7812/7912 Input Clamps
You can safely limit the voltage on the inputs by using a volatge dropping resistor between the +/-58V and the input to the regulators and putting 18 Volt Zener Diodes on the front of the regualtors. The Zeners will limit the voltage the regualtors see to 18 volts and the resistors will drop the extra 40 volts.
You can safely limit the voltage on the inputs by using a volatge dropping resistor between the +/-58V and the input to the regulators and putting 18 Volt Zener Diodes on the front of the regualtors. The Zeners will limit the voltage the regualtors see to 18 volts and the resistors will drop the extra 40 volts.
might as well go the SMPSU way...then a Linear Reg. and a choke...seriously...I dun think dropping from that high a voltage is a good idea...
Zeners
What is a SMPSU? There's no problem dropping the voltage. Look at the schematic of any high power solid state amp and it'll have high voltage (60 to 100) volt rails and it'll have zeners in there that create a regualted voltage for the front end of the amp where those voltage would be too high. I wouldn't use a choke and if I was going to I'd put it before the regulator. Between the resistor, zener, and regulators it'll be very quiet. If you need more power supply rejection use LM317/LM337 instead of 7812/7912.
li_gangyi said:
What is a SMPSU? There's no problem dropping the voltage. Look at the schematic of any high power solid state amp and it'll have high voltage (60 to 100) volt rails and it'll have zeners in there that create a regualted voltage for the front end of the amp where those voltage would be too high. I wouldn't use a choke and if I was going to I'd put it before the regulator. Between the resistor, zener, and regulators it'll be very quiet. If you need more power supply rejection use LM317/LM337 instead of 7812/7912.
Re: Zeners
Switched Mode Power Supply Unit
http://www.acronymfinder.com/af-query.asp?String=exact&Acronym=smpsu
BTW: What is lol which some people write here and there?
According to www.acronymfinder.com I can't find anything suitable.
Laugh Out Loud Laughing Out Loud
Lack of Love (game)
Ladies of Lallybroch
Land O' Lakes
Language of Literature
Language of Love
Last or Least
Laughing On Line
Lautes Online Lachen (German: Loud Online Laughter)
Lawyers on Line
League of Losers (wild 17 chess team)
Legend of Legaia (video game)
Less Of Lip
Lewd Obscene Language
Life of the Land
Limited Operation Life
List Of Lights
Little Old Lady
Live-On-Line
EE_Mark said:
Switched Mode Power Supply Unit
http://www.acronymfinder.com/af-query.asp?String=exact&Acronym=smpsu
BTW: What is lol which some people write here and there?
According to www.acronymfinder.com I can't find anything suitable.
Laugh Out Loud Laughing Out Loud
Lack of Love (game)
Ladies of Lallybroch
Land O' Lakes
Language of Literature
Language of Love
Last or Least
Laughing On Line
Lautes Online Lachen (German: Loud Online Laughter)
Lawyers on Line
League of Losers (wild 17 chess team)
Legend of Legaia (video game)
Less Of Lip
Lewd Obscene Language
Life of the Land
Limited Operation Life
List Of Lights
Little Old Lady
Live-On-Line
Switching Power Supplies are noisy
NEVER use a switching power supply in an audio amp if you want high quality. Switching supplies spew out lots of noise and no matter how much filtering you use you can never get rid of it all.
fdegrove said:
NEVER use a switching power supply in an audio amp if you want high quality. Switching supplies spew out lots of noise and no matter how much filtering you use you can never get rid of it all.
LOL Lying Out Loud
Mmm maybe you have a different acronymfinder in Sweden.
http://www.acronymfinder.com/af-query.asp?String=exact&Acronym=LOL&Find=Find
LOL Laugh Out Loud
LOL Laughing Out Loud
LOL Lack of Love (game)
LOL Ladies of Lallybroch
LOL Land O' Lakes
LOL Language of Literature
LOL Language of Love
LOL Last or Least
LOL Laughing On Line
LOL Lautes Online Lachen (German: Loud Online Laughter)
LOL Lawyers on Line
LOL League of Losers (wild 17 chess team)
LOL Legend of Legaia (video game)
LOL Less Of Lip
LOL Lewd Obscene Language
LOL Life of the Land
LOL Limited Operation Life
LOL List Of Lights
LOL Little Old Lady
LOL Live-On-Line
LOL Living on Line
LOL Load of Laughs
LOL Loads of Love
LOL Log On Later
LOL Longitudinal Output Level
LOL Lord Oh Lord
LOL Lords of Legend (gaming)
LOL Loss of Life (insurance)
LOL Loss of Light
LOL Loss of Load
LOL Loss of Lock
LOL Lot of Lamers
LOL Lots of Lag (on-line gaming)
LOL Lots Of Laughs/Laughter
LOL Lots of Losers (Rocket Arena 3 clan)
LOL Lots Of Love
LOL Lots Of Luck
LOL Love On Line
LOL Low Order Language
LOL Lower Operating Limit
LOL Loyal Orange Lodge
LOL Lunatics on Line
LOL Lying Out Loud
Looks like you where using the last LOL ;-)
Cheers,
Bas
Mmm maybe you have a different acronymfinder in Sweden.
