Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Tweeds on October 28, 2016, 05:05:38 pm
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Hello all, I'm building a DR single channel(trem channel) using standard tag board and wondering if there are any changes I need to make other than;
not installing the connections for V1, removing the bias network for V1, the socket, controls, etc,
and removing the 220K resistor (fed from V1 pin 6) that is marked with the [X] next to the [Y] (above preamp tube #6.
Thanks in advance.
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Sounds about right.
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Sounds about right.
Thanks much for the advice, good stuff.
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You might also want to double the last power string dropping resistor to keep the same voltages in the preamp stage. The last node is feedeing two tubes so when one preamp tube is "remowed" the current across the dropping resistor is halved and according the Ohm's law it's now only dropping half the voltage. Try sub the 10k resistor with 22k.
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You might also want to double the last power string dropping resistor to keep the same voltages in the preamp stage. The last node is feedeing two tubes so when one preamp tube is "remowed" the current across the dropping resistor is halved and according the Ohm's law it's now only dropping half the voltage. Try sub the 10k resistor with 22k.
That node actually feeds three tubes.
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That node actually feeds three tubes.
Good catch!. That is true. Then the difference would not be so dramatic.
{edit -- untangled quote -- PRR}
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Thanks, sounds like it might be needed? or leave it at 10K alone for the time being? Maybe I should place say? a 12K or 15K.
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I just used 10K and never gave it a thought.
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Thanks team...great board.
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Say I'm revisiting this,
I just found the single channel layout provided here by Doug. One thing I noticed was that both 220K resistors are removed from the circuit (I knew 220K for the [X] hookup/normal channel one would be taken out. Off Pin 2 V6
Should I take remove the remaining 220k[Y] location off v6 altogether then...
Someone on another board mentioned that I should add a straight wire to ground from the 220K(X) ...leaving "both" [y] and [X] 220k resistors in place as it helps compensate the "loading down of the circuit?
I guess I'll do that for now since I have one in place already, see how build sounds I suppose.
The layouts in the board section are amazing, what a resource...thanks.
Thanks...
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Someone on another board mentioned that I should add a straight wire to ground from the 220K(X) ...leaving "both" [y] and [X] 220k resistors in place as it helps compensate the "loading down of the circuit?
That will form a 2:1 voltage divider and cut your signal in half.
Those two 220Ks are used to mix the two channels together and also provide a bit of isolation between channels. Technically speaking, since you only have one channel you don't need either of the 220Ks. If you layout the board to accommodate both resistors you can experiment to see which way you prefer.
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Thanks so much, I'm glad I asked' I'll rune a wire from the "Y" connection point on the right of the board to the top of .001uf cap before the PI tube...
Good stuff..