Can anyone who's used LM1875 amps describe the speakers/drivers that work well and not so well with them, in terms of impedance loads?
Has anyone tried bi or tri-amping with them, also? Does this give them more capability to drive a general 2 or 3-way?
Has anyone tried bi or tri-amping with them, also? Does this give them more capability to drive a general 2 or 3-way?
I use the TDA2050 (which as far as I understand, is really, really close in comparison) for everything- powered speakers, a guitar amp, whatever.
I've also combined 3 of them with a 3 way xover and yea, you can pull more power when you have more chips. I use them most often with 4 ohm loads.
I have a stereo pair hooked up to some passive 3 way Aiwa 6 ohm speakers and they sound just fine to me. I don't think I've ever tried to drive a 2 ohm subwoofer or anything like that.
I'd be curious to hear if any particular speakers/circumstances DON'T work for these chips
I've also combined 3 of them with a 3 way xover and yea, you can pull more power when you have more chips. I use them most often with 4 ohm loads.
I have a stereo pair hooked up to some passive 3 way Aiwa 6 ohm speakers and they sound just fine to me. I don't think I've ever tried to drive a 2 ohm subwoofer or anything like that.
I'd be curious to hear if any particular speakers/circumstances DON'T work for these chips
Beware TDA2050 is out of production for quite a few years now, while LM1875 is still being made
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Hi
If you drive 4 ohms load with the LM1875 then please check the datasheet with the max power dissipation @4R load max 21Volt each rail. with 8R load about 28V should be ok.
look at this:
eBay mono LM1875 kit
chris
If you drive 4 ohms load with the LM1875 then please check the datasheet with the max power dissipation @4R load max 21Volt each rail. with 8R load about 28V should be ok.
look at this:
eBay mono LM1875 kit
chris
Thanks. I should have asked my question more clearly. I know the chip prefers an 8ohm load, but in reality, with e.g. basic 2-ways + crossover + box, impedance is going to drop nearer to 4 ohms at certain frequencies.
So I wanted to ask what speakers/drivers they're using that still work good despite that, and those that do not. Or are there more people using them with MTMs with 16ohm woofers?
So I wanted to ask what speakers/drivers they're using that still work good despite that, and those that do not. Or are there more people using them with MTMs with 16ohm woofers?
IMO a high sensivity speaker recommended according to my personal experiences.. Beneath 86dB sensivities will not be satisfactory for listening level..
Nominal 8 ohm speakers will drop no lower than 6 ohm and that only at some frequency between 250 and 400Hz, "8 ohm" amps stand that with no problem at all; besides you will not use amp clipping all the time, by any means.
And crossover separates woofer and tweeter, so they are never in parallel.
Even in cheesy "crossovers", such as a lonely cap in series with tweeter and woofer direct connected, there is a "built in" series inductor, part plain voice coil inductance (remember it has an iron core: the pole piece) ,part "reflected" mechanical inductance from cone mass, just look at speaker impedance curves.
In a nutshell: a nominal 8 ohm cabinet will be fine, unless very poorly made, no need to search for 16 ohm speakers.
That said, I have seen (and repaired) CHEESY Sony cabinets, with a straight through woofer and 3 (three, count´em) extra ... ummm .... "speakers", supposedly midrange, tweeter and super-tweeter or "spacial extender" 🙄 , an extra tweeter pointing sideways, all 3 simple cone speakers with a cheap electrolytic in series, say 22uF , 4.7uF and 2.2uF
I´d HATE to be an amp and try to drive that cabinet at mid-high frequencies. 😱
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Tda2050 is still in production but now the manufacturer is unisonic semiconductor. Same spec & as sturdy as ST made tda2050 😎
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And most importantly, under no circumstances swith left and right channel. It will force you to listen up side down, with all the blood rushing into your head.
But seriously, no need to overcomplicate things. What NareshBrd said.
Thanks.
WHERE can I buy 50 or 100 of them?
Unisonic won´t even answer my mails.
Not surprised, I guess less than 10.000 of anything is useless for them.
Btw even some counterfeit tda2050 can tolerate +/-25vDC at 4ohm load! This chip is much better than lm1875. Sad that ST discontinued this product 😡 
As with any chip amp
They can run 4 ohm loads.
Depending on the power supply voltages.
You need a large heatsink.
Also keep in mind depending on the speaker.
A " 30" or " 50" watt bookshelf speaker
might not really need more than 3 to 6 watts to reach full distortion.
So sure you hear amazing stories of running 25 volt rails or 50 volt
power supplys with 4 ohm loads.
That is because they were likely using 3 to 5 watts of power.
In a nutshell consider the 1875 a 18 watt amplifier.
And if you really expect to use 18 watts.
The heatsink needs to be around .6 C/W
.6 rated heatsink is very big.
Again in a nutshell 4 ohm loads are fine.
Just dont run the chip at high voltages
and use a large heatsink.
And assume you only need 3 to 10 watts
and many get away with the 1 to 2 C/W size heatsinks
because real world needed power is much lower for many applications.
But with any audio amp heat is enemy
and the bigger the heatsink the better.
They can run 4 ohm loads.
Depending on the power supply voltages.
You need a large heatsink.
Also keep in mind depending on the speaker.
A " 30" or " 50" watt bookshelf speaker
might not really need more than 3 to 6 watts to reach full distortion.
So sure you hear amazing stories of running 25 volt rails or 50 volt
power supplys with 4 ohm loads.
That is because they were likely using 3 to 5 watts of power.
In a nutshell consider the 1875 a 18 watt amplifier.
And if you really expect to use 18 watts.
The heatsink needs to be around .6 C/W
.6 rated heatsink is very big.
Again in a nutshell 4 ohm loads are fine.
Just dont run the chip at high voltages
and use a large heatsink.
And assume you only need 3 to 10 watts
and many get away with the 1 to 2 C/W size heatsinks
because real world needed power is much lower for many applications.
But with any audio amp heat is enemy
and the bigger the heatsink the better.
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Not a story, my own experience. According to datasheet it's not recommended to drive 4ohm load at +/-25vDC (Absolute max). I didn't care & ran the amp at full load, nothing happened(but you can hear protection circuitry) & i'm talking about a counterfeit chip!