apassgear said:
I upped the capacitance filtering the drive circuit for the CCS,
easy enough to do. Also I used a resistive divider to reset the
charge faster after turn-off. As it is, you want to wait a minute
after turn-off before turning it back on, or you still get a thump.
Vix said:
The amp can take a short all day. (Yawn).
The F2 is perfectly stable, I just trimmed it above 200 KHz
for a slightly more polished square wave.
I found the thump only objectionable on AER dm3's, and
presumed that compression drivers would also not want it,
although I believe that such compression drivers as TAD 4001's
would probably want some sort of passive hi-pass filter in
series with the driver regardless (just in case).
With Lowthers and Fostex, it was less of an issue. With the
slower turn on, you don't even notice it.
I tried the wire-wounds on the last R just for the hell of it, and
they just tuned it a tiny bit. (See the square wave in the
owner's manual). Not being a big square wave junkie, I don't
think it's a phenomena that we want to get very excited about -
I already had the holes in the board. Yours will probably be
different anyway.
It’s a pleasure and a privilege to get all this attention from Nelson on this thread.
He has given more than enough information on F2 to have many of you DIY’s start heating your irons to build this extraordinary fullranger amp. Besides we have a starting schematic which Nelson believes will work fine and it’s as easy to build as the original Zen which BTW myself built in 30 days after its publication on AA.
If you are waiting for the original circuit to be disclosed be prepared to wait at least 6 month (maybe less, who knows) until the last F2 is delivered.
He has given more than enough information on F2 to have many of you DIY’s start heating your irons to build this extraordinary fullranger amp. Besides we have a starting schematic which Nelson believes will work fine and it’s as easy to build as the original Zen which BTW myself built in 30 days after its publication on AA.
If you are waiting for the original circuit to be disclosed be prepared to wait at least 6 month (maybe less, who knows) until the last F2 is delivered.
Hi,
I just received a transformer yesterday. 600 W, with dual 32 V secondaries. That should give around 40 V or so after the rectification. Since I am going to build a “Transconductance Zen Lite” this should be fine. I am going to use ceiling 12 v halogen light bulbs. 3 of them in series per channel. I still did not decide about their wattage. I bought 20w ones. Will try 35w or 50w ones if needed. I will use an IRFP250N device. I still have to obtain filter capacitors. And I am going to employ the “Turn-on thump circuit” as described in the “Zen Lite” article. It works perfectly.
Unfortunately, due to the lack of free time, I don’t actually know when this will actually be ready. As soon as I have something “tangible” I will post here about the results…
There are no words that can express my thankfulness to Mr. Pass. I feel like taking a “distant learning” course, except that I pay nothing. Books are a good thing, but there is something special about the “live” interaction between the “author” and a “reader”. If we were living in the Ancient Greece, Mr.Pass would have been our tutor and a philosopher, and we would be faithful followers. Lessons would have taken place outside, on some beautiful Mediterranean island. Topic: How to appreciate all dimensions of music: depth, width of the soundstage, as well as the 'air' between instruments..etc” At the end of the day, under the light of candles (Think of Zen lite ) we would drink red wine and enjoy the music….
Back to the future…Since we are living in the 21st century and the earth has become a “global village” I think that this forum, with the generous help from the Master, does the trick….
Best regards,
Vix"
I just received a transformer yesterday. 600 W, with dual 32 V secondaries. That should give around 40 V or so after the rectification. Since I am going to build a “Transconductance Zen Lite” this should be fine. I am going to use ceiling 12 v halogen light bulbs. 3 of them in series per channel. I still did not decide about their wattage. I bought 20w ones. Will try 35w or 50w ones if needed. I will use an IRFP250N device. I still have to obtain filter capacitors. And I am going to employ the “Turn-on thump circuit” as described in the “Zen Lite” article. It works perfectly.
Unfortunately, due to the lack of free time, I don’t actually know when this will actually be ready. As soon as I have something “tangible” I will post here about the results…
There are no words that can express my thankfulness to Mr. Pass. I feel like taking a “distant learning” course, except that I pay nothing. Books are a good thing, but there is something special about the “live” interaction between the “author” and a “reader”. If we were living in the Ancient Greece, Mr.Pass would have been our tutor and a philosopher, and we would be faithful followers. Lessons would have taken place outside, on some beautiful Mediterranean island. Topic: How to appreciate all dimensions of music: depth, width of the soundstage, as well as the 'air' between instruments..etc” At the end of the day, under the light of candles (Think of Zen lite ) we would drink red wine and enjoy the music….
Back to the future…Since we are living in the 21st century and the earth has become a “global village” I think that this forum, with the generous help from the Master, does the trick….
Best regards,
Vix"
Vix said:
There are no words that can express my thankfulness to Mr. Pass. I feel like taking a “distant learning” course, except that I pay nothing. Books are a good thing, but there is something special about the “live” interaction between the “author” and a “reader”. If we were living in the Ancient Greece, Mr.Pass would have been our tutor and a philosopher, and we would be faithful followers. Lessons would have taken place outside, on some beautiful Mediterranean island. Topic: How to appreciate all dimensions of music: depth, width of the soundstage, as well as the 'air' between instruments..etc” At the end of the day, under the light of candles (Think of Zen lite ) we would drink red wine and enjoy the music….
