Dear Navin and friends
Hi!
My initial thoughts were of making the low power version. Later I realised it should be done so that it is can be converted into a higher power version also.
Cosidering the low power unit we can mount the BJTs on PCB and direct on heatsink in case of TO3 devices. With present suggestions I plan to incorporate on board 4 nos devices, making it suitable for both low and high power version.
Please give me few days time new artwork would be ready.
Regards
Rahul
Hi!
My initial thoughts were of making the low power version. Later I realised it should be done so that it is can be converted into a higher power version also.
Cosidering the low power unit we can mount the BJTs on PCB and direct on heatsink in case of TO3 devices. With present suggestions I plan to incorporate on board 4 nos devices, making it suitable for both low and high power version.
Please give me few days time new artwork would be ready.
Regards
Rahul
Hi!
I would assemble the lower power version. You can make a higher power one as board will be able to cater to both.
Regards
Rahul
I would assemble the lower power version. You can make a higher power one as board will be able to cater to both.
Regards
Rahul
Have you guys seen the JLH section at http://members.lycos.nl/anthonyvh/.
Great work featured here.
Vivek
Great work featured here.
Vivek
Well, I can comment on this one-I just replaced perfectly good caps and resistors with Caddocks and Multicaps last week on my 35 wpc p-p Welborne Labs power amp. Frankly, I couldnt hear any difference! Maybe I dont have golden years, maybe it's because I over 50, whatever the reason, I say go for value for money solutions...
George
Mhh..i wasnt following...was away for a couple of days.. bad health..this darn bangalore weather..ok...
many thanks Rahul and Tarun for the calrifications...but i still have some doubts..! just might be my ignorance...
I do agree that fuses are slow to act and hence its a chance...and obviously one cannot use the quick blow veriety...for u'll have time only to change them... but...
regarding nonlinearity...!
we say that fuses on output paths are nonlinear....I accept the fact that they indeed are non linear and have a measurable tempco.. but if we say that this fuse will cause distortion if used in the output, will the same not be the case when used in the power supply...My limited knowledge tells me that the Output power transitors are nothing but pass transitors. So u control their base current and they control a larger current coming directly from the power supply...
so suppose the fuse is put at the out put.. this large current has to pass through the fuse to get to the speakers...in doing so the fuse might get heated up momentarily and hence cause the distortion...suppose i move the fuse to the power supply...Then again the current which has to reach the speaker has to pass through this fuse. This current will be exactly same (or fractionally more) than the current that would have gone throgh the fuse in the earlier case. (yes for class A there will be a heavy bias current through the fuse at all times in the second case but will be absent in first case.)
Now the effect...will situation one and two be more or less similar...? Is it not just a question of either this side or that side of the pass transistor...
Have i missed something...
What have i missed..?
ajju
many thanks Rahul and Tarun for the calrifications...but i still have some doubts..! just might be my ignorance...
Rahul said:
I do agree that fuses are slow to act and hence its a chance...and obviously one cannot use the quick blow veriety...for u'll have time only to change them... but...
regarding nonlinearity...!
we say that fuses on output paths are nonlinear....I accept the fact that they indeed are non linear and have a measurable tempco.. but if we say that this fuse will cause distortion if used in the output, will the same not be the case when used in the power supply...My limited knowledge tells me that the Output power transitors are nothing but pass transitors. So u control their base current and they control a larger current coming directly from the power supply...
so suppose the fuse is put at the out put.. this large current has to pass through the fuse to get to the speakers...in doing so the fuse might get heated up momentarily and hence cause the distortion...suppose i move the fuse to the power supply...Then again the current which has to reach the speaker has to pass through this fuse. This current will be exactly same (or fractionally more) than the current that would have gone throgh the fuse in the earlier case. (yes for class A there will be a heavy bias current through the fuse at all times in the second case but will be absent in first case.)
Now the effect...will situation one and two be more or less similar...? Is it not just a question of either this side or that side of the pass transistor...
Have i missed something...
