Hi !
I saw an interesting video on the repair of an old Lecson Stereo Plus integrated amplifier
This amplifier uses an obsolete TDA7520 integrated amplifier that drives a pair of power darlingtons, one per channel
The TDA is a dual driver
I found the pdf online and was surprised by the extreme simplicity of the application circuit proposed in the datasheet
Since the Lecson mentioned above seems to sound really good, I wonder why this solution is less used and especially if there are non-obsolete parts with the same characteristics as the TDA7520
I tried to search but I'm confused
thanks to everyone and have a nice day
gino
I saw an interesting video on the repair of an old Lecson Stereo Plus integrated amplifier
This amplifier uses an obsolete TDA7520 integrated amplifier that drives a pair of power darlingtons, one per channel
The TDA is a dual driver
I found the pdf online and was surprised by the extreme simplicity of the application circuit proposed in the datasheet
Since the Lecson mentioned above seems to sound really good, I wonder why this solution is less used and especially if there are non-obsolete parts with the same characteristics as the TDA7520
I tried to search but I'm confused
thanks to everyone and have a nice day
gino
I recall some hype on power darlingtons when they arrived at the market about 50 years ago. Nowadays we know that they're rather slowish devices. Sorry, but I don't get why one should design an amplifier with either obsolete and inferior devices than we have today?
Best regards!
Best regards!
Hi 🙂 thank you very much for your kind and valuable reply
Actually i guess that this TDA chip can drive also a bjts complementary pair directly
To be honest i have only seen applications with darlingtons
One in the mentioned Lecson and another in an old kit
However more than a complete chip amp i like the idea of a chip driving an output stage
Actually i guess that this TDA chip can drive also a bjts complementary pair directly
To be honest i have only seen applications with darlingtons
One in the mentioned Lecson and another in an old kit
However more than a complete chip amp i like the idea of a chip driving an output stage
This was in fashion for a while. Marantz and others used similar ICs. Also some STK modules had similar approach. The chips that came after TDA7250 had power transistors integrated which made it smaller, cheaper and easier to integrate. Transistors can be made precise/matched when being onchip. That are some reasons why TDA7250 fell out of grace.
Such ICs often are sensitive, unique, obsolete and not pin compatible with other ICs. Avoid when possible. There are quite some very good TDA amplifier ICs that are pin compatible with eachother.
Such ICs often are sensitive, unique, obsolete and not pin compatible with other ICs. Avoid when possible. There are quite some very good TDA amplifier ICs that are pin compatible with eachother.
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Hi ! thank you very much for your valuable advice
The only thing that worries me is to have output devices that get very hot indeed on the same chip of VAS and driver stage
Is this a no issue ?
Good morning and thank you sincerely for the kind and precious advice
I have a psychological problem starting from scratch
In fact I tend to modify something existing often ending up ruining it more or less irreparably But I like to open look inside stick my hands
For example now that you mention the car amps one of my ideas was to cannibalize a good car power amplifier, bypass the internal switching power supply and power it with a dual linear power supply
I don't think that anyone in their right mind comes up with these ideas
I don't really like the idea of using a powerful 12VDC switching to power another switching inside the amplifier It seems like nonsense to me
What I like about car amps is the order in which they are built
Some seem like a work of art
And then being made to play loud they are designed with great attention to the thermal aspect
I have a psychological problem starting from scratch
In fact I tend to modify something existing often ending up ruining it more or less irreparably But I like to open look inside stick my hands
For example now that you mention the car amps one of my ideas was to cannibalize a good car power amplifier, bypass the internal switching power supply and power it with a dual linear power supply
I don't think that anyone in their right mind comes up with these ideas
I don't really like the idea of using a powerful 12VDC switching to power another switching inside the amplifier It seems like nonsense to me
What I like about car amps is the order in which they are built
Some seem like a work of art
And then being made to play loud they are designed with great attention to the thermal aspect
A more recent chip for roughly the same job was the LME49811 by TI, although it was just monaural. And when I said »was« I exactly meant it that way. It's also obsolete by now. In September 2013 Elektor magazine published the Q-Watt amplifier that featured this chip, but unfortunately also a Darlington-esque driver-power device configuration.
