Re: More on capacitors
Konnichiwa,
Not really. A 2,200uF Capacitor will result in approximatly twice the ripple, it's sort of six db of one, halve a dozend db of the other. I would think capacitor quality more important than value, so some changes in value to suit what is at hand are just fine.
The larger first capaictor has two effects. First, it will make the ripple lower (but we have regulators to take care of that anyway) and it will reduce the conduction angle (the time out of 360degrees = one cycle of the mains voltage) significantly, resulting in narrower, higher amplitude current peaks being drawn on each of the mains voltage's halve waves.
I consider this mostly a "bad thing"..... ;-)
Same as above, six db of one, halve a dozend db of the other. Use what is available, good quality and so on.
Okay, this important to understand. The Servos and motors are operating at fairly slow speeds (mechanical components with a given mass) and the servos attempt to enforce a certain behaviour to those masses with their inertia. This means that the servo circuits and motor drivers usually draw current in an irregeluar manner, with quite high peaks on a low average current, a lot in fact like a power amplifier driving a speaker with music. So we are looking here more at a powersupply for a woofer amplifier than for a digital/class A analog circuit.
Does that illuminate the issues at all?
Yup, completely agreed. Use 25...35V.
Same prnciple as before, use what's available. I used Samwaha "Tag" connection 10,000uF/35V "Audio Grade" tyoes, which where available and have good ripple rating and low ESR/ESL (for a capacitor of that size).
Sayonara
Konnichiwa,
Fin said:
Not really. A 2,200uF Capacitor will result in approximatly twice the ripple, it's sort of six db of one, halve a dozend db of the other. I would think capacitor quality more important than value, so some changes in value to suit what is at hand are just fine.
Fin said:
The larger first capaictor has two effects. First, it will make the ripple lower (but we have regulators to take care of that anyway) and it will reduce the conduction angle (the time out of 360degrees = one cycle of the mains voltage) significantly, resulting in narrower, higher amplitude current peaks being drawn on each of the mains voltage's halve waves.
I consider this mostly a "bad thing"..... ;-)
Fin said:
Same as above, six db of one, halve a dozend db of the other. Use what is available, good quality and so on.
Fin said:
Okay, this important to understand. The Servos and motors are operating at fairly slow speeds (mechanical components with a given mass) and the servos attempt to enforce a certain behaviour to those masses with their inertia. This means that the servo circuits and motor drivers usually draw current in an irregeluar manner, with quite high peaks on a low average current, a lot in fact like a power amplifier driving a speaker with music. So we are looking here more at a powersupply for a woofer amplifier than for a digital/class A analog circuit.
Does that illuminate the issues at all?
Fin said:
Yup, completely agreed. Use 25...35V.
Fin said:
Same prnciple as before, use what's available. I used Samwaha "Tag" connection 10,000uF/35V "Audio Grade" tyoes, which where available and have good ripple rating and low ESR/ESL (for a capacitor of that size).
Sayonara
Fin,
You really need to try some of this stuff for yourself - and believe what you're hearing. Don't get hung up on detailed component choices, get the fundamentals right (grounding, layout, well proven circuits) and sort the "audiovile" stuff later.
FWIW, I'm now at stage 1d (from post #186) and the only one I have doubts about is 1b although I think this relates more to implementation than component or topology choice. At some stage I will reverse 1b or maybe try another implementation (to improve the grounding).
I found that a better servo PSU gave an increase in scale and control, but the improved 5V supply for the main CD processor gave a more fundmental improvement to the music. In light of this I may tweak or improve the 5V PSU at some later stage, whereas I'm happy that there is not a lot of mileage in tweaking the 12V PSU.
I also think my comment about the CD723 being as good as my Arcam was a bit premature (I'm sure I mentioned in an earlier post that I'm frequently wrong).
If you look at Thorsten's recommendations, it's all about sorting the fundamentals, there's no snake oil or requirement for Peruvian virgins etc - that's why I decided to go with his mods (except perhaps the C37, which I have absolutely no idea about).
Dave
You really need to try some of this stuff for yourself - and believe what you're hearing. Don't get hung up on detailed component choices, get the fundamentals right (grounding, layout, well proven circuits) and sort the "audiovile" stuff later.
FWIW, I'm now at stage 1d (from post #186) and the only one I have doubts about is 1b although I think this relates more to implementation than component or topology choice. At some stage I will reverse 1b or maybe try another implementation (to improve the grounding).
I found that a better servo PSU gave an increase in scale and control, but the improved 5V supply for the main CD processor gave a more fundmental improvement to the music. In light of this I may tweak or improve the 5V PSU at some later stage, whereas I'm happy that there is not a lot of mileage in tweaking the 12V PSU.
