From the Amp Chip DIY Forum:
http://home.attbi.com/~greggbaker/Inv_chip_amp.gif
This should be an evolution of Thorsten's inverted GC schematic.
I understand all the changes in the amp , but....the power supply is a little strange.
Any ideas?
http://home.attbi.com/~greggbaker/Inv_chip_amp.gif
This should be an evolution of Thorsten's inverted GC schematic.
I understand all the changes in the amp , but....the power supply is a little strange.
Any ideas?
Koinichiwa,
Well, I don't know if you did follow the "What makes a good audio power transformer?" Thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=12611
In there I give the rationale for the dual transformer approach, the DC blocking and so on.
Something I have not drawn in is a high current, low resistance common mode choke with the associated X & Y Capacitors, such filters are controversial. It tend to use them more often than not though.
I would say that if you could get a suitable custom made unit with twice the primary turns, a small airgao to handle DC on the mains and fully symmetrical primary and secondary windings, with multiple electrostatic screens and with enough secondaries to power 2 Channels (that would mean 4pcs 30...48CT secondaries) you would have something as good or better than the approach using 4pcs of transformers.
It would likely have a long delivery time and be hideously expensive. Using multiple transformers, DC Blockers, field cancelling arrangements of windings et al will give you however 99% of the performance, if you buy surplus transformers it will be dead cheap too.
In cases where I have used powersupplies DC blocked, "low flux" connection and with leakage cancellation the results have been extremely pleasing.
Sayonara
Zldz said:
Well, I don't know if you did follow the "What makes a good audio power transformer?" Thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=12611
In there I give the rationale for the dual transformer approach, the DC blocking and so on.
Something I have not drawn in is a high current, low resistance common mode choke with the associated X & Y Capacitors, such filters are controversial. It tend to use them more often than not though.
I would say that if you could get a suitable custom made unit with twice the primary turns, a small airgao to handle DC on the mains and fully symmetrical primary and secondary windings, with multiple electrostatic screens and with enough secondaries to power 2 Channels (that would mean 4pcs 30...48CT secondaries) you would have something as good or better than the approach using 4pcs of transformers.
It would likely have a long delivery time and be hideously expensive. Using multiple transformers, DC Blockers, field cancelling arrangements of windings et al will give you however 99% of the performance, if you buy surplus transformers it will be dead cheap too.
In cases where I have used powersupplies DC blocked, "low flux" connection and with leakage cancellation the results have been extremely pleasing.
Sayonara
unfortunately here there is no REAL surplus market....
Koinichiwa,
Well, for one.
If Joe moved his point "G" to where the two PSU Capacitors join (as I always recommended) the sensitivity of his circuit to the wire between G and the join of two PSU Capacitors.... ;-)
If he used two bridges with good quality rectifiers and kept the rectifier returns separated I suspect the sound would clean up no end.
As for the bandwidth limiting, sure. It may help, much will depend upon the system. If the grounding is optimal, the recent revised schematic is employed in a suitably shielded enclosure and the bandwidth of the source is sufficiently narrow (like nothing wider bandwidth than SACD or DVD-A) I doubt it is neccesary.
Alternatively a pair of capacitors can be connected, one of 22pF Silver Mica between output and negative chip input and one of 220pF Silver Mica between negative chip input and ground. This should keep things stable, puts the -3db rolloff point where Joe likes it and makes the rollof absolutely stable without buffer.
I personally would probably put the rolloff much higher, I'd use 4.7pF/47pF I guess, but thats a matter of taste. Buffering? Not strictly needed, but if you like to, sure. I prefer the conceptual simplicity of not adding things that can be done without.
But in the end it's like cooking. No two chefs cook the same dish the same way. And no two of those eating these dishes will have exactly the same reaction to these.
I still prefer my ridiculously expensive (DIY) 300B SE Amplifers to anything else I came across (including gainclones - if not build by myself). Others may differ.
Sayonara
Nielsio said:
Well, for one.
If Joe moved his point "G" to where the two PSU Capacitors join (as I always recommended) the sensitivity of his circuit to the wire between G and the join of two PSU Capacitors.... ;-)
If he used two bridges with good quality rectifiers and kept the rectifier returns separated I suspect the sound would clean up no end.
As for the bandwidth limiting, sure. It may help, much will depend upon the system. If the grounding is optimal, the recent revised schematic is employed in a suitably shielded enclosure and the bandwidth of the source is sufficiently narrow (like nothing wider bandwidth than SACD or DVD-A) I doubt it is neccesary.
Alternatively a pair of capacitors can be connected, one of 22pF Silver Mica between output and negative chip input and one of 220pF Silver Mica between negative chip input and ground. This should keep things stable, puts the -3db rolloff point where Joe likes it and makes the rollof absolutely stable without buffer.
I personally would probably put the rolloff much higher, I'd use 4.7pF/47pF I guess, but thats a matter of taste. Buffering? Not strictly needed, but if you like to, sure. I prefer the conceptual simplicity of not adding things that can be done without.
But in the end it's like cooking. No two chefs cook the same dish the same way. And no two of those eating these dishes will have exactly the same reaction to these.
I still prefer my ridiculously expensive (DIY) 300B SE Amplifers to anything else I came across (including gainclones - if not build by myself). Others may differ.
Sayonara
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