Best regards!
Best regards!
Just try to create new devices. When they are constructed carefully and tidy just leave them be and use them. It is rewarding and satisfying. Good for selfesteem. It is manual labour and metal work is very Zen. With new DIYers it works to have stuff cut out from cardboard in real life size to have them place transformer, amplifier board, volume etc. on the best places with shortest wiring. This works way better than looking at screens IMHO. Your head must do 3D thinking and not a computer.
There are several good quality boards by LOSC with for instance TDA7388 that can be encased with a good quality linear LDO power supply. In fact I like such simple setups as they are cheap, small, reliable, good sounding, low in power consumption and generated heat and more the essence instead of useless features. I for sure don’t need more than 20W output power. Low power means that regulated PSUs are possible, no fan is necessary, heatsink is smaller etc. You can make it as steampunk or industrial looking as you like. Can show you a few pictures if you like.
There are several good quality boards by LOSC with for instance TDA7388 that can be encased with a good quality linear LDO power supply. In fact I like such simple setups as they are cheap, small, reliable, good sounding, low in power consumption and generated heat and more the essence instead of useless features. I for sure don’t need more than 20W output power. Low power means that regulated PSUs are possible, no fan is necessary, heatsink is smaller etc. You can make it as steampunk or industrial looking as you like. Can show you a few pictures if you like.
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Thank you very much again for your kind support
I was struck by the simplicity of the schematic I have to start easy
I have big problems even in just adding a IEC socket on the back of a unit with a captive cord that i hate
I would make detachable power cords mandatory by law That silly tail hanging out is annoying
In the past i have just assembled some kits starting from ready to use board
And also i have admired some restoration jobs i have seen on video performed on units taken from the garbage bin
I have two main goals now ... to check main transformers and caps quality with portable instruments
They are the most expensive parts in amps and also very critical
I have to understand what really matters in power supplies first
I was struck by the simplicity of the schematic I have to start easy
I have big problems even in just adding a IEC socket on the back of a unit with a captive cord that i hate
I would make detachable power cords mandatory by law That silly tail hanging out is annoying
In the past i have just assembled some kits starting from ready to use board
And also i have admired some restoration jobs i have seen on video performed on units taken from the garbage bin
I have two main goals now ... to check main transformers and caps quality with portable instruments
They are the most expensive parts in amps and also very critical
I have to understand what really matters in power supplies first
No need for detachable mains cables. It is not about reaching the highest goal when you need to learn the basic things. Tell me what the difference is between a fine quality mains cable of 1 meter and a detachable IEC cable of 1 meter? Exactly the latter has more contacts so more error possibilities. You are not going to walk every day with the amplifier in your hands are you?
For the mentioned relatively low power car amplifiers you will need a 12...15V PSU so a (2 x ) 12V transformer preferably an 80 to 120VA type. And an LDO PSU capable of 12...15V 5A.
These work fine (industry standard) and just need a drilled hole.
For the mentioned relatively low power car amplifiers you will need a 12...15V PSU so a (2 x ) 12V transformer preferably an 80 to 120VA type. And an LDO PSU capable of 12...15V 5A.
These work fine (industry standard) and just need a drilled hole.
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And, after all, what's your goal with the amplifier itself? There are literally umpzillion designs around, and many of them are easy to build, around components that aren't hard to source. No need to hang on to obsolete things.
Best regards!
Best regards!
Exactly. Follow the KISS principle and do not hurry, just build up skills slowly but always with best possible result of that moment. Encasing ready made modules may be the right job at the right moment. I guess priority now is a good working device.
