BWRX said:
Hi, This is a confusing matter, let's organize.
(1) the power I NEED
is actually several W. for instance, I applied 4.8 V and 0.23A was used(there are V/I meter on power supply, yes actual measured).
This is 1.1W and actual sound will be 85% = 0.94W.
It's enough for 500 sqft room, listening Classics.
I don't want to make earthquake.🙂
(2) Chip Spec not a real useage
I used TAS5121 and spec is 100W/chip @ 30V power supply.
This is too much from what I need and I have no interest to make > 10W power.
(3) Power Supply selection
So I'm using little LAB power supply. 18V/3A is too much for me.
(4) TAS5261 input signal and output power
TAS5261(or my TAS5121) can not recognize signal source is TAS5518 or TPA2001.
Still you can control final output power by PVDD. (tas5261.pdf page 1, right bottom)
So I will make paraphrase as..
If you apply too much PVDD to TAS5261, you need very(too) small analog attenuated input to TPA2001.
And, I think there are no relation between 3.3V and PVDD. TPA2001's gain setting only effects pulse width. (PWM input signal to TAS5261 have to be 3.3V, this is digital signal)
Control Volume by PVDD (final stage supply voltage) is completely different from "control the volume with a simple pot at the input just as you normally would" but please understand me🙂. They are already running in my room.
Hi Koon.
Sorry if I came across as too critical.
I did not realize you were quoting the specs given by the manufacturer for a specific rail voltage. I thought you were stating the power output specs of your prototype with the supply you were using because you didn't state otherwise.
I fully understand that little wattage can be used to achieve high SPLs. It's all about the sensitivity of your speakers and the volume of the room they're in. The amps I use in my system right now can only put out a maximum of 7Wrms into 8ohms. They get plenty loud with my 90dB @ 1W/1m speakers in my small room 🙂
Yes, I understand that TI's "power supply volume control" is different from a potentiometer. PSVC changes the gain of the amplifier without changing the level of the input signal, while a potentiometer volume control changes the level of the input signal without changing the gain. The advantage of the PSVC is that it maximizes the SNR, however it is at the expense of a more complicated power supply.
The TPA2001s gain setting does only effect pulse width, and pulse width determines the level of the audio signal.
Think of it this way: If the TPA2001D1 has a gain of 2 and you feed it a 1V peak signal, it would output a 2V peak signal (after filtering) between its outputs. You feed that same unfiltered PWM signal to the TAS5261 and the PWM signal will be scaled from 0-3.3 to 0-PVDD, or it will be increased PVDD/3.3 times and is directly related to the gain of the amplifier as I stated earlier.
I would also argue that a PWM signal is not a digital signal, but I think everyone has heard that argument enough already 😉
Sorry if I came across as too critical.
I did not realize you were quoting the specs given by the manufacturer for a specific rail voltage. I thought you were stating the power output specs of your prototype with the supply you were using because you didn't state otherwise.
I fully understand that little wattage can be used to achieve high SPLs. It's all about the sensitivity of your speakers and the volume of the room they're in. The amps I use in my system right now can only put out a maximum of 7Wrms into 8ohms. They get plenty loud with my 90dB @ 1W/1m speakers in my small room 🙂
KOON3876 said:
Yes, I understand that TI's "power supply volume control" is different from a potentiometer. PSVC changes the gain of the amplifier without changing the level of the input signal, while a potentiometer volume control changes the level of the input signal without changing the gain. The advantage of the PSVC is that it maximizes the SNR, however it is at the expense of a more complicated power supply.
KOON3876 said:
The TPA2001s gain setting does only effect pulse width, and pulse width determines the level of the audio signal.
Think of it this way: If the TPA2001D1 has a gain of 2 and you feed it a 1V peak signal, it would output a 2V peak signal (after filtering) between its outputs. You feed that same unfiltered PWM signal to the TAS5261 and the PWM signal will be scaled from 0-3.3 to 0-PVDD, or it will be increased PVDD/3.3 times and is directly related to the gain of the amplifier as I stated earlier.
