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Old 8th November 2009, 05:30 PM   #1
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Default Smartkit Preamp+psu

Please any advice is welcome.
So i have started building a preamplifier so i can use it for testing purposes of some final amps i wanna build in the future. I dont have the possibility of listening to many preamps as all my systems were integrated pre amp and final amp..this is my first pre amp construction,
So i bought two kits by a Greek company named Smartkit www.smartkit.gr
A preamp kit that they call : Audiophile Preamp class A and the recomended power supply called: Audiophile Power Supply +- 15v.. The transformer used will be a 100Va 2x18v torroidal.
I give you the schematics of both the preamp and the psu including the partlist (some are in Greek..sorrryy..)
Any improvement is welcome of course before i start building..So if you want to comment please feel free! I will post some photos soon..i am now in the proccess of choosing what casing to buy.

Preamp Schematic:

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Preamp Partlist:

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PSU Schematics:

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PSU Partlist:

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Old 8th November 2009, 05:52 PM   #2
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Hello ! "Smart" thing would be to eliminate first stage and go directly to C7 , unless you need that buffer to listen while you record ...Then , it seems that it is a little amplifier , with those beefy BD139-140 at the output , it should be able to drive long cables or in difficult settings . The audiophile rank of the PSU is just gained by adding RC snubbers at the diodes . The whole thing - a pre - could have been done with just an IC ,one pot , 4 resistor , 4 capacitors + 2 for compensation YMHO.
Also the supply ... 100 W it is an amplifier !
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Old 8th November 2009, 09:20 PM   #3
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any critical component that you may think an upgrade will do good?..this week i will assemble it.
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Old 8th November 2009, 10:00 PM   #4
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I also support picowallspeaker's suggestion. The obvious source of improvement will be to replace the 5534s, which were really great 30 years ago with something slightly more contemporary. It is really a matter of personal choice, so hopefully you have a drawer full of opamps like the rest of us
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Old 9th November 2009, 04:59 AM   #5
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Well i dont have any opamps around simply because i ve done in my life very few constructions, maybe 3-4 amps and thats all! So i dont have the experience to know which opamp is better..thars why i need your suggestions.if i change the opamp, it is done simply by changing the chip or do i need any extra mods? That what i want from the preamp is to be quiet, melodic and able to drive any final amp setup..
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Old 9th November 2009, 09:48 AM   #6
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Hello again . I also support the "less is best" way,so you can omit first stage and keep the rest . A good add-on is to have two potentiometers , or stepped attenuators , to control each channel independently. Also the power supply has too many diodes for my taste...
If you keep the tracks and cables (also unshielded) far from the transformer , you 'd probably have a quiet pre.
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Old 25th November 2009, 10:25 PM   #7
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well i assembled the preamp and its psu but i am still waiting for the torroid to come..actually they made a mistake and sent me the wrong one so now i have to wait an extra week as the torroid will be ordered and custom wind... :-(
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Old 25th November 2009, 10:29 PM   #8
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any direct replacement of the 5534 ?..by means of better sound maybe?..
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Old 25th November 2009, 11:21 PM   #9
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Better sound is achieved by a more complex circuitry inside the chip . Less is best !
I hope you kept the first torroid also -2 is better than 1-
Bye
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Old 25th November 2009, 11:24 PM   #10
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sure but since i cant change the circuitry can i use any other chip instead of the 5534?.. by the way the torroid they sent me was a 2x12v instead of 2x18v that i ordered..so now i have that 2x12v /100va for free!!!!he he..
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