So i got my hand on a biiig pile of tda7052 Ics.
these are 1 watt btls chips, power amplifiers.
with built in DC volume controll circuitry.
actualy i have no use for them, 1 watt is not enough for anything at all.
but the volume controll functionality is interesting.
what if i would use a handfull of them as a multichannel volume controll ?
what You people estimate, how bad it could sound as a preamp ?
these are 1 watt btls chips, power amplifiers.
with built in DC volume controll circuitry.
actualy i have no use for them, 1 watt is not enough for anything at all.
but the volume controll functionality is interesting.
what if i would use a handfull of them as a multichannel volume controll ?
what You people estimate, how bad it could sound as a preamp ?
The DC volume control bit tells me you've got TDA7052As or Bs - the original 7052 had fixed output.
If it is the plain 7052, no suffix, then tough luck:
40 dB gain = too much noise, too little dynamic range. The part actually is quite decent if you do the math, but still this won't do.
BTL output with a speaker load is the only documented mode of operation. When attempting to run it single-ended into a high-impedance load, you're out on your own.
A 7052A or B would seem more promising, assuming it does actually work single-ended. You will want to run it at near maximum voltage (like 15 V) in order to get some decent output voltage out of it while keeping noise at bay by using an approximately 5:1 voltage divider at the output (470:120 ohms or so?). In which case you can hope for a maximum output of about 900 mV, so you may have to ease up on the voltage divider a bit for full power output. Input overload level ought to suffice for typical adjustable-level sources like consumer soundcards or onboard audio.
With the burden of a speaker load removed, distortion levels should actually be far lower than specified. Not sure how much the electronic volume control would contribute.
If it is the plain 7052, no suffix, then tough luck:
40 dB gain = too much noise, too little dynamic range. The part actually is quite decent if you do the math, but still this won't do.
BTL output with a speaker load is the only documented mode of operation. When attempting to run it single-ended into a high-impedance load, you're out on your own.
A 7052A or B would seem more promising, assuming it does actually work single-ended. You will want to run it at near maximum voltage (like 15 V) in order to get some decent output voltage out of it while keeping noise at bay by using an approximately 5:1 voltage divider at the output (470:120 ohms or so?). In which case you can hope for a maximum output of about 900 mV, so you may have to ease up on the voltage divider a bit for full power output. Input overload level ought to suffice for typical adjustable-level sources like consumer soundcards or onboard audio.
With the burden of a speaker load removed, distortion levels should actually be far lower than specified. Not sure how much the electronic volume control would contribute.
whoo, You got it right.
many of them are 7052...
but it seems there is a good 2 dozen of them 7052A.
so i found this in the datasheet.
what gives if it never gets more than around 1 volt on the DC volume controll pin ?
that would be full volume, the question is that 500 uVolt of noise is a lot or not.
I think if i provide a dummy load for one of its outputs, the otherhalf can function normally.. at least i guess.
many of them are 7052...
but it seems there is a good 2 dozen of them 7052A.
so i found this in the datasheet.
what gives if it never gets more than around 1 volt on the DC volume controll pin ?
that would be full volume, the question is that 500 uVolt of noise is a lot or not.
I think if i provide a dummy load for one of its outputs, the otherhalf can function normally.. at least i guess.
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You'd be more interested in noise at low to normal volume settings.
Noise floor at minimum gain is specified as 20 µV, which with a 5:1 output attenuator would be down to 4 µV, or with 26 dB worth of power amp, ~80 µV at the output. Easily hi-fi worthy.
Now what about normal volumes? You'd want a gain of about 14 dB (+5) from the whole preamp, so accounting for the output attenuator the chip would have to deliver +28 dB. Since gain is given for BTL operation which effectively doubles voltage gain, you'd have to look for the +34 dB point - which as it happens, is near maximum.
So it is recommended that control voltage range between about 0.4 and 1.3-1.4 V. Should be easy to obtain with an R-pot-R setup if you're using a stabilized supply of known fixed voltage. I would precede that voltage divider with some RC filtering though, as you don't really want to amplitude modulated your signal with supply noise.
Normal volume tends to be at about unity gain for pre + power, so we'd be looking at a point about 40 dB down from +34 dB, or -6 dB. This is reached a little short of 0.8 V. Output noise still looks to be under 50 µV at this point, so you'd get <10 µV with 5:1 divider included.
It could only happen that you don't reach full power output like this, in which case you may have to live with maybe 3 dB more noise. Still quite Hi-Fi worthy though (certainly when compared to the usual old single-chip volume/tone ICs); an NJM4558 opamp at +16.5 dB gives about 10 µV, too, and that tends to yield barely audible noise. If in doubt you could always include jumpers for output attenuation selection.
I wouldn't use a dummy load if I can help it, distortion would certainly suffer. Sounds like a job for a makeshift setup on perfboard / protoboard and a scope in any case.
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thank you for the help.
sadly i tested 12 of them and they are bad fakes mostly, rest simply refuses to work.
the fake ones do power up but if the volume turns past around 0.9 volts they make wierd artifacts. under that they are pretty noisy.
i built the btl circuit as a test and thrown a 16 ohm small speaker on the output.
power was provided by a set of batteries i had around.
hmm.. i guess it would have been too good as a free score.
sadly i tested 12 of them and they are bad fakes mostly, rest simply refuses to work.
the fake ones do power up but if the volume turns past around 0.9 volts they make wierd artifacts. under that they are pretty noisy.
i built the btl circuit as a test and thrown a 16 ohm small speaker on the output.
power was provided by a set of batteries i had around.
hmm.. i guess it would have been too good as a free score.
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