Ok it starts to play...here are my first impression after 8 hours that the amp got power and after the 1st hour of listening (speaker are line sources which I build my self with 12 Fountek ribbons and 18 4" drivers from Eton per side, so a pretty high resolution system. Pre-Amp is a soulution 720 (currently 30000$, CD-Player is a Audionet VIP G2 with external power-supply, currently 12000$, so pretty "OK" frontend.):
- Good news: My Preamp is loud enough.
- The stage is deeper than with any other amp I had in my system (including triodes, Audionet AMP Iv2, MAX, CHORD, GRAAF, Counterpoint, and many more), It is very crisp, very controlled. I am just using one amp with one PSU as I planned monos (and the second one is still to be build), but still with this imperfect power suppply the stereo imagining is very good. The clearness and the crispness is much more real than the XA-60.5 which I own as well. The Xa is smoother though, softer, but makes a "sound" compared to the F4.
- Long-term...will this be the ultimate amp ? Well, I am looking forward to understand what will happen now durting burn-in. MAybe one of the other happy users can give me a forecast ???
What I would love to see is more body, more soul, less "control is everything" ( and man, this little thig seems to have muscles like hell, it controlls the speaker more than the Audionet MAX which are stupid big and heavy commercoal mono with unlimited power and damping factor). OK, I could put a tube-stage between the pre-amp and the F4, but I guess I would loose some of the inner tension and clearness of the F4, so I guess the trick is really either that it will get the character anyhow by burn in or to tune it with things like the optimal sounding PSU-CAPs or no RCA-JAckets, simply get you best cable and solder it to the PCB which without disruption goes to pre-amp etc. Any options already out there on this ?
I have right now not done a lot to optimize the F4 besides getting good Dale and Caddock Resistors and some Silmics for the PCB. My TRansformer actually is a cheap Reichelt piece which is humming like hell, I wanted to see if it makes sense to get a real expensive one (convinced); I as well have standard Panasonic TSA Powercaps and CRC filter, only one Peter Daniel PSU-board for both channels (I understand that that makes most sense when using it as a mono or should I go as well for a mono later to two independant PSUs ?).
It would be as well interesting to learning your listening experiences: Monos in XLR vs Bi-Amping etcetc...?
- Good news: My Preamp is loud enough.
- The stage is deeper than with any other amp I had in my system (including triodes, Audionet AMP Iv2, MAX, CHORD, GRAAF, Counterpoint, and many more), It is very crisp, very controlled. I am just using one amp with one PSU as I planned monos (and the second one is still to be build), but still with this imperfect power suppply the stereo imagining is very good. The clearness and the crispness is much more real than the XA-60.5 which I own as well. The Xa is smoother though, softer, but makes a "sound" compared to the F4.
- Long-term...will this be the ultimate amp ? Well, I am looking forward to understand what will happen now durting burn-in. MAybe one of the other happy users can give me a forecast ???
What I would love to see is more body, more soul, less "control is everything" ( and man, this little thig seems to have muscles like hell, it controlls the speaker more than the Audionet MAX which are stupid big and heavy commercoal mono with unlimited power and damping factor). OK, I could put a tube-stage between the pre-amp and the F4, but I guess I would loose some of the inner tension and clearness of the F4, so I guess the trick is really either that it will get the character anyhow by burn in or to tune it with things like the optimal sounding PSU-CAPs or no RCA-JAckets, simply get you best cable and solder it to the PCB which without disruption goes to pre-amp etc. Any options already out there on this ?
I have right now not done a lot to optimize the F4 besides getting good Dale and Caddock Resistors and some Silmics for the PCB. My TRansformer actually is a cheap Reichelt piece which is humming like hell, I wanted to see if it makes sense to get a real expensive one (convinced); I as well have standard Panasonic TSA Powercaps and CRC filter, only one Peter Daniel PSU-board for both channels (I understand that that makes most sense when using it as a mono or should I go as well for a mono later to two independant PSUs ?).
It would be as well interesting to learning your listening experiences: Monos in XLR vs Bi-Amping etcetc...?
If you are using each amp as a balanced monoblock then a single power supply per amp is best.
