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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

AD797 Preamp based on stolen trademark
AD797 Preamp based on stolen trademark
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Old 22nd September 2020, 02:52 PM   #121
Berlusconi is online now Berlusconi
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AD797 Preamp based on stolen trademark
Now, let me present a couple of measurements at the extremes: 5Hz, and 200KHz along with the response to 10 KHz wave.

In all three cases we have 1V square wave at the input.
Attached Images
File Type: png 5Hz.png (39.4 KB, 233 views)
File Type: png 200KHz.png (44.6 KB, 204 views)
File Type: png 10KHz.png (42.7 KB, 201 views)

Last edited by Berlusconi; 22nd September 2020 at 02:58 PM.
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Old 23rd September 2020, 09:37 AM   #122
ginetto61 is offline ginetto61  Italy
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AD797 Preamp based on stolen trademark
Quote:
Originally Posted by Berlusconi View Post
Thanks Ginetto,
Very kind of you. I do appreciate that... but that guy from youtube has another target audience: "audiophiles". .... No offense meant, this is strictly technical matter.
https://www.ti.com/lit/ds/symlink/lm317.pdf
Hi no offense taken ... no problem. I just like the man and i think he is honest in his story. Personally even if measurements do not tell of any issues to have the mains transformer inside the same case of the circuits board ... i do not like it. I much prefer to place the transformer outside and maybe put a lot of capacitance very close to the board circuit (energy storage). Actually is what i am thinking to do with one preamp i have at hand which has the mains transformer even soldered on the same board of the circuit ... i am even thinking to cut the board in two parts ... one the circuit ... the other the transformer on small rubber feet and shielded with copper.
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Old 23rd September 2020, 11:46 AM   #123
Berlusconi is online now Berlusconi
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AD797 Preamp based on stolen trademark
Dear Ginetto,

Lo so che lei č una persona gentile, e lo apprezzo molto.

Sometimes I have impression that sales departments want to ensure us that measurements mean nothing and then tell convincingly that customers gut feeling is the best basis for judgement. Then they have us in their pockets or should I say they have their hands in our pockets. For good music, girls, vine or meals that's the right reasoning but with technical stuff it is quite different thing. For example, i prefer classical music and the right choice is to select neutral audio equipment, which doesn't change the recording. From preamplifier I expect just verbatim gained copy of the input signal.

This preamplifier does exactly that: it doesn't sound at all it is dead silent and has an adequate response to the input signal.

I have two units and will build the third from verified components. Interestingly, Chinese "complete board" is rather fine, almost exactly the same I have built from the scratch. Except mine has better response to square waves: it consistently responds faster to square signal over the entire measuring range.

This is very good product.

Saluti!

Last edited by Berlusconi; 23rd September 2020 at 12:00 PM.
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Old 23rd September 2020, 12:30 PM   #124
ginetto61 is offline ginetto61  Italy
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AD797 Preamp based on stolen trademark
Quote:
Originally Posted by Berlusconi View Post
Thanks Ginetto,
Very kind of you. I do appreciate that... but that guy from youtube has another target audience: "audiophiles". ..
Hi ! i see your point and my brain of course tells me that you are very right.
But i am always torn between reason and feeling
For instance tube preamps/amps are clearly electrically inferior to solid state ones (i.e. higher noise and distortion)
Nevertheless someone love their sound so much more than solid state sound
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Old 24th September 2020, 09:29 AM   #125
Fossil is offline Fossil
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Quote:
Originally Posted by gigigirl View Post
Hi, Well as far as I know from their blurb the 1st pair of op-amps are an input buffer!! Whatever that means.

Anyway I received my Chinese AD797 op-amps today. Yes I know they are fake, but have used them before for testing my phono amp, then I replaced them with genuine one. The genuine ones definitely sounded better, but it was not night & day, they were very close.
So how did they sound, well initially very good, better that the 55 series, definitely brighter. I have left the playing on repeat in my 2nd system. I will do a more serious listen in a couple more days.
Also it occurred to me that the from pair of dual op-amps could be replaced with one of the many available, any suggestions.

Cheers
I picked up a few chinese 'muses' few wks ago and based on the prices, they gotta be fakes.
But they actually sound good, esp the muses01, without being over-analytical, that kinda in-your-face clarity.
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Old 24th September 2020, 09:36 AM   #126
ginetto61 is offline ginetto61  Italy
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AD797 Preamp based on stolen trademark
that should not be difficult ... take a compatible not bad sounding op-amp like i guess the TL082 (less than 1USD/piece) and stamp muses01 on it
and you end anyway with a very decent sound
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Old 24th September 2020, 10:01 AM   #127
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No experience with tl082. The one I took out was lm4562
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Old 24th September 2020, 10:51 AM   #128
ginetto61 is offline ginetto61  Italy
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AD797 Preamp based on stolen trademark
Quote:
Originally Posted by Fossil View Post
No experience with tl082. The one I took out was lm4562
Hi i was referring to a viable opamp for a fake muses01. And 1USD part can be sold for 10 times its price
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Old 24th September 2020, 03:08 PM   #129
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Point noted.
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Old 1st October 2020, 04:48 AM   #130
gigigirl is offline gigigirl
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Hi, One of the problems we have with this thread is that we are often taling about different board.
I upgraded my P/S because I was getting a little hum, now it is dead quite, however my Pre Amp board did not use 317/337 voltage regulators & had no voltage adjustment on the power supply of the board.
I have now replaced the cheap & cheerful V/C with a Tocos unit, which has opened things up a bit more & noticeably improved the top end.
Cheers
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