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Old 15th January 2014, 03:50 PM   #1
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Default Preamp between the DAC and the F5

Hi
I just by this good DAC base on the CS4398 that give a good parameters, I hope that I donít mistake but the exit of this DAC give me 2volts so generally I do not need a preamp between the DAC and the F5.
today I see the kit on ebay for the JC-2 preamp and I wonder if this kit can improve the sound in my system. DAC->pre?->F5
Thanks
By the way, after the cs4398 there is filter base on NE5532, I need to improve this?
thanks
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Old 15th January 2014, 10:38 PM   #2
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another important question:
why i need the usb dac anyway, in you guys tell me that:
cd player->sdif->sdif-dac-rca->preamp
is much quality then usb dac so i move all my music to cd.
thanks
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Old 15th January 2014, 10:39 PM   #3
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details ;

our replies are in your details .
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Old 16th January 2014, 09:14 AM   #4
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Sorry ZM but I don’t understand, I tray to be more spacious:
I alowes use PC for my music so its be obvious for me to chose DAC system with usb.
Just yesterday I understand the advantage of cd player, coax out, low noise compare to PC, I can buy more quality DAC then usb DAC, and the big advantage is to listen to music like old days.
So I decide to do switch  and instead buy usb DAC I can bay second hand cd player and quality DAC.
I order the jc-s pcb because guys in diyAudio say its sound great, but! The stupid DAC output 2vpp, and the F5 need 2vpp!
1) In general, pleas tell me guys if my steps for quality system is ok, I need your idea that I don’t spend money for nothing.
2) About the jc-2, I think maybe if the volume of the DAC is digital, so I can reduce it to 1vpp and the jc-2 amplify more??
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Old 16th January 2014, 12:19 PM   #5
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- room size and usual loudness of music ?
-speakers you're using - sensitivity ?

regarding your questions :

1) we can't judge that without details
2)it's always pity to decrease signal just to amplify it more ; of course - you always need to have headroom ,even in volume pot position , but no more then needed

read this , as info

What is Gain Structure?
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Old 16th January 2014, 12:53 PM   #6
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thanks ZM for the help.
my room size is about 4X4 meter and i use peerless Denmark 400rms 94 db

i think that if the digital output cd player is with volume control, so it reduce the exit volume in the dac, and its digital volume than i can use the jc-2.

thanks
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Old 16th January 2014, 01:01 PM   #7
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I'll just quote myself here, again:

Quote:
Originally Posted by Rodeodave View Post
With the F5's voltage gain of 15.3dB=20*log(x) and a maximum output voltage of +/-20V (from manual), the amplification factor x=10^(15.3/20)=5.82 and therefore the input voltage required to drive it to full output should be 20V/5.82=3.42V. Compare this to what your source can deliver, and decide on how much gain you'll need in the preamp stage.
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Old 16th January 2014, 01:28 PM   #8
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Quote:
Originally Posted by erez1012 View Post
thanks ZM for the help.
my room size is about 4X4 meter and i use peerless Denmark 400rms 94 db

i think that if the digital output cd player is with volume control, so it reduce the exit volume in the dac, and its digital volume than i can use the jc-2.

thanks
for start - make digital side of choice , then put plain 10K volume between it's output and F5

try , if you have enough SPL in your room - just make buffered volume ( say B1 or similar )

if you don't have enough swing for F5 , then make preamp , with 2-5x gain
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Old 16th January 2014, 01:35 PM   #9
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Rodeodave, thank you, and because i understand what you writ and read the post about the gain i understand that i need the stay with the DAC and the F5.
but i do not want my dac will be the preamp, just want 1vptp from it, or less and the jc-2 has multiple by 3.5, perfect for the F5.
i just read this article about digital vs analog volume controller that show that if i reduce the digital vol by -10db its not hurt the dynamic range. maybe its solution for me.
thanks

Last edited by erez1012; 16th January 2014 at 01:43 PM.
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Old 16th January 2014, 01:48 PM   #10
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ok ZM, about the F5 i see in the pcb change in the Z in impedance to 47K, maybe i can go back to the 100k Z in?
thanks

Last edited by erez1012; 16th January 2014 at 02:01 PM.
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