Tube rectification for the Ikes?

a DIY, modified Mullard 5-20 monoblock design

Tube rectification for the Ikes?

Postby SDS-PAGE » Tue Apr 03, 2012 9:30 pm

Don't know if this topic is covered already, but would tube rectification be feasible for the Ikes? I would imagine the value for the first cap would has to be reduced, but what else?
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Postby battradio » Tue Apr 03, 2012 9:34 pm

You would also want to up the transformer voltage 20 to 40 volts depending on what tube you use and might add one exta section of filtering to make up for lowing the fist cap for the tube rectifier
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Postby Shannon Parks » Wed Apr 04, 2012 5:04 am

The original Ikes used the Hammond 274BX. For 5AR4 operation, I switched to the Hammond 278X. You will change C9 and C10 to 100uF caps, so that the 5AR4 will see 50uF. The IRCL helps here, too.

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Re: Tube rectification for the Ikes?

Postby highflyin9 » Wed Jul 10, 2013 10:42 am

Just wanted to bump this, what would be the best way to add an extra section of filtering? Mounting another pair of 220uf, 400V caps and a pair of 100k resistors, one side going to ground, connected in series, but where should the other side be connected?

Pete Millett has a convenient little board that would do the trick to mount the two caps, two resistors and wire a jumper in the middle that I assume would work quite well.

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Re: Tube rectification for the Ikes?

Postby Shannon Parks » Thu Jul 11, 2013 6:08 am

highflyin9 wrote:Just wanted to bump this, what would be the best way to add an extra section of filtering? Mounting another pair of 220uf, 400V caps and a pair of 100k resistors, one side going to ground, connected in series, but where should the other side be connected?


Are you planning to add a little more capacitance at the B+ stage? Yes, just use two more of the 220uf, 400V caps and 100k resistors in series. So say B+ is at 500V, the first cap's + is at 500V and the - is at 250V, while the next cap (in series) is at 250V + and 0V - (each bypassed with a resistor). I presume that that is what Pete's board does. You can do real high voltages this way. Pretty much the only solution beyond the standard 450V rated caps.

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Re: Tube rectification for the Ikes?

Postby highflyin9 » Thu Jul 11, 2013 2:55 pm

Is this correct?

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Also, I could probably fit some 270uF caps in place of the 220uFs if that would be beneficial at all.
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Re: Tube rectification for the Ikes?

Postby Shannon Parks » Sat Jul 13, 2013 5:42 am

Follow this drawing from the ST35 that I've attached. Jumper D2 and leave D1 open. Connect the raw rectified B+ to J4-6. Connect one of the red secondary circuits to J4-7 (for the C- circuit). 270uF subs will be A-OK.

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