anatech said:
Hi Chris
At least I take your opinion. I am waiting for this enough days.
The silvered mica caps that i purchased from Farnell 
it is of brand CORNELL-DOUBILIER and as i think must be from the better in the market. Tell me if it right this. Also, can this type substitude the ceramic caps in all stages? For the rest caps, according to my choice of the smaller in dimensions due to PCB size and after the confirmation of J. Curl i decided the use of MKP type instead KP which as you know has very big size. For two days i spent much time for finding WIMA in many on line stores in Europe but nothing. Fortunatelly when i requested samples directly from WIMA factory, they redirected me in a German store that it has all the types in stock and it will post me the next days the caps.Fotios
Hi Fotios,
I try not to use capacitors that are large. They also become antennas for noise and other signals. A happy median is the best and you may need to shield them as well. Depends on your noise floor.
Hi Andrew,
-Chris
They are, but they also cost more than many others. There are some other old names in capacitor manufacture that are also expensive.
I try not to use capacitors that are large. They also become antennas for noise and other signals. A happy median is the best and you may need to shield them as well. Depends on your noise floor.
Hi Andrew,
In a high impedance circuit the dV/dT may distort the signal, I doubt any damage would occur.
-Chris
AndrewT said:
Your thought maybe (i am not so sure) it is right in this way. From the other hand, the term dV/dt it express the speed of voltage variation in the output of a electronic device when a signal applied in its input. It is right this? In capacitors this term express the speed of charge and discharge cycle. It is right also this? The charge and discharge cycle (all of these are my own thougths from experiments) of a capacitor depends on his dielectric material and his capacity. For example, i know that a MKT cap has faster discharge cycle from a MKP of the same capacity and for use in Triacs snubbers the MKT can cause damage TO THE TRIAC due to its steep discharge which cause high voltage instant spikes (except filtering around the Triac it exists also a capacitive loading from the filter itself that it is supposed protects the Triac!) and thus suggested the use of MKP cap due to its smoothness during discharge. I think from the kind of dielectric caused the damage limitation of dV/dt in the cap. Thus in circuits up to 250Vac we can see MKT caps for filtering. For higher voltage levels (such as in TV, in inverters etc) where the voltage levels are of much bigger value and the voltage spikes many times exceed the 2000V we see usually this MKP type exclusively. That is to say, one cap with WV of 1000Vdc must be in position to sustain instant spikes of 1600Vp. A polyester cap with this WV due to its small charge - discharge time (dV/dt) in comparison with a similar MKP, it will destroyed from these unpredictable voltage spikes. A polypropylene cap due to its larger charge - discharge cycle (dV/dt) it is in position to absorb these spikes (can this corresponds to the term inactivity of mechanics?). This is the way that i am thinking many times, the way of logic thought insteed the way of technical thought. I don't know if all the above are correct with certainity, maybe i am thinking in a wrong way. I don' know. For this reason i wish to discuss with you. I like also very much a documentation of the thougt instead a "dry" statement. Many times i preffer a geometrical or stereometrical or trigonometrical approach of a subject instead a direct mathematic approach with memorized equations.
That is Fotios
anatech said:
Hi again Chris
Unfortunatelly Cornell-Doubilier was the only brand of silvered mica caps that i find in Europe shops. Do you know how much it cost each part from Farnell? About 2 Euros including VAT! You are right they are very expensive.
For KP or MKP foil caps they offered in some logical price from WIMA. But it is some difficult to find them in the values that you preffer. Especially in 250Vdc (160Vac) which is a medium value for supplies from +/-60Vdc and above. There is another factory, less known, which offers greater variety of capacitances and voltages in better prices from WIMA or Roederstein and of the same quality as i have ascertained. His name it is ARCOTRONICS and found in Italy. I don't know if his products went to America. You can see these caps in my photos in the previous page; they are of the grey colour.
Fotios
Jan,
(Those regulators are quite harmful to the sound as well, another excellent example of unsuitable devices for audio use.)
...indicating wrong values applied.
(Those regulators are quite harmful to the sound as well, another excellent example of unsuitable devices for audio use.)
It would be an enhancement of sound quality.
Now, after properly executed listening tests you may find that there is a strong correlation between the sonic properties of capacitors and their physical size. Good sounding capacitors are always large. There is no exception to that condition whatsoever. You should feel extremely suspicious about small sized capacitors. You can in no way fool physics. Only yourself.
