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Old 26th September 2011, 02:31 AM   #71
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Quote:
Originally Posted by dodo View Post
I wish to know why LM317 type regulators were used as a current sources in shunt regulators
They tend to pass some high frequency garbages which is no good for any line pre

I wish to get some feedback from the author of this pre -comparitions to which other line amps let him to conclude about music reproduction quality level of his "toy"
There are couple of well reputated preamps ( Pumpkin , Aikido , No26 tube pre , B1 , DISPRE (PMA)
We donŽt have any problems with noise what so ever in this preamp.
Actually in normal use, you cannot hear any difference in noise level regardles of position of the volume control.
Also the PSU has been measured, no noise is present.
The LM317 current source solution was chosen, because of its enormous ripple and noise rejection, theoretically it is more than 160 dB.

Regarding comparisons, weŽve mostly compared it to high end preamps of different makes. But I donŽt really think that has any relevance any longer.
If you read in the original thread about the project, then you can find pretty much feedback about the sound. I can mention a few things from the feedback for you, which has been consistent throughout.
Several builders have said, that "there really isnŽt much to say about it. It seems as if it has little or no sound of its own."
Exactly that has been our goal. So mission accomplished on that.
Another thing that everyone has remarked is the bass reproduction, which they say "is very lively compared to their own preamps, and much deeper and controlled."
I hope this was what you needed.
Enjoy
But not a impressive way just as a part of the music
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Old 26th September 2011, 03:04 AM   #72
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About the need for schematics and maybe a discussion of it, and a short or long process going through every single point once again.
Obviously this is not necessary, we are now close to a thousand downloads of the BOM and building instructions, but only 4 people asked for schematics.
They all had them by mail.

So we will accept that this project is a "GO" for the lot and a "NOGO" for a few.

And if anyone should get the thought of somebody wanting to sell kits, just forget it. We will not sell you anything. YouŽll have to do it yourself.
We helped as much as we think we could, in building a preamp that works and is stable.
Send the Gerber files to i.e. Olimex (OLIMEX LTD ARDUINO MAPLE PINGUINO ARM AVR MAXQ MSP430 PIC LOW COST DEVELOPMENT BOARDS), and in a few days youŽll have your PCB.
Choose your vendor for the components and order for yourself and friends. But do not change anything. Every component has been evaluated thoroughly already.
You can freely choose between the Suncon electrolytics and Panasonic FM.
It is also possible to change the relays from Omron to Panasonic, probably this will save you money. But you also can leave them out, if you just need a single input, which will give you extra performance.
The footprint for the potentiometer can of course be used as solderpoints for a remote pot. The Alps pot can of course be replaced by P&G or likely.
But they are mostly unavailable and costly.

I really cannot see why anybody should feel bad about this.

But if you hear about anyone selling KITs please notify us.
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Last edited by Kurt von Kubik; 26th September 2011 at 03:19 AM.
 
Old 26th September 2011, 06:25 AM   #73
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For those assembling the pre-amplifier.

To do it right, you must connect the power supply board to the main board as follows:

When placed just towards one another, the leads from the PSU board should be crossed when connected to the main board.
This along with the polarity of the wall outlet, that produces the smallest potential from amplifier ground to local earth, will produce by far the best sound quality.

So keep that in mind.

Also be shure to chose the right power voltage. The building instruction will only show you the 230VAC connection. But that should quite logical anyway.

Anyways it would be nice if some of the downloaders who actually are building the amp, would write us some feedback.
Please do so.
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Old 26th September 2011, 09:58 AM   #74
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What exactly is this pre-amp used for? Is it to amplify the output of a moving coil pick-up or is it to modify the output from a CD player or other high level playback device.

Why would one want to put this thing between a CD player and an amplifier, to adjust the volume or to modify "distort" the sound somewhat. I see the bass is very impressive according to you thus it must be modifying the original signal, increase/shape/distort the bass (and possibly all other signals). I cannot see how otherwise it would make an original signal coming out of a CD player better than what it is without adding distortion or character that is not in the original output.

Just the fact that it sounds different from what comes out of the original source means that you are listening to something that changes or distorts the original signal.

If it was pure and added or subtracted nothing from the original signal then why would need one of these at all?

Last edited by Nico Ras; 26th September 2011 at 10:11 AM.
 
Old 26th September 2011, 10:29 AM   #75
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Why do you use BFR90/BFT92 in your amplifier. It is typically used for oscillators in garage door key-fobs, UHF TV antenna boosters, and the like. Is there a need to amplify RF signals in your design, it is not particularly suitable for low frequency.
 
Old 26th September 2011, 11:13 AM   #76
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Quote:
Originally Posted by Kurt von Kubik View Post
There will be no schematic published what so ever.
Then there is no interest whatsoever from this side.
 
Old 26th September 2011, 11:20 AM   #77
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Quote:
Originally Posted by Nico Ras View Post
What exactly is this pre-amp used for? Is it to amplify the output of a moving coil pick-up or is it to modify the output from a CD player or other high level playback device.

Why would one want to put this thing between a CD player and an amplifier, to adjust the volume or to modify "distort" the sound somewhat. I see the bass is very impressive according to you thus it must be modifying the original signal, increase/shape/distort the bass (and possibly all other signals). I cannot see how otherwise it would make an original signal coming out of a CD player better than what it is without adding distortion or character that is not in the original output.

Just the fact that it sounds different from what comes out of the original source means that you are listening to something that changes or distorts the original signal.

If it was pure and added or subtracted nothing from the original signal then why would need one of these at all?
Well
YouŽl have to study the output of i.e. a DAC and a CD player then.
A preamplifier has the job to drive cables and load, and thus protect the source against it. thatŽs just about it.
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Last edited by Kurt von Kubik; 26th September 2011 at 11:34 AM.
 
Old 26th September 2011, 11:31 AM   #78
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Quote:
Originally Posted by Nico Ras View Post
Why do you use BFR90/BFT92 in your amplifier. It is typically used for oscillators in garage door key-fobs, UHF TV antenna boosters, and the like. Is there a need to amplify RF signals in your design, it is not particularly suitable for low frequency.
They are used in the shunt regulator, and is particularly intended for HF. The shunt has a cut of frequency around 10 MHz.
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Last edited by Kurt von Kubik; 26th September 2011 at 11:59 AM.
 
Old 26th September 2011, 12:08 PM   #79
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What you are saying is that my CD player cannot be connected to the interconnection cables. My goodness, I must have stuffed up my CD player completely over the years connecting it through wires to my amplifier.

Where can I study DACs because I do not work in the insurance industry.
 
Old 26th September 2011, 01:05 PM   #80
simonov is offline simonov  Bulgaria
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@Nico Ras

If you open your CD player you will most probably find a standard arrangement of opamps. A single opamp is in many situations incapable of driving high capacitance loads (interconects with high parasitic capacitance). This will result in series of problems and of course will give the snake oil pseudo high-end cable dealers a way to drain some money from you.

Now, whether a preamplifier is needed in a particular system is a completely different issue and is a pure matter of a personal taste. One thing is for sure - some power amps represent a non easy to drive load(having a signal conditioning networks at the input) and that is where a preamp really helps.

Of course if a simple system is implemented (CD player -> integrated amplifier, or a high sensitivity power amp) and no signal switching is required, nor any other "bells and whistles", a simple high current output buffer is always an option. A CSS loaded emitter follower stage with about 20mA standing current would do just fine in driving almost any capacitive load. Another option is Burr Brown's BUF634.

Regards,
Venci
 

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