I would also argue that a PWM signal is not a digital signal, but I think everyone has heard that argument enough already 😉
If you were to come up with a fancy marketing term for it, that would be it 🙂
Technically, it is just a gain (voltage and current) stage.
Technically, it is just a gain (voltage and current) stage.
Brian,
Can we expand the term: TI's "power supply volume control"? I've seen a documentation on this but it seems way too complex for me to build it. Are the any examples of such volume control available in DIY world?
Marek
Can we expand the term: TI's "power supply volume control"? I've seen a documentation on this but it seems way too complex for me to build it. Are the any examples of such volume control available in DIY world?
Marek
Most amplifiers have a fixed gain, so we have to change the level of the input signal to change the level of the signal at the output. Power supply volume control changes the level of the signal at the output by changing the voltage of the power supply rail. This works with open loop class D PWM amplifiers because the level of the output signal is dependent on two things: the pulse widths and the voltage difference between the two output states. This changes the gain of the amplifier without changing the level of the input signal. This is easier to do with TI bridged output stages because a bridged output stage only requires a single voltage (0-PVDD).
TI's implementation of power supply volume control is simply a switch mode power supply with a variable reference voltage. Since the output voltage of the supply is proportional to the reference voltage, the output voltage can be changed by changing the reference voltage. This can be accomplished a number of ways. A digital way to do this is to use a DAC and a buffer. The digital word you provide to the DAC sets the reference voltage, which in turn sets the supply output voltage. There aren't many (if any) examples of this in the audio world because most supplies are designed to provide a constant output voltage that most amplifiers require.
TI's implementation of power supply volume control is simply a switch mode power supply with a variable reference voltage. Since the output voltage of the supply is proportional to the reference voltage, the output voltage can be changed by changing the reference voltage. This can be accomplished a number of ways. A digital way to do this is to use a DAC and a buffer. The digital word you provide to the DAC sets the reference voltage, which in turn sets the supply output voltage. There aren't many (if any) examples of this in the audio world because most supplies are designed to provide a constant output voltage that most amplifiers require.
TI's PSVC reference design is too complex for DIYers.
I think there are 2 way of easy implementation.
(1) Microcontroller programmable
Please see http://koon3876.blogspot.com/2006/11/easy-psvc-by-lm317.html
(2) Linear Amplifier
TAS5518 outputs 0V - 3.3V as PSVC reference voltage.
It should be applied to linear DC, Positive side only amplifier, as input voltage. if gain = 10, you will get 0V - 33V output.
I think there are 2 way of easy implementation.
(1) Microcontroller programmable
Please see http://koon3876.blogspot.com/2006/11/easy-psvc-by-lm317.html
(2) Linear Amplifier
TAS5518 outputs 0V - 3.3V as PSVC reference voltage.
It should be applied to linear DC, Positive side only amplifier, as input voltage. if gain = 10, you will get 0V - 33V output.
The TI implementation is complex, but it shouldn't be too difficult to make a variable output SMPS.
Your designs may work well for low power, but are not good for higher power use. My initial intended application for the TAS5261 is a sub amplifier.
Your designs may work well for low power, but are not good for higher power use. My initial intended application for the TAS5261 is a sub amplifier.
Ya, you're correct, variable power supply implemented with UC3849 will not have huge square inches.
Please see here.
http://koon3876.blogspot.com/2006/11/tact-s2150-inside.html
But switching power supply with variable voltage will have ..
http://koon3876.blogspot.com/2006/11/panasonic-xr70-inside.html
Way of TacT (large transformer + UC3849) will be better for DIY.
Please see here.
http://koon3876.blogspot.com/2006/11/tact-s2150-inside.html
But switching power supply with variable voltage will have ..
http://koon3876.blogspot.com/2006/11/panasonic-xr70-inside.html
Way of TacT (large transformer + UC3849) will be better for DIY.
Lookin' real good!!
(Next rev. I might be asking for the impossible: surface mount parts on one side, taller passive / active parts on reverse side. The idea would be to mount the board flat with the sm chips down, thermally connected to a flat aluminum case bottom to act as heat sinks for the board chips, the tall caps & coils, etc. sticking up = thus making for installation in a very slim height case.)