I also think my comment about the CD723 being as good as my Arcam was a bit premature (I'm sure I mentioned in an earlier post that I'm frequently wrong).
If you look at Thorsten's recommendations, it's all about sorting the fundamentals, there's no snake oil or requirement for Peruvian virgins etc - that's why I decided to go with his mods (except perhaps the C37, which I have absolutely no idea about).
Dave
Konnichiwa,
I would propose that once you are really through (right Op-Amp as I/V) it will be as good, if not better....
Actually, I am quite in favour of any number of highly esotheric principles in Audio Design, but only on top of and after teh fndamentals have been gotten right, not instead of getting them right.
Sayonara
Dave S said:
I would propose that once you are really through (right Op-Amp as I/V) it will be as good, if not better....
Dave S said:
Actually, I am quite in favour of any number of highly esotheric principles in Audio Design, but only on top of and after teh fndamentals have been gotten right, not instead of getting them right.
Sayonara
Fantastic!
Before I think of more questions to ask - I must say again that this is an excellent thread (for me anyway) and thank all of you who have provided such excellent answers and information. Hopefully others are getting as much out of this as I have.
Hi Thorsten
As I'm starting with a blank sheet and empty box of components, I might as well get the optimum values (if that is the right term).
So, I'll go with 470uF, 3,300uF or 4,700uF and some 100uF Nichicons Muse for the analogue stage. Then, just for variety, use Panasonic FC in the same values, for the DAC and decoder.
I actually understand this!
So - the larger value here is quite important in order to provide a reserve for the irregular demand.
Yes - quite a lot - thanks.
The Jamicons have relatively low impedance and high ripple current figures - can't find ESR/ESL figures for them. I will look for the Samwahas as well.
Hi Dave
A good friend in The Netherlands has been telling me this for months, and I do understand that the layout and implementation is more important. We have been working on ideas for improving the grounding, decoupling and power supplies.
The only capacitors available locally are Jamicons (or Hitano - if I order from Sydney). So - for me to get types that others have tried and had success with - I will be ordering from RS Components and some suppliers in the US, etc. In some cases, the audio grade stuff is comming in cheaper than the normal stuff. For example, the 4,700 Nichicon Muse FX is AUD$4.20 from the US, while the Panasonic FC 3,300uF is AUD$6.00 from RS Australia. The delivery from the US is no more expensive than delivery from Sydney. I'm not specifically chasing audio grade parts - but if they are still appropriate, and cheaper - then, why not.
Seems like you are going well. What would (or could) you do differently? Are you talking about connecting the ground pins of ICs directly to the groundplane, ensuring that no other circuits share any of the ground or supply traces etc?
It's good to hear that the improved servo supply brought about an improvement. I had read some comments by Guido Tent on this and tried to get more information on it by starting a thread:
Jitter induced by servos
Unfortunately, it didn't generate much interest. Now that Thorsten confirms this, and you have heard the results - there is no doubt.
Before I think of more questions to ask - I must say again that this is an excellent thread (for me anyway) and thank all of you who have provided such excellent answers and information. Hopefully others are getting as much out of this as I have.
Hi Thorsten
As I'm starting with a blank sheet and empty box of components, I might as well get the optimum values (if that is the right term).
So, I'll go with 470uF, 3,300uF or 4,700uF and some 100uF Nichicons Muse for the analogue stage. Then, just for variety, use Panasonic FC in the same values, for the DAC and decoder.
I actually understand this!
So - the larger value here is quite important in order to provide a reserve for the irregular demand.
Yes - quite a lot - thanks.
The Jamicons have relatively low impedance and high ripple current figures - can't find ESR/ESL figures for them. I will look for the Samwahas as well.
Hi Dave
A good friend in The Netherlands has been telling me this for months, and I do understand that the layout and implementation is more important. We have been working on ideas for improving the grounding, decoupling and power supplies.
The only capacitors available locally are Jamicons (or Hitano - if I order from Sydney). So - for me to get types that others have tried and had success with - I will be ordering from RS Components and some suppliers in the US, etc. In some cases, the audio grade stuff is comming in cheaper than the normal stuff. For example, the 4,700 Nichicon Muse FX is AUD$4.20 from the US, while the Panasonic FC 3,300uF is AUD$6.00 from RS Australia. The delivery from the US is no more expensive than delivery from Sydney. I'm not specifically chasing audio grade parts - but if they are still appropriate, and cheaper - then, why not.
Seems like you are going well. What would (or could) you do differently? Are you talking about connecting the ground pins of ICs directly to the groundplane, ensuring that no other circuits share any of the ground or supply traces etc?
