i recently dug out an amp made with tda2050 ant it still works well it has a different character to the lm 1875 amp i made a while ago, i hace also used the tda 7294 in a few amps also a pretty decent ic with a distinct character when compared to the lm3886 i'm listening to now, the tdas are also much cheaper here. all worth trying out that's why it's diy!
Hi, I have been building a TDA2050-based amp using the schematic proposed by ashok, and while one channel works perfectly, the other one is stuck at V+, with some variation in the output (towards zero), when a signal is fed. Does anyone here know what component could be faulty, to save me time so I don't have to check every component?
Check for a fine solder bridge between the pins of the IC.
Is the metal tab properly isolated from ground ? check it with your DMM.
If it's OK...
Disconnect C1 47uF. This is the negative feedback bypass capacitor.
With it removed the amp will have a dc gain of 1.
Check the dc voltage at pin 1 the +ve input. It should be less than 0.1 V and typically about 0.01V. You could (ac ) short the input to ground to prevent any noise pickup.
Check the DC voltage at Pin 2 the negative input and then the output pin 4. They should be almost the same as pin 1 ( not exactly the same !) . If it isn't , either you have some defective components / defective pin connections or a dead chip !
If all is well replace the cap C1 with another one and recheck it's polarity when connecting !
All voltages measured with respect to ground.
Is the metal tab properly isolated from ground ? check it with your DMM.
If it's OK...
Disconnect C1 47uF. This is the negative feedback bypass capacitor.
With it removed the amp will have a dc gain of 1.
Check the dc voltage at pin 1 the +ve input. It should be less than 0.1 V and typically about 0.01V. You could (ac ) short the input to ground to prevent any noise pickup.
Check the DC voltage at Pin 2 the negative input and then the output pin 4. They should be almost the same as pin 1 ( not exactly the same !) . If it isn't , either you have some defective components / defective pin connections or a dead chip !
If all is well replace the cap C1 with another one and recheck it's polarity when connecting !
All voltages measured with respect to ground.
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D).Sorry for posting for such a small problem, I guess I was too lazy to pull everything out.
Never saw this question earlier. I'm not very sure what you want to do but if it is what I think you mean , the answer is NO !
Don't change anything . Everything is working fine right now and going by the type of question you put up it looks like you could end up with a lot of problems if you change ANYTHING !
Cheers.
Don't change anything . Everything is working fine right now and going by the type of question you put up it looks like you could end up with a lot of problems if you change ANYTHING !
Cheers.
18.5 SUPPLY
You get about 26.5 vdc using AC * 1.44 = DC voltage, depending on your caps
You get about 26.5 vdc using AC * 1.44 = DC voltage, depending on your caps
not depending on your caps. Depends on voltage tolerances and transformer regulation and average load current.
I played with both chips and they both sound fine as long as proper circuit layout is employed. The TDA2050 has a bit more output swing at a given supply voltage and it has a higher peak current of 5 amps. The LM1875 has a higher max operating voltage for those who like to push things.
+/- 18 volts is the maximum I'd recommend with 4 ohm loads and around +/- 23 volts for 8 Ohm loads. The small IC needs to dissipate a lot of waste heat, so I'd mount the chip directly on a large heatsink (no insulators). Beware that doing this puts the negative rail on the heatsink so it must be isolated from the chassis.
+/- 18 volts is the maximum I'd recommend with 4 ohm loads and around +/- 23 volts for 8 Ohm loads. The small IC needs to dissipate a lot of waste heat, so I'd mount the chip directly on a large heatsink (no insulators). Beware that doing this puts the negative rail on the heatsink so it must be isolated from the chassis.
Mark,
I didn't see your post as it came during a period of great mental turmoil.
I prefer the LM1875. Many don't hear a difference between the two but on the same board I felt the LM1875 sounds very slightly better to my ears. Mainly on transient impact. This effect can vary depending on your source and your loudspeaker and music content ! As usual there are always enough variables that one must check things out in 'their own system'.
If you were to make a blind choice , take the LM1875.
Initially I used a 15-0-15 V transformer later changing to a 16-0-16 V transformer and the speakers are 6 ohms typically and dropping close to 4 ohms at HF. Plays loud and the heatsinks get hot but acceptable. Look at the pictures on the first page of this thread. At average listening levels the heatsinks are slightly warm. The chips are mounted directly on the heat sink with a mica washer and silicone grease.
Length of the heatsink is 105 mm and height is 50 mm. Depth of each fin is 40 mm. The fins are tapered and start off at 4mm at the base and end up 1mm at the tip. There are 10 fins.
I have some spare unused boards if anyone wants. Send a PM.
Cheers.
I didn't see your post as it came during a period of great mental turmoil.
I prefer the LM1875. Many don't hear a difference between the two but on the same board I felt the LM1875 sounds very slightly better to my ears. Mainly on transient impact. This effect can vary depending on your source and your loudspeaker and music content ! As usual there are always enough variables that one must check things out in 'their own system'.
If you were to make a blind choice , take the LM1875.
Initially I used a 15-0-15 V transformer later changing to a 16-0-16 V transformer and the speakers are 6 ohms typically and dropping close to 4 ohms at HF. Plays loud and the heatsinks get hot but acceptable. Look at the pictures on the first page of this thread. At average listening levels the heatsinks are slightly warm. The chips are mounted directly on the heat sink with a mica washer and silicone grease.
Length of the heatsink is 105 mm and height is 50 mm. Depth of each fin is 40 mm. The fins are tapered and start off at 4mm at the base and end up 1mm at the tip. There are 10 fins.
I have some spare unused boards if anyone wants. Send a PM.
Cheers.
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Dear Ashok,
Many thanks for the information I will find it very useful indeed, I've made a pair of Frugal Horns and I'm using an LM3875 at the moment, very cheaply made and using Thorsten's inverted circuit and the original GC configuration with just a pair of 1000uf caps.
For the LM1875 project I already have a 12-0-12 300 VA transformer and a Chinese power supply with a huge Bridge and 4 off 10,000 uf Nover caps. I've also used a couple of 1,000 uf caps across two of the Novers. This is in the box and connected up and I'm getting +/- 19 V at outputs, I expect that will go down when I connect the amp boards
For the amp boards I am using BrianGT's ChipAmp ones and have ordered the components from Cricklewood Electronics in London. I'll take a few pics and post them here when I'm done.
Mental turmoil is awful I do hope you are through it and out on the otherside.
Jim
Many thanks for the information I will find it very useful indeed, I've made a pair of Frugal Horns and I'm using an LM3875 at the moment, very cheaply made and using Thorsten's inverted circuit and the original GC configuration with just a pair of 1000uf caps.
For the LM1875 project I already have a 12-0-12 300 VA transformer and a Chinese power supply with a huge Bridge and 4 off 10,000 uf Nover caps. I've also used a couple of 1,000 uf caps across two of the Novers. This is in the box and connected up and I'm getting +/- 19 V at outputs, I expect that will go down when I connect the amp boards
For the amp boards I am using BrianGT's ChipAmp ones and have ordered the components from Cricklewood Electronics in London. I'll take a few pics and post them here when I'm done.
Mental turmoil is awful I do hope you are through it and out on the otherside.
Jim
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