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Old 3rd October 2011, 11:06 PM   #161
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Default Harmonics

Here is harmonics roughly -141 dB down from full output.
Attached Files
File Type: pdf Distortion Analysis.pdf (17.7 KB, 42 views)
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Old 3rd October 2011, 11:14 PM   #162
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Default SR 50V/uS

Slew rate plot
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File Type: pdf Transient Analysis.pdf (10.5 KB, 28 views)
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Old 3rd October 2011, 11:21 PM   #163
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Output Noise vs frequency. It can be seen that the pre-amp dynamic range is much superior to that of a 24bit D/A converter.
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File Type: pdf Output noise.pdf (9.1 KB, 25 views)
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Old 4th October 2011, 08:06 AM   #164
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Quote:
Originally Posted by Waly View Post
I am one of those that requested and received by email the full schematics. Obviously, I am not supposed to make these public without express permissions, however there are a few things that can be told about.

- First, the schematic posted here is the same with the signal chain schematic that I received. I'm not going to comment on the signal chain details (although there are lots of question marks regarding the design decision).

- The schematic I received has flagrant errors (like the negative power supply shorted to the servo opamp output, the negative supply parallel regulator current source having the pinout of a LM337 (which would, BTW, work fine as is) but claimed to be a LM317, etc...

- I've tried several times to discuss by email with the authors, but received nothing but pushbacks like "the schematic is correct as it is". Any common sense or simulation shows that implementing the schematic as distributed would lead to a pile of smoked silicon.

- There are some flagrant contradictions between the schematic, the BOM and the PCB pictures.

In conclusion, I wouldn't touch this design with a pole. I have no idea what are the authors after (certainly doesn't sound like DIY to me), I am not sure if the schematic was sent on purpose with flagrant errors (I am inclined to think so), or the authors have no idea what they are talking about, but I would warn anybody attempting to build this preamp to expect some significant troubles, both technical and in communication.

That's all folks, now back to my lurk mode...
There is a few flaws in the schematics, but not in the signal path.
So do not use the schematics to build the preamp, use the Gerbers available and follow the instruction.
We do not want anybody to build according to the schematics, as the layout is part of the performance. And of course the PCB is completely free of errors, as is the BOM.
There is no LM 337 only 4 pcs of LM317.
Your question marks about the design, is exactly what we do not want to discuss.
And if that keeps you from building it, that“s alright with us.
We care about the lot wanting to build our preamp, and less about the few people wanting to discuss it.
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Old 4th October 2011, 08:12 AM   #165
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Quote:
Originally Posted by Nico Ras View Post
For reference purpose or those who may be interested, attached please find my super linear dual complimentary symerty line amp and headphone driver. For those who are interested I have a full set of gerbers and boms. This pre-amp has been replaced in my commercial line-up with a newer version that improves the specs a tad more.

I started a write up for DIY Audio but did not find the time to complete it, sorry, but what is there may be useful.

Also the Pre-amp features a virtual earth thus is completely imune to earth loops and also needs no servo.
Why are you pushing alternative designs here in our thread?
It would be more natural to open your own thread, and help people out building it.

Btw. You design looks nice but it is full of caps.
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Old 4th October 2011, 08:43 AM   #166
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@Nico Ras

Just came across your picture of your project.
And I must say, that this kind of amp is exactly what we did not want to build.
This type of design was pretty much what we had already.
If you look at our design, you“ll see, that there is only one capacitor in each channel.
This is the cap determining the cut off frequency in the servo circuit, which is chosen to low to do anything else than temp drift.
There are not even decoupling caps in the power supply.
The design does not need bandwith limitation ore anything like that. It is perfectly stable @ any frequency without.
And believe me, it both performs and sounds much better without.

These things are often very hard to discuss. Most people want big power supplies with sufficient + electrolytic caps.
In our design we chose shunts, that equals 1.000.000µF pr. channel, but without the impedance problems of caps.
Besides being both a performance and soundwise superior solution, it also takes up a lot less of space and costs a lot less.

The straight forwardness, the compactness, the lack of caps, the very low noise and low impedance PSU, the low servo cut off and the choice of especially transistors, are the main reasons for the sound quality praised so much by those who build it up until now.
Some of these upsides can be measured, some cannot, or at least we do not know how to.
But believe me, these are matters of concern.
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Last edited by Kurt von Kubik; 4th October 2011 at 08:44 AM. Reason: forgot @
 
Old 4th October 2011, 09:02 AM   #167
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I just thought I put some life in the thread.
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Old 4th October 2011, 09:51 AM   #168
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Quote:
Originally Posted by Nico Ras View Post
I just thought I put some life in the thread.
The point is, that there is pretty much going on out of your sight.
The number of Mails and PM“s are substantial, and the number of downloads are amazing.
If no one will build it, and if no one of the guys who did build it after all likes it, then the thread should not be kept alive for any reason anyway.
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Old 4th October 2011, 10:26 AM   #169
Bonsai is offline Bonsai  Taiwan
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Quote:
Originally Posted by Nico Ras View Post
I just thought I put some life in the thread.
LOL!

Kurt, You have a strange and unique marketing approach - seems like 'just do it'.

But, a picture is worth a thousand words. Can you show one?

Anyway, whatever the outcome, good luck Kurt!

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Last edited by Bonsai; 4th October 2011 at 10:45 AM.
 
Old 4th October 2011, 10:49 AM   #170
PMA is offline PMA  Europe
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Quote:
Originally Posted by Kurt von Kubik View Post
@Nico Ras

Just came across your picture of your project.
And I must say, that this kind of amp is exactly what we did not want to build.
This type of design was pretty much what we had already.
This thread is extremely strange to me.
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