lm317 can be used at very high voltages as long as you do not ask it to drop too much voltage. I doubt 125Vout would be a problem as long as you didnt feed it more than ~135-140v
in that case I agree with hochopeper on both fronts, thanks for keeping us in the loop 😎 good boy 😉
Might be if do they a negative one?
I just had a quick look at Farnell on-line but didn't see one.
Is there no risk at all that the output voltage may lag behind the input voltage at power up such that, for a moment, the 37 Volt limit is exceeded. And the reverse for power down, even with the back diode. In the long term, failure is more likely?
there doesnt seem so, i've been running them at +/-45 and up to +/-65 for testing in my NTD1 IV stage for over a year and i've read of them being used at much higher voltages than that in tube amps
ha no, that makes perfect sense; after the other day I could imagine it would not have been pleasant facing further delay. but like we said, we are reasonable people and want the best outcome, so given the choice, I/we choose to go with your recommendation.AP2 said:
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There are potentially two problems that need design input to allow reliable working of 317 at high voltages.
1.) at start up the 317 sees the full voltage of the PSU at the input while the output sees a near short circuit due to an accumulation of capacitances in the load and around the 317 regulator.
2.) the +-6% of mains voltage variation can lead to a very high range of DC voltage at the input to the 317.
If either or both of these are not attended to, then reliability can be less than satisfactory.
1.) at start up the 317 sees the full voltage of the PSU at the input while the output sees a near short circuit due to an accumulation of capacitances in the load and around the 317 regulator.
2.) the +-6% of mains voltage variation can lead to a very high range of DC voltage at the input to the 317.
If either or both of these are not attended to, then reliability can be less than satisfactory.
Opc,
post1 states that the attached sch.pdf is not correct and gives a link to the corrected sch.pdf
That link took me to post742 where I see the same date (9/13/2011) and revision letter (D) as the first sch.pdf
Which sch.pdf version is corrected?
post1 states that the attached sch.pdf is not correct and gives a link to the corrected sch.pdf
That link took me to post742 where I see the same date (9/13/2011) and revision letter (D) as the first sch.pdf
Which sch.pdf version is corrected?
What regulation are you referring to
I don't know where to see it.
The Opc amp has provision to supply the whole PCB with a single dual polarity supply or to split the two halves and feed them from two sets of dual polarity supplies. But the stock PCB does not have any regulation built in, as far as I can see.
That may be why some are buying into the smps solution, since it (I think) has 4 outputs to feed the two halves of the PCB.
constant current or not?
Quite simply (if you want you can equate that to my mind capabilities) the chip cannot output 40mApk of load current unless the supply rails supply this extra current. The internals require a quiescent operating current and that is the value quoted in the datasheet
I assume this is the relevant paragraph, which I extracted from the datasheet of the 830.
Quite simply (if you want you can equate that to my mind capabilities) the chip cannot output 40mApk of load current unless the supply rails supply this extra current. The internals require a quiescent operating current and that is the value quoted in the datasheet
for those conditions including Iout=0
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the supply for the headphone amp Andrew, it plugs right in and is easily bent to the task by installing higher voltage caps, thats part of the design. I guess you missed the posts about that and didnt buy any? they were designed to work together
sure, but 40ma is hardly a big deal; I stopped talking about constant current several posts ago when you said you disagreed it was constant, I repeat, where in the performance of the actual amp in the most extreme full current loading at 100hz,1khz, 10khz did you see any sag that you think you can fix with a shunt reg? what transient are you expecting that the caps wont deal with first?
this is going nowhere though, like I said, go for your life!! I wish you well! show us and i'll probably follow suit as i've got some spare shunts, but at this stage i'm not seeing any reason for it and the mounting, particularly of those big red pcbs certainly wont be ideal, they'll be several times the size of the amp. even the black pcbs which are quite neat, will dwarf the amp and mounting them close enough is not an easy job. the sense lines adjust for the voltage drop of long lines no problem, but they cannot remove the effect of distance entirely
for sure the smps is convenient, but I doubt very much that is the driving force behind most of the purchases, its the incredible performance posted and most of that appeal is a small but regulated main high current output, plus it looks HOT!!
however I would still buy it if it was double the size, pink and missing the aux reg
an observer would possibly think this thread belonged in the power supplies section....
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Hi Andrew,
Just to be clear, I fully endorse you trying out the Salas regs, and I would be very interested to hear your opinion on how they compare to the standard regs, or even an unregulated supply. I would imagine the noise on the output would be lower, and that can never be a bad thing.
The LME draws so little current that it's pretty easy to have fun with the supply, so I think experimentation in this area is both easy, and could be rewarding.
As for your statement about current, however, I'm a little skeptical.
I have measured the supply current to the LME, and I can assure you that it does not budge even when driving a pair of mosfets to relatively high power. I had a test setup where there were 9 LME IC's each driving a pair of mosfets, with each channel outputting 200W into 8 ohms. The supply for the LME's was set to +/-75V from a separate regulated lab supply, and the current did not change at all from idle to full power and the meter on the supply had a 10mA accuracy.
The gates of the mosfets, in a linear amplifier like this, simply do not require any significant current to drive. The current required to drive them is diverted from the idle current, much as it is in a class A amplifier, causing little or no net change to the current drawn from the supply. Just because the IC is quoted as being capable of supplying 40mA pk, doesn't mean that it will in normal operation.
