I've used ALW super regs in various dacs and pre-amps with excellent results, I'm sure they would work wonders powering the op-amps in the UCD modules.
They do work best with their own separate transformers etc though so things could get a bit crowded.
Obviously make sure the input voltage of the regs isn't too high
Nice circuit Roger
Simple,cheap and effective😉
LM329's make a nice voltage reference too
They do work best with their own separate transformers etc though so things could get a bit crowded.
Obviously make sure the input voltage of the regs isn't too high
Nice circuit Roger
Simple,cheap and effective😉
LM329's make a nice voltage reference too
Regulators.....regulators!
Chris,
I wouldn't use the resistor as it just raises source impedance. Zeners can take the inrush current, no problem as long as they are rated high enough to dissipate the steady state stuff. Like at least a 1N47XX or a P6KEXX type should be fine.
I also have built my own design “super regulator” with so low of noise I couldn’t measure it as it was below the instruments threshold. This is way over kill for anything other than extremely sensitive circuits like RIAA stages. With careful selection of parts the circuit shown will come within a few percentage points of the best. I see no need to go further unless you just have to have the best and don’t care about money! One point about the circuit is to use a high quality Bourns multiturn cermet pot or equivalent. This is a key part to getting good performance and adjustability out of it.
T,
I have no experience with the LM329. I use the 431 is it is readily available, cheap and works very well. Seems about every SMPS has at least one in it. The only thing is you do have to run at least 10 milliamps through it for it to work properly. There are some low current versions available but you might as well go to a better spec’ed part at that point due to increased cost.
Roger
Chris,
I wouldn't use the resistor as it just raises source impedance. Zeners can take the inrush current, no problem as long as they are rated high enough to dissipate the steady state stuff. Like at least a 1N47XX or a P6KEXX type should be fine.
I also have built my own design “super regulator” with so low of noise I couldn’t measure it as it was below the instruments threshold. This is way over kill for anything other than extremely sensitive circuits like RIAA stages. With careful selection of parts the circuit shown will come within a few percentage points of the best. I see no need to go further unless you just have to have the best and don’t care about money! One point about the circuit is to use a high quality Bourns multiturn cermet pot or equivalent. This is a key part to getting good performance and adjustability out of it.
T,
I have no experience with the LM329. I use the 431 is it is readily available, cheap and works very well. Seems about every SMPS has at least one in it. The only thing is you do have to run at least 10 milliamps through it for it to work properly. There are some low current versions available but you might as well go to a better spec’ed part at that point due to increased cost.
Roger
If i have understood correctly, UCD slew rate is about 9V/us and is limited almost only by the output filter. How much this limit is coming from output cap? So what is slew rate of current cap and is good slew rate important parameter when selecting "hotrodding"- output cap?
Output cap quality
The slew rating (DV/DT) of a cap relates to its ESR directly and is a measure of how much internal instantaneous power it can handle. This is important only in that any cap used should be rated much higher than what it will actually see. This is distinctly different from amp slew limit which is a function of the value of the output filter parts and other reactive feedback components. This is a designed in value and is not affected with a different cap unless you change the value. Note; this is not recommended without doing a complete simulation to determine the other value changes as well. With this self oscillating design using a smaller cap you will be raising the frequency and increasing the distortion due to increased switching problems. Until considerably better switching transistors are available this is already at the practical limit. Bruno did his homework and it will be a mistake to try and second guess him in things that effect basic operation as this would. All the compromises were carefully thought out and every one has tradeoffs. Sorry, no simple answers like with class A triodes.
All this doesn’t mean the output cap quality don’t matter, it does. The cap quality will have a direct effect on the sonics and is one of the more sensitive parts in this regard.
