Preamp between the DAC and the F5

[erez1012]

Hi
I just by this good DAC base on the CS4398 that give a good parameters, I hope that I don’t 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

 

[erez1012]

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

 

[Zen Mod]

details ;

our replies are in your details .

 

[erez1012]

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??

 

[Zen Mod]

- 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

http://www.diyaudio.com/forums/diyaudio-com-articles/186018-what-gain-structure.html

 

[erez1012]

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

 

[Rodeodave]

I'll just quote myself here, again:

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.

 

[Zen Mod]

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

 

[erez1012]

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

 

[erez1012]

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

 

[mstomaso]

I had a similar problem with a Burning Amp, and I built a low-gain line stage using the BA-3 front end.

Power transformer: Antek 18V 100VA

Power supply: Broskie B-PS-1 bipolar regulator set at +/- 21 VDC

Voltage Amp: BA3 front end set with a gain of about five (13 db or so)

Volume control: a 50K pot, in a shunt config with a 47K resistor.

Enclosure: Galaxy 288 chassis

It is dead quiet, using the standard star ground and CL60 technique. (I was surrpised especially with the way everything is jammed in).

 

[mstomaso]

A photo pf the preamp is attached.

 

[AndrewT]

If your DAC can drive the cables to the power amplifiers, then you don't need a buffer stage.
Your signal level tells you, you probably don't need an amplification stage.

A volume control in the interconnect somewhere will control your volume.

BUT !!!!!!
The volume control will almost certainly require a buffer to drive it's output cables.

 

[erez1012]

hi mstomaso, my preamp is also gain by 3, but 2.5vpp from the AK4396 chip *3 its far away from what the F5 need.
AndrewT is right, but its hard to me accept the DAC as pre amp

my only solution is to do like AndrewT and ZM said, or decrease the digital output volume of the cd player and then put preamp of 3 gain.
thanks guys

 

[Andersonix]

By the way, after the cs4398 there is filter base on NE5532, I need to improve this?
thanks

Snip it out and use LM4562. If there's an LM7805 for DAC, try Murata 7805SR instead.

 

[erez1012]

i decide to use coupling capacitor instead of opamp on the cs4398 output stage so the voltage will be lower. i know the F5 no HPF, and i take off the HPF from the DAC too.
hope its not make trouble in the sound
thanks