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Old 2nd December 2011, 05:16 PM   #1111
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Yeap, you may be happy to have it the day you'll forget to tie something at the amp input !
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Old 2nd December 2011, 05:35 PM   #1112
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What damage would it do to the amp?
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Old 2nd December 2011, 05:43 PM   #1113
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If the grid of the input stage is left floating, you'll probably have at least big noise in the loudspeakers or, worst, ultra sonic oscillation that you can't hear but greatly overload any thing from tubes to power supply.
Never left a grid floating !

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Old 6th December 2011, 10:10 PM   #1114
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I was just checking the schematic again before powering up in the morning. And in Taj's drawings on the WIKI page Baby Huey PP EL84 amplifier - diyAudio, the no GNFB version omits the 470R resistor that is the lower half of the divider for the feedback.

If I decide that I don't want to use global feedback, should I take this 470R out of the circuit? Will leaving it in cause any unbalance in the design?

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Old 6th December 2011, 10:37 PM   #1115
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If I decide that I don't want to use global feedback, should I take this 470R out of the circuit? Will leaving it in cause any unbalance in the design?

Cheers
That is correct. Leave it out. It was I who actually modified that drawing by Taj. Because that is how I have built my Baby Huey. Well actually the one with the balanced/unbalanced option. And no feedback.
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Old 6th December 2011, 10:48 PM   #1116
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Nice Wiki Bas, Taj et al......

Waiting for my iron to warm up so that I can take out those 470r resistors....

Charlie, how can you bear to wait until tomorrow...

Last edited by Soonerorlater; 6th December 2011 at 10:56 PM.
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Old 7th December 2011, 01:47 PM   #1117
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Well ive fired it up, and everything seems to be in order, other than a higer HT than calculated.

I am actually reading about 320v on the anodes of the ecc803s', and on the last build this was around 180v. So trying to figure out the mistakes. The ccs appears to be wired correctly, getting about +18v though....

As for the RLD arrays, they are lit up like a christmas tree, one is drawing 81mA, and the other only 60mA. Can anyone give me an insight into possible mistakes with this please?

Going to double then triple check my wiring, it's been a very long lunch break so far, im glad ive got a friendly boss.

Charlie
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Old 7th December 2011, 02:13 PM   #1118
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I am actually reading about 320v on the anodes of the ecc803s', and on the last build this was around 180v.
It looks like there is no current being drawn by your driver stage. (Quite a few things could cause this)

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As for the RLD arrays, they are lit up like a christmas tree, one is drawing 81mA, and the other only 60mA
Try swapping the one pair with the other pair (EL84's) That would at least tell you that the tubes are not the culprits.
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Old 7th December 2011, 02:23 PM   #1119
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After swapping pairs the side that read 60mA now reads 73mA, and the other side is about the same.

As for the driver stage I will check my wiring once more.

Thanks
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Old 7th December 2011, 02:36 PM   #1120
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In the WIKI diagram, the ccs - should 0v at ecc803 be grounded? otherwise surely there is no reference to ground for the valves?
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