hi cristi
thank you very much for your help
i would like to go for the SAP 15 as recommended and a speaker protection ckt
on the power supply part, i was leaning towards linear supplies because its easy to replace components where i live if a fault occurs
SMPS is difficult
I was curious about using SMPS with high-quality Class B power amps.
AFAIK SMPS introduces high-frequency noise to the output rails, which then affect the sound quality of the power amp (I'm assuming ordinary Class B topologies which don't have extremely high PSRR specially at high frequencies). Is this correct?
If yes, can we take care of this by replacing the normal C with a C-R-C "pi" filter on each rail between the SMPS and the power amp's supply rails, where the value of each C will be equal to what one would normally use in a traditional PSU (e.g. 10,000uF/rail for a 100W Class B channel) and the R would be something like 0.5 Ohm 10-20Watt. Basically, I'm suggesting that for a 100W mono power amp, I'll put a 10,000uF capacitor block, then a resistor of 0.5 Ohm or so, then another 10,000uF capacitor block, on each rail.
Will this allow pretty much any SMPS, (e.g. you A350SMPS) to be used with any Class B amp?
AFAIK SMPS introduces high-frequency noise to the output rails, which then affect the sound quality of the power amp (I'm assuming ordinary Class B topologies which don't have extremely high PSRR specially at high frequencies). Is this correct?
If yes, can we take care of this by replacing the normal C with a C-R-C "pi" filter on each rail between the SMPS and the power amp's supply rails, where the value of each C will be equal to what one would normally use in a traditional PSU (e.g. 10,000uF/rail for a 100W Class B channel) and the R would be something like 0.5 Ohm 10-20Watt. Basically, I'm suggesting that for a 100W mono power amp, I'll put a 10,000uF capacitor block, then a resistor of 0.5 Ohm or so, then another 10,000uF capacitor block, on each rail.
Will this allow pretty much any SMPS, (e.g. you A350SMPS) to be used with any Class B amp?
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Since Class B does not have a constant input current, I'm assuming a CRC will not be particularly effective and will either waste power at high outputs or be too low in resistance to have any effect.
I've used 0.1 ohm resistors in a similar configuration and there is extremely little difference.
Using good decoupling will help avoid some of the issues caused by spurious switching noise, though it may be possible to get a switching supply with lower than 10mV of ripple and noise - which is difficult for even a good linear supply to achieve. As always, the devil is in the details.
I've used 0.1 ohm resistors in a similar configuration and there is extremely little difference.
Using good decoupling will help avoid some of the issues caused by spurious switching noise, though it may be possible to get a switching supply with lower than 10mV of ripple and noise - which is difficult for even a good linear supply to achieve. As always, the devil is in the details.
In realistic domestic use, Class B amps play at 1-5W RMS, and have a fairly high supply-line Zin, I would think. At very power levels, the PSU will see the amp as being almost straight-wire and will see the speaker impedance almost directly -- but at those power levels, who cares about small high-freq hash on the supply rails?
I would expect this too. I guess the difference will be more audible with more back-to-basics topologies which have worse PSRR. For instance, I remember a very good 55WPC DIY amp from Australia which recommends a dual-mono PSU, and apparently it's been confirmed in listening tests that this makes a difference. I suspect the amp has PSRR on the lower side. So I guess the C-R-C pi-filters will make audible differences only in the very high-end cases or with low-PSRR amps.
I was not hoping to reduce the magnitude of the ripple -- I just wanted to filter out the HF component from the ripple. Most Class B amps are quite immune to low-freq ripple of 10-20mV on the rails, I think.
Cristi,
From photo of your website:
300W LME49810 is at output power of 170W/8Ω with 3pairs of BJT
500W LME49810 is at output power of 320W/8Ω with 5pairs of BJT
1) What is the BJT used?
2) For stereo power amplifier, 2 pcs are required. Do you provide a pair of Left & Right mirror symmetry PCB?
3) Do plan to make LME49830 + Mosfet?
From photo of your website:
300W LME49810 is at output power of 170W/8Ω with 3pairs of BJT
500W LME49810 is at output power of 320W/8Ω with 5pairs of BJT
1) What is the BJT used?
2) For stereo power amplifier, 2 pcs are required. Do you provide a pair of Left & Right mirror symmetry PCB?
3) Do plan to make LME49830 + Mosfet?
Hi cristi,
Havnt spoken for some time, how are you?
Im looking for an amplifier for a pair of compression drivers that are 115db/1w.
I cannot use my ta3020v3d units I got from you a couple of years back, as the noise floor is too high for this extreme application- can you recommend an amp from your designs that would have the lowest noise floor at 0.1w??
Amp needs 20w+ output.
Havnt spoken for some time, how are you?
Im looking for an amplifier for a pair of compression drivers that are 115db/1w.
I cannot use my ta3020v3d units I got from you a couple of years back, as the noise floor is too high for this extreme application- can you recommend an amp from your designs that would have the lowest noise floor at 0.1w??
Amp needs 20w+ output.
The lowest noise floor class AB amplifiers are the LME49810 based amps, 300W and 500W versions and the LM4702 based amps, SAP1x, followed by MOS-FET and Bipolar versions.
I remember that your TA3020 boards were v2, not v3d, at that time only v2 was available, TA3020v3d is one of the newest version, with improved performances and noise ratio.
I remember that your TA3020 boards were v2, not v3d, at that time only v2 was available, TA3020v3d is one of the newest version, with improved performances and noise ratio.
i have a pair cristi`s smps1000a at 75volt.
i could use them and if i like them i will add linear supply 85volt for the
input stage.
have you heard them?
500W into 8r0 is equivalent to >89Vpk. You can't get 89Vpk from a 75Vdc, nor from an 85Vdc supply.
