortion SSA had brought. Thanks to Andrej's talent
Last, i would like to precise that my loudspeakers slows down after 16KHz, i do not like to reproduce trebles in excess, often added in mixes, and i'm more aware about dynamic and energy (they are JBL 1"drivers+spherical horn in wood, cut at 1000Hz). And i do not have my young ears anymore too. But I believe there is not so much interest to increase slewrate after something like 500V/Ás, while it cannot be bad and it is fun.

Now, if you like to reduce the bandwidth, and i know some CD with imperfect filters can be better that way, a low pass filter before the input will do it in a linear way, with coherency between phase, bandwidth and global slewrate, and will reduce further the chances of any TIM.

Quote:
Originally Posted by Lazy Cat View Post
What you did to Crescendo is just simply amazing, I am impressed.
I'm impressed too by the results. But the idea comes from you you. Did-you amaze yourself ;-)

Last edited by Esperado; 8th November 2011 at 11:59 PM.
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Old 9th November 2011, 07:44 PM   #1369
mikelm is offline mikelm  England
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Thanks Christophe for your comprehensive reply to my question.

From your description I suspect that as well the increase in slew rate, the other improvements you made significantly contributed to the increase in the sound quality and it sounds like you have a very nice amp - thx for sharing

mike
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Old 10th November 2011, 09:45 PM   #1370
sonnya is offline sonnya  Denmark
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I have packed the prototype today.

I had it on my system shortly -

MiniPC + itunes + M2Tech Young DAC - Amplifier (DUT) - Audiovector M1 Super.
The speakers needs to be upgraded but they are not bad bad...

I tested it on different types of music for 30minutes before packing it down.

The amp is not bad. You will very quickly notice if it dull to listen to.
It is musical no doubt about that.

There is less edge on the transient than on my CFB + EXICON. The detail level is good.
It has more details in the bottom, but i have made a fault on my CFB + EXICON.

The SSA and the CFB + EXICON has nearly the same bandwith of approx. 600KHz.

The servo in my amp has a minus 3dB point of 3.3Hz. On the Mirand AMP it is set too 0.3Hz (And this was stated to be bottomless on the hififorum.nu)

This this SSA it is set to 1Hz. It is in the Middle.... It the bottom detail level is also in the middle between those two.

The Mirand A1 AMP is more stable regarding DC offset than the SSA without SERVO, there the SERVO is only used for removing DC from a Source.

Regarding the SSA it is also there to control the "wild" swings. But at present time with DC servo the out floats below 1mV... So thats is okay. I could maybe lower DC invoke frequency, but that will time tell..

The Facit:

For the sound it is worth building - And as allways it is matter of taste... But i think most people would be very satisfied.

My opinion - There is still a lot of work to do on it! Many things need to be solved....., but the sound is worth it...

I will comment more on other amps, and in comparison. I have some sets of amps.. Mirand A1 V1.1, SITO Audio CFB + EXICON V1.1, FETZILLA and SITO/MIRAND A2 V1.1 (Next weeks)..

If the SSA was AC coupled with lower rail voltage it would make a PREAMP. There is no HISS...
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