Hi, Mr.Pass,
I have a question that I cannot hold
The bias at Q1 is about 10mA, and Q1 is MOSFET.
What happens if I put Jfet with 1mA bias at the position Q1 (with all R values and working point adjusted until the DC is still about 1/2rail and output bias is correct)?
The bandwith won't reach 100khz?
I have a question that I cannot hold
The bias at Q1 is about 10mA, and Q1 is MOSFET. What happens if I put Jfet with 1mA bias at the position Q1 (with all R values and working point adjusted until the DC is still about 1/2rail and output bias is correct)?
The bandwith won't reach 100khz?
lumanauw said:I have a question that I cannot hold
What happens if I put Jfet with 1mA bias at the position Q1 (with all R values and working point adjusted until the DC is still about 1/2rail and output bias is correct)?
The bandwith won't reach 100khz?
No Mr. Pass just my two cents: you will need to have enough idle current in the phase splitter to drive the gate capacitance of the output mosfets.
I used irfp140s (and FQA19N20), and the gate current peaks at about 600ua each. I tend to run my idle current at 10x of that, which means about 6ma through Q1. I used 470ohm resistors in place of the 220ohms used by Pass without any ill effect (so far).
It has no effect on bankdwidth, tho. and this thing has fairly narrow bandwidth: I guess due to low gain / low feedback.
The discussion about turning Haflers and Adcoms into PLH amps has been split out to here:http://www.diyaudio.com/forums/showthread.php?s=&threadid=64226
Let's keep this thread about general PLH design.
Anything to do with circuit boards, and installing same in these amps, including group buys, will be discussed in the new thread.
R7
With reference to Fig 8:
What is the function of R7, 392 Ohm?
The value of this resistor is very small in comparison to P3.
Even if P3 is nearly 0 ohm (this will never happen, a 50k
fully ccw always is a few hundred ohms), I can't imagine
anything going awfully wrong. Same holds for fully cw or
a broken pot (full 50k resistance).
Or am i overlooking a subtlety?
I can even see this pot being a 100k multiturn lin in case of
difficulty setting the DC output at midpoint. Especially if you
choose some other Fets to play with. Or you could raise R7 of
course. (silly me)
Regards.
With reference to Fig 8:
What is the function of R7, 392 Ohm?
The value of this resistor is very small in comparison to P3.
Even if P3 is nearly 0 ohm (this will never happen, a 50k
fully ccw always is a few hundred ohms), I can't imagine
anything going awfully wrong. Same holds for fully cw or
a broken pot (full 50k resistance).
Or am i overlooking a subtlety?
I can even see this pot being a 100k multiturn lin in case of
difficulty setting the DC output at midpoint. Especially if you
choose some other Fets to play with. Or you could raise R7 of
course. (silly me)
Regards.
After reading the PLH paper for the 10th round, I found something interesting. Hats off to Mr.Pass
PLH somekind of "push-pull" output stage amplifier, but the portion of the "push" and the "pull" can be modified from 1:1 AC portion to the upper working as CCS.
I just realize, this is the first time I see an amplifier design that can do this (and it is designed on purpose to do so).
I saw Musical Fidelity or Blomley controlling independently +output stage and -output stage, but PLH is doing something completely different.
All this time I tought that manipulating balances (like to get some H2 distortion) is done in the input differential legs. I never tought it also can be done in the output stage All this time I always tought push-pull output stage only works with 1:1 condition. PLH opened my eyes, that they are not necessarily be that way
The input is singleton, it cannot cancel 2nd harmonic. The output stage can be adjusted have 2nd harmonic. This should be better than Aleph
PLH somekind of "push-pull" output stage amplifier, but the portion of the "push" and the "pull" can be modified from 1:1 AC portion to the upper working as CCS.
I just realize, this is the first time I see an amplifier design that can do this (and it is designed on purpose to do so).
I saw Musical Fidelity or Blomley controlling independently +output stage and -output stage, but PLH is doing something completely different.
All this time I tought that manipulating balances (like to get some H2 distortion) is done in the input differential legs. I never tought it also can be done in the output stage
All this time I always tought push-pull output stage only works with 1:1 condition. PLH opened my eyes, that they are not necessarily be that way The input is singleton, it cannot cancel 2nd harmonic. The output stage can be adjusted have 2nd harmonic. This should be better than Aleph
lumanauw said:After reading the PLH paper for the 10th round, I found something interesting. Hats off to Mr.Pass
PLH somekind of "push-pull" output stage amplifier, but the portion of the "push" and the "pull" can be modified from 1:1 AC portion to the upper working as CCS.
I just realize, this is the first time I see an amplifier design that can do this (and it is designed on purpose to do so).
I saw Musical Fidelity or Blomley controlling independently +output stage and -output stage, but PLH is doing something completely different.
All this time I tought that manipulating balances (like to get some H2 distortion) is done in the input differential legs. I never tought it also can be done in the output stage
The input is singleton, it cannot cancel 2nd harmonic. The output stage can be adjusted have 2nd harmonic. This should be better than Aleph
it's done allready with tube PP amps
R7 mistery solved
Nelson, thank you for clearing that up. With a R7=47,5k the
setting of the output DC at midpoint is a breeze.