Good morning Lumba Ogir
Let me to explain you some things. Many from the persons that reply in this thread are proffesional with audio electronics. One from these persons it is also me. Our thoughts usualy are of engineering level; and you may be sure that no one of us spend so much time in real audition tests. We prefer to check our projects as for the quality of sound on the workbench with the generator and the oscilloscope. Most of us we don't have expensive instruments such a H.P. function generator of 1MHz or a real time analyzer of Audio Precision. But this is not an obstacle to make our measurements in a right manner. We are based on our knoweledge as a counter-weight in the medium quality of our instruments. As for me, because i am some hard of hearing i trust only in those i can see. It is like a blind man based on his sense of hearing, touch and smell. Personally me, i recognize your justice. After the completion of any of my projects i give it in my nephew for audition test, which is a very good musician and has some Hi-End devices , and after two days he gives me his evaluation.
No one from us he tries to impose in you his point of view. However some time it should we are landed in the real world. Who is this? This time i try to build 3 samples of power amplifiers (2 dual-mono and 1 monoblock) and 1 preamplifier not for my hobby but for earn my daily bread. This is my exclusive job; it is not an extra job. After their completion i will give them for review in a recognized Greek magazine (member of EISA awards) for review for presentation and probably for quality certification. The testers of this magazine - which has an age of 30 years - are so "fussy" more than you can imagine. Of course they support each Greek attempt but if evaluate a project for 8 in the scale of 10 as for the sound quality they will refer this graduation seperatelly, and for supporting they will refer that "this project has an excellent ratio of performance/cost". If i take one such evaluation, then i will consider my project as failure. And i have a "bad habit" to prove the value of my works with deeds, not words. For this reason i have placed this and two other threads-queries.
As for my sample, i have builded one 2 years ago, and yet if the caps included are not of so good quality, sounds nicelly. I maked this sample for fun, by turning one design of my P.A. amplifiers in one with better quality parts, lower supply voltage, and big heatsinks instead noisy fans. I can to confirm that this work was a piece of cake to me because my experience with devices of much higher supply level. The only thing that it distressed me a little, was the NFB level lowering.
You may take also into account another significant thing. I am in debt of 5000euros in my bank for the development of these projects. It should you are sure that i will fight tooth and nail for the success of my projects. It is a way without return. Maybe you remembered the post of J. Curl before two days for the choice of MKP caps; due to his big experience he occupy very well what i intend to make (not hobby, job). And in job may we are and a little practical. Thus we can't include in the PCB an enormous KP capacitor. It should we are reconciled between practicality and quality so that they have equilibrium in weight.
Fotios
Let me to explain you some things. Many from the persons that reply in this thread are proffesional with audio electronics. One from these persons it is also me. Our thoughts usualy are of engineering level; and you may be sure that no one of us spend so much time in real audition tests. We prefer to check our projects as for the quality of sound on the workbench with the generator and the oscilloscope. Most of us we don't have expensive instruments such a H.P. function generator of 1MHz or a real time analyzer of Audio Precision. But this is not an obstacle to make our measurements in a right manner. We are based on our knoweledge as a counter-weight in the medium quality of our instruments. As for me, because i am some hard of hearing i trust only in those i can see. It is like a blind man based on his sense of hearing, touch and smell. Personally me, i recognize your justice. After the completion of any of my projects i give it in my nephew for audition test, which is a very good musician and has some Hi-End devices , and after two days he gives me his evaluation.
No one from us he tries to impose in you his point of view. However some time it should we are landed in the real world. Who is this? This time i try to build 3 samples of power amplifiers (2 dual-mono and 1 monoblock) and 1 preamplifier not for my hobby but for earn my daily bread. This is my exclusive job; it is not an extra job. After their completion i will give them for review in a recognized Greek magazine (member of EISA awards) for review for presentation and probably for quality certification. The testers of this magazine - which has an age of 30 years - are so "fussy" more than you can imagine. Of course they support each Greek attempt but if evaluate a project for 8 in the scale of 10 as for the sound quality they will refer this graduation seperatelly, and for supporting they will refer that "this project has an excellent ratio of performance/cost". If i take one such evaluation, then i will consider my project as failure. And i have a "bad habit" to prove the value of my works with deeds, not words. For this reason i have placed this and two other threads-queries.
