Yeah you can though you'll probably want to increase the I/V resistor (currently 1k1) by a factor of 2 (if you're not using the passive filter) or 4 (if you plan a passive filter with 39mH inductors).
<edit> Btw matt - I recently came across this encouraging post over on Audiocircle - http://www.audiocircle.com/index.php?topic=134972.0 😀 A few views but no replies - do those guys not realize the qualities of NOS DACs?
<edit> Btw matt - I recently came across this encouraging post over on Audiocircle - http://www.audiocircle.com/index.php?topic=134972.0 😀 A few views but no replies - do those guys not realize the qualities of NOS DACs?
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good
Very interesting your scheme you use the dac as a current source for emitter but
way you don’t use the reference pin ?😛
Very interesting your scheme you use the dac as a current source for emitter but
way you don’t use the reference pin ?😛
The reference pin isn't used as a reference for the transistor that's right. It doesn't give the correct voltage. To get the highest swing I've set the reference voltage (3.8V) for the transistors as high as possible within the output compliance spec of the 1387 (up to 4.5V on a 6V supply).
An alternative
A connection like a NPN BJT with the base connected to the reference voltage of your TDA1387 and a Resistor connected from emitter to the GND.
The output on emitter Vout Ref is lower by a one Vbe
A connection like a NPN BJT with the base connected to the reference voltage of your TDA1387 and a Resistor connected from emitter to the GND.
The output on emitter Vout Ref is lower by a one Vbe
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Not quite ...
If you're getting highest performance for YOUR project at some ad hoc Vref of your choice, you're most likely SERIOUSLY compromised somewhere else in your DACs topology. Find n' fix those ... then come back to Vref PER DATASHEET SPECS.
Uh... not quite... the datasheet value for Vref is optimal. Philips didn't just toss off a convenient value for the sake of what most manufs (SoundBlaster, etc.) would use. They OPTIMIZED the 1387/1545A for the pwr/voltage/current available via commercial regulators.
If you're getting highest performance for YOUR project at some ad hoc Vref of your choice, you're most likely SERIOUSLY compromised somewhere else in your DACs topology. Find n' fix those ... then come back to Vref PER DATASHEET SPECS.
Looks like you misinterpreted my meaning. Let me spell it out a little more explicitly:
The reference pin isn't used as a reference for the transistor that's right. It doesn't give the correct voltage for biassing the I/V transistor.
The reference pin isn't used as a reference for the transistor that's right. It doesn't give the correct voltage for biassing the I/V transistor.
Alternative
This is a more clear circuit you can use the BC550 560 or the same smd BC850 860 🙂
Output on your R2
This is a more clear circuit you can use the BC550 560 or the same smd BC850 860 🙂Output on your R2
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This circuit doesn't suit my needs because the Vref for TDA1387 is roughly one sixth of the supply voltage. In this case that's 1V - after buffering with an NPN EF that becomes 0.4V meaning the I/V transistor goes into saturation unless its output swing is below 100mV or so. Far too low an output voltage range for my needs.
Hi guys,
for opamp folks I advise the LT1028 with 330pF, stable (4 Dacs and 1.3k feedback R).
I keep I eye on Richard's circuit and Matt's feedback 😉
for opamp folks I advise the LT1028 with 330pF, stable (4 Dacs and 1.3k feedback R).
I keep I eye on Richard's circuit and Matt's feedback 😉
errata corrige
Yes i have made a mistake this works well with TDA1543 and TDA1545 .🙁
Ok the output of tda1387 is a strange output .....😱, now i have read well the data sheet...the I/V stage have reference to ground .
If you connect my stage to the gnd as reference and a -6V on emitter Resistor of the first NPN it can work ?
Yes i have made a mistake this works well with TDA1543 and TDA1545 .🙁
Ok the output of tda1387 is a strange output .....😱, now i have read well the data sheet...the I/V stage have reference to ground .
If you connect my stage to the gnd as reference and a -6V on emitter Resistor of the first NPN it can work ?
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I cannot imagine how it works at all with TDA1543 and TDA1545 as their output compliance range doesn't go close enough to the 0V rail. Both need around 2V minimum on their output pins.
Do you happen to know which specific LT1028? LT1028AC or LT1028C? The datasheet on page 3 shows the two parts have some different specs. I'm not sure which specs matter for this application.
Also: buy them direct from Linear Technology, or roll the dice with AliExpress? I mean, are these opamps something that are likely to be faked?
I doubt that the 'A' version has any advantage in this application - its superiority is mainly in guaranteed noise and bandwidth which aren't particularly relevant here.
Matt and abraxalito:
I've ordered the 8x TDA1387 DAC and am now assembling my mouser order (I've got 3 to 4 weeks before the DAC arrives). You have suggested replacing the analog stage decoupling caps (specifically, "The stock DAC has two electrolytic and four film capacitors for opamp decoupling. Remove these capacitors and replace with as many 35V rated caps as you can fit. Find the lowest ESR you can get (Rubycon ZLH; Nichicon PW,HW; NCC KY, KZE)"). What should the target capacitance be?
Many thanks,
Scott
I've ordered the 8x TDA1387 DAC and am now assembling my mouser order (I've got 3 to 4 weeks before the DAC arrives). You have suggested replacing the analog stage decoupling caps (specifically, "The stock DAC has two electrolytic and four film capacitors for opamp decoupling. Remove these capacitors and replace with as many 35V rated caps as you can fit. Find the lowest ESR you can get (Rubycon ZLH; Nichicon PW,HW; NCC KY, KZE)"). What should the target capacitance be?
Many thanks,
Scott
There's no target capacitance as it depends on how many will fit within a short distance (say 5cm or so) from the opamps. If you liberate the PCB from its box more can be accommodated, but only you can decide on the mechanical constraints.
abraxalito:
Thank you, once again, for your prompt response! I'll start hunting for small diameter, low ESR 35V caps, favoring those listed in the wiki.
One other question: at some point in this thread, someone inquired whether it was necessary to remove the 1uF "105" caps on the underside of the pcb. I don't recall anyone answering the question. If 1000uF caps are soldered to the TDA1387s on the top side, do the 105 caps really need to be removed?
Regards,
Scott
Thank you, once again, for your prompt response! I'll start hunting for small diameter, low ESR 35V caps, favoring those listed in the wiki.
One other question: at some point in this thread, someone inquired whether it was necessary to remove the 1uF "105" caps on the underside of the pcb. I don't recall anyone answering the question. If 1000uF caps are soldered to the TDA1387s on the top side, do the 105 caps really need to be removed?
Regards,
Scott
I responded to that but as I haven't tried it with the 105 caps in place myself I can't give a definitive answer, so its 'suck it and see'. I believe it'll be fine but have no experimental evidence to back this up.
Abraxalito, is there a "formal" name for the turret boards you are using to assemble the additional circuits? I'm thinking the fancier "next gen" mods might be too complex to try to assemble point-to-point. I think doing like you with those boards might be an easier approach. But I can't seem to find anything on Mouser, but I'm probably just not using the right search terms.
The stuff I use I buy at the local electronics market, and occasionally on Taobao so I don't have to use any English name for it. I normally call it 'prototyping board'. You can find an example here : 20pcs 5x7 4x6 3x7 2x8 cm double Side Copper prototype pcb Universal Board for Arduino Free Shipping Dropshipping-in Other Electronic Components from Electronic Components & Supplies on Aliexpress.com | Alibaba Group