Someday soon SY will publish his high output tube preamp which might be more in the spirit of the F4 than a tube stage inserted between a pre and F4. Whether it will sound more like you want would only be resolved by trying it.. I would certainly think that the pre has a stronger effect on the sound than it would with a regular amp, but I haven't experimented.
It really is an amazing amp- the best I've ever had- although I haven't owned very many. At the moment mine mine is still ripped apart being rewired..
Someday soon SY will publish his high output tube preamp which might be more in the spirit of the F4 than a tube stage inserted between a pre and F4. Whether it will sound more like you want would only be resolved by trying it.. I would certainly think that the pre has a stronger effect on the sound than it would with a regular amp, but I haven't experimented.
It really is an amazing amp- the best I've ever had- although I haven't owned very many. At the moment mine mine is still ripped apart being rewired..
OK, 24 hours later...the breaking-in process is progressing, now the whole thing is smooth as silk and warm and delicate in sound. Now I would love to get the last little bid of transparency and "air". I am looking froward to assemble the second mono-block and we will see what this gives me (currently the PSU is not even separated per channel as written above, so I guess this will give a lot).
I will as well solder the Input cable directly to the pcbs to avoid any losses in plugs etc....still the X-former is humming like hell, I guess the already very impressive sound (this F4 sound much better than the 30000$ Soulution 710-Power-Amp which I had here as well) will become much more relaxed and impressive once the amp is really quiet when no music plays.
Any experience how long the break-in-period is going to be ?
I guess this really could be the amp I have been looking for over the last 20 years, thanks a lot Nelson !
I will as well solder the Input cable directly to the pcbs to avoid any losses in plugs etc....still the X-former is humming like hell, I guess the already very impressive sound (this F4 sound much better than the 30000$ Soulution 710-Power-Amp which I had here as well) will become much more relaxed and impressive once the amp is really quiet when no music plays.
Any experience how long the break-in-period is going to be ?
I guess this really could be the amp I have been looking for over the last 20 years, thanks a lot Nelson !
so, back to the matching excitement. So, I don't have any of those BF246 JFETs, or really any high current JFET devices.. so, I decided to replace the bottom of the first diagram in post #2302 with a LED + BJT CCS. I'm not sure if it's working though. Reference for the CSS portion of the circuit is this diagram:
I'm using a 2sc1815 and 8.1V battery (9v nominal). R1 is 2K. Vf of LED is 1.94v. Vbe is measuring 0.68V. R2 is a 500R pot.. The load is a 120R resistor, that's getting 0.60V across it, or 5mA which is what I want to match the JFETs at. The pot is measuring at 214R. So, I get I_r2 = (1.94 - 0.69) / 520 = 5.84mA. If I remove the 120R load resistor and measure using my ammeter, I get 4.02mA..I'm assuming this is due to a less than ideal ammeter.
Next, I connected the Gate of the 2sk170 to Vs+ in the above diagram and the Source to the collector of the BJT above (basically put it as the load). The attached the negative of another battery to the Gate and the positive of this second battery to the Drain. Now, I measure Vgs and get 0.73V, the same thing that I get if I don't connect the positive of the second battery... not too exciting. Then I put a 47.5R resistor between the drain of the 2sk170 and the positive of the second battery, and I get 0.46V... and after 30 seconds, still measures 0.46V. Vgs ranges from 0.2V to 1.5V on this device. So maybe it's working... I take a break, come back and remeasure it and it's 0. I remove the second positive supply and I get 0.73V... reconnect the positive, and after a while I get 0 Vgs.
So..... can anyone throw me a bone? Is my CCS working? Is the Vgs measurement working? Any recommended changes to the values I'm using?
Trying to learn
An externally hosted image should be here but it was not working when we last tested it.
I'm using a 2sc1815 and 8.1V battery (9v nominal). R1 is 2K. Vf of LED is 1.94v. Vbe is measuring 0.68V. R2 is a 500R pot.. The load is a 120R resistor, that's getting 0.60V across it, or 5mA which is what I want to match the JFETs at. The pot is measuring at 214R. So, I get I_r2 = (1.94 - 0.69) / 520 = 5.84mA. If I remove the 120R load resistor and measure using my ammeter, I get 4.02mA..I'm assuming this is due to a less than ideal ammeter.
