It's the heavy stuff you add into the bottom of a boat to stop it falling over.
Ballast resistance normally refers to the big white resistors at the output of parallel outputs and parallel amplifers, and these resistors serve to absorb the small differences (turns the differences into heat--these resistors are wee little ceramic radiant heaters, effectively). Had there been no ballast resistance, then the differences between the devices loads each other instead, for a somewhat worse outcome.
The reference is wirewound resistors; so, of course actual wire also works. Ever noticed that all in one (supply-is-on-the-amplifier-board) products can sound much worse than separate supply and amplifier board. The difference in sound and indeed outcome, is the dc umbilical cable serving as a resistor--a ballast resistor (between the much different size caps on the supply board verses the amplifier board).
If you connect different size batteries directly parallel, explosion or really poor performance results. Capacitors are less volatile, so of the two possibilities, what you get is poor performance. No need to spend extra for that problem. lolz!
So in all seriousness, a powersupply board with:
Bridge rectifiers - 10000uF - 4700uF - 4700uF - 3300uF - terminal - wire to amp boards is degrading SQ/performance of the amp? And could even be unsafe?
The above caps is of course per rail.
Wiring to amp boards is done using RK0.5mm² (AWG20), about 15-20cm of each: pos, gnd, neg.
Bridge rectifiers - 10000uF - 4700uF - 4700uF - 3300uF - terminal - wire to amp boards is degrading SQ/performance of the amp? And could even be unsafe?
The above caps is of course per rail.
Wiring to amp boards is done using RK0.5mm² (AWG20), about 15-20cm of each: pos, gnd, neg.
Hold up a sec.
The project was made chronologically.
Due to some progress after making the bulky power supply board. . . the progress was that business with the diodes (serving for R) and parallel caps (half ESR) on the amplifier board; then, after that happenstance, a simpler power supply board works perfectly well.
That was a fantastic outcome of installing a modicum of caveman/basic practical filter at the amplifier board. Also, it is spelled exactly like my nickname. Anyhow! The power supply!
After applying the indicated mods to the amplifier board, then you have no need of a complicated power supply board. Instead:
Power supply board can have a pair of 6800u (OR!!!! pair of 10000u) Per Each Rail along with an ordinary bridge rectifier. The diyaudio store has a board for it, although the simplicity of 2 caps per rail (4 caps total) does not actually require a board.
What you can take from this comment is that DC filters are easier, cheaper, and more straightforward to use when they're on the amplifier board. . . so that you have no need of a complex power supply.
P.S.
If you put similar but different size caps together directly parallel, it will result in ringing and the worst performance possible, audibly. When paralleling caps, try always to put identical caps together for a greater (and lower loss) value OR add a far, far, farout smaller value ceramic or polyester cap, plus some prayer and some scope. DO use ballast resistance every time there is a difference in cap value. It could be pitch, it could be a diode, it could be a resistor or it could be a cable, but the ballast between different values of capacitors is mandatory with no exceptions permitted. There's probably at least 3 handfulls of people more clever than me, and I'm confident of that because I know them or we have spoken. The thing is that odd combinations of caps can work, and that has the awfully inconvenient problem of manufacturing variance; because, if they haven't varied yet, its like Murphey's law, in that there will be a really costly change, permanent, a few days before your production run. It did happen to me. That was educational.
Well, it does seem likely that the smarter people learn more easily than I do. And I hope that you're one of them. I do desire that; because, it would also help me in that I'd another smarter person to talk to (ask for help when I get tangled) and that will make finer things to do that work more gloriously. It doesn't happen separately, but it does happen really often together. Rock out! And then rock out even better.
I could always just use 2x 10000uF per rail.
Is that enough for the intended use as a subwoofer amp?
It is going to drive one Dayton 15" IB/channel.
The Toroidal transformer is 2x24VAC/300VA.
Looks perfect except that the transformer VA might be short (I'd need to know the "A" and the speaker load ohms to tell). In the case of a shortfall on the transformer amperage, consider the TDA8950 for your subwoofer amplifier.
I couldn't answer that question reasonably without knowing the ohms/loading of all of the speakers connected.
The Woofers are 8ohm according to datasheet.
300VA ~ 300W if I'm not mistaking?
Anyway, 230VAC mains, 2x24VAC secondaries, 300VA Toroidal transformer.
Or what "A" was it that you were asking about?
I had the option of this and a 500VA 2x24VAC that I have, I think it was somewhere in this thread I was told the smaller one would be ok.
The woofers are in an H-baffle and I'm more interested in quality than quantity(live in an apartement, and I have an almost 5month old daughter).
Going TDA7293 may contradict quality over quantity, but with dipole compensation etc, a good amp with enough power is very costly.
If I get SPDIF - I2S/USB-I2S in to work well on the FreeDSP(s) I have, I'll use that with two DAC's connected to the GPIO's of the FreeDSP board, having the ADAU1701 do only the processing of the digital signal and using WM8805 or PCM2706 for I2S in and, probably, ES9023 for I2S to line out.
In essence having the signal digital to the DSP where it gets "divided" at 250hz.
Anything above that goes unprocessed to the DAC - AMP - passively x-overed mids/highs.
Anything below 250hz gets a 6dB/oct gain (apart from a sharp HP-filter at around 30-40hz), then to DAC - AMP - Dayton 15" IB woofers.
He's just asking about the transformer power.
The A is amperes.
