Yes ofcause, and i allready know, that you knew, that i'll be very gain-hungry (as usual) ...
The fact is, that for driving the F4 max you need around 25v swing (right
), and this is not a big problem, with the DAC i have, giving ~1,6v out., but with old recording's etc... from my pearl with a grado prestige silver MM (4MV @ 3,54 CMV-45degrees), this is not good enough.
Well, it might be that i have another problem, but it would be with my F4's then.
But enough of that, i will ofcause try, to see, how much i can suck out of it, but i was hoping some explanation about the feedback-net please
Jesper.
The fact is, that for driving the F4 max you need around 25v swing (right
), and this is not a big problem, with the DAC i have, giving ~1,6v out., but with old recording's etc... from my pearl with a grado prestige silver MM (4MV @ 3,54 CMV-45degrees), this is not good enough.Well, it might be that i have another problem, but it would be with my F4's then.
But enough of that, i will ofcause try, to see, how much i can suck out of it, but i was hoping some explanation about the feedback-net please
Jesper.
lykkedk said:Yes ofcause, and i allready know, that you knew, that i'll be very gain-hungry (as usual) ...
The fact is, that for driving the F4 max you need around 25v swing (right
Well, it might be that i have another problem, but it would be with my F4's then.
But enough of that, i will ofcause try, to see, how much i can suck out of it, but i was hoping some explanation about the feedback-net please
Jesper.
then build another phono preamp
instead of that wimpy one you havewhat specifically you need to know regarding feedback?
leave input resistors as they are ; increase resistors from output side to input ; observe clarity and form of squares on CRO ....... and soon you'll leave F4s in closet ..... because you'll not need them .....
we already cover some issues in
thread ; why repeating them ?just one thing : you'll have more swing with Drek then with UberDrek .........
tip:
buy Klipsch Horns ........... that way - you'll need 5W per side
I tried different things, with the Drek , and here is the result's.
All result's will be published on my little site HERE, click on drek when entering.
I will try to explain as good as i can.
all result's is with jp1 shorted (otherwise, the inputgnd is floating, i tried to leave it open, and then you can only use unbalanced output, is this something to do with my problems --- ANY suggestions ???)
1. With -in-gnd and 1khz 1vac on +in, it gives nicely 5vac out unbalanced, and 10vac balanced ... no problem here.
2. Around ~1,5vac on input, the output oscillate's a bit on the sine-wave (se my webpage), and it look's like if you place probe reversed e.g. hotprobe on -out and gndprobe on +out, it accept's a little more (~0,2vac - 0,3vac) on input before oscillating.
3. The funny thing, is that if i only meassure on unbalanced out (either +out or -out, with +out grounded ofcause), this does not occour. I donno if there is some mistake on my circuit, guess i will only could tell, when my next channel is done. (ANY suggestion ???)
My thought, is that's it's something with the inductor? but i donno.
Magura, was speaking about placing a resistor over the inductor, but i havent tried it yet. (donno if it has to be a power-resistor or if a 1/4w will do).
I did not make any listningtest yet, as i would like to solve this problem first (My dac gives around 1,6vac out, and this is just the critical point here)
The Drek, become's thermal stable very quickly, but you have to use some cooling Alu' profiles (look my webpage), and it seem's that it sucks more power than does btw. (This i due to Magura having some to do with it i think ) Bigger the better with that guy... Giving me some great help btw. ... thx. Morten.
Any INPUT ON THIS IS VERY APPRECIATED THANK'S
Jesper.
, and here is the result's.All result's will be published on my little site HERE, click on drek when entering.
I will try to explain as good as i can.
all result's is with jp1 shorted (otherwise, the inputgnd is floating, i tried to leave it open, and then you can only use unbalanced output, is this something to do with my problems --- ANY suggestions ???)
1. With -in-gnd and 1khz 1vac on +in, it gives nicely 5vac out unbalanced, and 10vac balanced ... no problem here.
2. Around ~1,5vac on input, the output oscillate's a bit on the sine-wave (se my webpage), and it look's like if you place probe reversed e.g. hotprobe on -out and gndprobe on +out, it accept's a little more (~0,2vac - 0,3vac) on input before oscillating.
3. The funny thing, is that if i only meassure on unbalanced out (either +out or -out, with +out grounded ofcause), this does not occour. I donno if there is some mistake on my circuit, guess i will only could tell, when my next channel is done. (ANY suggestion ???)
My thought, is that's it's something with the inductor? but i donno.
Magura, was speaking about placing a resistor over the inductor, but i havent tried it yet. (donno if it has to be a power-resistor or if a 1/4w will do).
I did not make any listningtest yet, as i would like to solve this problem first (My dac gives around 1,6vac out, and this is just the critical point here)
The Drek, become's thermal stable very quickly, but you have to use some cooling Alu' profiles (look my webpage), and it seem's that it sucks more power than
does btw. (This i due to Magura having some to do with it i think ) Bigger the better with that guy... Giving me some great help btw. ... thx. Morten.Any INPUT ON THIS IS VERY APPRECIATED THANK'S
Jesper.
it can be more problem with PSU Lykkkkkkkk is using ;
either you have one GND in system too much , or not enough;
point is that CRO probe gnd is in safety gnd ; for start : do your measures from GND to both outputs ( gnd to + , then gnd to - ) , THEN either find balanced probes , either find a way to cut (temporary) CRO' safety GND ;
point is that you must do same things with audio GNDs and safety GND - as with any other apparatus .
either you have one GND in system too much , or not enough;
point is that CRO probe gnd is in safety gnd ; for start : do your measures from GND to both outputs ( gnd to + , then gnd to - ) , THEN either find balanced probes , either find a way to cut (temporary) CRO' safety GND ;
point is that you must do same things with audio GNDs and safety GND - as with any other apparatus .
ZenMod, this was my thought through, regarding, that the probe's act different, when placing them reversed... but i forgot to write before, that it also oscillates, but at higher inputlevel ...
also i am not sure, it''s a problem, it might just be, that it's sound beautiful ... (i have my thought's through)
Jesper.
also i am not sure, it''s a problem, it might just be, that it's sound beautiful ... (i have my thought's through)
Jesper.
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