Can we lower (halve) the power in a Hoffman AC30 c

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PhatTele
Junior tube assistant
Posts: 8
(2/20/04 11:18 am)
 Can we lower (halve) the power in a Hoffman AC30 circuit?
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 Considering the Hoffman AC30 design, can we pull two power tubes to lower the power to an AC15 equivelent? And, if we can, which tubes (outer or inner) are the better choice to pull and why? Thanx...
 
Tiny Daddy
I will work on all amps
Posts: 502
(2/20/04 11:43 am)
 Re: Can we lower (halve) the power in a Hoffman AC30 circuit
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 Half power will still sound almost as loud. You could use fewer or less-efficient speakers for a better result.
 
GroundhogKen
Forum Moderator
Posts: 2290
(2/20/04 7:01 pm)
 Re: Can we lower (halve) the power in a Hoffman AC30 circuit
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 You can pull two power tubes, but then you MUST double the cathode resistor--say 50 ohms to 100 ohms. Actually anything from 100 to 150 would be OK. If you pull two tubes without changing the cathode resistor, the remaining two will light up like red hot pokers.

You might also want to use a different output transformer tap. If your cabinet is 16 ohms total, connect it to the 8 ohm tap, for example.

This will give you half the power, but your ears won't perceive it to be half the volume. If it's "too damn loud" to start with, halving the power will still be "pretty close to too damn loud".


Ken
 
PhatTele
Junior tube assistant
Posts: 9
(2/20/04 7:43 pm)
 Re: Can we lower (halve) the power in a Hoffman AC30 circuit
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 Alright, that all definately makes sense.

Fortunately, this amp is working out great as a 30 watt. I put in a Master Volume (which still needs some tweaking) and that's doing a lot to control the overall loudness when it's needed. I was just curious if there was some more flexibility available with this circuit.

Thanx
 
Rotting27
Junior tube assistant
Posts: 121
(2/21/04 2:35 am)
 ReL
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 You could add two pairs of cathode resistors and caps (1 pair to two EL84s each). That way you could pull two tubes or leave all 4 in at the drop of a hat!
 
 
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