Roger
Pasi P said:
The slew rating (DV/DT) of a cap relates to its ESR directly and is a measure of how much internal instantaneous power it can handle. This is important only in that any cap used should be rated much higher than what it will actually see. This is distinctly different from amp slew limit which is a function of the value of the output filter parts and other reactive feedback components. This is a designed in value and is not affected with a different cap unless you change the value. Note; this is not recommended without doing a complete simulation to determine the other value changes as well. With this self oscillating design using a smaller cap you will be raising the frequency and increasing the distortion due to increased switching problems. Until considerably better switching transistors are available this is already at the practical limit. Bruno did his homework and it will be a mistake to try and second guess him in things that effect basic operation as this would. All the compromises were carefully thought out and every one has tradeoffs. Sorry, no simple answers like with class A triodes.
All this doesn’t mean the output cap quality don’t matter, it does. The cap quality will have a direct effect on the sonics and is one of the more sensitive parts in this regard.
Roger
Re: Output cap quality
Are you sure that both of you talk about the same thing??
Roger talks about technical aspect of what power a capacitor can handle while I have the feeling that Pasi P wants to know whether the slew rate of the UcD can be improved by changing the output cap.
Pasi P is correct to think that the output cap limits the slew-rate. This is true for designs that take the feedback before the output filter. However, UcD takes the feedback after the filter and therefore the slew-rate is almost cap and load impedance independent.
Best regards
Gertjan
sx881663 said:
Are you sure that both of you talk about the same thing??
Roger talks about technical aspect of what power a capacitor can handle while I have the feeling that Pasi P wants to know whether the slew rate of the UcD can be improved by changing the output cap.
Pasi P is correct to think that the output cap limits the slew-rate. This is true for designs that take the feedback before the output filter. However, UcD takes the feedback after the filter and therefore the slew-rate is almost cap and load impedance independent.
Best regards
Gertjan
Slew rate??
Yes, sometimes I am not too clear. 🙄 I was trying to separate a caps slew rate spec. from the actual amps slew rate. One has nothing to do with the other. Reading it on a cap spec sheet can be confusing as to what it really means. Basic rate of voltage change (volts/us) is determined by available current and capacitive value. Only changing the cap value will affect this unless the current source can be boosted somehow. The cap value was carefully chosen and shouldn't be arbitrarily changed. There are a lot of not easily measured effects that would occur with a change to a lower value, not the least of which would be increased EMI.
Roger
Yes, sometimes I am not too clear. 🙄 I was trying to separate a caps slew rate spec. from the actual amps slew rate. One has nothing to do with the other. Reading it on a cap spec sheet can be confusing as to what it really means. Basic rate of voltage change (volts/us) is determined by available current and capacitive value. Only changing the cap value will affect this unless the current source can be boosted somehow. The cap value was carefully chosen and shouldn't be arbitrarily changed. There are a lot of not easily measured effects that would occur with a change to a lower value, not the least of which would be increased EMI.
Roger
Found this in an old newsgroup concerning slew rate (it's nothing official...)
So is the slew rate a factor in the relatively limited bandwidth of class-D amps?
I've also read that lower slew rates have a more "tube like" sound.
Still *sounds* fine to me though 😀
Edit: Of course, it all seems a bit like THD, "unreal" specs... Who's going to drive 200W of say, 10khz into their speakers. You won't be happy doing that...
So is the slew rate a factor in the relatively limited bandwidth of class-D amps?
I've also read that lower slew rates have a more "tube like" sound.
Still *sounds* fine to me though 😀
Edit: Of course, it all seems a bit like THD, "unreal" specs... Who's going to drive 200W of say, 10khz into their speakers. You won't be happy doing that...
Hi,
one thing that is often overlooked in class-D is current slew rate limitation imposed by the output inductor. In UcD400 with 60V supply voltage slew rate is Vsupply/Lout =60V/30uH=2A/us. So even without output capacitor, slew rate into 4 ohm load can not exceed 8V/us. BTW, 30uH inductor is nicely calculated to give just 21.2kHz full power bandwidth into 4 Ohm.