As for my sample, i have builded one 2 years ago, and yet if the caps included are not of so good quality, sounds nicelly. I maked this sample for fun, by turning one design of my P.A. amplifiers in one with better quality parts, lower supply voltage, and big heatsinks instead noisy fans. I can to confirm that this work was a piece of cake to me because my experience with devices of much higher supply level. The only thing that it distressed me a little, was the NFB level lowering.
You may take also into account another significant thing. I am in debt of 5000euros in my bank for the development of these projects. It should you are sure that i will fight tooth and nail for the success of my projects. It is a way without return. Maybe you remembered the post of J. Curl before two days for the choice of MKP caps; due to his big experience he occupy very well what i intend to make (not hobby, job). And in job may we are and a little practical. Thus we can't include in the PCB an enormous KP capacitor. It should we are reconciled between practicality and quality so that they have equilibrium in weight.
Fotios
I could not help noticing the -ve blanket statement about the silver mica caps. If you are using decent ones (typically around $1-$2 for 22pF to 68pF value range and V rating of 500V) you should be able to get some very good results.
On the regulators (317 or 7812 varieties), I've never had oscillation problems as long as I decoupled them well. In my case, its always a 1uF stacked foil capacitor right at the input and one right at the output. I've probably designed hundreds of circuits (that have gone into volume production) with this approach and can honestly say I' have neve r had a problem. So, don't fret, just use decent caps and all will be well.
On the regulators (317 or 7812 varieties), I've never had oscillation problems as long as I decoupled them well. In my case, its always a 1uF stacked foil capacitor right at the input and one right at the output. I've probably designed hundreds of circuits (that have gone into volume production) with this approach and can honestly say I' have neve r had a problem. So, don't fret, just use decent caps and all will be well.
Bonsai said:I could not help noticing the -ve blanket statement about the silver mica caps. If you are using decent ones (typically around $1-$2 for 22pF to 68pF value range and V rating of 500V) you should be able to get some very good results.
On the regulators (317 or 7812 varieties), I've never had oscillation problems as long as I decoupled them well. In my case, its always a 1uF stacked foil capacitor right at the input and one right at the output. I've probably designed hundreds of circuits (that have gone into volume production) with this approach and can honestly say I' have neve r had a problem. So, don't fret, just use decent caps and all will be well.
Hi Bonsai and thanks for your interest
Me also in voltage regulators i use one 220nF in input and one 100nF in output, MKT type and the two. Also me never i had smoothing problems with these different values.
As for the silver mica caps, i thing you understand that it is obvious their use in the first samples at least. We may don't forget that: "The customer has always the right". And we moreover we are customers of certain other.
Fotios
Finally i believe that i will abolish this cursed capacitor of 2,2mF in input. The only work that offers it is the blocking of a possible D.C. part in the input signal. If happens such something then the preamplifier has failure and must repaired. As for the danger of passing this dc part to the speakers, by no way. Because in my amplifier i have included a proffesional grade protection circuit that will indicate immediately the problem and it will short the feedback and shut down momentarilly the output relay to protect the amplifier and the speakers. Thus the owner of preamplifier will be forced to give this for repair.
Fotios
Fotios
fotios said:
Fotios,
I think you should be carefull. Some preamps give out very small DC like a few 10mV or more without being broken. This can lead to several volts across the speaker to trigger your protection circuit.
If you take out the input blocking, you can never use such preamps! This will limit your options, so you must take this decision only if you want this.
Jan Didden
janneman said:
My good friend Jan
Of course that you wrote it is by 100% correct and thank you for your marking. You showed me a right way so that I decrease the sensitivity of protection circuit in 40 to 50mV. Also i am not sure that i will remove the 2,2mF input cap because in my PCB there is enough space and for this cap.
Thanks for your assistance to my big effort. Now I am drawing the schematic plans of my “Hi-End”??? (We will see this!) amplifier. When I finish these you wait for a personnel post of circuit for reviewing from you.
Fotios
I hope we get to see your nice pre... DIM (do it myself) is no fun
I am thinking of rebuilding my Preamp too.... I'm happy with the buffer itself..but I share a transformer between 2 channels... (works beatutifully driving headphones) and I also have shared grounding on the input and output cables... and of course shared ground in the pan control.... totaly nulifying all my efforts in building 2 DX monoblocks. You can only have so many potentiol ground loops before it bites you in the ***....