It's good to hear that the improved servo supply brought about an improvement. I had read some comments by Guido Tent on this and tried to get more information on it by starting a thread:
Jitter induced by servos
Unfortunately, it didn't generate much interest. Now that Thorsten confirms this, and you have heard the results - there is no doubt.
More on capacitors
Hi Thorsten
How specific to the CD7xx are your power supply designs and recommendations?
In light of the above coments, would it be reasonable to apply similar power supply arrangements to other CD players and to use similar capacitor values?
What type of factors would would cause a departure from the 3R3 - 470Uf - 10R - 4700uF approach?
Hi Thorsten
How specific to the CD7xx are your power supply designs and recommendations?
In light of the above coments, would it be reasonable to apply similar power supply arrangements to other CD players and to use similar capacitor values?
What type of factors would would cause a departure from the 3R3 - 470Uf - 10R - 4700uF approach?
Re: More on capacitors
Konnichiwa,
Modestly so, they apply everywhere where currents are not excessive (eg modern players).
Yes, but make sure that the supply can deliver the required current at the required voltage.
Considerably higher supply currents for any of the sections/IC's in the player.
Sayonara
Konnichiwa,
Fin said:
Modestly so, they apply everywhere where currents are not excessive (eg modern players).
Fin said:
Yes, but make sure that the supply can deliver the required current at the required voltage.
Fin said:
Considerably higher supply currents for any of the sections/IC's in the player.
Sayonara
More on capacitors
OK - the analogue output stage will consist of one dual opamp. If I use something like OPA2134 ( which a lot of people seem to like in this type of CDP), it will require about 8mA. This is all that will be on that supply. Should I change anything?
The TDA1545 in the CD723 uses about 6-8mA. The DAC in the 624 uses about 60mA (Idda=20ma, Iddd=40ma). The max is about 120mA. This is all that will be on this supply. Does anything need to be changed?
The SAA7310 decoder uses about 35-50mA. This is all that will be on this supply. Does anything need to be changed?
How much higher is "considerably higher"? Is there a range that these supplies are suitable for?
Sorry for asking these questions about a different circuit and a machine that you have not worked on - but maybe the 624 can pirate some ideas from the 723.
Kuei Yang Wang said:
OK - the analogue output stage will consist of one dual opamp. If I use something like OPA2134 ( which a lot of people seem to like in this type of CDP), it will require about 8mA. This is all that will be on that supply. Should I change anything?
The TDA1545 in the CD723 uses about 6-8mA. The DAC in the 624 uses about 60mA (Idda=20ma, Iddd=40ma). The max is about 120mA. This is all that will be on this supply. Does anything need to be changed?
The SAA7310 decoder uses about 35-50mA. This is all that will be on this supply. Does anything need to be changed?
How much higher is "considerably higher"? Is there a range that these supplies are suitable for?
Sorry for asking these questions about a different circuit and a machine that you have not worked on - but maybe the 624 can pirate some ideas from the 723.
Re: More on capacitors
Konnichiwa,
What I would suggest you do is to model each supply in Duncan Amplifiers PSU Designer.
The timeconstants in the circuit I propose (1,500uS/102Hz for the first RC and 47,000uS/3.4Hz) are intended to provide a reasonable level of filtering and a "slow down" of the charge pulses. I would keep these about the same but adjust the rest of the circuit.
For example, a circuit PSU supplying 10mA to a "Class A" circuit (no material change in current with signal) may very well use larger value Resistors and smaller value capacitors (eg. 10R/150uF/33R/1500uF) and with a fairly high impedance (low power) transformer. On the other hand a circuit drawing 100mA with a strong modulation of the current (say +/-80%) like a class AB Amplifier would require a lower resistive component and larger value capacitors (eg. 1R5/1000uF/4R7/10,000uF) and a higher power transformer.
Simply use PSUD to simulate the "worst case", meaning currents at the Datasheet (plus dynamic current) limits and the mains voltage at the lowest permissable and then make sure the output voltage after the Filter is enough to avoid the datasheet limit dropout voltage for the specified regulator. Take care to include a reasonable model of the mains transformer as well.
That way your PSU is designed for the specific application and suited for it. Usually that is the only way to get the best results. Also always check the step response of the PSU Circuit to a 50% change in current, more so when LC supplies are used!
Sayonara
Konnichiwa,
Fin said:
What I would suggest you do is to model each supply in Duncan Amplifiers PSU Designer.
The timeconstants in the circuit I propose (1,500uS/102Hz for the first RC and 47,000uS/3.4Hz) are intended to provide a reasonable level of filtering and a "slow down" of the charge pulses. I would keep these about the same but adjust the rest of the circuit.