http://www.acronymfinder.com/af-query.asp?String=exact&Acronym=LOL&Find=Find
LOL Laugh Out Loud
LOL Laughing Out Loud
LOL Lack of Love (game)
LOL Ladies of Lallybroch
LOL Land O' Lakes
LOL Language of Literature
LOL Language of Love
LOL Last or Least
LOL Laughing On Line
LOL Lautes Online Lachen (German: Loud Online Laughter)
LOL Lawyers on Line
LOL League of Losers (wild 17 chess team)
LOL Legend of Legaia (video game)
LOL Less Of Lip
LOL Lewd Obscene Language
LOL Life of the Land
LOL Limited Operation Life
LOL List Of Lights
LOL Little Old Lady
LOL Live-On-Line
LOL Living on Line
LOL Load of Laughs
LOL Loads of Love
LOL Log On Later
LOL Longitudinal Output Level
LOL Lord Oh Lord
LOL Lords of Legend (gaming)
LOL Loss of Life (insurance)
LOL Loss of Light
LOL Loss of Load
LOL Loss of Lock
LOL Lot of Lamers
LOL Lots of Lag (on-line gaming)
LOL Lots Of Laughs/Laughter
LOL Lots of Losers (Rocket Arena 3 clan)
LOL Lots Of Love
LOL Lots Of Luck
LOL Love On Line
LOL Low Order Language
LOL Lower Operating Limit
LOL Loyal Orange Lodge
LOL Lunatics on Line
LOL Lying Out Loud
Looks like you where using the last LOL ;-)
Cheers,
Bas
OK, I thought so but I can't figure what is so funny because these "lol"'s are in plain text. Skinnyboy uses it a lot for example.fdegrove said:
Hi,
His way of indicating he's having fun, I suppose?
I have no idea what it is he's smoking...
Cheers,😉
His way of indicating he's having fun, I suppose?
I have no idea what it is he's smoking...
Cheers,😉
lets stick to the topic...yes I do know that most amps with an opamp infront have got zeners...but even then we push for seperate supplies as it improves the sound a lot...so it's up to you...either a zener/Linear regulator with a suitable resistor in front...or a seperate trfo...SMPSUs are not fit for audio..except in cars where there issimply no other choice...
You can use a couple of cheap variable regulators to pre-regulate the voltages to a safe input level for the 12 V regulators. Use LM317 and LM337 for example. These regulators do not care how high the input voltage is; the restriction is that the input - output cannot be more than a certain limit. This is because they are not referenced to ground (like 78xx types) but instead, the adjustment terminal floats. So use the LM317/337 to drop to about +-30 V (check the input-output limits for them though), and use that as the input for the 7812/7912.
(p.s. try to get "A" versions of the 12 V regulators: LM7812A for example; they have lower output noise).
(p.s. try to get "A" versions of the 12 V regulators: LM7812A for example; they have lower output noise).
yeah and the T version can source an upgraded 3A like the 78T12...the L version is for 100mA...like a 78L12...becareful what you get there...I woulkd personally see if I can wind a few windings for 15VAC, get it rectified filtered and then regulated down using a Linear Reg...but that will depend on what kinda trafo you're planning to use...
