To increase the damping factor will require some feedback network resistor "tweaking". This is likely because the transconductance of the output lateral fets or possibly the jfets is different from what was used to determine the feedback network resistor values.
Yes, I know. Rsen plays an important role here and one has to be extremely careful that it doesn't become a generator.
It's a balancing act between the amount of negative and positive feedback so that the output resistance gets lower but the other parameters remain the same.
It's a balancing act between the amount of negative and positive feedback so that the output resistance gets lower but the other parameters remain the same.
I think I used a 100K pot from the current sense resistor back to the input junction. This allowed me to dial in the DF for various loads and worked well.
wtnh, thanks for the handy tip.
As lhquam has already shown, in order to increase the DF, the ratio Rfbn/R1 must be increased. I checked in my sim that at R1 = 33k the DF raises up to 80. On the other hand, the distortion factor also increases a little.
As lhquam has already shown, in order to increase the DF, the ratio Rfbn/R1 must be increased. I checked in my sim that at R1 = 33k the DF raises up to 80. On the other hand, the distortion factor also increases a little.
That is probably because the net amount of negative feedback has decreased be increasing the amount of positive current feedback.
You are right. All in all, I'm very satisfied with the sound at the moment, so I'll leave the fine tweaking until the days get shorter again.😉
I understand the concept of first selling the original 100 before posting the circuit, but...
if it doesn't go as it should go, sometimes it should go as it does go
Seems harsh to keep this community waiting for as long at it does if the commercial run has gone stale for the last couple of units
The first Firstwatt models moved with much more enthousiasm, papa has made too many, niche market's filled up!?
this post prob. doesn't solve anything, but my alternative was keep complaining to the wife 😉
F7 is near EOL unless there is a hue and cry from distribution.
In any case I see that I have about 2,000 pairs, so clearly there will be
enough left over for some DIY activity.
So sit tight until after the DIY SONY VFETs are put to bed...
In a couple of weeks the're near EOL for 2 years
I understand the concept of first selling the original 100 before posting the circuit, but...
if it doesn't go as it should go, sometimes it should go as it does go
Seems harsh to keep this community waiting for as long at it does if the commercial run has gone stale for the last couple of units
The first Firstwatt models moved with much more enthousiasm, papa has made too many, niche market's filled up!?
this post prob. doesn't solve anything, but my alternative was keep complaining to the wife 😉
so here it is
appologies for the double post
late at night on the phone
something went wrong
can't find the delete post button
late at night on the phone
something went wrong
can't find the delete post button
Please, continue to complain to your wife rather than to us. You will get much more sympathy from her than from us.
Instead of being passive and demanding, be active and truly add to the knowledge of the community. There is ample information and a resonable good guess about the design in this thread. A few has even built their own F7 work-alike.
A staring point would be the guesstimates in this thread. You can even use the F5 boards as a starting point if you don't want to go breadboard style. Though there is a crucial difference in pin out between F5 boards and F7 that you will have to find for yourself.
Instead of being passive and demanding, be active and truly add to the knowledge of the community. There is ample information and a resonable good guess about the design in this thread. A few has even built their own F7 work-alike.
A staring point would be the guesstimates in this thread. You can even use the F5 boards as a starting point if you don't want to go breadboard style. Though there is a crucial difference in pin out between F5 boards and F7 that you will have to find for yourself.
why not just buying one, original..... and speeding up Revelation Day?
Wifee should be proud, you're investing in Cause....
Wifee should be proud, you're investing in Cause....
You mean to tell me that this thread does not have a schematic attached to it?
It's at the end of the thread.You mean to tell me that this thread does not have a schematic attached to it?
Proposal to Jason and Team: include special Forum Rule, strictly Pass orientated
"To whomever: Whenever you feel tiniest amount of Decline of his Generosity, just shoot him.
Hope once will be enough to teach him how to behave in future"
"To whomever: Whenever you feel tiniest amount of Decline of his Generosity, just shoot him.
Hope once will be enough to teach him how to behave in future"
I'm not saying anything bad about NP's amp,,But,Every amplifier schematic,s is good,but you have to put the right schematic Amplifier in your right combination,have we the same complete installation as Nelson Pass 😀😀😀🥴
A couple of week ago I completed an F7 clone. I was lucky and could buy boards from @mareli as well as tips about components values and which output mosfets to use.
Early on I decided to use whatever I had in store for the build. The result looks truly hideous but works really well, as long as nobody else is at hand. Electrical safety is somewhat optional as it is just now. No children and kids nearby anyway.
Input jfets are not matched. Mosfets are Excion ECW20N20/ECW20P20, the most expensive parts by far.
Power supply is whatever I had from way back. A 120VA 2x18V toroid, standard 35A rectifiers. Six Rifa PEH169 capacitors that I bought as surplus 30 years ago (I have a few more....).
Cooling fins and fans I had from a previous build and so on.
Because of the capacity of the transformer I have set the current to 600 mA only. This is more or less the practical limit of 120 VA. It gets slightly warm but not more than that.
The capacitors works really well, I formatted them carefully and after a few times there are very little losses from them, in practical terms none at all.
I had done one session where I adjusted the distortion to be 0.40% 2nd harmonic and 0.1 3rd. No adjustment or measurement of DF yet.
Sound? - Wonderful, this is really something other than my F6 and more in line with my ACA mini. Very dynamic, revealing, big sound stage, and tight bass. I have to trim the damping factor to get the best out of it. That part remains.
The only trouble is that it seems to bring out deficiencies in other parts of my gear (or if it is the F7 itself, have to check).
Next up is finding a suitable case for it, and upgrading the transformer and rectifiers. And maybe more caps....
Early on I decided to use whatever I had in store for the build. The result looks truly hideous but works really well, as long as nobody else is at hand. Electrical safety is somewhat optional as it is just now. No children and kids nearby anyway.
Input jfets are not matched. Mosfets are Excion ECW20N20/ECW20P20, the most expensive parts by far.
Power supply is whatever I had from way back. A 120VA 2x18V toroid, standard 35A rectifiers. Six Rifa PEH169 capacitors that I bought as surplus 30 years ago (I have a few more....).
Cooling fins and fans I had from a previous build and so on.
Because of the capacity of the transformer I have set the current to 600 mA only. This is more or less the practical limit of 120 VA. It gets slightly warm but not more than that.
The capacitors works really well, I formatted them carefully and after a few times there are very little losses from them, in practical terms none at all.
I had done one session where I adjusted the distortion to be 0.40% 2nd harmonic and 0.1 3rd. No adjustment or measurement of DF yet.
Sound? - Wonderful, this is really something other than my F6 and more in line with my ACA mini. Very dynamic, revealing, big sound stage, and tight bass. I have to trim the damping factor to get the best out of it. That part remains.
The only trouble is that it seems to bring out deficiencies in other parts of my gear (or if it is the F7 itself, have to check).
Next up is finding a suitable case for it, and upgrading the transformer and rectifiers. And maybe more caps....