OK that's obvious. But what difference makes switching from C1+C2 (F4) to C101 (BA-2) ?
as I said - that's same thing made in two different ways
probably main reason for having different approach with BA2 is - to have that 10uF cap on FE pcb , thus allowing some flexibility - different use of FE itself , not just with BA2 output ;
say that you want to use BA2 FE as standalone gain stage - preamp duty or something ... it's handy to have that cap on pcb
probably main reason for having different approach with BA2 is - to have that 10uF cap on FE pcb , thus allowing some flexibility - different use of FE itself , not just with BA2 output ;
say that you want to use BA2 FE as standalone gain stage - preamp duty or something ... it's handy to have that cap on pcb
Quick question.
I have Peter Daniel's F4 boards that I'm doing some experimentation with. The boards have a pair of ground pads in the middle of a pair of electrolytic caps that sit across the positive and negative rails. This ground isn't connected anywhere else on the board.
The other ground connection is the input signal ground.
I have a ground in my chassis and will have two boards in bridged configuration.
My choices are to bring both of these two pads back to my common ground point and a third wire from XLR pin 1. In other words, one wire from the XLR input and then two wires from each board.
Also, I could run two wires from XLR pin 1, one to each board, then a jumper wire from the signal ground on the board, to the other ground pad mentioned above, then a single wire to the common PSU ground. This would be simpler to wire up for me.
The third possibility, one I'm not convinced would even work, is to just run the signal ground to the board, and not connect it back to the PSU ground.
Also, perhaps there is another configuration. What would you guys recommend?
I have Peter Daniel's F4 boards that I'm doing some experimentation with. The boards have a pair of ground pads in the middle of a pair of electrolytic caps that sit across the positive and negative rails. This ground isn't connected anywhere else on the board.
The other ground connection is the input signal ground.
I have a ground in my chassis and will have two boards in bridged configuration.
My choices are to bring both of these two pads back to my common ground point and a third wire from XLR pin 1. In other words, one wire from the XLR input and then two wires from each board.
Also, I could run two wires from XLR pin 1, one to each board, then a jumper wire from the signal ground on the board, to the other ground pad mentioned above, then a single wire to the common PSU ground. This would be simpler to wire up for me.
The third possibility, one I'm not convinced would even work, is to just run the signal ground to the board, and not connect it back to the PSU ground.
Also, perhaps there is another configuration. What would you guys recommend?
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With regard to the above question.... meh, I just picked one. I'll bring the XLR pin 1 back to common ground, and run a wire on the board to jumper the two grounds, then bring this back to common ground point.
So, first channel working.
I am at 267mV across the .47 resistors after 1.5 hours. The back of the heat sink near the device is at 42C. So, .57A or 1.13A bias?
The Vgs of my devices measure:
3.40375
3.40663
3.40772
5.03350
5.03510
5.03682
DC offset is about 1mV or so. Didn't bother to ground the input.
Ok, 1 down 3 to go?
So, first channel working.
I am at 267mV across the .47 resistors after 1.5 hours. The back of the heat sink near the device is at 42C. So, .57A or 1.13A bias?
The Vgs of my devices measure:
3.40375
3.40663
3.40772
5.03350
5.03510
5.03682
DC offset is about 1mV or so. Didn't bother to ground the input.
Ok, 1 down 3 to go?
I am looking at putting together some F4 boards and putting them into a non-working audio alchemy OM-150 amp. I have the optional second power supply for the OM-150, so there are two outboard power supplies. Each one is simply a transformer and a rectifier, and I measure about 47 V+/- give or take, and there is a center tap ground.
I tried reading a good portion of this thread, and I believe I have seen the rail voltage change somewhat as the schematics evolved. I was thinking that I need to cut the voltage in half. If I use the PS0 schematic, should I be able to make the proper voltage divider by putting another 2K2 resistor between the rectifier and the CRC circuit? I am assuming the resistor would need a pretty high wattage rating.
I am not a complete noob, but this is my first power amplifier project, and any help would be greatly appreciated. Here is a picture of the amp and a link with more pictures.
More images
I tried reading a good portion of this thread, and I believe I have seen the rail voltage change somewhat as the schematics evolved. I was thinking that I need to cut the voltage in half. If I use the PS0 schematic, should I be able to make the proper voltage divider by putting another 2K2 resistor between the rectifier and the CRC circuit? I am assuming the resistor would need a pretty high wattage rating.
I am not a complete noob, but this is my first power amplifier project, and any help would be greatly appreciated. Here is a picture of the amp and a link with more pictures.
An externally hosted image should be here but it was not working when we last tested it.
More images
Another thing that I am wondering is if it would be ill advised to put four F4 boards in this chassis. With the boards I got from DIY audio, it seems that I can fit two boards on each side, with one of them upside down. I think that the heat sink would be less densely populated than it is now, but the OM-150 runs hot as a high-biased class AB. I am wondering if stuffing four F4 channels in it would be too hot.
nope ;
only way is to separate actual secondary windings , and to use them with electronically assisted voltage divider , to have +/- 23V5
look at Quad 306 ( and bigger ones ) for that schematic detail ; search on forum .
even if you do that - those heatsinks look as good for 100W dissipation per side , so - just two channels of F4 are possible to squeeze in
only way is to separate actual secondary windings , and to use them with electronically assisted voltage divider , to have +/- 23V5
look at Quad 306 ( and bigger ones ) for that schematic detail ; search on forum .
even if you do that - those heatsinks look as good for 100W dissipation per side , so - just two channels of F4 are possible to squeeze in
The amp came with a PSU, and then the second PSU was purchased as an add-on. Also, only one channel is broken. It sounds like it would be easier to buy a new transformer or transformers, sell the add-on PSU, and use the transformer in the first PSU with the one working channel as a mono amp in some other chassis. I think plitron was recommended?
So, channel 2 came up great!
Channel 3 has a small issue, as the offset is +100mV with the offset trimmer set to its maximum (500 ohms). I am letting it warm up nevertheless. I'm assuming the issue might be something with my JFETs? My Vgs is at 5.03 and 3.36 for the two MOSFET types with all devices matched in each triple within < 0.01mV (confirmed by measuring each device in situ).
Channel 3 has a small issue, as the offset is +100mV with the offset trimmer set to its maximum (500 ohms). I am letting it warm up nevertheless. I'm assuming the issue might be something with my JFETs? My Vgs is at 5.03 and 3.36 for the two MOSFET types with all devices matched in each triple within < 0.01mV (confirmed by measuring each device in situ).
Maybe a larger value trimmer is called for.
That would make sense. Does this imply that my difference between my Vgs is too large for the circuit to handle (as opposed to something with the JFETs?)? Thanks! Getting close!