For example, a circuit PSU supplying 10mA to a "Class A" circuit (no material change in current with signal) may very well use larger value Resistors and smaller value capacitors (eg. 10R/150uF/33R/1500uF) and with a fairly high impedance (low power) transformer. On the other hand a circuit drawing 100mA with a strong modulation of the current (say +/-80%) like a class AB Amplifier would require a lower resistive component and larger value capacitors (eg. 1R5/1000uF/4R7/10,000uF) and a higher power transformer.
Simply use PSUD to simulate the "worst case", meaning currents at the Datasheet (plus dynamic current) limits and the mains voltage at the lowest permissable and then make sure the output voltage after the Filter is enough to avoid the datasheet limit dropout voltage for the specified regulator. Take care to include a reasonable model of the mains transformer as well.
That way your PSU is designed for the specific application and suited for it. Usually that is the only way to get the best results. Also always check the step response of the PSU Circuit to a 50% change in current, more so when LC supplies are used!
Sayonara
Re: Re: Re: More on capacitors
Konnichiwa,
Yes.
Select a constant current load, select stepped load and enter the before step and after step value of current and the time you want the step to occur. Make sure the step is within the time window selected to be displayed and it may be usefull to introduce the step after the PSU's intial setteling is complete. This usually means very long display times (30 seconds) and zooming in strongly on the step.
Sayonara
Konnichiwa,
Bricolo said:
Yes.
Bricolo said:
Select a constant current load, select stepped load and enter the before step and after step value of current and the time you want the step to occur. Make sure the step is within the time window selected to be displayed and it may be usefull to introduce the step after the PSU's intial setteling is complete. This usually means very long display times (30 seconds) and zooming in strongly on the step.
Sayonara
PSU Design
Hi Thorsten
This seems like good software and it produces very nice graphs with colourful traces. It is also quite user friendly. However, I'm not sure what I'm supposed to be looking for.
Which trace should I be looking at, and what should it look like?
I assume it is the trace for the last component in the filter and that it should be as smooth as possible while maintaining the required voltage??
Also, where did you get the time constants from and what should I be doing with them?
Maybe someone could attach an image here of what it is supposed to look like - or even attach a psu file (with the extention changed to one that is valid).
Hi Thorsten
This seems like good software and it produces very nice graphs with colourful traces. It is also quite user friendly. However, I'm not sure what I'm supposed to be looking for.
Which trace should I be looking at, and what should it look like?
I assume it is the trace for the last component in the filter and that it should be as smooth as possible while maintaining the required voltage??
Also, where did you get the time constants from and what should I be doing with them?
Maybe someone could attach an image here of what it is supposed to look like - or even attach a psu file (with the extention changed to one that is valid).
Re: PSU Design
Konnichiwa,
All of them, intially at least, for didactic reasons.
I'd suggest you take a few different supplies, maybe a very basic one and vary topology and parts values and observe how the various currents and voltages change. Some items (such as the diode switching noise and LC tank circuits in the mainstransformer) are not modeled and you need to retain the need to damp these in the back of your hear when working with PSUD.
In essence, but other traces (Transformer current, especially waveform) also have their uses.
Timeconstant is R*C and relates inversely to the -3db Frequency. 3180uS equals 50Hz, meaning an RC circuit with a riven R*C giving 0.003180 will have a -3db point of 50Hz. Using a 100Hz (120Hz for USoA) -3db point on the input filter keeps the higher harmonics down and "slows" the current flow from the rectifier, making overall the current draw less "spikey".
Using a much lower -3db Point (say 2.5Hz) for the second RC filter will reduce any 100Hz ripple substantially, as we have a 6db/Octave lowpass. So any (100Hz) ripple on the first cap will, with a 2.5Hz/0.064S Filter, be attenuated by around 32db. Following that with a good regulator (LM1085) will knock any ripple another 75db down.
Now having our example supply (3R3/470u/10R/4,700uF) with a 15V/30VA Transformer and schottky rectifiers supplying around 50mA we get 20.5V across the second capacitor, with 22mV peak-Peak (around 8mV rms) with a fairly close to sinewave waveform (few high order harmonics). Then using a single regulator (LM1085) correctly impemented we drop the ripply by a factor of around 10,000 to 0.8uV which is around two times the self noise of the regulator with 15V Output and 122db below 1V.
It is obvious that with only 22mV P-P ripple and 20.5V raw voltage at nominal our regulator always works with more than 3V across it, avoiding the worse performance "dropout" region. (20.5V - 10% = 18.6V so 3.6V across the Regulator.
