Happy holiday everyone. I have a friend who is having a hard time finding a home receiver ( that is low in distortion ) and can drive down to 4 ohms? Also most diy tweeters are at 4 ohms now like his vifa ring tweeter. So he started looking at car audio amps. So can he run a 8 ohm speaker on a 4 ohm car amp? Please help me? Thanks jm
He surely can, but power output will go down. A 12V supply less, say, 1V Vcesat per rail are 10Vpp. RMS are about 7.071V, squared are 50V². Into a 4Ω it will be about 6.25W, into a 8Ω, only 3W.. Quadruple values for bridge operation.
It is usually possible to use higher impedance that recommended, but not always less that this value (Speaking about solid state devices). In such a case you will get lower power at also lower distortion, as a general rule.
I bet any "car amp" he´s considering will have an SMPS rising battery 12.6V to whatever rail voltages the amp needs.
And a "car amp" will need some robust 12.6V power supply to feed it.
I´m not sure what´s referred to as "receiver" (FM radio tuner + amplifier combination),they have not been popular for decades now ... maybe he means "amplifier"?
What´s his intended Audio source?
And many (most?) amplifiers can drive both 4 and 8 ohm loads, not sure about the "hard time" finding them.
And a "car amp" will need some robust 12.6V power supply to feed it.
I´m not sure what´s referred to as "receiver" (FM radio tuner + amplifier combination),they have not been popular for decades now ... maybe he means "amplifier"?
What´s his intended Audio source?
And many (most?) amplifiers can drive both 4 and 8 ohm loads, not sure about the "hard time" finding them.
In such a case, the values given will be different but the essential concept is the same.
A 2 channel stereo receiver. No FM or am tuners. The audio sources is turn table and CD player and TV with 2 channel duties. I have looked at the recent market and I have seen 2 channel reciver's from 6 ohms to 8 ohms but, not 4 ohms to 8 ohms? My friends tweeters are vifa ring radiator tweeters rated at 4 ohms. Last time I tried running my magapan MG 12's on Marantz integrated amp rated at 8 ohms only ( years ago ?) So the amp was popping fuses and the company said it was my speakers ohms load doing it. So I ended up selling both due to miss information on the amps ohms out put. So I put a post on here to see where it would go and if I was heading in the right direction? I hope this helps? Jeff
Just a little clarification that may help in getting your direction
A receiver is a combination of tuner, preamp, and amplifier in one chassis.
You need a preamp + amp. In one chassis, that would be called an integrated amplifier. The preamp section will need a phono input.
4 ohm stable amps are available. I haven't looked in a long time, they may not be in the mass market arena, and they may be expensive. There are plenty here in DIY😉
I'd post a request in the solid state forum for recommended 4-ohm stable units, and throw in your constraints -price, power needed, phono input, etc.
A receiver is a combination of tuner, preamp, and amplifier in one chassis.
You need a preamp + amp. In one chassis, that would be called an integrated amplifier. The preamp section will need a phono input.
4 ohm stable amps are available. I haven't looked in a long time, they may not be in the mass market arena, and they may be expensive. There are plenty here in DIY😉
I'd post a request in the solid state forum for recommended 4-ohm stable units, and throw in your constraints -price, power needed, phono input, etc.
Yes Tim that's it. A indgraded amplifer. He was looking at the class d and class t amps because he wanted a small compact size. I told him a A\B amplifer would be better up to 20khz which most class D and T amps don't reach. I hope this helps? I do have a sony reciver but, I didn't give it to him because it said 8 ohms only or you could damage the reciver. Thanks again Tim. Jeff
Be sure whatever he gets has a phono input, turntables require a specific equalization curve to be applied in order to sound right.
I don't know much about Class D or T, but I would agree to stay away from cheap ones if you want full range output.
You can probably pick up a used integrated amp or receiver at reasonable price, minimum impedance is usually written near the speaker terminals. I'd check second hand stores and pawn shops if you want to go that route- be sure to test that all functions work. I've gotten quite a few at yard/estate sales in the $10-$25 range with only about 30% of them fully functioning. Most of the people said they worked fine.
Osvaldo says 4Ω stability is common now, you may want to check your nearest Best Buy, etc before going to too much trouble.
I don't know much about Class D or T, but I would agree to stay away from cheap ones if you want full range output.
You can probably pick up a used integrated amp or receiver at reasonable price, minimum impedance is usually written near the speaker terminals. I'd check second hand stores and pawn shops if you want to go that route- be sure to test that all functions work. I've gotten quite a few at yard/estate sales in the $10-$25 range with only about 30% of them fully functioning. Most of the people said they worked fine.
Osvaldo says 4Ω stability is common now, you may want to check your nearest Best Buy, etc before going to too much trouble.
Many of the commonly available integrated units found at thrift stores are chip amps with weak power supplies. This is very frustrating for diy since these are hardly worth the time.
If you look on local classifieds you can find stuff, do a little research and get something that’s worth using.
Car amps won’t gain you much after the hassle of finding a healthy 12v power supply.
If you look on local classifieds you can find stuff, do a little research and get something that’s worth using.
Car amps won’t gain you much after the hassle of finding a healthy 12v power supply.
Ok good to know about the car amps. I will keep looking for him on e bay and maybe audiogon. Thanks for the advice. Jeff
Yes. I have been going to garage sales and yard sales the last month nothing. Yes I will make sure it works before I buy one. I did have a class d amp when they first came out and I didn't like the pop noise from the discharge power cap ( if I said that right?). Thanks for your advice. Jeff
That's a good point, phase. I've only picked up one IC receiver- a 70's Pioneer. But that's because I know what I'm looking for, I pass up pansy receivers constantly.
On the other hand- no matter where it comes from- if it's rated for 4 ohm operation, it should have enough guts for this job.
On the other hand- no matter where it comes from- if it's rated for 4 ohm operation, it should have enough guts for this job.
Local is almost always better if you can, I wouldn’t want to hassle with potential non-functioning equipment and shipping damage.
Probably potentially better deals with yard sales, as mentioned by tsmith, but that could take some time.
Common auto stereos are rated ~22Watts/channel based in a bridged output into 4 Ohms from a ~14Volt power (engine running), ie no switch mode supply required.
sqrt(22*2*4)=13.27 Volts
1V Vcesat would be unacceptable in such an amplifier so they are usually CFP or FET outputs, often class-D.
sqrt(22*2*4)=13.27 Volts
1V Vcesat would be unacceptable in such an amplifier so they are usually CFP or FET outputs, often class-D.
OP mentioned car Amplifiers, not car radios or "stereos" labels which bring memories of "cassettes" and such. 😱
Googling "car amplifier" brings 500/1000W units in the first page, which obviously use SMPS to get high voltage rails, usually >>35V , none about "straight 12V" ones which were standard in the 80´s or so.
Googling "car amplifier" brings 500/1000W units in the first page, which obviously use SMPS to get high voltage rails, usually >>35V , none about "straight 12V" ones which were standard in the 80´s or so.
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