What have i missed..?
ajju
A good reference can be found in the TITAN2000 article that appeared sometime back in Elecktor...It has a very elaborate protection system..And looks a decent design. Any body tried them. However the method of current sensing on output etc might not be of any direct use to us in this project. The current sensing there was done on the basis of the voltages developed across the emitter resitances of the Output devices.
However circuits of interest would be
o A relatively simple soft start mechanism presented in the article.
o A heat Sink Fan control.
o Power supply Under voltage protection.
o Overdrive protection.
All these protection mechanism act independently, but are meshed together finally in a statemachine type controller. So if a fault occurs the system trips and it has to be reset manually. There is no self recovery.
Would any of these be worth considering.??
Btw I too liked Roadkill's idea of using a SCR for the purpose of
Softstart as well as a voltage regulator. That is if we are absolutely certain that the harmonics can be filtered out...otherwise its going to be nasty. It will also be an improvement in terms of eficiency and thermal management.
Btw have we decided on a power supply...are we going ahead with a series pass regulator.?
On a different note...I was getting a real weird thought...Can a Hall-effect device be used in some way to get the output DC protection...
Advantage...It is not going to interfere with the output path...
I mean it is not going to sit directly on that path but will more be taking advantage of a parasitic..a constant magnetic field devleloped by a DC flowing through the speaker interconnect wire.... Does any one have any thoughts...?
Or... Atleast call me stupid...in chorous 😀 Louder please...sorry i cant hear u..! 😀 😀
ajju
Ajju:
The description appears to turn the fuse more into a current limiting device rather than a portection device.
The supply is regulated so if we are putting fuse in unregulated section I do not see how drastically it is going to affect the biasing of output transistors.
Do I already see audiophiles running to remove the fuse from main lines right upto power house and listen to the improvement in sound.
Thyristors in primary is commonly used as a pre regulator mainly to keep dessipation low . In industrial applications I have seen 300-400W class PSU employ such scheme. at 125VA I feel we can skip.
No doubt a soft start and DC protection will be good safety measure.
Coupling the field of signal line is a standard practice no not in audio but in RF. A torroidal core having nuber of turns is slipped over the main conductor or the coax in case of RF. A google on Breune Bridge or SWR bridge will yield more on subject.
I recommend using 317 and 337 based supply with series pass transistors.
Regards
Rahul
The description appears to turn the fuse more into a current limiting device rather than a portection device.
The supply is regulated so if we are putting fuse in unregulated section I do not see how drastically it is going to affect the biasing of output transistors.
Do I already see audiophiles running to remove the fuse from main lines right upto power house and listen to the improvement in sound.
Thyristors in primary is commonly used as a pre regulator mainly to keep dessipation low . In industrial applications I have seen 300-400W class PSU employ such scheme. at 125VA I feel we can skip.
No doubt a soft start and DC protection will be good safety measure.
Coupling the field of signal line is a standard practice no not in audio but in RF. A torroidal core having nuber of turns is slipped over the main conductor or the coax in case of RF. A google on Breune Bridge or SWR bridge will yield more on subject.
I recommend using 317 and 337 based supply with series pass transistors.
Regards
Rahul
Fuse in supply rails versus fuse in speaker output
If the fuse (or any other non-linear component) is in the supply rails, the effect of this may not be as pronounced as in the case when the fuse will be in the speaker output path.
But one point, which Rahul makes, is very true. My comment applies more to Class B amps. In a Class A amp things are different:
I think you've missed PSRR of the power amp.ajju said:Have i missed something...
If the fuse (or any other non-linear component) is in the supply rails, the effect of this may not be as pronounced as in the case when the fuse will be in the speaker output path.
But one point, which Rahul makes, is very true. My comment applies more to Class B amps. In a Class A amp things are different:
- the ebb and flow of current to the speaker is not reflected (at least not as much) in the supply rails in a Class A amp. Therefore people can even consider regulated PSU for Class A amps, where they would be a very bad idea in Class B amps. This means that even if you put a fuse in the supply rail of the Class A amp, it may not see as much ebb and flow of current level, hence may not introduce as much non-linear distortion, as in the case of the supply rail of a Class B amp.