So, with a simple RCRC Filter plus regulator we have made a supply with -122dbv noise level.
Had we omited the first RC and second R we would get a higher DC voltage at 22V but also 5 times the ripple and with a much worse waveform (very steep slopes and spikey, not rounded peaks suggesting a lot of high order harmonics. Had we then used a generic 7815 Regulator we would have had at least 10db less ripple rejection on top of 14db more ripple, so our output noise would be around -98dbV (still not bad) but likely with a lot more than a little 100Hz ripple, most likely a lot of higher order components would have made through the regulator.
Also, the conduction angle for the direct 4,700uF Capacitor is quite low, current is conducted only for 1mS within the whole 10mS halve cycle of the 50Hz mains wave with nearly 0.65A peak and a fairly "peaky" peak. The RCRC circuit has a much wider conduction angle, conducting almost 3mS out of 10mS of the mains halve wave and with a current peak < 0.35A and very gentle slopes.
Try following the above in PSUD and I think you will get a feel for what things mean.
Sayonara
Konnichiwa,
Fin said:
All of them, intially at least, for didactic reasons.
Fin said:
I'd suggest you take a few different supplies, maybe a very basic one and vary topology and parts values and observe how the various currents and voltages change. Some items (such as the diode switching noise and LC tank circuits in the mainstransformer) are not modeled and you need to retain the need to damp these in the back of your hear when working with PSUD.
Fin said:
In essence, but other traces (Transformer current, especially waveform) also have their uses.
Fin said:
Timeconstant is R*C and relates inversely to the -3db Frequency. 3180uS equals 50Hz, meaning an RC circuit with a riven R*C giving 0.003180 will have a -3db point of 50Hz. Using a 100Hz (120Hz for USoA) -3db point on the input filter keeps the higher harmonics down and "slows" the current flow from the rectifier, making overall the current draw less "spikey".
Using a much lower -3db Point (say 2.5Hz) for the second RC filter will reduce any 100Hz ripple substantially, as we have a 6db/Octave lowpass. So any (100Hz) ripple on the first cap will, with a 2.5Hz/0.064S Filter, be attenuated by around 32db. Following that with a good regulator (LM1085) will knock any ripple another 75db down.
Now having our example supply (3R3/470u/10R/4,700uF) with a 15V/30VA Transformer and schottky rectifiers supplying around 50mA we get 20.5V across the second capacitor, with 22mV peak-Peak (around 8mV rms) with a fairly close to sinewave waveform (few high order harmonics). Then using a single regulator (LM1085) correctly impemented we drop the ripply by a factor of around 10,000 to 0.8uV which is around two times the self noise of the regulator with 15V Output and 122db below 1V.
It is obvious that with only 22mV P-P ripple and 20.5V raw voltage at nominal our regulator always works with more than 3V across it, avoiding the worse performance "dropout" region. (20.5V - 10% = 18.6V so 3.6V across the Regulator.
So, with a simple RCRC Filter plus regulator we have made a supply with -122dbv noise level.
Had we omited the first RC and second R we would get a higher DC voltage at 22V but also 5 times the ripple and with a much worse waveform (very steep slopes and spikey, not rounded peaks suggesting a lot of high order harmonics. Had we then used a generic 7815 Regulator we would have had at least 10db less ripple rejection on top of 14db more ripple, so our output noise would be around -98dbV (still not bad) but likely with a lot more than a little 100Hz ripple, most likely a lot of higher order components would have made through the regulator.
Also, the conduction angle for the direct 4,700uF Capacitor is quite low, current is conducted only for 1mS within the whole 10mS halve cycle of the 50Hz mains wave with nearly 0.65A peak and a fairly "peaky" peak. The RCRC circuit has a much wider conduction angle, conducting almost 3mS out of 10mS of the mains halve wave and with a current peak < 0.35A and very gentle slopes.
Try following the above in PSUD and I think you will get a feel for what things mean.
Sayonara
PSU Design
Hi Thorsten
Thanks for the lessons - I'm now getting results that look meaningful. And it's starting to make sense!
OK - I've done this - and it is really interesting!
Obviously many combinations can give a similar result.
Is the optimum for the first RC achieved by using a small capacitor/large resistor combination, that still obtains 1500uS, a smooths waveform and the required voltage?
Also interesting - now that I'm using the right variables
OK - I understand the concept - but you must have obtained the 3180uS elsewhere.
Does this mean it is 1590uS for a -3db point of 100Hz?
Are there tables (or similar) with these values?
OK - I can see where the 0.064S comes from, having started with 3180uS for 50Hz, however, I might have some other questions about this later - just have to think of them first.
