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Old 30th September 2011, 10:48 PM   #151
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See now your thread is dead, just because of the all knowing attitude.
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Old 2nd October 2011, 08:16 AM   #152
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Quote:
Originally Posted by Nico Ras View Post
See now your thread is dead, just because of the all knowing attitude.
That is quite alright
A lot is going on behind the scene.
Just give the guys a little time to assemble it, maybe they will be back to write a bit about it.
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Last edited by Kurt von Kubik; 2nd October 2011 at 08:21 AM.
 
Old 3rd October 2011, 12:10 PM   #153
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We do not measure succes in comments in this thread actually, but in people interested enough to use the links and download the gerbers and building instructions.
So far 647 people linked to the files from this great site alone already.
If just 1% of those will do the project, then we very soon will hear about their real life sonic impression of the finished project, and not just opinions of the schematics.
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Old 3rd October 2011, 02:16 PM   #154
oshifis is offline oshifis  Hungary
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I have no patience to read through all 16 pages, but I am interested in others opinions of the schematics. Is it a tube, transistor, FET or integrated circuit based preamplifier? Does it contain phono and MC stage, or only line input? Thanks and sorry if it has been discussed before.
 
Old 3rd October 2011, 05:17 PM   #155
Waly is offline Waly  United Kingdom
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Quote:
Originally Posted by oshifis View Post
I have no patience to read through all 16 pages, but I am interested in others opinions of the schematics. Is it a tube, transistor, FET or integrated circuit based preamplifier? Does it contain phono and MC stage, or only line input? Thanks and sorry if it has been discussed before.
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...
 
Old 3rd October 2011, 06:07 PM   #156
Bonsai is offline Bonsai  Taiwan
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VFA OPA_1.jpg



You can try this. Its a voltage feedback amplifer and it sims at about 2.5ppm at unity gain, and 10ppm at a gain of 5 into 600 Ohms. Output is a simple emitter follower - so its designed to run class A. I have aboard layout, but I have not ordered or built any yet.

The pinouts are:-

1 = high output class A - link to -ve supply rail
2 = inverting input
3 = non inverting input
4 = -ve rail - up to 20V
5 = compensation cap
6 = Optional bypass for constant current regulator diodes.
7 = output
8 = +ve supply rail - up to 20V

To zero the output, you can use a servo as you would with a normal op-amp.

I'll do a bipolar input version in the next week or so and then a CFA version with the same pinouts

All dual bipolar transistors are 2% beta match from NXP.

R1 and R2 can be replaced with 0 Ohm links for lower noise, but this will require some adjustment of the comp cap value (which will typically lie between 22pF and 100pf depending on your gain setting.

The comp cap in this design is connected between the comp pin 5 and the output.

Happy experimenting!

(mods, you may want to move this to a separate thread - I leave it up to you to decide)
Attached Files
File Type: zip VFA OPA_1.zip (42.3 KB, 16 views)
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Last edited by Bonsai; 3rd October 2011 at 06:29 PM.
 
Old 3rd October 2011, 09:38 PM   #157
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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.
Attached Files
File Type: pdf HP Amp Rev 08 Schematic.pdf (68.7 KB, 82 views)
File Type: pdf RASLine&HP Amp Rev 11.pdf (66.9 KB, 65 views)
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Old 3rd October 2011, 09:49 PM   #158
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The Gerbers
Attached Files
File Type: zip Gerber Plots R09.zip (169.1 KB, 21 views)
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Old 3rd October 2011, 09:56 PM   #159
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An early prototype
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File Type: jpg Picture 0351.jpg (105.2 KB, 161 views)
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Old 3rd October 2011, 09:58 PM   #160
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The above files are a free for all - you may do with them whatever you please.

Kind regards

Nico
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