Back to the future…Since we are living in the 21st century and the earth has become a “global village” I think that this forum, with the generous help from the Master, does the trick….
No doubt
Bias current
F2 has 24V DC voltage and 2.7A bias current.
If the impedance of speaker is 4ohm, maximum current can be reach to 2.7A because maximum voltage in speaker terminal is 12V ideally.
But, in case of 8ohm speaker, 2.7A is too much. If F2 can be designed only for 8ohm speaker so that the bias current can be reduced to half value, maximum power consumption can be reduced to half. Am I correct?
F2 has 24V DC voltage and 2.7A bias current.
If the impedance of speaker is 4ohm, maximum current can be reach to 2.7A because maximum voltage in speaker terminal is 12V ideally.
But, in case of 8ohm speaker, 2.7A is too much. If F2 can be designed only for 8ohm speaker so that the bias current can be reduced to half value, maximum power consumption can be reduced to half. Am I correct?
bias current level
Thank you for reply, Mr. Pass.
I have a toroidal transformer with 24V output, 500VA.
I can get 32V using this tranformer.
If the bias current is 2.7A, total power loss will be 86W which is higher than 64W of F2. In this case, bigger heatsink is required and the power dissapation of each FET is quite high compared with F2. If I decrease the bias current to 2.0A, total power dissapation become to 64W, similar to F2.
Will the distortion be too high in this case? ( The impedance of my speaker 8 ohm.)
I have a back loaded horn speaker 'Swan' which is famous in Japanese diy community. The driver of Swan is Fostex FE-108S which has 8ohm impedance. Is there any way to design the EQ network to fit my speaker to F2?
Thank you for reply, Mr. Pass.
I have a toroidal transformer with 24V output, 500VA.
I can get 32V using this tranformer.
If the bias current is 2.7A, total power loss will be 86W which is higher than 64W of F2. In this case, bigger heatsink is required and the power dissapation of each FET is quite high compared with F2. If I decrease the bias current to 2.0A, total power dissapation become to 64W, similar to F2.
Will the distortion be too high in this case? ( The impedance of my speaker 8 ohm.)
I have a back loaded horn speaker 'Swan' which is famous in Japanese diy community. The driver of Swan is Fostex FE-108S which has 8ohm impedance. Is there any way to design the EQ network to fit my speaker to F2?
To use the 24v trafo;
You could use the ZEN-regulator to bring down the rail voltage, to the same level as the original. Take a look at the ZEN papers:
http://www.passdiy.com/projects/zenv3-1.htm
The one in figure 3, would be easy to hardwire.
Good luck
Steen.
Hi Guys,
My good friend just completed a mock up of the F2 based on Mr Pass's generous information and the schematic posted by apassgear.
We've tried this F2 clone on the Coral Flat10, Coral Triaxial and a Beta 8. All the drivers exhibited superb bass... Best match IMO was with the Beta 8... The F2 is definitely the best amp I've herad driving the Beta 8. Ba big thnak you to Nelson Pass for sharing with us, high efficiency Fullranger users, such a magnificient amplifer.
My good friend just completed a mock up of the F2 based on Mr Pass's generous information and the schematic posted by apassgear.
An externally hosted image should be here but it was not working when we last tested it.
We've tried this F2 clone on the Coral Flat10, Coral Triaxial and a Beta 8. All the drivers exhibited superb bass... Best match IMO was with the Beta 8... The F2 is definitely the best amp I've herad driving the Beta 8. Ba big thnak you to Nelson Pass for sharing with us, high efficiency Fullranger users, such a magnificient amplifer.
Bill,
Nice to see you have an F2 working and that you liked it. Those are good news to others who intend to build it.
What kind of supply does it has? looks like a CLC.
Any suggestions on componets used and values related to the schematic? What resistance values are you using on the sources?
Happy listening!!!
Nice to see you have an F2 working and that you liked it. Those are good news to others who intend to build it.
What kind of supply does it has? looks like a CLC.
Any suggestions on componets used and values related to the schematic? What resistance values are you using on the sources?
Happy listening!!!
I separately came up with a schematic very similar to the F2 amp that apassqear has posted. I used LM317 as the regulator. And it also has a SE BJT(NPN) VAS as the input stage. The source resistors of the two power MOSFET (P is IRF9450, N is IRF610) are of different value for distortion and sounding tunning. The bias current is about 800mA. So not a whole lot of technical outout power. The power rail is at 21V. I just happen to have a xformer output at 24V and LM317 need about 3 V headroom to deliver reasonable output. I also put a 12V Zener to regular the gate drive voltage for the current source.
For distortion less than 1%, it can only output ONE watt. But it sounds more than it. I used it to run LS3/5a which is not an efficient speaker but it's my best now. It sounds close to a tube amp, very nice sounding.
Have gone thru different bad and nice sounding phases during the experimenting of the circuit. Vocal could be very aggressive and too forward sometimes. I have it settled now.
