A 470uf bootstrap cap for the P3A makes much better bass
10 or 22 uf input cap for better bass and parallel with film cap for better treble
Also, a 100pf in place of the 220pf for the input may help treble. I've always used 100pf on the input of amps.
Destroyer X has mentioned bypassing the feedback resistor to gnd with a 1nf cap (or 10nf I can't recall) to enhance the treble, although I've never yet tried that myself
10 or 22 uf input cap for better bass and parallel with film cap for better treble
Also, a 100pf in place of the 220pf for the input may help treble. I've always used 100pf on the input of amps.
Destroyer X has mentioned bypassing the feedback resistor to gnd with a 1nf cap (or 10nf I can't recall) to enhance the treble, although I've never yet tried that myself
fotios said:
Hey, rabbitz
To not misunderstand me - i'm not so good in English like Sakis - i made a joke to he. Because Sakis is living in the capital of Greece Athens, instead me i'm living in a small town in north Greece. As you know in big cities the people works continuously from 9am to 6pm. Instead all of us where are living in small towns, we have the benefit of the midday work interval from 2pm to 6pm.
Well, that i said to Sakis was that i am drinking my midday beer before lunch and he must be worked at this time instead to browse the forum; and i suggested to he a nice and cheap (0,55euros the 0,5lt bottle) beer brand Henninger. Poverty knows no laws.
Fotios
I thought you had a keyboard gone crazy.
Tessier
I would have to hire a secretary to type for me i had to explain it all here, theres maths involved too. I am not sure if i could explain it that well to you either, although i have a ee degree i have never worked in the electronics field and some of us like me are not born good teachers. Kinda waste i know, guess i went to study for my hobby. So how about i give you some homework .
I have never built a amp without phase lead since my teens and what i learnt then was from Linsley Hood whos amps and preamps i built as kits *Not talking about his famous JLH*. Also i studied some of his commercial designs, most from the 70s and early 80s. I soon discovered building other japanese kit amps, despite having incredible specs compaired to his, they just sounded outright crap.
Diiference was only the use of a simple single cap. Now think of it this way, incredible specs and a little trick if you wanna call it that, that has a very positive effect on sound.........
I suggest you google the net and study everything he has on audio. There is a specific paper where he explains the concept *1977 or 1978* although with the help of modern simulators you can learn much more about its effects. Look for articles he wrote for wireless, if i can remember correctly it was published there too.
I have emigrated here and could not bring everything with me so i dont have these articles with me and not in digital format but maybe on the net youll find them.
A must read too is Dr Leach on his feedforward paper. This is definetly on the net somewhere.
Alex
I would have to hire a secretary to type for me i had to explain it all here, theres maths involved too. I am not sure if i could explain it that well to you either, although i have a ee degree i have never worked in the electronics field and some of us like me are not born good teachers. Kinda waste i know, guess i went to study for my hobby. So how about i give you some homework .
I have never built a amp without phase lead since my teens and what i learnt then was from Linsley Hood whos amps and preamps i built as kits *Not talking about his famous JLH*. Also i studied some of his commercial designs, most from the 70s and early 80s. I soon discovered building other japanese kit amps, despite having incredible specs compaired to his, they just sounded outright crap.
Diiference was only the use of a simple single cap. Now think of it this way, incredible specs and a little trick if you wanna call it that, that has a very positive effect on sound.........
I suggest you google the net and study everything he has on audio. There is a specific paper where he explains the concept *1977 or 1978* although with the help of modern simulators you can learn much more about its effects. Look for articles he wrote for wireless, if i can remember correctly it was published there too.
I have emigrated here and could not bring everything with me so i dont have these articles with me and not in digital format but maybe on the net youll find them.
A must read too is Dr Leach on his feedforward paper. This is definetly on the net somewhere.
Alex
homemodder said:
Hi
Ok, I will google.