- since Class A amps have regulated PSU, you can use current foldback and other tricks to ensure over current protection, so fuses may not be needed.
- At least for the JLH design, the PSRR will probably be much worse than in the case of more classic Class B designs.
Bangalore's got the most schizophrenic weather ever... anyway, back to the audio 🙂
If you use an SCR as a regulator, it will introduce switching harmonics into the power line. How well these can be filtered depends on how much money you pour in to capacitors, chokes, etc. How much this matters depends on the amplifier's PSRR. I've never built a JLH amp, so I've got no clue about it's PSRR. Since the amp draws a lot of quiescent current, the filter caps wont have much smoothing effect, and the extra noise due to the SCRs will be more apparent.
However, if you use the SCRs just as a switch, they wont behave any differently from regular diodes (except for slightly more forward drop), and won't introduce any additional switching harmonics.
Tarun, the PSRR of any amplifier will be better at low frequencies than at higher ones. The distortion introduced by a fuse will be LF only, since the thermal mass of the fuse wire wont allow a heating action to take place fast enough to cause distortion at higher frequencies.
Oh, yeah, the fuse in a power supply is meant in case the current limit or any other active protection fails. This is not designed to save your amplifier from a painful death, it's designed to prevent your amp from setting your house on fire. So please be responsible and use a fuse!
If you use an SCR as a regulator, it will introduce switching harmonics into the power line. How well these can be filtered depends on how much money you pour in to capacitors, chokes, etc. How much this matters depends on the amplifier's PSRR. I've never built a JLH amp, so I've got no clue about it's PSRR. Since the amp draws a lot of quiescent current, the filter caps wont have much smoothing effect, and the extra noise due to the SCRs will be more apparent.
However, if you use the SCRs just as a switch, they wont behave any differently from regular diodes (except for slightly more forward drop), and won't introduce any additional switching harmonics.
Tarun, the PSRR of any amplifier will be better at low frequencies than at higher ones. The distortion introduced by a fuse will be LF only, since the thermal mass of the fuse wire wont allow a heating action to take place fast enough to cause distortion at higher frequencies.
Oh, yeah, the fuse in a power supply is meant in case the current limit or any other active protection fails. This is not designed to save your amplifier from a painful death, it's designed to prevent your amp from setting your house on fire. So please be responsible and use a fuse!Thanks Roadkill,
The brief comments are really helpful.
Here I feel our target is to provide ourself with true high class amp. Introducing new technologies, would create unecessary complications. I suggest we get going with the basic design, enjoy the sheer pure music and then once comfortable with the ckt involve extra frills.
Kindly also keep in mind while on topic we still do not have a Class A amp available in mkt for audiophile needs. This is something unique being done in our country for the first time involving support of lot from friends all over the subcontinent.
I am thankful to all contributing in this forum
Regards
Rahul
The brief comments are really helpful.
Here I feel our target is to provide ourself with true high class amp. Introducing new technologies, would create unecessary complications. I suggest we get going with the basic design, enjoy the sheer pure music and then once comfortable with the ckt involve extra frills.
Kindly also keep in mind while on topic we still do not have a Class A amp available in mkt for audiophile needs. This is something unique being done in our country for the first time involving support of lot from friends all over the subcontinent.
I am thankful to all contributing in this forum
Regards
Rahul
Oh no no...The argument was on the nonlinearity of the fuse.
and i was not pointing to the effect it had on the biasing of a transistor...!
Tracking back a little bit...
How is a fuse nonlinear...!
This is what i understood.
A fuse is nonlinear because it has got a measurable tempco...
measurable means how measurable...If i remember correctly Copper also has a positive tempco of approx.003 0r something..!
And these or a similar conductor will be used for pad to pin bonding inside a packaged semiconductor device. only alloys like constantan, nichrome etc have got extremely low tempcos..of the order of 10e-4 or 10e-5. What is this value generally for a fuse wire..?