Best regatds,
Jaka Racman
one thing that is often overlooked in class-D is current slew rate limitation imposed by the output inductor. In UcD400 with 60V supply voltage slew rate is Vsupply/Lout =60V/30uH=2A/us. So even without output capacitor, slew rate into 4 ohm load can not exceed 8V/us. BTW, 30uH inductor is nicely calculated to give just 21.2kHz full power bandwidth into 4 Ohm.
Best regatds,
Jaka Racman
Hi,
You make it sound like the UCD module is dancing on the razor's edge.
I agree one should be aware of the system, I dont' think a full simulation will be of any help given some of the other devices in question are encapsulated, and trying to get at that may be highly destructive.
I think if you stay within what Bruno recommended it will be A OK without having to worry about the rest of it. You may really like what a faster Fs can do especially at higher power output, assuming we can afford the extra heat. It may also open up other capacitor possibilities /sizes etc.
I somehow doubt frequency was Bruno's concern when he gave those limits to play with, filter response is likely to be "more"
the issue, that will be thrown off long before an increased Fs becomes an issue I think.
It would be interesting to see how fast the modules can clock at without self destructing, but I think there's a pretty good margin from what it's at now. I say that because I agree with you, homework was done to say the very least, and it is built well. A slight increase to something like 600Khz seems reasonable.
Disclaimer of the day:
Obviously I'm assuming alot here.. but only if _you_ take _my_ word on it where _your_ module is concerned.
Regards,
Chris
You make it sound like the UCD module is dancing on the razor's edge.
I agree one should be aware of the system, I dont' think a full simulation will be of any help given some of the other devices in question are encapsulated, and trying to get at that may be highly destructive.
I think if you stay within what Bruno recommended it will be A OK without having to worry about the rest of it. You may really like what a faster Fs can do especially at higher power output, assuming we can afford the extra heat. It may also open up other capacitor possibilities /sizes etc.
I somehow doubt frequency was Bruno's concern when he gave those limits to play with, filter response is likely to be "more"
the issue, that will be thrown off long before an increased Fs becomes an issue I think.
It would be interesting to see how fast the modules can clock at without self destructing, but I think there's a pretty good margin from what it's at now. I say that because I agree with you, homework was done to say the very least, and it is built well. A slight increase to something like 600Khz seems reasonable.
Disclaimer of the day:
Obviously I'm assuming alot here.. but only if _you_ take _my_ word on it where _your_ module is concerned.
Regards,
Chris
Language barrier!
Chris,
Sorry, I didn't mean to imply that at all. No actually this is the most solid amp I have had experience with, nothing seems it faze it! Wide operating voltages, wide load range, bring em on!
The point I was trying to make was that the present values were chosen carefully using parameters we are not fully aware of. I do realize there is quite a bit of slop to cover production tolerances, different vendors, etc. and probably a lot of room to maneuver but I don't want anyone to fry a module because of a statement I make. I would be less careful of my own but don’t want to have to replace it either.
Roger
Chris,
Sorry, I didn't mean to imply that at all. No actually this is the most solid amp I have had experience with, nothing seems it faze it! Wide operating voltages, wide load range, bring em on!
The point I was trying to make was that the present values were chosen carefully using parameters we are not fully aware of. I do realize there is quite a bit of slop to cover production tolerances, different vendors, etc. and probably a lot of room to maneuver but I don't want anyone to fry a module because of a statement I make. I would be less careful of my own but don’t want to have to replace it either.
Roger
Jaka Racman said:
Thanks for the reply. Yes the entire output filter is involved not just the cap. There also is the time between clocks to consider as an ultimate limit. As you pointed out the limit was carefully chosen. I do wonder if the upper limit could be extended a bit so it was flatter at least to 20KHz. Do you think this would have much of a negative effect on residual noise and EMI?
Roger
Hi Roger,
Well, IIRC small signal bandwidth of UcD is about 35kHz, and is not load dependant until power bandwidth limit comes into effect. But full power bandwidth at 20kHz into low impedance is not necessary for music signals, in fact it might be even preferable to limit it. You could increase power bandwidth into low impedance load by decreasing inductance to 14uH and increasing filter capacitor to 1.5uF. That could be simply achieved by paralleling aditional capacitor and inductor to the existing ones.