Next, I connected the Gate of the 2sk170 to Vs+ in the above diagram and the Source to the collector of the BJT above (basically put it as the load). The attached the negative of another battery to the Gate and the positive of this second battery to the Drain. Now, I measure Vgs and get 0.73V, the same thing that I get if I don't connect the positive of the second battery... not too exciting. Then I put a 47.5R resistor between the drain of the 2sk170 and the positive of the second battery, and I get 0.46V... and after 30 seconds, still measures 0.46V. Vgs ranges from 0.2V to 1.5V on this device. So maybe it's working... I take a break, come back and remeasure it and it's 0. I remove the second positive supply and I get 0.73V... reconnect the positive, and after a while I get 0 Vgs.
So..... can anyone throw me a bone? Is my CCS working? Is the Vgs measurement working? Any recommended changes to the values I'm using?
Trying to learn
Ok, my second unit is up and running, so I have now two configured as balanced driven mono-blocks. What can I say ?
I am impressed. This is the best amp I ever build and ever listened to. IT has everything I hoped for - transparency - yes a lot. Holographic 3D-imaging - yes, the walls disappear and everything is so far mor in space. Speed & timbre - the vibrance of each note is somethng you can feel.
This amp is a drug. And not a soft one.
Nelson, wonderful. This is all someone could hope for. Thanks a lot.
I will stop looking around and will simply focusing on this amp and how to get the best out of it. Which power-supply cap / local caps on the board vs. only one central power-supply etcetc. Voodoo-Parts like BlackGates or Caddocks - this ting is so wonderful, now I want to understand how to tweak the last bit of potential out of it. If anyone already started that journey, please share with me/us what you found out so far to get the last bid of potential out of it (I did not a lot: Simic II-Caps for the circuit, Dale-Resistors, Caddocks as cathode resistors, Schottky-Diodes, but only one PSU per Mono-Block with normal PAnasonic TSA-Caps 22000*4)
I am impressed. This is the best amp I ever build and ever listened to. IT has everything I hoped for - transparency - yes a lot. Holographic 3D-imaging - yes, the walls disappear and everything is so far mor in space. Speed & timbre - the vibrance of each note is somethng you can feel.
This amp is a drug. And not a soft one.
Nelson, wonderful. This is all someone could hope for. Thanks a lot.
I will stop looking around and will simply focusing on this amp and how to get the best out of it. Which power-supply cap / local caps on the board vs. only one central power-supply etcetc. Voodoo-Parts like BlackGates or Caddocks - this ting is so wonderful, now I want to understand how to tweak the last bit of potential out of it. If anyone already started that journey, please share with me/us what you found out so far to get the last bid of potential out of it (I did not a lot: Simic II-Caps for the circuit, Dale-Resistors, Caddocks as cathode resistors, Schottky-Diodes, but only one PSU per Mono-Block with normal PAnasonic TSA-Caps 22000*4)
Uhm... Being this the "official" F4 thread, I suppose it's the best place for the following question: what do you guys think of matching it with my Audible Illusions Modulus 3A (first series) preamp?
This preamp has got a 24-30dB selectable gain, but no clue about maximum output voltage. And it's got a 1.2 kohm output impedance.
That huge (and actually annoying, even at the minimum 24dB, with "standard" power amps) gain suggests me that this could be a great marriage (and I love the M3A sound).
My loudspeakers are Royal Device Laura Studio mkII (98.5 dB/W/m).
Any thoughts?
Giacomo
This preamp has got a 24-30dB selectable gain, but no clue about maximum output voltage. And it's got a 1.2 kohm output impedance.
That huge (and actually annoying, even at the minimum 24dB, with "standard" power amps) gain suggests me that this could be a great marriage (and I love the M3A sound).
My loudspeakers are Royal Device Laura Studio mkII (98.5 dB/W/m).
Any thoughts?
Giacomo
Nelson Pass said:The amp is 47K in, so no complaints about loading, and that it more
than enough gain.
Thank you Nelson. You gave me support, years ago, with a Son of Zen project which I never accomplished (lack of funds...)... But this is finally the right time I build something yours.
I'm very excited and I owe you a big thanks, at the very least.
Giacomo