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18Watt.com • Best Tube Position
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Best Tube Position

Posted: Fri 03/17/23 11:44 am
by riley0
This diagram shows 2 ECL & 1 12AX.
Whats best position for placing these tubes?
My guess would be - power tubes closer to OT, the negative of this is longer ground runs and 12ax7 input run...
If the 12ax7 is closer to OT its closer to input/ground but the power tubes now have longer reach to OT.

Re: Best Tube Position

Posted: Sat 03/18/23 7:07 pm
by KagliostroAmpwww
https://metrodcmusic.com/blogs/guitar-k ... er-chassis

https://robrobinette.com/How_To_Go_From ... Layout.htm


or, if you prefer the transformer at oposite sides look to the Hiwatt Chassis Layout (power tubes on the oposite side of the shield)
chassisValves.png
K

Re: Best Tube Position

Posted: Mon 03/20/23 5:32 pm
by riley0
Chassie, transformers, input, fuse are irremovable.
This is already an existing PCB amp I'm trying to turn point to point.
It sits vertical in cab...

Think I've done pretty good job so far using pcb layout (not sure to carry out or leave it as is)...Just playing around, learning. I have all parts except G10 board, so just cheap project.

Been complicated fitting it all onto 35cm x 12cm...Does anyone think this is insane or do ppl try this..

Re: Best Tube Position

Posted: Mon 03/20/23 7:21 pm
by KagliostroAmpwww
Oh, I understand

what can I say ... I'm a fan of PCB amp conversion

---

If you want to change the hole disposition on the chassis you can cover the whole surface with a thin sheet of aluminium (say 1mm or 1.5mm) and fix it to the chassis with rivets, then put new holes where is required

K

Re: Best Tube Position

Posted: Thu 03/30/23 3:02 pm
by KagliostroAmpwww
This is what I'm doing starting from a Samic Solid State amp to convert in a Gibson GA-5T Skylark '61 the 6BM8 version
Samick Smart 2.jpg
IMG_20191010_113819.jpg
IMG_20191010_113900.jpg
IMG_20191010_113907.jpg
IMG_20191010_113944.jpg
The Top original chassis was too short so I modified the speaker baffle to have the Top chassis 60mm tall
The added chassis on the Bottom is for the Power Supply only, note that it is shorter than the Top chassis as to don't touch the speaker basket

K

Re: Best Tube Position

Posted: Sat 04/01/23 12:58 pm
by riley0
Tight space your working with, are you mounting tubes external down towards speaker?
I fitted my tubes on-board (20cm x 11cm) piggy-backed a few parts and use whats at hand until ready to order..
Those 6BM8 don't like over 300v on the plates, but they don't give off much heat and they sound great for a little 10w bedroom amp..
You'll have to keep us upto date on the progress..

Re: Best Tube Position

Posted: Sat 04/01/23 4:49 pm
by KagliostroAmpwww
Yes tubes will be mounted top side down

I want to go on with that project but don't know about time terms

If you want I can post some schematic and Layout I have draw till now but It Is a low W SE amp not a 18W PP amp

K