In theory, this could even decrease EMI, since it would allow Mosfets to achieve resonant transitions over larger output signal amplitudes. In praxis, paralleling would certainly worsen EMI, replacement could achieve equal results if replacement cap would have equally low ESL.
But I do not think this is a god idea to implement. Finally, here is quote what Bruno wrote about the subject:
Best regards,
Jaka Racman
Well, IIRC small signal bandwidth of UcD is about 35kHz, and is not load dependant until power bandwidth limit comes into effect. But full power bandwidth at 20kHz into low impedance is not necessary for music signals, in fact it might be even preferable to limit it. You could increase power bandwidth into low impedance load by decreasing inductance to 14uH and increasing filter capacitor to 1.5uF. That could be simply achieved by paralleling aditional capacitor and inductor to the existing ones.
In theory, this could even decrease EMI, since it would allow Mosfets to achieve resonant transitions over larger output signal amplitudes. In praxis, paralleling would certainly worsen EMI, replacement could achieve equal results if replacement cap would have equally low ESL.
But I do not think this is a god idea to implement. Finally, here is quote what Bruno wrote about the subject:
Best regards,
Jaka Racman
did bypass coupling cap mod what next ?
Hi guys , I am new at this .
just did the short the coupling cap mod.
mearsur dc offset .012v & .029v . is that good enought ?
sound is great , before mod the bass was thin now I have good bass.
so what is the next mod ? that a newbie like me can do ?
thanks for any help .😀
Hi guys , I am new at this .
just did the short the coupling cap mod.
mearsur dc offset .012v & .029v . is that good enought ?
sound is great , before mod the bass was thin now I have good bass.
so what is the next mod ? that a newbie like me can do ?
thanks for any help .😀
Re: did bypass coupling cap mod what next ?
These are good numbers. I gather you have a preamp that already has caps on the output? Be aware of the fact that the next one may be direct coupled and introduce more offset. You would want to try it first by measuring the amp the output without the speakers connected. I have seen systems work fine with up to .6 volts or so but would recommend it be less than .06 volts for the best sound. Even a small amount of offset will heat the voice coil of the speaker which hurts its performance. Remember the voice coil is low DC resistance so it doesn’t take much voltage to get significant current.
Roger
jj2 said:
These are good numbers. I gather you have a preamp that already has caps on the output? Be aware of the fact that the next one may be direct coupled and introduce more offset. You would want to try it first by measuring the amp the output without the speakers connected. I have seen systems work fine with up to .6 volts or so but would recommend it be less than .06 volts for the best sound. Even a small amount of offset will heat the voice coil of the speaker which hurts its performance. Remember the voice coil is low DC resistance so it doesn’t take much voltage to get significant current.
Roger
the pre amp is a 10K passive with no cap.
what do mean ?
"Be aware of the fact that the next one may be direct coupled and introduce more offset"
next pre amp or next mod ?
do you think I should put a 2.2 Auricaps at the input to be safe , since I have a few tube pre amp that I would to try .
Thanks.😀
what do mean ?
"Be aware of the fact that the next one may be direct coupled and introduce more offset"
next pre amp or next mod ?
do you think I should put a 2.2 Auricaps at the input to be safe , since I have a few tube pre amp that I would to try .
Thanks.😀
Caps and stuff
Yes, I was referring to the next preamp you might try.
The passive preamp can introduce no DC when it is turned all the way down even with a lot coming in. It is safe as long as you always turn it down all the way when you turn the power on. If you hear loud clicking as you turn the control up that is telling you there is DC coming from the source and you need to stop and check it out. You also may see woofer cone motion.
