slightly overrated IMO,
you'll get around 44-0-44 rectified and that's equal to 88v DC
CMIIW
well, it's your call🙂
you'll get around 44-0-44 rectified and that's equal to 88v DC
CMIIW
well, it's your call🙂
If you could distinguish genuine from fake easily, the fakers would long be out of business.
Yes. The principle is to make something as simple as possible and at the same time as complex as necessary. The Gaincard, while being simple, follows basic rules of engineering. The 3-resistor amp does not and is likely to make his owner sorry, e. g. when it leads to speaker destruction for lack of any DC protection whatsoever.
It seems like there will be too much voltage. I couldn't calculate it but 88V is bit too near to LM3886 maximum voltage. The best way would be buying a new transformer, but is there a good way to drop voltage of this transformer? It's not so expensive to buy new one; 2x24V 225VA is 42€ and 2x24V 300VA is 56€ in my nearby electronicstore. Would these work?
Did some calculations. I'm getting in to these things I think. If it's 24V, and there is maybe max 3volts over the 24V. It's calculated 27 V x 1,4 x 2 = 75,6 V and that's when there is no stress. LM3886 handles 84V, so 24V is good. So the only question for now is there a good way to drop 2x30V voltage?
Before you buy the new transformer, perhaps download the Overture_Design_Guide and check your calculation.
www.national.com/vcm/national3/en_US/.../Overture_Design_Guide15.xls
www.national.com/vcm/national3/en_US/.../Overture_Design_Guide15.xls
Hi,
if you have a toroid, it is fairly easy to remove a dozen turns and re-measure the secondary open circuit voltage.
28.3Vac open circuit when your mains is exactly at it's nominal supply voltage is sufficiently inside the 84Vdc to allow the mains to rise to a +6% tolerance.
This method reduces the primary and the secondary VA slightly due to the same current maxima applying.
if you have a toroid, it is fairly easy to remove a dozen turns and re-measure the secondary open circuit voltage.
28.3Vac open circuit when your mains is exactly at it's nominal supply voltage is sufficiently inside the 84Vdc to allow the mains to rise to a +6% tolerance.
This method reduces the primary and the secondary VA slightly due to the same current maxima applying.
Ok. I'm not going to remove turns. I did use that calculator that Piggy suggested and if I used it right it says that 2x24V transformer would be ok. I think I'm going to buy that 2x24V 225VA toroid after package has arriver from chipamp.com. Or 300VA?
If the price different is 14 Euro, I will pick the 225VA.
It may worth to check the price of the Nuvotem in your country before buying from the local shop.
It may worth to check the price of the Nuvotem in your country before buying from the local shop.
Hey again!
Amplifier kit has arrived and been built. I have not yet bought transformer. Still wondering what would be the right voltage. 18-24V, lets see.. But now I have a new question to ask. I have ALPS motorized pot, which works with remote control. Chip need about 100mA, max. 200mA. I would like to add this volume control pot in the same box where the amplifier is. What would be the best way to get power to that thing? It needs 4,5-5,5V and as mentioned max. 200mA and it is ON when the amplifier is. My power supply is "stereo" -> only one toroid. And the kit is LM3886 from the chipamp.com.
Amplifier kit has arrived and been built. I have not yet bought transformer. Still wondering what would be the right voltage. 18-24V, lets see.. But now I have a new question to ask. I have ALPS motorized pot, which works with remote control. Chip need about 100mA, max. 200mA. I would like to add this volume control pot in the same box where the amplifier is. What would be the best way to get power to that thing? It needs 4,5-5,5V and as mentioned max. 200mA and it is ON when the amplifier is. My power supply is "stereo" -> only one toroid. And the kit is LM3886 from the chipamp.com.
Get a second small transformer only need 1Va. So anything bigger than that will do. just wire the second transformer in parallel with the amps transformer.
7805 on the positive leg of the power supply? Its only 100-200ma, thats 10x less then what the amps gonna pull.
antek is your friend
antek is your friend
I thought about 7805. It would be so simple. Does it make any difference that other PSU's voltage channel takes that 200mA more than other? Channels are then not identical, if another has that regulator. It's not a problem for me, if it's no problem for the sound.
And if I buy another transformer and it is in the same box as the amplifier parts, is it okay that it is not toroidal. Can it be something like this? Partcon Verkkokauppa with this Partcon Verkkokauppa
edit. Mankysteve's last comment makes second question useless 🙂
And if I buy another transformer and it is in the same box as the amplifier parts, is it okay that it is not toroidal. Can it be something like this? Partcon Verkkokauppa with this Partcon Verkkokauppa
edit. Mankysteve's last comment makes second question useless 🙂
And again I have a little question. My amp is going to be driven by line-level signal from CD-player and computer. Before amp, there is 10k volume pot (passive preamp 😛). I was wondering is it possible to add passive bass boost/reduce or/and tone boost/reduce? I've been searching for information, but haven't found an answer.
I have looked all kind of tone stack. Almost all of them are baxandall, with 100k pots. I'm not searching for that kind of a tone stack. I know that passive components can't produce gain. What I'm searching for is three "reduce" buttons. First to reduce bass, second to reduce mids, third to reduce treble. "BassBoost" would be reduced mids and treble. When all buttons "up", it would be same as bypass. Haven't seen it done like this, but I would like this kind of assembly. Reducing would be maybe 1db? What do you think?
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