PCB design techniques for Tube Amps - diyAudio
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Old 8th October 2007, 06:23 AM   #1
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Default PCB design techniques for Tube Amps

Hey all, Don here over from the guitar tube amp world. I have built a number of amps using turrets and eyelets and want to now try out PCB. It has worked well for my power supplies and switching boards, now I am faced with the preamp and PI. I am looking for suggestions on PCB design tips for tube amps.

Here is what I have collected so far:

- use double sided, with plated through holes
- keep low impedance lines away from high impedance ones
- signal on one side of the board, power and ground on the other
- avoid parallel traces - either on the same side or opposite sides
- if lines cross (either side of the board) try to cross at 90 degrees


Any other suggestions? What about heater traces? Also not so sure about how to design with ground planes - won't this create a lot of capacitance?

Perhaps any web sites or books on this?

thanks!
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Old 8th October 2007, 08:15 PM   #2
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Try and get a program called Protel, or what is now Altium 6 - it's a great schematic and PCB-layout program..dead handy

L
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Old 8th October 2007, 08:31 PM   #3
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If I recall, Morgan Jones's book "Building Valve Amplifiers" recommends against using traces for heaters, as it complicates the design (heaters need lots of current too). It might be better to hard wire the heater pins (with tightly twisted wire of course).
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Old 8th October 2007, 09:34 PM   #4
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Hi,

One other thing I'd like to suggest is 2.4mm board and 2oz copper. That's what the tube experimeter PCB's I sell are made from and so far, no lifted or cooked traces

Cheers!


PS: Fellow wetcoaster, you within "coffee range" of Chilliwack?
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Old 8th October 2007, 10:25 PM   #5
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Hey all thanks for the replies.

Geek, I am on the island so a little far away for coffee, alas. I would love to check out your shop and vice versa. Do you do your PCBs in your shop or farm it out? I would love to find thick double sided board that has photo resist on it for my at home prototypes. I currently use MG chemicals boards - a little lightweight.

Blisterfingers, I just ordered that book! I am looking forward to reading it.

Psychobiker, I thought autorouters were a no-no in the tube amp world. Regardless I 'll will investigate.

thanks!.
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Old 8th October 2007, 10:39 PM   #6
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Hi,

Well, we'll have to meet you on the Island at Planet10's summer diyAudio festival or something

Quote:
Originally posted by d1camero
Do you do your PCBs in your shop or farm it out?
Import most of them ready made.

Cheers!
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Old 11th October 2007, 05:53 AM   #7
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Hey all you tube/PCB experts, I am starting to design a double sided board and I m wondering about the layers. What is best?


- signal on bottom side
- power and switch signals on top side

where to put the ground - should it be a ground plane?


This is a preamp board with a few 9 pin sockets on it.

thanks
Don
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Old 11th October 2007, 06:35 AM   #8
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We have been trained to never auto route with Protel.
Very very nice piece of software for schematic, PCB design

L
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Old 11th October 2007, 07:19 AM   #9
cerrem is offline cerrem  United States
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There are design rules for trace width and how thick, oz. of copper...depending on the current density..
I have designed boards that handle 30 Amps for reliable flight operations.....so the heaters for tubes should not be a problem if done correctly...
Ground plane is the only way to go....
Stay away from vias in audio path.....

Chris
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Old 11th October 2007, 01:20 PM   #10
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In re-reading my note, obviously I was a touch mess up. My question, better put is here:

I am using a two-sided board. What sides do I put the B+, signal and ground plane on?

So far, the signal is on the bottom side, and the B+ is on the top. I am not sure which side to put the ground.

thanks
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