OK - I've tried to model this and got values quite close to those you quote. Getting there!
This arrangement seems to work for a current draw up to 115mA - then the voltage at C2 starts to drop below about 18.5V. If more current is required, the obvious solution is to use a larger transformer or reduce the values of the resistors while increasing the values of the capacitors?
Is it better if you start with a slightly higher voltage or is that just a waste?
Well - that's what is in the CDP now - so the new PS should be a big improvement.
This also makes sense now.
I did - and I think I've got most of it.
I have attached a few of the psu files (disguised as zip files).
This one is my attempt at modelling Thorsten's description above, ie. 15V/1A TF, 3.3R-470uF-10R-4700uf-50mA.
Hi Thorsten
Thanks for the lessons - I'm now getting results that look meaningful. And it's starting to make sense!
OK - I've done this - and it is really interesting!
Obviously many combinations can give a similar result.
Is the optimum for the first RC achieved by using a small capacitor/large resistor combination, that still obtains 1500uS, a smooths waveform and the required voltage?
Also interesting - now that I'm using the right variables
OK - I understand the concept - but you must have obtained the 3180uS elsewhere.
Does this mean it is 1590uS for a -3db point of 100Hz?
Are there tables (or similar) with these values?
OK - I can see where the 0.064S comes from, having started with 3180uS for 50Hz, however, I might have some other questions about this later - just have to think of them first.
OK - I've tried to model this and got values quite close to those you quote. Getting there!
This arrangement seems to work for a current draw up to 115mA - then the voltage at C2 starts to drop below about 18.5V. If more current is required, the obvious solution is to use a larger transformer or reduce the values of the resistors while increasing the values of the capacitors?
Is it better if you start with a slightly higher voltage or is that just a waste?
Well - that's what is in the CDP now - so the new PS should be a big improvement.
This also makes sense now.
I did - and I think I've got most of it.
I have attached a few of the psu files (disguised as zip files).
This one is my attempt at modelling Thorsten's description above, ie. 15V/1A TF, 3.3R-470uF-10R-4700uf-50mA.
Re: PSU Design
Konnichiwa,
Yes, I tend to look at conduction angle, ripple waveform and step response when comparing different circuits. Obviously the output voltage needs to right and ripple low, but it is IMNSHO preferable to have a large conduction angle and a bit higher ripple with a "soft" waveform than to minimise ripple at the cost of a unpleasant (spikey - indicates high order harmonics) ripple waveform and narrow conduction angle.
More or less. All things are tradeoffs. The larger the input resistor and the smaller the input capacitor the wider the conduction angle but equally regulation suffers, maing such a circuit suitable only for "class A" circuits. You can compensate the resistive losses by boosting the primary volateg, but you then need to account for the higher potentioal "no load" voltage in the safety ratings for components.
Thus, for any given pricepoint and level of component quality there will be a "sweet spot" where you get best performance within a given budget and component quality.
Yes, 3180uS corresponds to 50Hz, a very common EQ value in Tape Head (and LP) playback EQ's, I know the usual EQ Timeconstants very well and also how they relate to frequency.
A good shorthand is to remember that 1uS = 159,115Hz.
Yup. I'd say increase the Transformer current rating and reduce Filter Resistor Values with increased Filter Capacitor Values.
More Voltage means more reserve for filtering/regulation (increase Input Resistor preferably) but also requires higher safety ratings for components. This is a tradeoff.
Sayonara
Konnichiwa,
Fin said:
Yes, I tend to look at conduction angle, ripple waveform and step response when comparing different circuits. Obviously the output voltage needs to right and ripple low, but it is IMNSHO preferable to have a large conduction angle and a bit higher ripple with a "soft" waveform than to minimise ripple at the cost of a unpleasant (spikey - indicates high order harmonics) ripple waveform and narrow conduction angle.
Fin said:
More or less. All things are tradeoffs. The larger the input resistor and the smaller the input capacitor the wider the conduction angle but equally regulation suffers, maing such a circuit suitable only for "class A" circuits. You can compensate the resistive losses by boosting the primary volateg, but you then need to account for the higher potentioal "no load" voltage in the safety ratings for components.
Thus, for any given pricepoint and level of component quality there will be a "sweet spot" where you get best performance within a given budget and component quality.
Fin said:
Yes, 3180uS corresponds to 50Hz, a very common EQ value in Tape Head (and LP) playback EQ's, I know the usual EQ Timeconstants very well and also how they relate to frequency.
A good shorthand is to remember that 1uS = 159,115Hz.
Fin said:
Fin said:
Yup. I'd say increase the Transformer current rating and reduce Filter Resistor Values with increased Filter Capacitor Values.
