I ordered four of the chips from profusion and also two more of those boards from Amazon. Ordered quality electrolytic caps as well.
Another issue is the DC polarity of these large caps. They need some DC bias, ideally equal to the AC peak value. Perhaps you could add opposing diodes on the caps.
I see where in bridged mode there will be no real DC voltage across the caps.
The idea will be to hopefully use the amp in bridged mode without the speaker coupling caps. If testing with an 8 ohm dummy load proves that to be reliable I'll buy a mono speaker protection kit and replace the on board relay with a DPDT relay. That way I don't have to worry about the DC balance suddenly going out of whack.
Now if I were building an amp from scratch using the 2050 chip I'd replace one of the 22k resistors with a 50k trimpot so that I had a way to tweak the DC voltage on the output so that I could make it equal.
Now if the bridged configuration works well in testing I might get a larger heatsink and mount both chips to it then get some L-brackets to mount the boards to the heatsink so that I am not putting stress on the chip leads.
The idea will be to hopefully use the amp in bridged mode without the speaker coupling caps. If testing with an 8 ohm dummy load proves that to be reliable I'll buy a mono speaker protection kit and replace the on board relay with a DPDT relay. That way I don't have to worry about the DC balance suddenly going out of whack.
Now if I were building an amp from scratch using the 2050 chip I'd replace one of the 22k resistors with a 50k trimpot so that I had a way to tweak the DC voltage on the output so that I could make it equal.
Now if the bridged configuration works well in testing I might get a larger heatsink and mount both chips to it then get some L-brackets to mount the boards to the heatsink so that I am not putting stress on the chip leads.
Running these in bridged configuration increases the distortion slightly.
Is that due to how they get the signal for the other amp and would distortion be less if both amps were fed from a phase splitter provided the phase splitter has extremely low distortion itself?
Is that due to how they get the signal for the other amp and would distortion be less if both amps were fed from a phase splitter provided the phase splitter has extremely low distortion itself?
Yes, but if that level of THD matters then maybe you should not bother with chip-amps. I had a cheap stereo with bridged chip-amps that I altered the way they were bridged, and it sounded very nice as a result, mostly because I got rid of most of the capacitors, and then my wife sold it in a garage sale. 🙄
Thinking I might have a use for a bridged version using the two amps.
I need 40Vac at 30Hz to power some 120V mirror ball motors with the whole thing drawing under 40 watts.
I currently have a class d amp with a small step up transformer, however that causes some RFI. Now if this amp running bridged can put out at least 45Vrms then I can eliminate the transformer and class d amp which eliminates the RFI and makes the whole thing smaller.
Now when I connect the amps bridged should I rely on the power supply grounds or should I connect the input grounds of both amps together and also the output grounds together.
I need 40Vac at 30Hz to power some 120V mirror ball motors with the whole thing drawing under 40 watts.
I currently have a class d amp with a small step up transformer, however that causes some RFI. Now if this amp running bridged can put out at least 45Vrms then I can eliminate the transformer and class d amp which eliminates the RFI and makes the whole thing smaller.
Now when I connect the amps bridged should I rely on the power supply grounds or should I connect the input grounds of both amps together and also the output grounds together.
Wiring the amp for bridged mode was very easy. R4 is close to the input terminal block so all I had to do was remove the volume control from the board and solder a 22k resistor from the junction of R4 and C4 to the + audio input terminal and solder a wire to pin 4 of the chip on the amp connected to the + speaker lead.
Now when I remove the output coupling caps, I will need to just run a wire from the + speaker terminal on the speaker jack to the + audio input terminal.
I measured the voltage between pin 4 of both chips and it was 22mV and increasing slightly. Once the new chips come in I suspect that voltage will be lower than that. I will then remove the output coupling caps from the circuit.
With both amps running on 24Vdc I get 15.12Vrms out with no load.
Once I get the correct chips how much RMS voltage no load should I expect to see with running the amp at 40Vdc?
The main reason I modified the amp I use at work to operate in bridged mode is so that I could remove the output coupling caps. That amp I'll likely keep it powered at 24Vdc as I do not need the extra wattage produced by a higher B+ voltage unless there is a benefit to running the amp at a higher B+ voltage. Also each amp will run at half the output power for the same volume level I normally run the speaker at.
The amp is now this.
Here's a photo of the second amp installed. All I need to do is add a couple holes to the bottom of the chassis where the heatsink will be over so some air can move over the second heatsink.
So how much power can this amp put out into 8 ohms with a B+ of 45Vdc?
One thing I like about the board is that there's a ground plane on both sides of the board.