300VA / 230Vac gives 1.3Aac at the input if the transformer is 100% efficient. An allowance for 95% efficiency increases the input to 1.37Aac
300VA/{24+24}Vac gives 6.25Aac at the output. But this is not much good to you, nor to him, since it ONLY applies when the load is resistor.
You will pass the output into the rectifier and smoooth it with some capacitors. That makes it a capacitor input filter loading the secondary and the current rating must be de-rated according to the manufacturer's guidance.
Ok, making it a bit easier (for me).
Is the transformer enough to drive the woofers at reasonable levels?
IIRC (not able to check now) it's a Velleman transformer.
I don't recall what the amp modules are supposed to deliver (power) given the info already available about the transformer?
I have had the transformer for several years, never putting it to use.
The 500VA one I used to power a bridge-clone or what it was called (one LM4780/channel).
Until one channel burned that is.
Is the transformer enough to drive the woofers at reasonable levels?
IIRC (not able to check now) it's a Velleman transformer.
I don't recall what the amp modules are supposed to deliver (power) given the info already available about the transformer?
I have had the transformer for several years, never putting it to use.
The 500VA one I used to power a bridge-clone or what it was called (one LM4780/channel).
Until one channel burned that is.
The usual rule that seems to apply pretty well is:
The transformer VA should be 1 to 2 times the total maximum output power of the amplifier.
i.e. a 100W into 8ohms amplifier will work pretty well when powered from any transformer rated from 100VA to 200VA for ordinary domestic duty, even a loud party.
If you have two 200W amplifiers (total 400W) inside a case sharing a transformer, then you will find that a 400VA to 800VA will do the job for domestic duty.
The transformer VA should be 1 to 2 times the total maximum output power of the amplifier.
i.e. a 100W into 8ohms amplifier will work pretty well when powered from any transformer rated from 100VA to 200VA for ordinary domestic duty, even a loud party.
If you have two 200W amplifiers (total 400W) inside a case sharing a transformer, then you will find that a 400VA to 800VA will do the job for domestic duty.
The maximum output specified is with 10% distortion. Though I don't know who would try to used any audio-equipment like that?
The above is taken from a listing of a kit based on the same PCB and schematic
I don't know, not now atleast since having taking my pain meds, how to translate the above into realistic figures.
The above is taken from a listing of a kit based on the same PCB and schematic
I don't know, not now atleast since having taking my pain meds, how to translate the above into realistic figures.
read the datasheet fully.
ask questions on the parts you don't understand.
The distortion should be quoted at various supply voltages and @ various distortion levels (clipping). 10% is terrible. Even 1% due to clipping looks bad on a scope.
See if they have values for 0.1% and/or 0.5%
Some are incapable of getting down to much below 0.1% so they avoid quoting max power at this (typical max power), because the measurement would look bad in comparison to competitors.
ask questions on the parts you don't understand.
The distortion should be quoted at various supply voltages and @ various distortion levels (clipping). 10% is terrible. Even 1% due to clipping looks bad on a scope.
See if they have values for 0.1% and/or 0.5%
Some are incapable of getting down to much below 0.1% so they avoid quoting max power at this (typical max power), because the measurement would look bad in comparison to competitors.
I was looking at the datasheet. I'd say that for my needs, 300VA transformer is enough. Atleast as long as I live in an apartement.
Can I get about 2x80W @ 8ohm that is good enough, even if the dipole woofers sound better with more power.
The best I have had them sound was when driven by one UcD400/channel. Unfortunately I had to sell that amp a few years back.
Can I get about 2x80W @ 8ohm that is good enough, even if the dipole woofers sound better with more power.
The best I have had them sound was when driven by one UcD400/channel. Unfortunately I had to sell that amp a few years back.
You know better than anyone what you are trying to achieve but if I were building a similar system I would use 300VA. Going to 500VA has its advantages, the regulation will be better but I suspect that it would have minimal impact on performance.
Others may disagree and I would be happy to read their thoughts.
I agree.
two channels of 80W will work well with a transformer rated from 160VA to 320VA.
There will be very little if any improvement in performance by going to 3.125times the total maximum power.
But is 80W actually available as maximum power? Or is that a 10% distortion value used to pull in the gullible customer?
two channels of 80W will work well with a transformer rated from 160VA to 320VA.
There will be very little if any improvement in performance by going to 3.125times the total maximum power.
But is 80W actually available as maximum power? Or is that a 10% distortion value used to pull in the gullible customer?
Hello All:
I recently purchased 2 boards in hopes of building a high fidelity stereo amplifier to drive the main speakers in my recently commandeered music/HT converted bed room. This will be my first endeavor at building a power amp. I just completed soldering up a phono preamp kit: DAK Genera
I am looking for a source selector - volume control/preamp kit to match with this amp. Obviously, I'll be running the phonographic record player as a source. In addition I'll need to play music from my cd player, music server and iphone, so four input sources total. One more thing, I plan on building the speakers. They are TBD for now.
I recently purchased 2 boards in hopes of building a high fidelity stereo amplifier to drive the main speakers in my recently commandeered music/HT converted bed room. This will be my first endeavor at building a power amp. I just completed soldering up a phono preamp kit: DAK Genera
I am looking for a source selector - volume control/preamp kit to match with this amp. Obviously, I'll be running the phonographic record player as a source. In addition I'll need to play music from my cd player, music server and iphone, so four input sources total. One more thing, I plan on building the speakers. They are TBD for now.