Fin said:
More Voltage means more reserve for filtering/regulation (increase Input Resistor preferably) but also requires higher safety ratings for components. This is a tradeoff.
Sayonara
PSU Design
Hi Thorsten
This makes a lot of sense - especially if you can reduce the ripple at a later stage - if necessary. Is there a simple means of determining the conduction angle or length of time that a circuit conducts, and a guide to what one should be aiming for?
Previously, you mentioned that 3ms was better that 1ms - how high can it go (obviously 10ms is max. - and impossible)?
So - with my 2*22V 25VA transformer - I could increase the value of the first resistor and reduce the value of the first capacitor. However, I would need to maintain the peak to peak voltage at capacitor 2, below about 22mv. Is there any point in maintaining this at a lower level? What would be the minimum capacitor value you would consider?
As you say above, I would also need to ensure that all components before the regulator are rated above the no-load voltage of the rectified voltage. Therefore, I should use 50V capacitors and 5W resistors.
The higher primary voltage also provides the option to include additional filtration. Is it worthwhile adding more RC filters? I noticed that an extra 20ohm/2,200uF RC brings the peak to peak down to less than 1mv.
Now it all fits together.
Does the increase in transformer current rating cause the conduction angle to widen - therefore allowing an increase in the capacitor size - or - is the adjustment in the RC values just to minimise the required increase in the size of the transformer - and therefore, the cost?
This is just hypothetical, as my situation is the reverse - higher voltage and more current than is required.
I know this partly answers some of what I have asked above - but - are you suggesting that, due to the higher voltage of my transformers, I should increase the input resistor? If so, is there a reasonable value that you would not exceed? I assume that the capacitor needs to be reduced in value at the same time - or are you talking about altering the nature of the filter?
If you still have a higher than required voltage, what would you do next? More filtering or more regulators or both? Should I now start to consider pre/post regulators, with each optimised differently?
With the transformers that I have, it looks like there is plenty of reserve for filtering/regulation. I hope that, from a sound quality point of view, this is a good thing.
Hi Thorsten
This makes a lot of sense - especially if you can reduce the ripple at a later stage - if necessary. Is there a simple means of determining the conduction angle or length of time that a circuit conducts, and a guide to what one should be aiming for?
Previously, you mentioned that 3ms was better that 1ms - how high can it go (obviously 10ms is max. - and impossible)?
So - with my 2*22V 25VA transformer - I could increase the value of the first resistor and reduce the value of the first capacitor. However, I would need to maintain the peak to peak voltage at capacitor 2, below about 22mv. Is there any point in maintaining this at a lower level? What would be the minimum capacitor value you would consider?
As you say above, I would also need to ensure that all components before the regulator are rated above the no-load voltage of the rectified voltage. Therefore, I should use 50V capacitors and 5W resistors.
The higher primary voltage also provides the option to include additional filtration. Is it worthwhile adding more RC filters? I noticed that an extra 20ohm/2,200uF RC brings the peak to peak down to less than 1mv.
Now it all fits together.
Does the increase in transformer current rating cause the conduction angle to widen - therefore allowing an increase in the capacitor size - or - is the adjustment in the RC values just to minimise the required increase in the size of the transformer - and therefore, the cost?
This is just hypothetical, as my situation is the reverse - higher voltage and more current than is required.
I know this partly answers some of what I have asked above - but - are you suggesting that, due to the higher voltage of my transformers, I should increase the input resistor? If so, is there a reasonable value that you would not exceed? I assume that the capacitor needs to be reduced in value at the same time - or are you talking about altering the nature of the filter?
If you still have a higher than required voltage, what would you do next? More filtering or more regulators or both? Should I now start to consider pre/post regulators, with each optimised differently?
With the transformers that I have, it looks like there is plenty of reserve for filtering/regulation. I hope that, from a sound quality point of view, this is a good thing.
Re: PSU Design
Konnichiwa,
Look at the current through the transformer, zoom in if neccesary, that should make it clear....
Choke input and purely resistive load manage close to 180degrees/10mS condcution time (50Hz mains).
Yes.
Yes, but this will increase ripple.
Not neccesarily. A little more or less rarely makes a huge difference. I usually apply to any changes in secondary circuits the 6db rule. Unless the improvement is near 6db (or the disimprovement) I don't loose sleep, unless the original result was marginal.
Maybe, you can do a worst case simulation with PSUD and establish the actual values for LIMIT and also look at the operational behaviour.
Usually. If you slit the R and C you get more ripple rejection.