Now when I remove the output coupling caps, I will need to just run a wire from the + speaker terminal on the speaker jack to the + audio input terminal.
I measured the voltage between pin 4 of both chips and it was 22mV and increasing slightly. Once the new chips come in I suspect that voltage will be lower than that. I will then remove the output coupling caps from the circuit.
With both amps running on 24Vdc I get 15.12Vrms out with no load.
Once I get the correct chips how much RMS voltage no load should I expect to see with running the amp at 40Vdc?
The main reason I modified the amp I use at work to operate in bridged mode is so that I could remove the output coupling caps. That amp I'll likely keep it powered at 24Vdc as I do not need the extra wattage produced by a higher B+ voltage unless there is a benefit to running the amp at a higher B+ voltage. Also each amp will run at half the output power for the same volume level I normally run the speaker at.
The amp is now this.
Here's a photo of the second amp installed. All I need to do is add a couple holes to the bottom of the chassis where the heatsink will be over so some air can move over the second heatsink.
So how much power can this amp put out into 8 ohms with a B+ of 45Vdc?
One thing I like about the board is that there's a ground plane on both sides of the board.
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Just measured the amp's output bridged into 16 ohms. It puts out 11.65 watts at 400Hz with 24Vdc B+.
Will test it at work Monday and see if there's any audible improvement given the speaker coupling caps are no longer in the circuit.
What I might do is get an AnTek transformer and build somewhere between a 24-40V power supply. I might also include a speaker protection circuit in the power supply.
Will test it at work Monday and see if there's any audible improvement given the speaker coupling caps are no longer in the circuit.
What I might do is get an AnTek transformer and build somewhere between a 24-40V power supply. I might also include a speaker protection circuit in the power supply.
The bridged version I think sounds a little better in the treble and I also do not have that pop in the speaker when I turn the amp off due to the output coupling caps being removed.
Might get a further improvement when I install the legitimate 2050 chips and the better electrolytic caps.
Might get a further improvement when I install the legitimate 2050 chips and the better electrolytic caps.
Honestly I think even the bass sounds a bit better.
The amp goes as loud as I need and then some.
The amp goes as loud as I need and then some.
So I made the mistake of ordering 2.2uF non-polar caps for C1.
All I have is some quality 3.6uF 125V caps. Will use those instead. That might improve the sound somewhat as there's a slightly lower low frequency phase shift.
All I have is some quality 3.6uF 125V caps. Will use those instead. That might improve the sound somewhat as there's a slightly lower low frequency phase shift.
There is a DC bias voltage of 1/2 B+ on the + end of C1 with the - end going to the input so a polarized cap is what has to be there.
If this was a dual supply circuit then I would likely use a film cap for C1.
If this was a dual supply circuit then I would likely use a film cap for C1.
I have some UTC 2050 chips and some TI lm1875, pm if still in need for them.
Thanks for the offer but I already ordered four from profusion.
I'll keep you in mind if I order more of these amps.
I'll keep you in mind if I order more of these amps.
The chips came in today. Installed two on the second set of boards that are currently not being used. The offset between the + speaker output of each board is 181mV.
Is that ok or too high?
What I will do is replace the two chips on the two boards at work then see the offset they have.
If the offset is similar I will swap one of the boards around and see if that solves the offset issue.
That said is 181mV of offset something to actually worry about?
Is that ok or too high?
What I will do is replace the two chips on the two boards at work then see the offset they have.
If the offset is similar I will swap one of the boards around and see if that solves the offset issue.
That said is 181mV of offset something to actually worry about?
I got the other two chips installed on the two amp boards I use at work. The voltage difference between both outputs is 84mVdc with a B+ of 44Vdc. THat was measured with the bottom off the amp chassis and there was only some airflow over one heatsink which is directly in front of the 60 X 10 mm 12V fan running on 5Vdc. The difference has likely dropped a little with the bottom on and some airflow over the other heatsink.
The amp sounds good.
Here's a better schematic of the amp. I will order the bridge rectifier, transformer and capacitor this Thursday when I get paid. Nice thing is since I am using a toroidal transformer I can put a two prong cord on the power transformer and a couple banana plugs on the secondary and won't even need a case for the transformer. The bridge rectifier and cap will be mounted inside the amplifier case.
The amp sounds good.
Here's a better schematic of the amp. I will order the bridge rectifier, transformer and capacitor this Thursday when I get paid. Nice thing is since I am using a toroidal transformer I can put a two prong cord on the power transformer and a couple banana plugs on the secondary and won't even need a case for the transformer. The bridge rectifier and cap will be mounted inside the amplifier case.
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