I am working on construction of a tube pre-amp that I want to be as quiet as possible. I will be building it in two chassis. One with power supply and the other with the amplifier and RIAA.
I would like to use a perforated aluminum plate for the bottom with ventilation holes in strategic places in the top plate.
Question is - will I lose the noise rejection I'm looking for compared to a more solid chassis?
I would like to use a perforated aluminum plate for the bottom with ventilation holes in strategic places in the top plate.
Question is - will I lose the noise rejection I'm looking for compared to a more solid chassis?
If you use good quality valves that a low on microphonics, it will make no difference either way.
The chassis will not cause the noise whichever you choose.
The chassis will not cause the noise whichever you choose.
I neglected to say this is a Phono-stage and I am concerned that the perforated sheets will allow noise IN, not cause noise.
Take a look at Audio Research components. Excellent reviews and perforated top and bottom covers.
Why trap the heat in, let it breath and enjoy longer lasting tubes and circuitry with no noise issues.
Why trap the heat in, let it breath and enjoy longer lasting tubes and circuitry with no noise issues.
I'm not sure. There will be:
Two cascade current sources
Four 1KΩ 5W Mills resistors
Four 300Ω 2W resistors
Two 330KΩ 2W resistors
Two 47KΩ 2W resistors
Two 21.5KΩ 1W resistors
Two 3.18KΩ 1W resistors
Two 80Ω 1W resistors
Two 4.7KΩ 12W resistors
Two 30H Chokes
I just would like for all this to remain cool.
My question is how much shielding am I giving up by using a perforated aluminum bottom plate versus a solid one. The whole chassis is aluminum.
Thanks!
If you are using p-p hard wiring, some shielding may be worthwhile.
If using a well designed pcb, it may not be a big factor.
Shielding loss will be related to the amount of surface removed by the holes.
This assumes a mm phono preamp, not mc. Tube shields can help also,
though you didn't mention anything about the tubes. They will be inside?
How about posting the schematic?
If using a well designed pcb, it may not be a big factor.
Shielding loss will be related to the amount of surface removed by the holes.
This assumes a mm phono preamp, not mc. Tube shields can help also,
though you didn't mention anything about the tubes. They will be inside?
How about posting the schematic?
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Tubes and the large caps will be exposed. Will be P2P wiring. I'll as the guy I got the schematic from if ok to post here.
Short answer: no.
It would be a problem if you had, say, a Magnetron or at least an UHF oscillator inside, because holes can work as "slot antennas" but no problem at Audio frequencies.
Plan to keep the input tube(s) close to the input sockets, with short, direct connections.
Aluminum will catch up microwaves, however with more broadband frequency I think steel will catch and shield a lot more, i have to research if aluminum is a good antenna to shield AM and FM radio...
In any case the holes will not hinder the metal ability to shield the interior from some electromagnetism.
A real shield has two layers, you still need to measure each path to ground and be the same length to null the parasitics effect in the power supply...
You should be good 🙂
grid stoppers of proper values prevent the Mhz from being amplified , so use them everywhere, they don't lower your sound quality 🙂
In any case the holes will not hinder the metal ability to shield the interior from some electromagnetism.
A real shield has two layers, you still need to measure each path to ground and be the same length to null the parasitics effect in the power supply...
You should be good 🙂
grid stoppers of proper values prevent the Mhz from being amplified , so use them everywhere, they don't lower your sound quality 🙂
Aluminium with small holes will block RF up to the frequency where the holes are a few percent of wavelength. At very low frequencies you need the aluminium to be at least a few skin depths in thickness.
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