I'm just curious from which local dealer you bought from, usually I am quite skeptic of most of them here in Finland (Partco, Bebek, Starelec etc etc..) they may be ok for hobbyist level stuff as long as one is aware these shops don't necessary adhere to strict quality standards, one have to ask them strictly if they can assure the origin of the part, some semiconductor parts may not necessary be relabeled but counterfeits meaning they may or may not work quite similarly to original brands, and as jmfahey mentioned some components may be rejects etc..
There's no mention of heatsinking in this thread nor do I see any picture of one, I hope you have it mounted onto one.
And btw 60V is a bit much for a chip that can't handle more than 20W.
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Rampo is so stubborn about lm1875, he will never learn.
LM3886 was my suggestion, and others. Simple solution.
He dismissed it by some stupid power comment. He does not realize power from the amplifier is controlled by the voltage input. Even 1000 watts amplifier can be used to power 5 watt speaker, if voltage on the input is under control.
At normal listening, we rarely use one or two watts to the speaker.
Not to mention mid and tweeter, where few hundred milliwatts is all it takes.
No matter what power chip is used. All controlled by the volume pot.
LM3886 was my suggestion, and others. Simple solution.
He dismissed it by some stupid power comment. He does not realize power from the amplifier is controlled by the voltage input. Even 1000 watts amplifier can be used to power 5 watt speaker, if voltage on the input is under control.
At normal listening, we rarely use one or two watts to the speaker.
Not to mention mid and tweeter, where few hundred milliwatts is all it takes.
No matter what power chip is used. All controlled by the volume pot.
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How do I know they are fake?
- looks like they are fake 1875, because measuring resistors pin to pin LM1875 "fake" is just same as TDA 2030. In should not be so.
can't you try to repair original woofer amp board?
- You mean mid and highrange amp, possibly, but original BD transistor types are not any more available, tryed equivalent type, which don't work well; distorted sound.
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Random thoughts...
Given the 1 ohm emitter resistors why not try replacing the outputs with a pair of power FET's being sure to add a 220 ohm gate stopper resistor to each. Bias to around 50ma for safety. R679 would probably need reducing to get the bias in range as you would need to develop around 8 volts across the bias spreader.
Given the 1 ohm emitter resistors why not try replacing the outputs with a pair of power FET's being sure to add a 220 ohm gate stopper resistor to each. Bias to around 50ma for safety. R679 would probably need reducing to get the bias in range as you would need to develop around 8 volts across the bias spreader.
@Rampo
Yes, I already saw that 60V max, that's valid only for genuine parts bought from a reliable source such as Mouser, DigiKey etc.
Now your turn, how about reciprocate a bit and answer peoples questions, thanks.
ps. I made a mistake in previous post, power rating should be 30W.
Yes, I already saw that 60V max, that's valid only for genuine parts bought from a reliable source such as Mouser, DigiKey etc.
Now your turn, how about reciprocate a bit and answer peoples questions, thanks.
ps. I made a mistake in previous post, power rating should be 30W.
Hi, already answered to peoples questions.
Same questions are made all the time, all answered once and twice, thanks all.
FAKE 1875 is over. Thanks for all.
Rampo
Same questions are made all the time, all answered once and twice, thanks all.
FAKE 1875 is over. Thanks for all.
Rampo
Even better, amplifier can only deliver what comes from the power supply.
That 57 V supply allows maximum 49 Vpp (Darlingtons have around 4 Vce loss each) so maximum possible V RMS out into speaker is 17 so some 36 W RMS.
Perfectly possible for two TO220 Darlingtons or an LM3886; way too much for an LM1875, even if original
I would try again to repair original amp.
It is not a problem of "wrong Darlingtons" per se, in fact I would use higher rated TIP142/147 if they fit the heatsink (TO218/247 case instead of TO220)
Distortion heard may come from having other bad components or lack of biasing but in principle that amp should be quite repairable.
Darlington problem is in it's inside resistors values, impossible to find totally suitable equivalent types.
Sorry but I disagree, I have listened extensively to various 47Labs amplifiers including Gaincard, that use the LM1875 and they sound excellent. I heard them on Avantgarde Duo, Sonus Faber and other speakers. I probably know one not very obvious trick why they sound better than the average gainclone tho... partly because of the black gate caps and how the power supply has been built and there is another trick. I also made a number of gainclones, but I could not reach that level of magic, however they still sound very good for diy amps.
The LM1875 is a great chip amplifier I have built loads and they all work
IF YOU KNOW WHAT YOU ARE DOING !! from the DIY help desk
IF not build a validated kit from one of the many trust worthy suppliers .. honestly 🙄
IF YOU KNOW WHAT YOU ARE DOING !! from the DIY help desk
IF not build a validated kit from one of the many trust worthy suppliers .. honestly 🙄
Because this member has zero knowledge of electronics but pretends to do so .. even with valued advice from experienced constructors, on this forum we are getting more and more of these posts .. contribute nothing and take all
TDA 7294 is good to 100V, IIRC, and 100W, so it will work very well at 60V.
For $4, it is quite a decent priced unit.
And cheaper than a 1875 at 8 Euros.
For $4, it is quite a decent priced unit.
And cheaper than a 1875 at 8 Euros.
Here in India I get plate amps ranging from 2.5 W to 1000W per channel RMS, it is easy to choose what I need, chip and transistor based amps are sold in a wide variety, and I am sure there will be many choices on international sites as well.
The restriction of power suply voltage is unclear, it may simply be a way to cut costs.
In any case, knowledge and experience seem lacking, so I am leaving this thread.
The restriction of power suply voltage is unclear, it may simply be a way to cut costs.
In any case, knowledge and experience seem lacking, so I am leaving this thread.
Thread closed pending further action- Status
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