I have brought this topic over to here as it's the most logical section for it - I started the post here: http://www.diyaudio.com/forums/showthread.php?postid=1526060#post1526060
What I'm trying to do is disconnect the bottom of the schematic that supplies the main VDD (10 to 40V) & some other supplies +- 15V +-5V.
I can supply the main VDD from 24V battery & the improvement in sound is huge compared to SMPS VDD.
So I wondered would there be an improvement if I also used the battery to supply the PS to the digital ICs? I can run it for about 2-3mins off battery & it seems to be much cleaner, clearer sound but not enough time for a real evaluation.
Here's my dilemma:
When I disconnect this part of the circuit & plug in a 24V DC from SLA Battery into the red line that gives VDD & thse other supplies, I get an error message of DCDect being 0V instead of 5V.
When I leave it connected in but break the red line connection to VDD & the +-15V & +-5V and instead feed the 24V DC into the red line, I get the switching IC (IC701) beginning to click after a short while at which point I turn off the amp.
I know I could fool the circuit by putting 5V on the DCdet line but I would feel safer if I knew why the DCDET is not being set to 5V correctly with my battery connection.
The schematic comes in 3 parts, the first one I've attached (Part 1) - it is the main switcher which supplies VDD & goes on to supply +-15V and +-5V on next schematic. This schematic (Part 1) also has a standby circuit, at the top and the main VDD switcher is complicated by the fact that is is a variable voltage volume control - controlled by a reference voltage which comes from the volume control. The +-Sense signal & the volcnt signal are part of this control loop.
What I'm trying to do is disconnect the bottom of the schematic that supplies the main VDD (10 to 40V) & some other supplies +- 15V +-5V.
I can supply the main VDD from 24V battery & the improvement in sound is huge compared to SMPS VDD.
So I wondered would there be an improvement if I also used the battery to supply the PS to the digital ICs? I can run it for about 2-3mins off battery & it seems to be much cleaner, clearer sound but not enough time for a real evaluation.
Here's my dilemma:
When I disconnect this part of the circuit & plug in a 24V DC from SLA Battery into the red line that gives VDD & thse other supplies, I get an error message of DCDect being 0V instead of 5V.
When I leave it connected in but break the red line connection to VDD & the +-15V & +-5V and instead feed the 24V DC into the red line, I get the switching IC (IC701) beginning to click after a short while at which point I turn off the amp.
I know I could fool the circuit by putting 5V on the DCdet line but I would feel safer if I knew why the DCDET is not being set to 5V correctly with my battery connection.
The schematic comes in 3 parts, the first one I've attached (Part 1) - it is the main switcher which supplies VDD & goes on to supply +-15V and +-5V on next schematic. This schematic (Part 1) also has a standby circuit, at the top and the main VDD switcher is complicated by the fact that is is a variable voltage volume control - controlled by a reference voltage which comes from the volume control. The +-Sense signal & the volcnt signal are part of this control loop.
Second part of SMPS schematic - Part 2 contains the +-15V & +-5V which is derived from the VDD feed. It also contains another switcher which generates BK+3V, BK+3.3V, BK+5.7V among others and is generated from the standby voltage.
Any change in sound is likely to be produced by the much higher AC output impedance of batteries and long external wirings in comparison with a well regulated SMPS. That kind of digital amplifiers exhibit 0dB PSRR.
Add some impedance in series with the speakers, maybe with non-linear elements to simulate the exponential/logarithmic I/V characteristic of batteries and you will get a similar result...
Add some impedance in series with the speakers, maybe with non-linear elements to simulate the exponential/logarithmic I/V characteristic of batteries and you will get a similar result...
Eva,
I am saying that the sound with batteries supplying the main VDD i.e. the output stage is far superior to using the "well regulated SMPS" - it has more detail & nuances in the sonic reproduction & is quieter - more of the emotion of the piece is conveyed.
From what you're saying, I gather you're not a fan of batteries and seem to have a rigid stance about this? I can tell you, in this instance, the batteries are superior by a long ways. Maybe it's the quality of the SMPS - it improved when I put a large cap between it & the output stage
Now can we not get into an argument over battery Vs SMPS - I just wanted to find out how to bypass this complicated SMPS.
I discovered that the DCDET signal is actually generated by a microprocessor (which is powered on by the standby PS), so it is based on the timing of the supplies coming up. But this should be exactly the same as if I was powering it from the SMPS?
I am saying that the sound with batteries supplying the main VDD i.e. the output stage is far superior to using the "well regulated SMPS" - it has more detail & nuances in the sonic reproduction & is quieter - more of the emotion of the piece is conveyed.
From what you're saying, I gather you're not a fan of batteries and seem to have a rigid stance about this? I can tell you, in this instance, the batteries are superior by a long ways. Maybe it's the quality of the SMPS - it improved when I put a large cap between it & the output stage
Now can we not get into an argument over battery Vs SMPS - I just wanted to find out how to bypass this complicated SMPS.
I discovered that the DCDET signal is actually generated by a microprocessor (which is powered on by the standby PS), so it is based on the timing of the supplies coming up. But this should be exactly the same as if I was powering it from the SMPS?
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