Do you know if a phase lead capacitor can be ad in that circuit ?
http://www.diyaudio.com/forums/attachment.php?postid=1521996&stamp=1211917681
Thanx
Cheer
Paul
Today .....
i went for a small excercise ....
i builted my shelf a P3A amplifier but done everything the wrong way on perpus .....i firstly wanted to see how it shows on scope then wanted to listen
things i ve done wrong
---used 1943-5200 chinese made
---used bd139-140 form totaly unknown supplier ( no name at all on them )
---didnt match ltp ,ccs,and vbe
--- classic carbon resistors
---rest of the caps ceramics (feedback,miller)
more or less used everything available from the bench ....and biassed at 30ma .....
results : bandwidth limited , then square wave test looked not realy proper at 10KHZ and beyond that started to get trinagle ....
listening tests low ends where kinda emty and seemed in a way out of phase midle was average with an idea of depth like all midle sounded behind the speaker ..... as about high it was a total mess compaired to all other a builted ..... messy and dirty no detail at all .....
nice .... small litle stuff makes a hell of a diference !!!!
i went for a small excercise ....
i builted my shelf a P3A amplifier but done everything the wrong way on perpus .....i firstly wanted to see how it shows on scope then wanted to listen
things i ve done wrong
---used 1943-5200 chinese made
---used bd139-140 form totaly unknown supplier ( no name at all on them )
---didnt match ltp ,ccs,and vbe
--- classic carbon resistors
---rest of the caps ceramics (feedback,miller)
more or less used everything available from the bench ....and biassed at 30ma .....
results : bandwidth limited , then square wave test looked not realy proper at 10KHZ and beyond that started to get trinagle ....
listening tests low ends where kinda emty and seemed in a way out of phase midle was average with an idea of depth like all midle sounded behind the speaker ..... as about high it was a total mess compaired to all other a builted ..... messy and dirty no detail at all .....
nice .... small litle stuff makes a hell of a diference !!!!
Hi!
I'm looking forward to populate a ESP P3A pcb in the next weeks. But I wonder about some of the elctrolytic caps.
For the C+ and C- electros I guess low esr 100uF/63V would be ok, as these are part of the power supply.
But what about C5 and C3? What are these supposed to do, and what kind of cap would be suitable?
According to the BOM C5 is supposed to be 100uF/63V (same as C+ and C-), C3 is supposed to be 100uF/6,3V.
What do you think about these? Low esr or not, evntually a tantalum for C3? Or just ordinary multi purpose electrolytics?
Perhaps I should go for Panasonic FC for all of these caps, would this be a decent choice?
Thanks a lot!
Martin
I'm looking forward to populate a ESP P3A pcb in the next weeks. But I wonder about some of the elctrolytic caps.
For the C+ and C- electros I guess low esr 100uF/63V would be ok, as these are part of the power supply.
But what about C5 and C3? What are these supposed to do, and what kind of cap would be suitable?
According to the BOM C5 is supposed to be 100uF/63V (same as C+ and C-), C3 is supposed to be 100uF/6,3V.
What do you think about these? Low esr or not, evntually a tantalum for C3? Or just ordinary multi purpose electrolytics?
Perhaps I should go for Panasonic FC for all of these caps, would this be a decent choice?
Thanks a lot!
Martin
good quality elctrolytics is plain ok ....no extremes there it will work even with the most simple ....
xmmm here is a nice project :
since you are working on a pcb for P3A here is my 2 cents .....
---1) having the psu caps on board is a question of choise either you like to have them or you dont
---2) then ideal pcb should have
*power traces as thick and small is possible
*ground trace as small is possible
*short distance between colector resistors
*feedback trace short, close to the midle of the output trace
*by pass and decoupling as close to the power trs possible
*no ground plane
*star ground philosophy
* a zobel return that doesnt mess up with input signal
* symmetry just for the looks
* ccs transistor as close to the ltp possible
* possibility to common heatsink drivers and VBE
* posiblity for a thermal junction fro ltp stage
*probably a few others that i miss on a sunday morning
---3) keeping most or ll of these rules is almost not possible in a single leyer pcb then gain dual leyer might be too expensive to make for a P3A or result with other issues such is capacitance or inductunce between traces ..
i will be more than happy to see yours ...since i design pcb's for P3A for three years now and never managed to fullfill all the rules in a single leyer
kind regards sakis
xmmm here is a nice project :
since you are working on a pcb for P3A here is my 2 cents .....