Perhaps if it's driving 10 pairs of mosfets at a very high slew rate, then you might start to exceed the idle current, but I'm not sure how realistic that is.
Either way, I wouldn't let that dissuade you from trying the shunt regs, as there could be a variety of other benefits to using them, noise being one of the most important IMO.
Please do let us know what you find!
Cheers,
Owen
Just to be clear, I fully endorse you trying out the Salas regs, and I would be very interested to hear your opinion on how they compare to the standard regs, or even an unregulated supply. I would imagine the noise on the output would be lower, and that can never be a bad thing.
The LME draws so little current that it's pretty easy to have fun with the supply, so I think experimentation in this area is both easy, and could be rewarding.
As for your statement about current, however, I'm a little skeptical.
I have measured the supply current to the LME, and I can assure you that it does not budge even when driving a pair of mosfets to relatively high power. I had a test setup where there were 9 LME IC's each driving a pair of mosfets, with each channel outputting 200W into 8 ohms. The supply for the LME's was set to +/-75V from a separate regulated lab supply, and the current did not change at all from idle to full power and the meter on the supply had a 10mA accuracy.
The gates of the mosfets, in a linear amplifier like this, simply do not require any significant current to drive. The current required to drive them is diverted from the idle current, much as it is in a class A amplifier, causing little or no net change to the current drawn from the supply. Just because the IC is quoted as being capable of supplying 40mA pk, doesn't mean that it will in normal operation.
Perhaps if it's driving 10 pairs of mosfets at a very high slew rate, then you might start to exceed the idle current, but I'm not sure how realistic that is.
Either way, I wouldn't let that dissuade you from trying the shunt regs, as there could be a variety of other benefits to using them, noise being one of the most important IMO.
Please do let us know what you find!
Cheers,
Owen
much as I like the Salas regs, I too figured noise would be the main benefit here thus my first posts, but if lowest noise is the objective there are other designs that are worth a try too, such as the modified higher voltage teddy, a modified super reg, batteries (a lot of batteries). the midrange high voltage does however put the salas at the front of the pack of the most easily bent to the task. I actually like the idea of the reflektor here too
I was looking at something like the composite super regs from synaesthesia's phono RIAA for the front end, my only questions with the salas here are that its tuned for performance thats not really key here like low output impedance and dynamic performance.
but it'll be a while before I play with these sort of tweaks, i'd like to draw a line under the building for a while to work on my speakers and enjoy some music. ive spent far too much time messing with power supplies already due to the sheer number of them in my dac and being so into lowZ headphones uber-low noise is a big deal. That was part of the motivation for buying a ready made PSU unit is I could see myself spending another good chunk of money and time on power supplies for these 4 amps
but again, have fun and do tell how you go
I was looking at something like the composite super regs from synaesthesia's phono RIAA for the front end, my only questions with the salas here are that its tuned for performance thats not really key here like low output impedance and dynamic performance.
but it'll be a while before I play with these sort of tweaks, i'd like to draw a line under the building for a while to work on my speakers and enjoy some music. ive spent far too much time messing with power supplies already due to the sheer number of them in my dac and being so into lowZ headphones uber-low noise is a big deal. That was part of the motivation for buying a ready made PSU unit is I could see myself spending another good chunk of money and time on power supplies for these 4 amps
but again, have fun and do tell how you go
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Roberto, I think you read too much into my message, I tried to make it clear that I dont believe you are out to steal from us, if I did I wouldnt have sent my money because there was already a delay I knew about before this GB.....if you remember I covered this with you in email.
but I sent my money and to a certain extent encouraged others to do the same because I think its a great product and because I trust you, I still trust you to send my PSUs, that is not and never has been in question. I do not believe you are that type of guy, I just think you have not dealt with the communication well at all, telling things that are so easily seen through; probably because you dont want to disappoint people, or maybe think we will run away and take our money with us.
its just that I made it very clear in here and by email, that whatever the reasonable amount of time you needed for them to be ready, thats what I wanted to hear and if there was a problem, I wanted to hear about that too; doing otherwise only serves to make people restless when it doesnt come to pass.
we waited a long time since the beginning of the project to build the best amp we can, waiting some more is no problem.
its simple really, give yourself enough tome to do each batch and try to give a realistic estimate based on the ones you have already built including any supplies orders, as long as the communication is open, none of us have any problem (within reason, it cant go on forever)
this can certainly be recovered, no permanent damage is done. we still love youjust talk to us
Truth usually hurts
good luck
can we just move on please rather than digging it over again? give Roberto a chance to continue with the new trend without bringing up old news. those in the GB expecting shipping all had a chance to say our peace and I think Roberto handled it pretty well in the end, we dont really need to bring it up again, its not productive
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perhaps yes, but it wont nor should it, stop conversation of it in relation to this amp, nor will it stop those who wish to talk down SMPS in general.
clocktower is not in the GB, but I gather had previous dealings with AP2 in relation to NCORE which is the one that had issues with delay, which are all dealt with, thus my decision to push ahead, but cautiously. I guess clocktower still has old feelings on the matter, but this is not the time or place to dig them over again IMO
clocktower is not in the GB, but I gather had previous dealings with AP2 in relation to NCORE which is the one that had issues with delay, which are all dealt with, thus my decision to push ahead, but cautiously. I guess clocktower still has old feelings on the matter, but this is not the time or place to dig them over again IMO