If you change fig. 8 (or have it changed), you could have another
look at the text. A small typo in the sentence:
The Source of Q1 follows the Gate input signal
and drives the transistor Q3 in Common Source mode (voltage and...
Q3 should be Q2
ref:
http://www.passdiy.com/pdf/PLH_amplifier.pdf
and my first post in this thread:
http://www.diyaudio.com/forums/showthread.php?postid=722040#post722040
I like the circuit very much. Thanks.
Regards
Nelson, thank you for clearing that up. With a R7=47,5k the
setting of the output DC at midpoint is a breeze.
If you change fig. 8 (or have it changed), you could have another
look at the text. A small typo in the sentence:
The Source of Q1 follows the Gate input signal
and drives the transistor Q3 in Common Source mode (voltage and...
Q3 should be Q2
ref:
http://www.passdiy.com/pdf/PLH_amplifier.pdf
and my first post in this thread:
http://www.diyaudio.com/forums/showthread.php?postid=722040#post722040
I like the circuit very much. Thanks.
Regards
Phl ?jlh
Hi All Dyers
Well Phl what have we here there is only one and that is JHL in my view no diss respect to the Mr Nelson as there is a man who knows what he is taking about I haft to say I have only built the Bride of Zen pre amp And my view on his pre amp is good But building in the Uk wee have I guess a different prospective on Sound to you chaps in the states u see my self and some others feel that the Mosfet Trans and all these can t caps do distort sound I think if your are gowning to build this amp Pleas have A look as Geoff Moss’s Site http://www.tcaas.btinternet.co.uk/ go have a look This man is very help full
Chers
Hi All Dyers
Well Phl what have we here there is only one and that is JHL in my view no diss respect to the Mr Nelson as there is a man who knows what he is taking about I haft to say I have only built the Bride of Zen pre amp And my view on his pre amp is good But building in the Uk wee have I guess a different prospective on Sound to you chaps in the states u see my self and some others feel that the Mosfet Trans and all these can t caps do distort sound I think if your are gowning to build this amp Pleas have A look as Geoff Moss’s Site http://www.tcaas.btinternet.co.uk/ go have a look This man is very help full
Chers
no fence-but I didn't have impression that anybody here have intention to disrespect JLH (amp or person )
besides ,regarding UK "prospective of sound" - all depends what you think with that .........
on one side you have (or we-if you wish) LS 3/5 nad on the other side is "best buy of all times" known as Wharfedale Diamond (any incarnation ) ;
I can make better box any time almost with drivers from boom boxes.....
so-let's just forget about US or UK prospective and lets talk and build anything we want ...
hehe-even if is french or dutch origin .......
ps. I'm more tube than sand guy ,but I never make mistake saying that all sand amps are bad ,mebbe just becouse I grew up with mostly German pro gear around me......
)besides ,regarding UK "prospective of sound" - all depends what you think with that .........
on one side you have (or we-if you wish) LS 3/5 nad on the other side is "best buy of all times" known as Wharfedale Diamond (any incarnation ) ;
I can make better box any time almost with drivers from boom boxes.....
so-let's just forget about US or UK prospective and lets talk and build anything we want ...
hehe-even if is french or dutch origin .......
ps. I'm more tube than sand guy ,but I never make mistake saying that all sand amps are bad ,mebbe just becouse I grew up with mostly German pro gear around me......
PHL JLH
no fence-but I didn't have impression that anybody here have intention to disrespect JLH (amp or person )
besides ,regarding UK "prospective of sound" - all depends what you think with that .........
Sorry to all
There was no offence intended by me regarding UK or other country’s I just think us in UK think a little different at times we tend to like a more lade back sound yes My LS 3/5 Are still working well Yes I am building the Phl so much Help will be welcome How About A PCB for PHL But First I Will Finish The JLH Headphone Amp Circuit 1 http://www.tcaas.btinternet.co.uk/jlhphones.htm
Sorry I slapped my Wrests for that last Post
no fence-but I didn't have impression that anybody here have intention to disrespect JLH (amp or person )
besides ,regarding UK "prospective of sound" - all depends what you think with that .........
Sorry to all
There was no offence intended by me regarding UK or other country’s I just think us in UK think a little different at times we tend to like a more lade back sound yes My LS 3/5 Are still working well Yes I am building the Phl so much Help will be welcome How About A PCB for PHL But First I Will Finish The JLH Headphone Amp Circuit 1 http://www.tcaas.btinternet.co.uk/jlhphones.htm
Sorry I slapped my Wrests for that last Post
Optimum Current Ratio
Dear Nelson,
In Fig. 13 of your article, you showed a relative constant level of distortion from 20 Hz to 2 kHz with a current ration of 2/3. I assume the Y-axis to be THD (total harmonic distortion).
I wonder if the content of the distortion (mainly 2nd order?) remains more or less constant, or do they change significantly with frequency.
Would you care to show some figures on that ?
Much obliged,
Patrick
Dear Nelson,
In Fig. 13 of your article, you showed a relative constant level of distortion from 20 Hz to 2 kHz with a current ration of 2/3. I assume the Y-axis to be THD (total harmonic distortion).
I wonder if the content of the distortion (mainly 2nd order?) remains more or less constant, or do they change significantly with frequency.
Would you care to show some figures on that ?
Much obliged,
Patrick
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