---1) having the psu caps on board is a question of choise either you like to have them or you dont
---2) then ideal pcb should have
*power traces as thick and small is possible
*ground trace as small is possible
*short distance between colector resistors
*feedback trace short, close to the midle of the output trace
*by pass and decoupling as close to the power trs possible
*no ground plane
*star ground philosophy
* a zobel return that doesnt mess up with input signal
* symmetry just for the looks
* ccs transistor as close to the ltp possible
* possibility to common heatsink drivers and VBE
* posiblity for a thermal junction fro ltp stage
*probably a few others that i miss on a sunday morning
---3) keeping most or ll of these rules is almost not possible in a single leyer pcb then gain dual leyer might be too expensive to make for a P3A or result with other issues such is capacitance or inductunce between traces ..
i will be more than happy to see yours ...since i design pcb's for P3A for three years now and never managed to fullfill all the rules in a single leyer
kind regards sakis
Just one simple question ... why is there a miller cap in the negative rail driver transistor ??
About VAS, styroflex and other types of miller caps - if I find a scope I'll check it out how it's doing.
Another thing - I made my PCB design already, and these days when I have some spare time I'll try the P3A with a current mirror in the diff. stage and a CCS in VAS.
Err...sorry for dusting off such an old thread, but my concept didn't quite work out, is there anyone good with sym programs, willing to help me? I sim'd my schematic with multisim, and there it worked fine, but in reality it's not the same thing, or it needs further research with a better sim program. If anyone is willing to help i'll post a detailed schematic later, or maybe tomorrow tops.
An externally hosted image should be here but it was not working when we last tested it.
Uploaded with ImageShack.us
This is my current setup, and something is wrong, cause they didn't fire right up (like the original P3A does), I need some help making these f-ing boards to work, cause I'm one step from trhowing them out the window.
Oh, and the input cap is an 1uF non-polar. Also I don't have a scope.
hello.
my opinion:
the text says d1 should be a standard led in green.........
your power supply voltage is lower (25v),you should lower r8 to 15k (for 22k)................
the voltage drop across r6,r17 should be around 0,7v...........i think you must increase r6,r17 to 560 ohm or so............100 ohm is to small.
greets
my opinion:
the text says d1 should be a standard led in green.........
your power supply voltage is lower (25v),you should lower r8 to 15k (for 22k)................
the voltage drop across r6,r17 should be around 0,7v...........i think you must increase r6,r17 to 560 ohm or so............100 ohm is to small.
greets
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I can't see much wrong with this.
I do have five points, but each are quite minor and I doubt they will significantly affect/reduce the problem.
The 2sb/d for VAS and it's CCS are the wrong type. You need low Cob, very high fT devices here. Not a driver transistor.
The mirror only balances the LTP currents if the gain and current through the VAS and mirror devices arranges that the base current of the VAS exactly equals the sum of the base currents of the mirror devices. This requires hFE VAS = 220/560 * hFE mirror at the currents in the operating quiescent state. But only if Vbe Q3 = Vbe Q12. You can measure Vdrop across 560r & 220r (R7 & R9) to determine the respective currents.
Add degeneration resistors to the LTP emitters and the VAS emitter.
The two drivers Q5 & Q8 are passing <3mA and dissipating <70mW
What does the datasheet tell you about 2sb/d when Ic~3mA and sometimes <<3mA?
Add base stopper resistors to outputs and drivers. You can always short them/remove them if not required.
I do have five points, but each are quite minor and I doubt they will significantly affect/reduce the problem.
The 2sb/d for VAS and it's CCS are the wrong type. You need low Cob, very high fT devices here. Not a driver transistor.
The mirror only balances the LTP currents if the gain and current through the VAS and mirror devices arranges that the base current of the VAS exactly equals the sum of the base currents of the mirror devices. This requires hFE VAS = 220/560 * hFE mirror at the currents in the operating quiescent state. But only if Vbe Q3 = Vbe Q12. You can measure Vdrop across 560r & 220r (R7 & R9) to determine the respective currents.
Add degeneration resistors to the LTP emitters and the VAS emitter.
The two drivers Q5 & Q8 are passing <3mA and dissipating <70mW
What does the datasheet tell you about 2sb/d when Ic~3mA and sometimes <<3mA?
Add base stopper resistors to outputs and drivers. You can always short them/remove them if not required.
