I am trying to build the Rozenblit (transcendent sound) grounded grid preamp. Any advice you can offer on the PCB layout would be most appreciated (see schematic and my current board layout below). As this is a commercial design I have omitted the component values, however I can say that the valves are 12AU7s. If you are interested in building the preamp I suggest downloading Rozenblit's book from his website.
Cheers,
Greg.
Cheers,
Greg.
I would not got with a ground plane for audio circuits as you don't have control of where the ground currents flow in the plane. They might flow past a high-impedance input and couple into it. I recommend using a star ground instead.
It looks like your tubes are very close together. I'd double-check with the data sheet to make sure the minimum spacing requirement isn't violated. I'd probably have them 2-3 inches (50-75 mm) apart so they can get rid of their heat. Also, for some tubes (I think it's mostly beam power pentodes, but maybe others as well) should be oriented in a particular way to avoid coupling between tubes. Speaking of orientation. It's obviously up to you, but if you intend to show the tubes in the final chassis, it might look better if they're all oriented in the same way.
Personally I would prefer to have the connections to the board alone one side or maybe opposite sides of the board. I like using connectors or terminal strips for that as it makes assembly and maintenance easier. Also, you'll need mounting holes if the board goes in a chassis.
~Tom
It looks like your tubes are very close together. I'd double-check with the data sheet to make sure the minimum spacing requirement isn't violated. I'd probably have them 2-3 inches (50-75 mm) apart so they can get rid of their heat. Also, for some tubes (I think it's mostly beam power pentodes, but maybe others as well) should be oriented in a particular way to avoid coupling between tubes. Speaking of orientation. It's obviously up to you, but if you intend to show the tubes in the final chassis, it might look better if they're all oriented in the same way.
Personally I would prefer to have the connections to the board alone one side or maybe opposite sides of the board. I like using connectors or terminal strips for that as it makes assembly and maintenance easier. Also, you'll need mounting holes if the board goes in a chassis.
~Tom
Hi
Do the modules that you are using for the tubes have a hole at the very center on the symbol? and will this result in a pad or hole in the center of each tube socket? If so you must route around that center hole. Also I have had no problem with ground plane on tube circuts. Perhaps I have just been lucky. Other wise looks you are well on your way. Check and re-check the routing!
Do the modules that you are using for the tubes have a hole at the very center on the symbol? and will this result in a pad or hole in the center of each tube socket? If so you must route around that center hole. Also I have had no problem with ground plane on tube circuts. Perhaps I have just been lucky. Other wise looks you are well on your way. Check and re-check the routing!
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Thanks both of you. Firechief, as far as I am aware my sockets do not have a centre pin, but I will look in to that and modify the design as soon as they arrive.
Tom, many thanks for your input. I did fear that the tubes may have been too close together, but I placed them that way partly because I had to to make them fit on the maximum board size of the free version of eagle, and partly to keep signal paths short. This was clearly a mistake now.
I will get the commercial version of eagle and design a new board with wider tube spacings. I will also remove the ground plane as you suggested.
As far as tube orientation goes, it's irrelevant from an aesthetics point of view in this case as they will be in a metal box.
I appreciate your input and will hopefully get back to you soon with a new design.
Thanks,
Greg.
Tom, many thanks for your input. I did fear that the tubes may have been too close together, but I placed them that way partly because I had to to make them fit on the maximum board size of the free version of eagle, and partly to keep signal paths short. This was clearly a mistake now.
I will get the commercial version of eagle and design a new board with wider tube spacings. I will also remove the ground plane as you suggested.
As far as tube orientation goes, it's irrelevant from an aesthetics point of view in this case as they will be in a metal box.
I appreciate your input and will hopefully get back to you soon with a new design.
Thanks,
Greg.
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