So the argument for a fuse is nonlinear is that there is a noticeable resistance change depending on current flow. (the resistance change being brought about by pronounced resistive heating as a result of a high tempco).
Thus the nonlinearity effecteivly is the nonlinearity seen in a fuse resistance with respect to temperature....hence as AC(Low frequency audio signal) flows there will be a nonlinear fluctuation in resistance of the fuse which causes _audible_ distortion in the output...Am i correct in saying so.?
If that is the case, what i asked in my previous post is, will it matter where the fuse is as long as it is in the path leading to the output.(if at the speaker output or at the power suppLy input side of the pass transitor.)
Rahul, your answer is perfectly valid. If i put the fuse prior to regulation i can prevent the fuse resistance from affecting the circuit. Fair enough..!
Well may be not. Even though your supply comes from miles and miles away through the exposed atmosphere, through the windy countrysides, in sun rain and snow, and that too throuh dirty Aluminium wire... all that u need to clean the mess up is 2 meter length of $$$$ worth audiophile grade wire (gold silver ...OFC..99.999999%..?? with nylon jacket and teflon underwear). 😀
Ohh Sorry..One shouldnt make such comments if one cant experience it..Actually a good portion of this population including me is part deaf..! We arent fortunate enough..! 🙁
Many thanks for the pointers. Btw I was talking of detecting DC or extreme low frequencies with the device. Do u mean to say that one can detect DC with the SWR bridge..I though it is nothing but a current loop...something similar to a clamp meter.?
I dint quite understand this Tarun. If the Amp has a low PSRR, it simply means that effect of a spurious signal on the supply line is more likely to affect the output. Is the following understanding correct.? Assume the JLH has a PSRR of about 60...Now do you mean to say that the nonlinearities due to the Fuse(which supposedly will cause a power supply noise) wont have a profound effect on the output as would have been if the fuse was sitting directly on the output. Hmmm...then that makes a good point..!!
But I still wonder how audible it is going to be...I've not heard anything from a fuse except for a rare "pop" when the fuse vaporises under extreme conditions..😀
ajju
and i was not pointing to the effect it had on the biasing of a transistor...!
Tracking back a little bit...
How is a fuse nonlinear...!
This is what i understood.
A fuse is nonlinear because it has got a measurable tempco...
measurable means how measurable...If i remember correctly Copper also has a positive tempco of approx.003 0r something..!
And these or a similar conductor will be used for pad to pin bonding inside a packaged semiconductor device. only alloys like constantan, nichrome etc have got extremely low tempcos..of the order of 10e-4 or 10e-5. What is this value generally for a fuse wire..?
So the argument for a fuse is nonlinear is that there is a noticeable resistance change depending on current flow. (the resistance change being brought about by pronounced resistive heating as a result of a high tempco).
Thus the nonlinearity effecteivly is the nonlinearity seen in a fuse resistance with respect to temperature....hence as AC(Low frequency audio signal) flows there will be a nonlinear fluctuation in resistance of the fuse which causes _audible_ distortion in the output...Am i correct in saying so.?
If that is the case, what i asked in my previous post is, will it matter where the fuse is as long as it is in the path leading to the output.(if at the speaker output or at the power suppLy input side of the pass transitor.)
Rahul, your answer is perfectly valid. If i put the fuse prior to regulation i can prevent the fuse resistance from affecting the circuit. Fair enough..!
Well may be not. Even though your supply comes from miles and miles away through the exposed atmosphere, through the windy countrysides, in sun rain and snow, and that too throuh dirty Aluminium wire... all that u need to clean the mess up is 2 meter length of $$$$ worth audiophile grade wire (gold silver ...OFC..99.999999%..?? with nylon jacket and teflon underwear). 😀
Ohh Sorry..One shouldnt make such comments if one cant experience it..Actually a good portion of this population including me is part deaf..! We arent fortunate enough..! 🙁
Many thanks for the pointers. Btw I was talking of detecting DC or extreme low frequencies with the device. Do u mean to say that one can detect DC with the SWR bridge..I though it is nothing but a current loop...something similar to a clamp meter.?
