Hi,noob question about power supply or transformer for a TDA1521 chip amp.The input voltage shows a 12-0-12 configuration.Printed on the board AC12x2.This leads me to think I need a 12volt center tap transformer?Now the confusion.Should it be AC on the secondary side?Should the amperage be 3.0 or less for the TDA1521 chip?Where the power connects to the board in the next trace there is a GBU808 bridge rectifier,so I think I should use a AC 12-0-12 transformer.Can anyone help me to find the proper transformer or power supply?
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A TDA1521 can handle up to +/-21Vdc of supply voltage. A 12-0-12Vac transformer will result in +/-17-18VDC so it is fine. Both a 12Vac-0-12Vac transformer and a 2x12Vac transformer are useful because the last type is just connected to form an external center-tap.
The voltage(s) on the secondary of a (magnetic) transformer is ALWAYS AC.
The transformer should have a power of 80VA-100VA for a stereo version with two TDA1521 chips and half of that if you make a mono version with only 1 chip.
The voltage(s) on the secondary of a (magnetic) transformer is ALWAYS AC.
The transformer should have a power of 80VA-100VA for a stereo version with two TDA1521 chips and half of that if you make a mono version with only 1 chip.
Thank you for your reply.Here is a better description on the chip amp.... Description:
Name: TDA521 analog amplifier board
Chip: TDA1521 （Philips）
Supply voltage: AC dual 12V
Supply current: 2-4A
Output: 30W x 2
Amplifier type: pure A analog amp
Channels: left-right dual channels
Size: 80*70*46mm
It's a one chip TDA1521 that outputs to stereo speakers.I've found a diagram of a transformer 120volts center tap 12-0-12 2A. I would like to have the maximum output without hurting the chip.I think a 12-0-12 3A would be ok,but I'm not sure.If it is ok to post a picture of the chip board unit I could do that.Thanks again for your help.
Name: TDA521 analog amplifier board
Chip: TDA1521 （Philips）
Supply voltage: AC dual 12V
Supply current: 2-4A
Output: 30W x 2
Amplifier type: pure A analog amp
Channels: left-right dual channels
Size: 80*70*46mm
It's a one chip TDA1521 that outputs to stereo speakers.I've found a diagram of a transformer 120volts center tap 12-0-12 2A. I would like to have the maximum output without hurting the chip.I think a 12-0-12 3A would be ok,but I'm not sure.If it is ok to post a picture of the chip board unit I could do that.Thanks again for your help.
Yes sorry, I forgot for a moment that it is a stereo-chip. The transformer power I suggested is then 80VA-100VA.
Your suggestion of 3A corresponds to a 75VA transformer so we are close in our estimations.
The transformer power is a balance between the maximum continuous output power and the crest-factor of music.
My estimation is based on that the rectified voltage should be 16-17V when loaded with 8 Ohm speakers and 15-16V with 4 Ohm speakers.
Thus, with 8 ohm speakers the output power per channel should ideally be 18W. With 4 Ohm speakers 32W. This is without taking the saturation drop in the output stage into account. The datasheet promises 2x12W in 8 Ohm at +/-16V. FIG.11 of the datasheet hints about the same in 4 Ohm but at a lower supply voltage because the current limit is dominant with 4 Ohm. It is clearly an amplifier intended for 8 Ohm. Assuming a rather low efficiency of 50%, the 12W becomes 24W supply for each channel and with two channels 50W.
As such a 50VA transformer power should be sufficient with the crest-factor leaving a margin. I guess a slightly bigger transformer with less heating costs little more. Your suggestion of 3A (corresponding to 75VA) is fine. 4 Ohm operation could leave higher values but the maximum peak current limit may not allow this.
Do you intend to use 8 Ohm speakers?
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Thank for your reply.Yes,I plan to series two 4ohm speakers on each channel for 8 ohm per channel.I am currently looking for a CT transformer in that 50VA range.If I post what I found could you just confirm that the trans would be ok.Thanks again.
I can give it a look. I believe 60VA is a standard. EI-core or toroidal, that is less important. Transformers are heavy and accordingly expensive in transport. Therefore, a nearby country with moderate wages is often where you find the best purchases.
Yes,I just looked at my reply.I was going backwards in my thinking.I'll actually look to buy a 4 amp trans in the 16-19 volt range.I think that will work for what I want without overheating any components of the chip board.Thanks,I'll let you know when I find the transformer.
The 16-19V are rectified DC voltages. As the rectification gives you around 1.4 times the transformer voltage you need around 12Vac from the transformer.
Ok,thanks.I was get the AC 12 volts mixed up with the 12 x 1.414 rectified dc voltage in my calculations.So I can try a 12volt AC 3-4 amp transformer.Thanks for all your help.I post when I find one I think will work.
In a change of plans,I'm going to try Mean Well RS-35-12 type of power supply.Do you know if Elekner is a good brand?Sorry,if I'm not suppose to post name brands.It seems to be too difficult to find a 12-0-12 transformer for the exact specifications I want.Thanks for any information you can give me.
Thanks PRR,I thought since the RS 35-12 had a V+ and a V- on the DC side that's how it was supposed to connect to the 12-0-12 input of the chip amp board.It shows a 12+ and a 12- on the board with the Vg=0 in the middle.This has confused me from the start.I have a 7377 chip amp with just a +,- that I connect with jumpers from a barrel jack.Much easier!!
Just FYI, I made a TDA1521 amp for Youtube playing with a pair of 5" JBL AV speakers. I just used a 24V SMPS and use pairs of resistors and very big caps to produce a virtual ground. To my ear, the sound is normal, powerful and satisfactory.
Also FYI, the TDA7377 amp use BTL output config so that it can use single-rail supply without the need of output capacitor.
Also FYI, the TDA7377 amp use BTL output config so that it can use single-rail supply without the need of output capacitor.
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