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Old 19th June 2004, 12:15 AM   #1
edsmith is offline edsmith  Australia
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Default Does more tubes = more filter capacitors?

I was thinking about adding an extra tube gain stage into my diy 50 watt marshall. There are 6 six filter capacitors in it now, but do i need any more if i add an extra tube for more gain after the first gain tube? I hope not, because they are so expensive!

I was planning to have this gain stage switchable.

Thanks alot guys
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Old 19th June 2004, 12:36 AM   #2
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Hi,

Quote:
There are 6 six filter capacitors in it now, but do i need any more if i add an extra tube for more gain after the first gain tube? I hope not, because they are so expensive!
No, normally you don't.

Expect the B+ rail to sag a few volts with the added tube and make sure the heaterxfmr can supply the extra current for the tube: 150mA @ 12.6V or 300mA @ 6.3V.

You may still want to use an extra PS cap to decouple the B+ of the 12AX7 locally. A few F would do some good there already.

Cheers,
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Old 19th June 2004, 06:21 PM   #3
benny is offline benny  Australia
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hi,

with the added current draw of the tube, apart from the sag, you will also get more ripple on you DC, but not really anything worth worrying about... if you want, cuz you're aussie also, at jaycars they sell 10uF 450V electro caps for $2.80... this will compensate for it, and i think if you have a problem with this being expensive, then what the hell are you doing building tube gear anyway???

good luck, i hope your mod turns out to sounds good.

cheers
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Old 20th June 2004, 10:16 PM   #4
edsmith is offline edsmith  Australia
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Thanks alot for the advice fellas!
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