I dint quite understand this Tarun. If the Amp has a low PSRR, it simply means that effect of a spurious signal on the supply line is more likely to affect the output. Is the following understanding correct.? Assume the JLH has a PSRR of about 60...Now do you mean to say that the nonlinearities due to the Fuse(which supposedly will cause a power supply noise) wont have a profound effect on the output as would have been if the fuse was sitting directly on the output. Hmmm...then that makes a good point..!!
But I still wonder how audible it is going to be...I've not heard anything from a fuse except for a rare "pop" when the fuse vaporises under extreme conditions..😀
ajju
Dear Ajju and friends,
There are physical limitations that we have to live with. The fuse for all said and done is a non linear device if we can avoid it is best done so. Similarly we can hardly do anything with the physical limitaions of PCBs, connecting wires, bonding leads etc .
At times we have to ignore the basic limitations eg expansion of measuring rod while purchasing cloth.
It is best to concede with circumstance that are beyond our control.
Now about this cable stuff and another practical limitation, blind tests have been inconclusive.
We all know our ears can barely detect 3db of change. Now I always held of opinion if a sense organ of our body can barely differentiate twice the intensity how is it going to differentiate few extra milliohms??? In other words I still consider our ears as one of the worst sense organs.
So ultimately it boils down to limitations of the equipment as well as limitaions of our hearing.
My point I say there is a lot of scope in what we can live with so I suggest we take all decision within the field of physical limitations
Regards
Rahul
There are physical limitations that we have to live with. The fuse for all said and done is a non linear device if we can avoid it is best done so. Similarly we can hardly do anything with the physical limitaions of PCBs, connecting wires, bonding leads etc .
At times we have to ignore the basic limitations eg expansion of measuring rod while purchasing cloth.
It is best to concede with circumstance that are beyond our control.
Now about this cable stuff and another practical limitation, blind tests have been inconclusive.
We all know our ears can barely detect 3db of change. Now I always held of opinion if a sense organ of our body can barely differentiate twice the intensity how is it going to differentiate few extra milliohms??? In other words I still consider our ears as one of the worst sense organs.
So ultimately it boils down to limitations of the equipment as well as limitaions of our hearing.
My point I say there is a lot of scope in what we can live with so I suggest we take all decision within the field of physical limitations
Regards
Rahul
Ajju,
Simply forgot about the coupling of low freq field same principal is adopted in car Tachometers that couples low frequency pulses from sparkplug to the measuring device.
Your suggestions I feel hold true. As for DC it is simple matter of detecting unusual high potiantial at out put.
regards
Rahul
Simply forgot about the coupling of low freq field same principal is adopted in car Tachometers that couples low frequency pulses from sparkplug to the measuring device.
Your suggestions I feel hold true. As for DC it is simple matter of detecting unusual high potiantial at out put.
regards
Rahul
I agree with you cent percent...
What annoys me is the unnecessary hype created around what is not measurable or observable. For xample, you might have seen products like wires or conductors with an arrow marking the direction in which the current should flow in them. I really dont understand this. May be tomorrow some one will claim that he/she heard better sonics when the interconnect direction is in the direction of earths gravity..that might be because earths gravity is easing the electron flow..who knows...such vague comments put me off.. Now i got the feeling that our fuse discussion was also getting into those realms..
I would love to follow and construct this project but at the same timei prefer to be a bit realistic. As u say we can contruct the base version and then ppl can start experimenting/improving on it.
I'm Extremely sorry if i've ruined the enthusiasm of ppl with my comments...!
ajju
What annoys me is the unnecessary hype created around what is not measurable or observable. For xample, you might have seen products like wires or conductors with an arrow marking the direction in which the current should flow in them. I really dont understand this. May be tomorrow some one will claim that he/she heard better sonics when the interconnect direction is in the direction of earths gravity..that might be because earths gravity is easing the electron flow..who knows...such vague comments put me off.. Now i got the feeling that our fuse discussion was also getting into those realms..
