Hi Damir,
How critical are the 3K8 resistors (R13, R15)? They are not standard values (or at least common) as far as I can tell. Can you use 3K9 or 3K83 instead, or should we make the value up from paralleled or series resistor networks?
Paul
How critical are the 3K8 resistors (R13, R15)? They are not standard values (or at least common) as far as I can tell. Can you use 3K9 or 3K83 instead, or should we make the value up from paralleled or series resistor networks?
Paul
It is not critical. With higher value you will get less current trough cascode transistors Q23, Q24, but difference is less then 1 mA. You can use 3k9 or 3k83.
Damir
Hi all
I like to share my initial impression after a short, around 1hour, listening session on my desktop setup.
Detail is the same as or a bit less than dcb1, it has more weight specially on the bass, but dcb1 has wider soundstage (if im not mistakenly use this term). And I believe this would change in a better way if I give it more listening time and put it in my main system.
My desktop setup is: deadbeef, odac, gainwire2, F5 clone, dali lektor2.
I should mention as usual this impression is limited to my setup, room and my hearing for sure.
I hope this might help for one whos deciding to build this great preamp.
I like to share my initial impression after a short, around 1hour, listening session on my desktop setup.
Detail is the same as or a bit less than dcb1, it has more weight specially on the bass, but dcb1 has wider soundstage (if im not mistakenly use this term). And I believe this would change in a better way if I give it more listening time and put it in my main system.
My desktop setup is: deadbeef, odac, gainwire2, F5 clone, dali lektor2.
I should mention as usual this impression is limited to my setup, room and my hearing for sure.
I hope this might help for one whos deciding to build this great preamp.
Here is his temporary setup. First listening he did with the jumpers in CFA position.
Damir
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If you can dearly compare it with the dcb1, it surely must be something special... and it has gain.... can barely wait to build it myself 🙂
Looking forward to hearing this.
My build is well on the way. Only parts I'm missing now are some TO 220 mounting kits. Thought I had some but evidently not. Frustrating.
My build is well on the way. Only parts I'm missing now are some TO 220 mounting kits. Thought I had some but evidently not. Frustrating.
darbost did some more listening, and now in both mode, CFA and NGFB.
"I have done some comparison and this is what I think
In CFA setup, everything is very detail, imaging (position of the sound) is fantastic. But i believe because it is so detail vocal sometime sounds harsh. Where as in NGFB, vocal sounds softer but the imaging is lesser or flatter and i could set the volume one step higher without being too loud. Since I mainly listen to vocal specially female, during my relax listening my prefer setup is NGFB.
I hope this is clear for you.
I should say once again this is a great preamp and I very much like it, cant wait to test it in my main system.
"
ps. As in my age my hearing is not as acute as it was long time ago, I did not notice all that differences when the preamp was used different mode, and it is good to know others impressions.
BR Damir
This is the same as many others say about CFA. I also hear the CFA better imaging, detail. I think it is why so many HiEnd mfr use CFA.
THx-RNMarsh
CFA
Hi Damir,
If you don't mind, I will try your line amp as an input buffer in my CFA project (Here). I don't need an output buffer, but will use all the rest. I am sure it will show even better results that the one I designed based on OTA idea.
BTW, have you got PCB design in some PCAD ASCII or any other transfer-compatible format?
Thank you,
Valery
Hi Damir,
If you don't mind, I will try your line amp as an input buffer in my CFA project (Here). I don't need an output buffer, but will use all the rest. I am sure it will show even better results that the one I designed based on OTA idea.
BTW, have you got PCB design in some PCAD ASCII or any other transfer-compatible format?
Thank you,
Valery
Richard, totally agree. This is what I practically noticed with my prototype. Had no chance to assess the scene yet (got one channel prototype so far), but the fast-front mid-high frequency sounds are remarkably natural.
I have wished to find the reason for this sonic characteristic thru designers SIM's. But, it still alludes us. It doesnt appear to be related to (static) THD.
THx-RNMarsh
The Cfa's i have heard are airy and fast sounding but have lacked tone and body. I am close to finishing my preamp, but will be out of town for most of the week. NOt sure if thats enough time to ship to you Richard.
Well, must be a combination of THD (no additional harmonics), intermodulation distortion (not always as low as THD, requires special attention), phase shift (light and as constant within the bandwidth as possible) and slew rate (following fast rises/falls as precise as possible).
By the way, noticed an interesting effect in my CFA - never saw anything like this before. Square wave handling depends on input (and thereby output) amplitude. At small amplitudes it a little bit undershoots, then shape becomes perfectly square and at the higher amplitudes it a little bit overshoots.
Compensation
Got it!
The reason of the above effect was too "aggressive" lead compensation in VAS (transimpedance part of the system - C6, C16). 47 pF would be good for VFA design, but in my case 5.1 pF is more than enough for maintaining stability and totally removing overshoot on square wave an any level.
Got it!
The reason of the above effect was too "aggressive" lead compensation in VAS (transimpedance part of the system - C6, C16). 47 pF would be good for VFA design, but in my case 5.1 pF is more than enough for maintaining stability and totally removing overshoot on square wave an any level.
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