Simple circuit, low output but yet very enjoyable. I believe it will match very well with high efficient speaker. For LS 3/5A, I can heard that it's a bit exhausted at high output. But the clipping is not too offensive.
Happy diy...
Kam
For distortion less than 1%, it can only output ONE watt. But it sounds more than it. I used it to run LS3/5a which is not an efficient speaker but it's my best now. It sounds close to a tube amp, very nice sounding.
Have gone thru different bad and nice sounding phases during the experimenting of the circuit. Vocal could be very aggressive and too forward sometimes. I have it settled now.
Simple circuit, low output but yet very enjoyable. I believe it will match very well with high efficient speaker. For LS 3/5A, I can heard that it's a bit exhausted at high output. But the clipping is not too offensive.
Happy diy...
Kam
apassgear said:Bill,
What kind of supply does it has? looks like a CLC.
Any suggestions on componets used and values related to the schematic? What resistance values are you using on the sources?
Happy listening!!!
Hi Tony,
The mock up F2 is completely made from recycled parts we had laying around, we did try the CRC first but as we had a pair of chokes around , we decided to try the chokes (CLC)and we found the sound to be slightly better. The parts/configurations are as follows :
48000uF 40V - 0.68mH - 48000uF 40V per
channel.
Output capacitor is 3X4700uF parallel with 1uF MKP
capacitor.
Z5 is 20V
R5 is 392K
R4 is 560K
R13 is 0R73 6W
R1 is 0R22 25W
R10 is 15R 15W
EI power transformer 2X18V 150VA
15V-0-15V 100VA (not used)
0-9V 25VA (not used)
Q1 IRFP240
Q2 IRF9640
Q3 ZTX550
Kam,
Nice experience, this only confirm what I commented on my previous post.
I think anybody with an old original Zen, with good supply filtering could attempt the simple modifications required to make a current source amp.
Simply change: (Based on the previous schematic)
Biasing resistors, R4 and R5
Add source resistor for Q1, R13
Loading resistor, R10
Lower value of input cap, C2
That’s all, just make sure you have enough heatsinking for the new bias that you may set.
Nice experience, this only confirm what I commented on my previous post.
I think anybody with an old original Zen, with good supply filtering could attempt the simple modifications required to make a current source amp.
Simply change: (Based on the previous schematic)
Biasing resistors, R4 and R5
Add source resistor for Q1, R13
Loading resistor, R10
Lower value of input cap, C2
That’s all, just make sure you have enough heatsinking for the new bias that you may set.
I found that my amp is very sensitive to power supply noise. It became very hash sounding when:
1. Before I put in the LM317 regulator. The power line ripple is able 300 mV at the time even with 20K+30K uF cap. The ripple was about 10 times less as seen at the output. It could be heard on the speaker. That smeared the sound stage badly.
2. Poor component lay-out. When I was just wired all the things together loosely, it sounded very good. But when I put it all together nicely, it became very hash sounding. It was due to power noise coupling that I had to re-arrange the AC-DC power as far away from the amp input and then it came back to life again.
You don't get these experience by purchasing your solution but diy...
Kam
1. Before I put in the LM317 regulator. The power line ripple is able 300 mV at the time even with 20K+30K uF cap. The ripple was about 10 times less as seen at the output. It could be heard on the speaker. That smeared the sound stage badly.
2. Poor component lay-out. When I was just wired all the things together loosely, it sounded very good. But when I put it all together nicely, it became very hash sounding. It was due to power noise coupling that I had to re-arrange the AC-DC power as far away from the amp input and then it came back to life again.
You don't get these experience by purchasing your solution but diy...
Kam
Kam,
Nice to see you were able to mostly solve the problem.
Having higher input impedance this amp seems to be more like a valve unit but in any case having a shot and isolated connection at the signal input is always recommended to avoid cross coupling.
Zen amps, the ones I’ve worked with, have been sensitive to supply ripple so it’s a good idea to have a well filtered PSU. At least a CRC or CLC filtering or a regulated supply as you have done. If you ever upgrade the regulator to something like it was proposed on the schematic let us know of the results since this will be interesting for others attempting this project.
Nice to see you were able to mostly solve the problem.
Having higher input impedance this amp seems to be more like a valve unit but in any case having a shot and isolated connection at the signal input is always recommended to avoid cross coupling.
Zen amps, the ones I’ve worked with, have been sensitive to supply ripple so it’s a good idea to have a well filtered PSU. At least a CRC or CLC filtering or a regulated supply as you have done. If you ever upgrade the regulator to something like it was proposed on the schematic let us know of the results since this will be interesting for others attempting this project.
BTW said:
Bill,
Even though I haven’t tested it myself it seems odd that you have a higher resistor on R4 position than on R5.
As far as I have work on similar Zen circuits R4 has been about half of R5 to have a symmetrical clipping at the output. But this can only be confirmed with an Oscope, and this is the reason to use a pot at R4 position which will enable adjustment for symmetrical clipping. All this will ensure you have maximum output power before clipping occurs.
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