Using a tube preamp will not be a problem going direct in with the amp DC coupled as the pre has to have an output cap, no need for another one. However if the pre has no turn on mute circuit you will have to turn it on first and let it warm up before turning on the amp. Turn off is the opposite, turn off the amp first then the pre.
Roger
Yes, I was referring to the next preamp you might try.
The passive preamp can introduce no DC when it is turned all the way down even with a lot coming in. It is safe as long as you always turn it down all the way when you turn the power on. If you hear loud clicking as you turn the control up that is telling you there is DC coming from the source and you need to stop and check it out. You also may see woofer cone motion.
Using a tube preamp will not be a problem going direct in with the amp DC coupled as the pre has to have an output cap, no need for another one. However if the pre has no turn on mute circuit you will have to turn it on first and let it warm up before turning on the amp. Turn off is the opposite, turn off the amp first then the pre.
Roger
off topic
cheap transformer volume controls
I have a 10K Stepped Attenuator , can I connect it to only one set of tap (winding) of the transformer of a "radioshack 100W In-Wall Stereo Volume Control" part # 40-987,and use it like a transformer volume control ?
variable pot, fix transformer.
cheap transformer volume controls
I have a 10K Stepped Attenuator , can I connect it to only one set of tap (winding) of the transformer of a "radioshack 100W In-Wall Stereo Volume Control" part # 40-987,and use it like a transformer volume control ?
variable pot, fix transformer.
I have plans to make passive pre amp using Dact stepped attenuator.
(6ch attenuator after my Orions 3-way active filter to keep noise low)
I have think if i put in the box also (3 pcs) this active preamp module http://www.dact.com/html/line_stages.html , and bypass input stage of UCD.
Quality of this module should be better than input stage of UCD. Ofcource it cost with psu(s) not so little but not arm and leg. Any downside if i do that?
Should this active module better to put near UCD or in attenuator box?
(6ch attenuator after my Orions 3-way active filter to keep noise low)
I have think if i put in the box also (3 pcs) this active preamp module http://www.dact.com/html/line_stages.html , and bypass input stage of UCD.
Quality of this module should be better than input stage of UCD. Ofcource it cost with psu(s) not so little but not arm and leg. Any downside if i do that?
Should this active module better to put near UCD or in attenuator box?
Re: off topic
This could be done but why? I would expect a big hit on sound quality as this transformer is made for speaker level signals and would be way too low of impedance for line level use. If you just are looking for extra "free" (not really) gain you need to use something like the Jensen JT11 that was made for this kind of application. It has a split primary and secondary so with the primary in parallel and the secondary in series you have a 2:1 gain increase. If this isn't enough you really need some active device or the gain of the amp can be set higher. Also put the control inside the amp box and make it into an integrated. Doing this allows short connections to the amp and you don't have to have extra noise or HF roll off.
Roger
jj2 said:cheap transformer volume controls
I have a 10K Stepped Attenuator , can I connect it to only one set of tap (winding) of the transformer of a "radioshack 100W In-Wall Stereo Volume Control" part # 40-987,and use it like a transformer volume control ?
variable pot, fix transformer.
This could be done but why? I would expect a big hit on sound quality as this transformer is made for speaker level signals and would be way too low of impedance for line level use. If you just are looking for extra "free" (not really) gain you need to use something like the Jensen JT11 that was made for this kind of application. It has a split primary and secondary so with the primary in parallel and the secondary in series you have a 2:1 gain increase. If this isn't enough you really need some active device or the gain of the amp can be set higher. Also put the control inside the amp box and make it into an integrated. Doing this allows short connections to the amp and you don't have to have extra noise or HF roll off.
Roger
Pasi P said:
I doubt very seriously it is better sounding than the UcD input stage especially if you have the 8620 version. The Idea of making your passive with this part is not all bad and I am sure it will beat most commercial units when it is finished.
Don’t Jumper out the input circuit of the UcD as this defeats the amps fully balanced operation. There are many and various reasons why this is bad but the bottom line is it wouldn't sound as good.
Roger
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