I explained how to do this in post 216 right above. Cut the traces that provide Vdd (3.5v) to pins 30 and 31 and you will get the lowest gain of 21.6dB. You need a magnifier, a sharp exacto razor with a pointy tip and steady hands.
TDA7492 differential input
I replaced the input caps on TPA3116D2 board with lundahl LL 1540 high impedance , high input input transformers with great results ( no pops, , no hum , better dynamics , smoother sounding )
I wonder if I could do it also with the TDA7492 As I can see on the schematic the TDA7492 also has differential input ( but all the boards sold are Single ended input . The problem with transformer input is that there should be no dc flowing through the secondairy winding so both diff inputs (one side ) should have the same voltage or no voltage on it .
Maybe somebody knows if this is the case or tried input tranformer (unbalanced in , balanced out with TDA 7492
)
I replaced the input caps on TPA3116D2 board with lundahl LL 1540 high impedance , high input input transformers with great results ( no pops, , no hum , better dynamics , smoother sounding )
I wonder if I could do it also with the TDA7492 As I can see on the schematic the TDA7492 also has differential input ( but all the boards sold are Single ended input . The problem with transformer input is that there should be no dc flowing through the secondairy winding so both diff inputs (one side ) should have the same voltage or no voltage on it .
Maybe somebody knows if this is the case or tried input tranformer (unbalanced in , balanced out with TDA 7492
An externally hosted image should be here but it was not working when we last tested it.
)
I see no reason for why you can't use an input trafo with the 7492. I've used one with the TDA8932 which has a similar differential input.
You might be able to eliminate the input coupling capacitors too, if your trafo has a CT. It would be something of an experiment though - there are two pins on the device which might be suitable for connecting to the CT, VREF (pin 34) or SVR (pin 29). I'd suggest measuring the DC voltage on both and comparing it to the DC voltage on the input pins. If either of them has the same voltage then they'd be suitable as a connecting point for the CT and the input caps can be eliminated (shorted).
You might be able to eliminate the input coupling capacitors too, if your trafo has a CT. It would be something of an experiment though - there are two pins on the device which might be suitable for connecting to the CT, VREF (pin 34) or SVR (pin 29). I'd suggest measuring the DC voltage on both and comparing it to the DC voltage on the input pins. If either of them has the same voltage then they'd be suitable as a connecting point for the CT and the input caps can be eliminated (shorted).
The output of the LL1540 is floating See pic )
so there is no center tap
I want to remove all input caps otherwise it makes no sense to use input transformers .
For R channel the balanced output has to be connected to pin 33(INNB and 32(INPB)
and L channel to 22 (INPA) and 23 (INNA)
The points is : is there any dc (or voltage difference ) between p 33 and p32 and the same question for p 22 and p23
I measured 1,8 v over p32 but p23 i could not measure so far because it is under the heatsink and the cap is probably tiny (smd ) .
An externally hosted image should be here but it was not working when we last tested it.
so there is no center tap
I want to remove all input caps otherwise it makes no sense to use input transformers .
For R channel the balanced output has to be connected to pin 33(INNB and 32(INPB)
and L channel to 22 (INPA) and 23 (INNA)
The points is : is there any dc (or voltage difference ) between p 33 and p32 and the same question for p 22 and p23
I measured 1,8 v over p32 but p23 i could not measure so far because it is under the heatsink and the cap is probably tiny (smd ) .
I could remove the heatsink and measured voltage just behind the 1 uF smd cap
it is 2V ; just the same voltage as the outer leg of the 1uF input cap . so voltage behind both caps is the same and the conclusion is that I can use the LL1540 input transformer because no dc is should flow through the secondairy of transformer
That is promising !
it is 2V ; just the same voltage as the outer leg of the 1uF input cap . so voltage behind both caps is the same and the conclusion is that I can use the LL1540 input transformer because no dc is should flow through the secondairy of transformer
That is promising !
hello
does these Sanyo have the same characteristics as the Panasonic oscons ?
100 25V 220UF 8x10mm Sanyo SMD Aluminum Solid Capacitor | eBay
i want to use them as bypass with Panasonic fm 2200uf/25 v on TDA7492
does these Sanyo have the same characteristics as the Panasonic oscons ?
100 25V 220UF 8x10mm Sanyo SMD Aluminum Solid Capacitor | eBay
i want to use them as bypass with Panasonic fm 2200uf/25 v on TDA7492
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thanks for your reply
i don,t have the Panasonic OSCON 330uF 25V SEPF caps .
They are hard to get in the Netherlands and quit expensive on ebay that,s why
i looked for an alternative ( Sanyo as in in the link former message )
they Sanyo are smd but that is no problem , i can solder wires to it
i don,t have the Panasonic OSCON 330uF 25V SEPF caps .
They are hard to get in the Netherlands and quit expensive on ebay that,s why
i looked for an alternative ( Sanyo as in in the link former message )
they Sanyo are smd but that is no problem , i can solder wires to it
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there are other caps with good numbers like chemicon psg series.
but you can get 'decent caps' for much less money.
especially for a low cost amp.
here is a link to german discount shop.
10 pcs KZE caps for 0.80€.
the only downside might be that they are a bit old (but never used)
Elko, 470 µF, 25 V, 10 Stück, NIPPON CHEMI-CON KZE - Bauelemente / Bauteile - Passive Bauelemente - Elkos / Goldcaps - Pollin Electronic
but you can get 'decent caps' for much less money.
especially for a low cost amp.
here is a link to german discount shop.
10 pcs KZE caps for 0.80€.
the only downside might be that they are a bit old (but never used)
Elko, 470 µF, 25 V, 10 Stück, NIPPON CHEMI-CON KZE - Bauelemente / Bauteile - Passive Bauelemente - Elkos / Goldcaps - Pollin Electronic
as far as i can see Panasonic OSCON 330uF 25V SEPF are not sold by conrad.nl . if so , could you provide me a link
There are only selling to bussines , not to private persons as they stated
besides that minimum order is 50 e
I just checked mine, and ended up needing to reverse it. Sounds even better now. I kept jacking with it, wondering why the bass was better than stock, but still a touch lacking. I've got all the stuff to do the snubber mod, maybe this holiday weekend I'll do that and test it on some other speakers I've got around the house.