Mr. Pass,
I am very interested by your F4 Firstwatt amplifier , no feedback, no voltage gain. My tube préamplifier have an output level in extensively sufficient voltage (Unbalanced and balanced mode ) for a good working of the F4.
I have Martin Logan Vantage speakers. (sensitivity 92dB, nominal, impedance 4ohms)
The Vantage uses a 8" aluminum-cone woofer along with a 200W amplifier (active subwoofer) and a passive traditional electrostatic transducer. (Crosssover frequency 400Hz).
But this speakers have a minimal impedance of 1ohm to 20KHz.
I know that there is not a lot of energy to 20KHz, also, can you say to me if you made tests with a F4 on the low impedances. The working is it correct ?
What configuration of the F4 is preferable with my MartinLogan?
Must me to add other pairs of Mosfet?
Thank you for your answer
Darry
I am very interested by your F4 Firstwatt amplifier , no feedback, no voltage gain. My tube préamplifier have an output level in extensively sufficient voltage (Unbalanced and balanced mode ) for a good working of the F4.
I have Martin Logan Vantage speakers. (sensitivity 92dB, nominal, impedance 4ohms)
The Vantage uses a 8" aluminum-cone woofer along with a 200W amplifier (active subwoofer) and a passive traditional electrostatic transducer. (Crosssover frequency 400Hz).
But this speakers have a minimal impedance of 1ohm to 20KHz.
I know that there is not a lot of energy to 20KHz, also, can you say to me if you made tests with a F4 on the low impedances. The working is it correct ?
What configuration of the F4 is preferable with my MartinLogan?
Must me to add other pairs of Mosfet?
Thank you for your answer
Darry
I have received some requests for my shortened layout, so I thought I could just as well upload it.
The space between transistors is 4cm and the whole board is 25cm long. I have only marked one mounting hole, but it should be possible to drill at least one more somewhere, so you can mount it as nice as steenoe did it!!
Component numbers are the same as papas, except for the prefix 1xx on one of the channels.
ps and pdf files along with a couple of notes:
http://viller.org/audio/2007apr_f4/
The space between transistors is 4cm and the whole board is 25cm long. I have only marked one mounting hole, but it should be possible to drill at least one more somewhere, so you can mount it as nice as steenoe did it!!
Component numbers are the same as papas, except for the prefix 1xx on one of the channels.
ps and pdf files along with a couple of notes:
http://viller.org/audio/2007apr_f4/
I confess that I'm still underwhelmed by the idea of using such different parts in the front end...but yes, music can be made to come out if you try hard enough.
I would suggest the use of a pot between the Sources of unmatched JFETs. Each end of the pot goes to a Source. The wiper becomes the output node. Set the pot such that the DC offset (relative to ground) is least. Use the smallest value pot you can get away with. If 10 Ohms will do it, then use 10...if it takes 50 Ohms or 100 Ohms, then so be it. If you're finding that you need something like 500 or 1000 Ohms, try different JFETs.
No, you won't get DC at the output--the DC blocking caps will see to that. But don't say that I didn't warn you if you test the distortion and find that it's much, much higher than you expected.
By all means, experiment, but do so intelligently.
Grey
P.S.: I'm surprised that no one has asked if you can use MOSFETs at the input. The answer is yes, but it will take a few more parts. If you want, I suppose you could call this Hint #3, although it's not necessarily headed down the same path as #1 and #2.
I would suggest the use of a pot between the Sources of unmatched JFETs. Each end of the pot goes to a Source. The wiper becomes the output node. Set the pot such that the DC offset (relative to ground) is least. Use the smallest value pot you can get away with. If 10 Ohms will do it, then use 10...if it takes 50 Ohms or 100 Ohms, then so be it. If you're finding that you need something like 500 or 1000 Ohms, try different JFETs.
No, you won't get DC at the output--the DC blocking caps will see to that. But don't say that I didn't warn you if you test the distortion and find that it's much, much higher than you expected.
By all means, experiment, but do so intelligently.
Grey
P.S.: I'm surprised that no one has asked if you can use MOSFETs at the input. The answer is yes, but it will take a few more parts. If you want, I suppose you could call this Hint #3, although it's not necessarily headed down the same path as #1 and #2.
Re: Re: F4 power amplifier
Nelson,
Significance of "Balanced with stock circuit " ???