(Next rev. I might be asking for the impossible: surface mount parts on one side, taller passive / active parts on reverse side. The idea would be to mount the board flat with the sm chips down, thermally connected to a flat aluminum case bottom to act as heat sinks for the board chips, the tall caps & coils, etc. sticking up = thus making for installation in a very slim height case.)
The parts should be here next week. Time permitting, I should be able to have a board built and ready for functional testing late next week. If all goes well I'll start putting everyones orders together. If you just ordered a board and cores/wire your order will get shipped out sooner than those with parts kits.
FastEddy said:Lookin' real good!!
(Next rev. I might be asking for the impossible: surface mount parts on one side, taller passive / active parts on reverse side. The idea would be to mount the board flat with the sm chips down, thermally connected to a flat aluminum case bottom to act as heat sinks for the board chips, the tall caps & coils, etc. sticking up = thus making for installation in a very slim height case.)
Ed, you can do that with this board! I designed it that way from the beginning 🙂 It is intended to be mounted with the TAS5261 thermally connected to a flat aluminum heatsink of any size. The TAS5261 is the tallest component on that side of the board.
The wound toroids will have a height of about 1.25" off the board and the 4 large electrolytic caps will be the tallest components at 35.5mm for the 1500uF 63V caps I'll be using.
" ... I designed it that way from the beginning It is intended to be mounted with the TAS5261 thermally connected to a flat aluminum heatsink of any size. The TAS5261 is the tallest component on that side of the board. ..."
Well, Super!! (I didn't catch you napping) ... good approach = low profile board w/ large heatsink covering about the same sq/in. as the board itself plus a little more width & depth for connections, knobs, etc. = makes for a nice small container.
....
I may be trying to mount this board inside of another device ... maybe something like a DIY tweaked and hopefully improved dual channel pre-amp ala: http://www.behringer.com/MIC2200/index.cfm?lang=ENG = US$100 or less at online stores everywhere ... this thing gets terrible reviews, mostly 'cause the solid state EQ circuit is garbage, but the tube pre-amp side is quite good and suitable for some DIY upgrades to better quality. So, firsbee away the EQ board, rewire and tweak for quality audio, adding this 2 channel, high efficiency Class-D output stage >> seems like a good idea. Considering that the TPA2000 may have a distinct advantage as a controller / mixer / FX selector, etc. or even as a substitute EQ ... The idea here is to make a very light weight, tube front end pre-amp for stage performance = very road worthy with lots of options for switching input and output. .... Them musicians can't seem to kick the tube habit ... mostly cause they can distort them for their own "special sound". ... What say you?
Well, Super!! (I didn't catch you napping) ... good approach = low profile board w/ large heatsink covering about the same sq/in. as the board itself plus a little more width & depth for connections, knobs, etc. = makes for a nice small container.
....
I may be trying to mount this board inside of another device ... maybe something like a DIY tweaked and hopefully improved dual channel pre-amp ala: http://www.behringer.com/MIC2200/index.cfm?lang=ENG = US$100 or less at online stores everywhere ... this thing gets terrible reviews, mostly 'cause the solid state EQ circuit is garbage, but the tube pre-amp side is quite good and suitable for some DIY upgrades to better quality. So, firsbee away the EQ board, rewire and tweak for quality audio, adding this 2 channel, high efficiency Class-D output stage >> seems like a good idea. Considering that the TPA2000 may have a distinct advantage as a controller / mixer / FX selector, etc. or even as a substitute EQ ... The idea here is to make a very light weight, tube front end pre-amp for stage performance = very road worthy with lots of options for switching input and output. .... Them musicians can't seem to kick the tube habit ... mostly cause they can distort them for their own "special sound". ... What say you?
Aside: writing this from the Spruce Cafe & WiFi Bakery, Boulder Colorado on a lengthy road trip visiting family all over the rockies for Thanksgiving ... heading back through the Nevada desert Sunday. (The ride: http://www.mazdausa.com/MusaWeb/displayPage.action?pageParameter=modelsMain&vehicleCode=CX7 = all wheel drive version in ice blue ... Absolutely the greatest highway car I ever had, but very medioker audio (the CD player won't play any of my DVD-A discs = 
)
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