Eg. if instead of 10R/4700uF on our earlier example you use 3R3/2,200uF/3R3/2,200uF/3R3/2200uF after 3R3/470uF on the input you get 20.45V instead of 20.5V, but with only 3.4mV Peak-Peak ripple instead of 22mV....
Even if you change the input RC to 3R3/100uF you still have only 5.2mV Peak-Peak ripple with 20.2V and the conduction angle widens a little more.
If we "design in" your 22V/0.5A Transformer and use 22R/100u/10R/2,200uF/10R/2,200uF/10R/2200uF we get 26V DC with 0.5mV peak-peak ripple. Peak currents (for 50mA DC out) are below 0.2A and the current draw is very "rounded", almost a nice sinewave. nearly 4mS conduction time equal 72degrees conduction angle.
Comparing this (for fun) with a single 4,700uF Capacitor has a conduction angle of 27 Degrees and nearly 0.5A peaks with 32V DC overlaid with 90mV Peak-Peak ripple.
I think this illustrates well the differences.
Yes, usually a larger cap need a larger transformer, but noit because the conduction angle widens, but rather due to issues inherent to transformers.
To a degree. In the above example our RCRCRCRC filtered supply draws 88mA RMS from the transformer for 50mA out, the single 4700uF Cap causes 133mA RMS to flow and the first circuit limits current peaks to 195mA, the second draws 435mA peaks.
You can increase the timeconstant if you like. There are no hard and fast rules, except perhaps the 6db rule. PSUD allows you to try a lot of arrangements, work out two you think most likely build both and listen.... ;-)
Depends how far you want to go. Adding a TL/LM431 Shunt after the LM1085/317 series regulator is naturally a good thing, as is adding several RC filter circuits. The less noise the better. Where do you want to draw the line? You can go so far that even with AC powered gear there is no observable ground leakage and PSU noise is down to and limited purely by the active regulation device feeding the signal circuit. It does take a lot of effort to get this far and may not give better sound anyway...
Sayonara
Konnichiwa,
Fin said:
Look at the current through the transformer, zoom in if neccesary, that should make it clear....
Fin said:
Choke input and purely resistive load manage close to 180degrees/10mS condcution time (50Hz mains).
Fin said:
Yes.
Fin said:
Yes, but this will increase ripple.
Fin said:
Not neccesarily. A little more or less rarely makes a huge difference. I usually apply to any changes in secondary circuits the 6db rule. Unless the improvement is near 6db (or the disimprovement) I don't loose sleep, unless the original result was marginal.
Fin said:
Maybe, you can do a worst case simulation with PSUD and establish the actual values for LIMIT and also look at the operational behaviour.
Fin said:
Usually. If you slit the R and C you get more ripple rejection.
Eg. if instead of 10R/4700uF on our earlier example you use 3R3/2,200uF/3R3/2,200uF/3R3/2200uF after 3R3/470uF on the input you get 20.45V instead of 20.5V, but with only 3.4mV Peak-Peak ripple instead of 22mV....
Even if you change the input RC to 3R3/100uF you still have only 5.2mV Peak-Peak ripple with 20.2V and the conduction angle widens a little more.
If we "design in" your 22V/0.5A Transformer and use 22R/100u/10R/2,200uF/10R/2,200uF/10R/2200uF we get 26V DC with 0.5mV peak-peak ripple. Peak currents (for 50mA DC out) are below 0.2A and the current draw is very "rounded", almost a nice sinewave. nearly 4mS conduction time equal 72degrees conduction angle.
Comparing this (for fun) with a single 4,700uF Capacitor has a conduction angle of 27 Degrees and nearly 0.5A peaks with 32V DC overlaid with 90mV Peak-Peak ripple.
I think this illustrates well the differences.
Fin said:
Yes, usually a larger cap need a larger transformer, but noit because the conduction angle widens, but rather due to issues inherent to transformers.
Fin said:
To a degree. In the above example our RCRCRCRC filtered supply draws 88mA RMS from the transformer for 50mA out, the single 4700uF Cap causes 133mA RMS to flow and the first circuit limits current peaks to 195mA, the second draws 435mA peaks.
Fin said:
You can increase the timeconstant if you like. There are no hard and fast rules, except perhaps the 6db rule. PSUD allows you to try a lot of arrangements, work out two you think most likely build both and listen.... ;-)
Fin said:
Depends how far you want to go. Adding a TL/LM431 Shunt after the LM1085/317 series regulator is naturally a good thing, as is adding several RC filter circuits. The less noise the better. Where do you want to draw the line? You can go so far that even with AC powered gear there is no observable ground leakage and PSU noise is down to and limited purely by the active regulation device feeding the signal circuit. It does take a lot of effort to get this far and may not give better sound anyway...
Sayonara
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