500W into 4r0 is equivalent to >63Vpk.
You should be able to get that from a 75Vdc supply. You will be able to easily achieve that with an 85Vdc supply.
But this will only happen if the current demand can be met, without significant drop in the supply voltage.
For 63Vpk into a resistor test load, the PSU must be able to deliver >15Apk to the load.
For effective performance into a reactive speaker the minimum current delivery must be at least 30Apk into a 4ohms load and preferably >45Apk. Again without significant drop in supply voltage.
Can either supply deliver those levels of current to the load?
500W into 4r0 is equivalent to >63Vpk.
You should be able to get that from a 75Vdc supply. You will be able to easily achieve that with an 85Vdc supply.
But this will only happen if the current demand can be met, without significant drop in the supply voltage.
For 63Vpk into a resistor test load, the PSU must be able to deliver >15Apk to the load.
For effective performance into a reactive speaker the minimum current delivery must be at least 30Apk into a 4ohms load and preferably >45Apk. Again without significant drop in supply voltage.
Can either supply deliver those levels of current to the load?
For a Class AB amplifier such as LME49810 based one, there is no advantage at all to supply the power stage with more than +-70 to +-75V while willing to achieve 500W on 4R. any extra voltage will only increase the amplifier losses, reducing the efficiency. The power supply has regulated output voltage and if the maximum current is exceeded the smps will simply shut down for a brief period (2 sec.) and restart again if the overcurrent condition was removed. will not drop the voltage or sag like a classic mainstransformer+rectifier bridge+caps power supply.
while doing the math I found the RMS current for 500W 4R ~11.2 and peak current ~16R. even in the worse case scenario where the speaker impedance drop to half, the peak current will be ~22.3A, slightly less than the values calculated earlier.
The power supply which @Back wants to use can deliver approx. 6.5A at +-75 V and a peak of 8A. You might want to say that is far less than required, that's true, if we use the amp for playing sine or square waves, but for music with crest factor of 1/8 to max. 1/3 I would say that it might be enough. For this application (LME49810 Amp + A1000SMPS) some extra 8200-10000uF caps should be added on each rail.
The smps will provide the average power, then the large caps will provide the energy reserve for peaks. In this way we might get it work much more cheaper than using a power supply capable to deliver 45A at +-75V (6750W) for a 500W class AB amplifier.
while doing the math I found the RMS current for 500W 4R ~11.2 and peak current ~16R. even in the worse case scenario where the speaker impedance drop to half, the peak current will be ~22.3A, slightly less than the values calculated earlier.
The power supply which @Back wants to use can deliver approx. 6.5A at +-75 V and a peak of 8A. You might want to say that is far less than required, that's true, if we use the amp for playing sine or square waves, but for music with crest factor of 1/8 to max. 1/3 I would say that it might be enough. For this application (LME49810 Amp + A1000SMPS) some extra 8200-10000uF caps should be added on each rail.
The smps will provide the average power, then the large caps will provide the energy reserve for peaks. In this way we might get it work much more cheaper than using a power supply capable to deliver 45A at +-75V (6750W) for a 500W class AB amplifier.
the supplies are 1100watt continues with adjustable voltage 75-95volt and i will use
one per channel.
no voltage drop, they are regulated.
here is the datasheet with current capabilty vs voltage but i think your calculations
are too stiff.
suppose that the psu is capable to deliver that current.
that would be translated to at least 1500watt peaks.
you think the module will be able to survive that?
the load will be about 3ohms so it`s even worse.
p.s.have you heard them?
one per channel.
no voltage drop, they are regulated.
here is the datasheet with current capabilty vs voltage but i think your calculations
are too stiff.
suppose that the psu is capable to deliver that current.
that would be translated to at least 1500watt peaks.
you think the module will be able to survive that?
the load will be about 3ohms so it`s even worse.
p.s.have you heard them?
cristi those power supplies powering hypex ucd2k`s (ok they are more efificient but still) where able to
easily to drive the speakers to their limit.
i believe the power is enough but my question have to do with how they
sound.
ps.i believe i could change a resistor to make them go lower than 75 volts
since the load is small?
minimum is 3 ohm at 180hz i measured it.
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On the last boards version, R43, the resistor in series with the potentiometer which allow voltage adjustment. for lower voltage need to reduce the value of this resistor proportionally with the value which you want to obtain. Do not use larger value and never start the power supply without this resistor as the control loop will be open, and the output voltage will jump to extreme values, over +-100V and can possibly damage components, especially the capacitors.
Cristi,
I'd like to build a two-channel 500W-LME4981 amplifier.
Is the SMPS2000R sufficient or would the SMPS3K6QR be a better choice? I notice the 3k6 has dual output voltages. Would this be a better match for the separate driver and power stage capable LME4981?
Any other thoughts and considerations?
I'd like to build a two-channel 500W-LME4981 amplifier.
Is the SMPS2000R sufficient or would the SMPS3K6QR be a better choice? I notice the 3k6 has dual output voltages. Would this be a better match for the separate driver and power stage capable LME4981?
Any other thoughts and considerations?
SMPS2000R can be used to supply two LME49810-500W modules, it has regulated output voltage so the higher voltage rails for driver and input stage is not absolutely required like when a linear supply or unregulated output smps is used. the output voltage of SMPS2000R can be adjusted to about 80-82V (+-84v version) to be able to deliver the rated output power. If the full power is not always required, and slightly lower power dissipation is the goal, the +-72V version is suitable as well with the output voltage set to +-75V. In any case the amplifier modules must be installed with the heatsink outside the housing for better cooling or a cooling fan should be used for better cooling.
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