Humms with the monoblocks... but is quiet on my chipamp which also has a shared transformer, like the buffer.
I suppose I should start with getting 2 transformers for the buffers... make 2 regulator boards... (completed layout for Nuuk's preamp PSU with 2 stage regulation, last night)...but they will have to get their own external box due to size...
If the humm persists I will then split the input grounds... If it is still there, I will remove the pan control and make use of seperate volume pots, and a master volume control...(for mommy) My satelite dish receiver puts out a pretty uneven signal, channel vs channel...
I am thinking of rebuilding my Preamp too.... I'm happy with the buffer itself..but I share a transformer between 2 channels... (works beatutifully driving headphones) and I also have shared grounding on the input and output cables... and of course shared ground in the pan control.... totaly nulifying all my efforts in building 2 DX monoblocks. You can only have so many potentiol ground loops before it bites you in the ***....
Humms with the monoblocks... but is quiet on my chipamp which also has a shared transformer, like the buffer.
I suppose I should start with getting 2 transformers for the buffers... make 2 regulator boards... (completed layout for Nuuk's preamp PSU with 2 stage regulation, last night)...but they will have to get their own external box due to size...
If the humm persists I will then split the input grounds... If it is still there, I will remove the pan control and make use of seperate volume pots, and a master volume control...(for mommy) My satelite dish receiver puts out a pretty uneven signal, channel vs channel...
Nordic,
If you get two transformers but not change the wiring that gives you the hum, you will still have hum!
The good way to do this is to make sure you have no ground problems in the first place. Try to draw out the physical arrangement of all ground related wiring. This means transformer mid points, supply cap grounds, amplifier grounds (all signal and load return grounds), the grounds of the input- and output caps, etc. This should be a physical drawing as much as like the actual wire position and length.
When you do this you will see for example that at some points there is a wire between two signal grounds that carries supply return current. That is the type of stuff that gives you humm!
Jan Didden
If you get two transformers but not change the wiring that gives you the hum, you will still have hum!
The good way to do this is to make sure you have no ground problems in the first place. Try to draw out the physical arrangement of all ground related wiring. This means transformer mid points, supply cap grounds, amplifier grounds (all signal and load return grounds), the grounds of the input- and output caps, etc. This should be a physical drawing as much as like the actual wire position and length.
When you do this you will see for example that at some points there is a wire between two signal grounds that carries supply return current. That is the type of stuff that gives you humm!
Jan Didden
Considering my noob skills I don't think I did too badly at the time... I think in terms of loops within each individual channel I did OK..but I never thought outside of that box in terms of loops from one channel returning via the other...
I just remembered I had to sever the mains earth (was connected through isolation network), to kill the humm when I set it up with the chipamp... forceing the buffer to find earth via the amplifier.. rather than allowing the amp to find ground through the buffer... (hey it worked 100s
).
Maybe I should investigate how it interacts with the new amp, when grounded correctly.
That is the beauty of non commercial design... you can zone in on minor particulars and get to zen.
I just remembered I had to sever the mains earth (was connected through isolation network), to kill the humm when I set it up with the chipamp... forceing the buffer to find earth via the amplifier.. rather than allowing the amp to find ground through the buffer... (hey it worked 100s
).Maybe I should investigate how it interacts with the new amp, when grounded correctly.
That is the beauty of non commercial design... you can zone in on minor particulars and get to zen.
Hi Fotios,
I strongly agree with Jan here. Just use a good foil / film cap here. The smaller it is, the less trouble it will cause. This is just to say that if you need a 1 uF, don't install a 100 uF to lower the cutoff point.
Hi Nordic,
Again, Jan has steered you along the right road. Look at your circuit to chassis coupling. Using two main supplies will only complicate the grounding. Don't forget that L and R grounds are connected together in the preamplifier.
-Chris
I strongly agree with Jan here. Just use a good foil / film cap here. The smaller it is, the less trouble it will cause. This is just to say that if you need a 1 uF, don't install a 100 uF to lower the cutoff point.
Hi Nordic,
Again, Jan has steered you along the right road. Look at your circuit to chassis coupling. Using two main supplies will only complicate the grounding. Don't forget that L and R grounds are connected together in the preamplifier.
-Chris