The funny thing about SMPS-hate in audio is that the usual 50Hz transformer plus diode bridge and storage capacitors is also a SMPS because there are four switching components [diodes] performing a total of 400 switch on and switch off events per second and with a duty cycle of les than 30% [typ 15%] so peak switching currents are 4..7 times total output current and heating losses are 4..7 times grater than expected
Funier is the fact that toroidal or EI transformers usually humm strongly because they are operated at a too high magnetic flux and AC mains allways contains some DC so the core is periodically saturating, instantaneusly performing as if there were no core and generating huge instantaneous stray magnetic fields [the simple loop-of-wire probe allways tells the truth]
Even funnier is the fact that 50Hz supplies use no filtering, no shielding and no attention is put on the layout to cancel magnetic fields caused by those high currents flowing through long wires forming big loops so all those ripple voltages and currents [translated into magnetic fields] fully in the audio range [100Hz-20Khz] reach directly all small-signal circuits in the nearhood
In comparison, I think that the classical DIY 50Hz supply in noise terms is fully comparable to a unshielded, unfiltered, loosy regulated flyback SMPS [high peak current, low duty cycle as in 50Hz] with random subsonics on its output [due to AC mains peak value fluctuations when my fridge or my washing machine turns on]
To get low noise from a 50Hz [SMPS] supply, SMPS design techniques should also be used, dont't think that it won't radiate and generate any noise just because it runs at 50Hz
Belive it or not, most simple DIY 50Hz supplies won't be able to pass any EMI tests
Don't like switching? Use batteries but don't blame SMPS, 50Hz supplies are as SMPS as 50Khz or 100Khz ones and I prefer some milivolts of 100Khz or 200Khz ripple rather than some volts of 50Hz-20Khz ripple since it's by far outside the audio band and it can't be worse than having it fully in the audio band
For down regulating 58V to 12V I suggest going discrete
A very simple alternative [and less noisier than 78xx I think] would be to use some cheap TO-126 or TO-220 100V darlington transistors [see BD68x and TIP 1xx families] with heatsinks [or placed in the main heatsink together with output devices] as emitter followers with zeners as references to ground, with everything properly biased and capacitively decoupled
Having such a high gain [10.000], load steps of say 50mA should cause only milivolts of voltage drop
Instead of a zener, a TL431 shunt reference could be used to get very high line regulation [for this option, a simple transistor works better because too high gain will cause unstability troubles because TL431 has already high internal gain and usually needs some compensation]
For very low currents [10mA or less] you can even supress the buffer transistor and use a simple 5..10W resistor plus zener or resistor plus TL431 network
All these options will have slow and progressive turn-on as the supply voltage rises [defined by an RC filter] and will be operative before the output stage has enough supply voltage to deliver any dangerous DC component
Funier is the fact that toroidal or EI transformers usually humm strongly because they are operated at a too high magnetic flux and AC mains allways contains some DC so the core is periodically saturating, instantaneusly performing as if there were no core and generating huge instantaneous stray magnetic fields [the simple loop-of-wire probe allways tells the truth]
Even funnier is the fact that 50Hz supplies use no filtering, no shielding and no attention is put on the layout to cancel magnetic fields caused by those high currents flowing through long wires forming big loops so all those ripple voltages and currents [translated into magnetic fields] fully in the audio range [100Hz-20Khz] reach directly all small-signal circuits in the nearhood
In comparison, I think that the classical DIY 50Hz supply in noise terms is fully comparable to a unshielded, unfiltered, loosy regulated flyback SMPS [high peak current, low duty cycle as in 50Hz] with random subsonics on its output [due to AC mains peak value fluctuations when my fridge or my washing machine turns on]
To get low noise from a 50Hz [SMPS] supply, SMPS design techniques should also be used, dont't think that it won't radiate and generate any noise just because it runs at 50Hz
Belive it or not, most simple DIY 50Hz supplies won't be able to pass any EMI tests
Don't like switching? Use batteries but don't blame SMPS, 50Hz supplies are as SMPS as 50Khz or 100Khz ones and I prefer some milivolts of 100Khz or 200Khz ripple rather than some volts of 50Hz-20Khz ripple since it's by far outside the audio band and it can't be worse than having it fully in the audio band
For down regulating 58V to 12V I suggest going discrete
A very simple alternative [and less noisier than 78xx I think] would be to use some cheap TO-126 or TO-220 100V darlington transistors [see BD68x and TIP 1xx families] with heatsinks [or placed in the main heatsink together with output devices] as emitter followers with zeners as references to ground, with everything properly biased and capacitively decoupled
Having such a high gain [10.000], load steps of say 50mA should cause only milivolts of voltage drop
Instead of a zener, a TL431 shunt reference could be used to get very high line regulation [for this option, a simple transistor works better because too high gain will cause unstability troubles because TL431 has already high internal gain and usually needs some compensation]
For very low currents [10mA or less] you can even supress the buffer transistor and use a simple 5..10W resistor plus zener or resistor plus TL431 network
All these options will have slow and progressive turn-on as the supply voltage rises [defined by an RC filter] and will be operative before the output stage has enough supply voltage to deliver any dangerous DC component
Cacaded Regulators
Unless you plan to put some filters between the regulators don't put regulators back to back; they can osciallatr between one another. A much better and simpler way would be to use a resistor and a zener diode. Since the resistor would work better than the regulator, cost less, tolerate heat better, and doesn't need filtering there is no benefit to risking the ocillations that can occur when 2 regulaors are used in series.
macboy said:
Unless you plan to put some filters between the regulators don't put regulators back to back; they can osciallatr between one another. A much better and simpler way would be to use a resistor and a zener diode. Since the resistor would work better than the regulator, cost less, tolerate heat better, and doesn't need filtering there is no benefit to risking the ocillations that can occur when 2 regulaors are used in series.
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