"Balanced" mode corresponds to the diagram of the page 8 (mono balanced connections)
For me, "stock circuit" would correspond to the diagram of the page 9 (parallel mono connections)
"Balanced with stock circuit" = mixture of these 2 configurations would require 4 units stereo amplifiers ???
Do you want to lighten me?
Thank you
Darry
Nelson Pass said:
For the ML's I recommend balanced drive with the stock
circuit.
Nelson,
Significance of "Balanced with stock circuit " ???
"Balanced" mode corresponds to the diagram of the page 8 (mono balanced connections)
For me, "stock circuit" would correspond to the diagram of the page 9 (parallel mono connections)
"Balanced with stock circuit" = mixture of these 2 configurations would require 4 units stereo amplifiers ???
Do you want to lighten me?
Thank you
Darry
Well of course you can do that, although I haven't bothered
to try.
So I mean balanced with one chassis per channel.
I did run original Zens balanced and parallel at 40 watts using
two stereo chassis per channel. It was really a big improvement
with extra power and the 2nd harmonic cancellation.
to try.
So I mean balanced with one chassis per channel.
I did run original Zens balanced and parallel at 40 watts using
two stereo chassis per channel. It was really a big improvement
with extra power and the 2nd harmonic cancellation.
Nelson Pass said:
Even if the basic sounds are very good with either 2nd or 3rd harmonics, I still subjectively prefer the 2nd harmonic distortion. In my renewal chain of diy amps, in general, I live longer with 2nd harmonics. For me, 3rd harmonics tend to give me a hint of tension to my ears while 2nd harmonics are more relaxed and natural ^^.
Banned
Joined 2002
Banned
Joined 2002
Jason,
Just trying to get you to think a bit. Yes, of course it all depends on the heatsink, so take the 160W, find out what the R-theta value of your heatsink is in °C/W, do a little multiplication, and voila, you'll know the answer to your question.
BTW, Nelson gives a very good discussion of the heat management issue in the service manual.
When I have (actually I always have) co-op students and engineers-in-training working under me, I don't have time to hand hold them through every decision, so I give them a very simple but effective golden rule to working on my projects: Don't come to me with a question or problem until you have a proposed answer or solution prepared, but as long as you have taken that step it doesn't matter how close you are to the right / best / good answer or solution, I will not only help select the course of action, but explain all the why behind it. I then enforce that rule rather strictly both on them and me. I have yet to find a training tool or method that 1) generates better productivity in my group, and 2) generates greater personal benefit for those working under me.
Why do I mention all of this, Jason, and why are I and some others at this forum a little harsh with you. From your interaction on the forum I can clearly sense that you have the ability and Babowana's response echo's my opinion as well, but more frequently of late you default to taking the easy route of getting someone else to go to the trouble of giving you the answer instead of thinking it through yourself. I hope this isn't too blunt, but you're selling yourself short, and I am certain that you have better in you.
As they say in the HR business, give yourself a stretch goal: state the question, provide what you think is the right answer with your reasoning, and ask for feedback. You'll be surprised how much you already know, as well as how fast your learning accelerates.
Hopefully somewhat less harsh,
Terry
Just trying to get you to think a bit. Yes, of course it all depends on the heatsink, so take the 160W, find out what the R-theta value of your heatsink is in °C/W, do a little multiplication, and voila, you'll know the answer to your question.
BTW, Nelson gives a very good discussion of the heat management issue in the service manual.
When I have (actually I always have) co-op students and engineers-in-training working under me, I don't have time to hand hold them through every decision, so I give them a very simple but effective golden rule to working on my projects: Don't come to me with a question or problem until you have a proposed answer or solution prepared, but as long as you have taken that step it doesn't matter how close you are to the right / best / good answer or solution, I will not only help select the course of action, but explain all the why behind it. I then enforce that rule rather strictly both on them and me. I have yet to find a training tool or method that 1) generates better productivity in my group, and 2) generates greater personal benefit for those working under me.
Why do I mention all of this, Jason, and why are I and some others at this forum a little harsh with you. From your interaction on the forum I can clearly sense that you have the ability and Babowana's response echo's my opinion as well, but more frequently of late you default to taking the easy route of getting someone else to go to the trouble of giving you the answer instead of thinking it through yourself. I hope this isn't too blunt, but you're selling yourself short, and I am certain that you have better in you.
As they say in the HR business, give yourself a stretch goal: state the question, provide what you think is the right answer with your reasoning, and ask for feedback. You'll be surprised how much you already know, as well as how fast your learning accelerates.
Hopefully somewhat less harsh,
Terry