My TDA7297 amplifier of 2 x 3W. Relay based input control. R-core transformer with ideal rectifier and 22,000 µF cap. NOS aluminium volume knob (recycled). I just built it as I had all parts but it turned out to be a serious amplifier so it stayed.
Don't even think of reusing old casings/old amplifiers. You will discover there are way too many holes at exactly the wrong places. Better find an affordable new casing. I paid 10 or 20 Euro for this one. Just think at least 3 times how stuff should be placed optimally.
My TDA7297 amplifier of 2 x 3W. Relay based input control. R-core transformer with ideal rectifier and 22,000 µF cap. NOS aluminium volume knob (recycled). I just built it as I had all parts but it turned out to be a serious amplifier so it stayed.
Don't even think of reusing old casings/old amplifiers. You will discover there are way too many holes at exactly the wrong places. Better find an affordable new casing. I paid 10 or 20 Euro for this one. Just think at least 3 times how stuff should be placed optimally.
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You are clearly right but i tripped on a power cord 😡
and i like connectors like those medical grade They are work of art And i also like to play with cables
It is almost the only diy activity i did intensively
And i move often units to try different combinations
I understand that cheap commercial units have a big potential marred by some savings on critical parts
Mains transformers are very critical The very good amps have great transformers
i have seen industrial refurbished ones quite cheap And the same for caps
Thanks but my idea was different Fwiu the 12VDC enter a step up DC to dual DC switching mode converter that generates the dual power supply
I would try to replace the step up with a mains transformer diodes bridge and caps
Powering a car amp with a dual linear power supply
There is an immense quantity of used power amps around I bought one for 20 euros
I would place it on the top of a cabinet containing PS caps and mains transformer to make a power amp
As you could read I used a new R-core transformer which is about the best one can use. When building new devices and thinking creative one can find nice new parts for not too much.
You don't need a dual PSU as car amplifiers only need 1 voltage. DC to DC converters are 666 in audio. Nothing but trouble. Just build linear if it is about best possible sound quality.
And it is not at all about quantity. You can have 100 amplifiers but you will use only 1. Better build a simple but good quality one (1) maxxed out in the important aspects and be proud, discard the rest so you don't trip over their power cords 🙂 Quantity won't make you happy, quality will. Quantity will cost you valuable time, time in which you could have built your best amplifier.
You don't need a dual PSU as car amplifiers only need 1 voltage. DC to DC converters are 666 in audio. Nothing but trouble. Just build linear if it is about best possible sound quality.
And it is not at all about quantity. You can have 100 amplifiers but you will use only 1. Better build a simple but good quality one (1) maxxed out in the important aspects and be proud, discard the rest so you don't trip over their power cords 🙂 Quantity won't make you happy, quality will. Quantity will cost you valuable time, time in which you could have built your best amplifier.
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Hi ! yes 🙂 it was my mistake in the end And as you say a uncut cable is always better that a cable with two connectors in between
Maybe it is a marketing idea but most expensive amps come with detachable power cords I guess it is a marketing idea anyway
my idea is to bypass the internal switching power supply Imho car amps are designed to be used in confined spaces with low ventilation
So the thermal issues are taken into account seriously Maybe amps have extensive heatsinks I like this very much
Moreover if one knows the product the car audio lovers are even sicker than home hifi lovers they change units very rapidly an the thrift stores are full of them at shockingly low prices
Well 2x3W is very low I wonder which speakers you use However me too i am moving to high efficiency speakers
I think they have the potential to sound more dynamic and require much less power to sing But this
i see But i really need more power because i am still experimenting with different speakers I would like to be able to drive speakers with different sensitivity and impedance Maybe i should select the speakers first and then the amp ?
but the idea of a universal amp is also intriguing An amp for all speakers
very true But there is a psicological reason When i was young i could not afford a stereo system So i dreamed about the equipment i was seeing in the magazine I know that i am not a balanced person