I would love to follow and construct this project but at the same timei prefer to be a bit realistic. As u say we can contruct the base version and then ppl can start experimenting/improving on it.
I'm Extremely sorry if i've ruined the enthusiasm of ppl with my comments...!
ajju
Rahul,
Let's examine fuse protection on a power amplifier.
Someone here stated that the fuse doesn't protect the amplifier, just prevents setting the house on fire if something goes wrong. Quite true.....
If some circuit condition decides to threaten the output devices, generally the most fragile part of the circuit, then nothing will prevent it. You can fit SOAR protection (a problem only for bipolar transistors, but not mosfets), or wrap an overload transistor around the voltage amp, and this will prevent anything short of a 4" nail across the outputs from taking out the OP stage. However, and given the clear intention in this forum to create an amplifier of exemplary performance, such measures are usually audible. Some less than others, of course, but in most instances audible, and not particularly nice audible either.
So, what are the options? Consider the economics...
A great speaker is expensive, and one should protect against inflicting the rail voltage on its voice coil for more than half a second. Obviously this is a huge issue for powerful amplifiers, of say 100W and more, which are almost always Class AB. Output devices are merely silicon, and in the scheme of things inexpensive. What do you pay for a good set of outputs? Maybe $US10? This is trivial compared to a $US100 speaker driver, and since SS accidents wreak their havoc in less than 20 uS, it is wise to accept the inevitability of broken output stages in order to protect the valuable speakers. This is, after all, the modern technical equivalent of offering sacrifices for the greater good, and it makes a lot of sense.
If a heavy current flows from the amp to the speaker driver, a 5A fuse will protect the voice coil very well. As someone sagely remarked, thermal issues will limit the distortion introduced (H3 mostly, as it is symmetrically compressive) to very low frequencies, but this distortion is almost musical since it produces only higher bass harmonics which harmonise. The added insurance is worth it, and the thermal considerations will only prevail at extremely low frequencies, around 25Hz. How often do we hear 25Hz in music?
I use 5A fuses on the power rails of the AKSA 55, and 7.5A on the AKSA 100. No one has ever complained of this minimalist arrangement, no one has commented on bass distortion, and no speaker or home has ever caught fire. If your circuit is Class A, then the standing current will be high anyway, and the current variation rather less than a Class AB circuit like the AKSA. This significantly reduces the thermal distortion. I suggest rail fuses are a good idea, inexpensive, safety oriented, and effective, without costing sonics at all. I'm not so sure about SOAR or VAS protection circuits. It's really difficult to design something which is sonically unobtrusive, I can promise you.
Cheers,
Hugh
Let's examine fuse protection on a power amplifier.
Someone here stated that the fuse doesn't protect the amplifier, just prevents setting the house on fire if something goes wrong. Quite true.....
If some circuit condition decides to threaten the output devices, generally the most fragile part of the circuit, then nothing will prevent it. You can fit SOAR protection (a problem only for bipolar transistors, but not mosfets), or wrap an overload transistor around the voltage amp, and this will prevent anything short of a 4" nail across the outputs from taking out the OP stage. However, and given the clear intention in this forum to create an amplifier of exemplary performance, such measures are usually audible. Some less than others, of course, but in most instances audible, and not particularly nice audible either.
So, what are the options? Consider the economics...
A great speaker is expensive, and one should protect against inflicting the rail voltage on its voice coil for more than half a second. Obviously this is a huge issue for powerful amplifiers, of say 100W and more, which are almost always Class AB. Output devices are merely silicon, and in the scheme of things inexpensive. What do you pay for a good set of outputs? Maybe $US10? This is trivial compared to a $US100 speaker driver, and since SS accidents wreak their havoc in less than 20 uS, it is wise to accept the inevitability of broken output stages in order to protect the valuable speakers. This is, after all, the modern technical equivalent of offering sacrifices for the greater good, and it makes a lot of sense.