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QUOTE=mjf
the voltage drop across r6,r17 should be around 0,7v...........i think you must increase r6,r17 to 560 ohm or so............100 ohm is to small.
greets[/QUOTE]
sorry, i made a mistake..................you need not 0,7v drop across r6,r17 in your shematic.the comment above is for the original p3a shematic.
greetings
the voltage drop across r6,r17 should be around 0,7v...........i think you must increase r6,r17 to 560 ohm or so............100 ohm is to small.
greets[/QUOTE]
sorry, i made a mistake..................you need not 0,7v drop across r6,r17 in your shematic.the comment above is for the original p3a shematic.
greetings
After listening to the original P3A for awhile, I've decided to give the "upgraded" borads a try once again. My first issue was that I had all the voltage of the positive rail in the output, but found that the PCB hadn't etched good between two tracks, and fixed that problem. The other thing that I've missed to do the first time is to put insulators between the outputs and the heatsink.
Excluding those two problems, the first PCB fired just fine, except I have -2.5V in the output, I think my current mirror isn't working like it's supposed to.
My test measurements tell that Q3 is set up for about 2.2mA, and Q12 to about 5.6mA. (is that too little Ic for the VAS?)
Also, R6/R17 are now 220ohms, and I've added the same value degeneration resistors for the LTP emitters, and still nothing, when measuring the Vdrop across R6 and R17 the result is that the two LTP trans. are drawing different currents. I also removed C6.
p.s. One experiment that I've made - when increasing the Ic (~twice) for the LTP for a second (by paralelling R7 with another 560ohm resistor), the voltage in the output becomes ~twice, about -4.7V. What does this tell us?
Excluding those two problems, the first PCB fired just fine, except I have -2.5V in the output, I think my current mirror isn't working like it's supposed to.
My test measurements tell that Q3 is set up for about 2.2mA, and Q12 to about 5.6mA. (is that too little Ic for the VAS?)
Also, R6/R17 are now 220ohms, and I've added the same value degeneration resistors for the LTP emitters, and still nothing, when measuring the Vdrop across R6 and R17 the result is that the two LTP trans. are drawing different currents. I also removed C6.
p.s. One experiment that I've made - when increasing the Ic (~twice) for the LTP for a second (by paralelling R7 with another 560ohm resistor), the voltage in the output becomes ~twice, about -4.7V. What does this tell us?
Please ignore my previous post, I fixed all of my problems but a new weird one appeared. This is the final circuit, this is what's on my boards. After adding the emitter resistor to Q4 the offset dropped drastically, and after adding the degeneration resistors to the LTP one of the boards managed to go down to +0.5mV! The other has about -4mV. I also reduced C3 because of an initial -5V start up "thump" at the speakers.
I fired my boards one by one with the power supply I am intending to use in my final amp, but I have a 60W tungsten lamp wired in series with the primary winding of the trafo. This way I can't burn anything while testing, and also the intensity of light gives me a clue how much consumption I have.
The problem is this : I tried 39pF for the miller cap, but there was oscillation (at 5MHZ), bumped up to 47pF - still oscillation, but smaller amplitude, 68pF - perfect! After fixing that I started to do my wiring in the amp for input signal/volume control/output/power for two boards, everything! After everything was done I decided to set my bias on the both boards, and when I clicked the power button - surprise! Too much consumption by the amp, some kind of oscillation and I can't find out where it's coming from, after all - both boards were working fine when they were fired up one by one, and I even tested them at full power when I was still experimenting.
Any ideas? I'll try later to take a picture of the scope for you guys to see the signal at the output.
p.s. One other question - why is there a miller cap at the negative rail driver in the original schematic?
I fired my boards one by one with the power supply I am intending to use in my final amp, but I have a 60W tungsten lamp wired in series with the primary winding of the trafo. This way I can't burn anything while testing, and also the intensity of light gives me a clue how much consumption I have.
The problem is this : I tried 39pF for the miller cap, but there was oscillation (at 5MHZ), bumped up to 47pF - still oscillation, but smaller amplitude, 68pF - perfect! After fixing that I started to do my wiring in the amp for input signal/volume control/output/power for two boards, everything! After everything was done I decided to set my bias on the both boards, and when I clicked the power button - surprise! Too much consumption by the amp, some kind of oscillation and I can't find out where it's coming from, after all - both boards were working fine when they were fired up one by one, and I even tested them at full power when I was still experimenting.
Any ideas?
I'll try later to take a picture of the scope for you guys to see the signal at the output.p.s. One other question - why is there a miller cap at the negative rail driver in the original schematic?
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