If a heavy current flows from the amp to the speaker driver, a 5A fuse will protect the voice coil very well. As someone sagely remarked, thermal issues will limit the distortion introduced (H3 mostly, as it is symmetrically compressive) to very low frequencies, but this distortion is almost musical since it produces only higher bass harmonics which harmonise. The added insurance is worth it, and the thermal considerations will only prevail at extremely low frequencies, around 25Hz. How often do we hear 25Hz in music?
I use 5A fuses on the power rails of the AKSA 55, and 7.5A on the AKSA 100. No one has ever complained of this minimalist arrangement, no one has commented on bass distortion, and no speaker or home has ever caught fire. If your circuit is Class A, then the standing current will be high anyway, and the current variation rather less than a Class AB circuit like the AKSA. This significantly reduces the thermal distortion. I suggest rail fuses are a good idea, inexpensive, safety oriented, and effective, without costing sonics at all. I'm not so sure about SOAR or VAS protection circuits. It's really difficult to design something which is sonically unobtrusive, I can promise you.
Cheers,
Hugh
Hugh, I quite agree that some blown output devices are
definitely preferrable to blowing a speaker considering the
economics. On the rail fuses, are you sure a 5A rating isn't
really a bit on the high side (although I confess not having
calculated on the current draw of your amps). While I suppose
there are variations between brands, the info I have is that
for fast fuses in that range, if I is the rated current then the
min and max times for the fuse to blow are
current min time max time
-------------------------------------
2.1*I ..................... 30 min
2.75*I....50ms.........2 s
4.1*I......10ms.........300ms
10*I.........................20ms
These figures applies to 5x20mm fast glass fuses of brand
Littlefuse.
definitely preferrable to blowing a speaker considering the
economics. On the rail fuses, are you sure a 5A rating isn't
really a bit on the high side (although I confess not having
calculated on the current draw of your amps). While I suppose
there are variations between brands, the info I have is that
for fast fuses in that range, if I is the rated current then the
min and max times for the fuse to blow are
current min time max time
-------------------------------------
2.1*I ..................... 30 min
2.75*I....50ms.........2 s
4.1*I......10ms.........300ms
10*I.........................20ms
These figures applies to 5x20mm fast glass fuses of brand
Littlefuse.
Thanks Christer,
I'd not seen these figures; just computed the rating on the basis of peak driver current.
I will revise my thoughts; perhaps 3A and 5A would be more suitable!
Do you yet have email?
Cheers,
Hugh
I'd not seen these figures; just computed the rating on the basis of peak driver current.
I will revise my thoughts; perhaps 3A and 5A would be more suitable!
Do you yet have email?
Cheers,
Hugh
I think I'd understood you right the first time itself. And the point about the PSRR stands. Anything which introduces fluctuations in current flow in the supply rails will probably have less effect at speaker output, than the same thing sitting on the speaker output itself. The difference will be due to the amp's PSRR.ajju said:
The comments Roadkill made about LF distortion and an amp's PSRR being better at LF all make sense to me.
Yes, that's what I meant. I'll make the same statement again, but I'm being careful here. All I'm saying is that it will have a greater effect if it's on the output rails directly. How much greater? I don't know.
This is one question I've never dared to ask on these forums. How audible is Hugh's Nirvana upgrade compared to the standard component set he provides for his AKSA? George, who has the AKSA, couldn't hear any changes when he upgraded components in his Welbourne Labs amp. (George uses his AKSA with the Nirvana upgrades, I believe.) Would he have heard any audible difference if he'd built his amp without the Nirvana upgrades? This is not a question I ask on these forums, given the number of people who can hear audible differences when they shift from an aluminium heatsink to a thick copper bar. 😀
On the other hand, I had the good fortune to have two audio CD players at home at one point, at home. And I could hear differences between them. I have also had the good fortune to have a top-end cassette deck (one of the best ever made anywhere at any time) and I have heard how it sounds "better" than a CD. I've learned that fine distortions can be audible even to my untrained ears. Of course, whether the fuse will be audible is not something I can answer.
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