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Post subject: Twin Reissue questions
Posted: Fri Jun 29, 2012 7:24 am
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Hello all, first time post, first time Twin owner....

Just bought a new Twin reissue, to replace my aging AC-30. Not knowing the amp well enough, I have some questions. The reason I went with the Twin was to get a cleaner tighter sound than the Vox. What I've found is that the Twin needs to be played loud to get the tone I'm looking for, and is fine playing out, but in my small studio, just to loud. It was suggested on another forum to remove 2 of the power tubes to cut power in half.

Is this a recommended fix, if so which of the four tubes. Thanks Rich


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Post subject: Re: Twin Reissue questions
Posted: Fri Jun 29, 2012 8:38 am
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Hi comsound,

I wouldn't call it a "fix", but you can remove a pair of output tubes for approx half-power if you want, either inner pair or outer pair. You might want to check the bias while you are at it.

The instructions for using two output tubes, as well as biasing, used to be in the manual. Just be sure to turn off the amp and let the tubes cool before removing. :idea:

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Post subject: Re: Twin Reissue questions
Posted: Fri Jun 29, 2012 9:31 am
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Rock Star, So are you saying that the overall bias would change removing 2 tubes?
I just re-read the manual, although in five different languages, it only says refer biasing to a trained professional, nothing about the half power mod. Do you know of a link that could give me a little more info? Thanks again


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Post subject: Re: Twin Reissue questions
Posted: Fri Jun 29, 2012 9:51 am
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Set the bias current properly to begin with, having all four output tubes installed. Many times this will improve the sound, as typically the factory setting is cold. Then, with the bias set, if you remove two output tubes, the bias current will be roughly half, as it should be, no need to readjust.

Exactly which Twin do you have? The older manuals have the info on tubes and biasing.

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Post subject: Re: Twin Reissue questions
Posted: Fri Jun 29, 2012 11:01 am
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Its a new 65 reissue, the manual is pretty basic.


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Post subject: Re: Twin Reissue questions
Posted: Fri Jun 29, 2012 2:19 pm
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Twin Reverb? "Twin" is quite different from "Twin Reverb", but the same principle, using only two output tubes, will work on either. It is the older "Twin" manuals that have the info, and the adjustments described in those manuals wouldn't apply to the "Twin Reverb". The "Twin Reverb" doesn't have test points for checking the bias like the "Twin" does.

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Post subject: Re: Twin Reissue questions
Posted: Tue Jul 10, 2012 1:52 pm
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Removing two power tubes (going from 85 watts to about 40) will not allow a Twin Reverb to be "cranked" in an apartment or small room any more than using full power.
Cutting the power in half DOES NOT reduce the loudness by half.
To do that, the power must be reduced by a factor of 10, i.e., from 85 watts to 8.5 watts, which is still plenty loud in a small room.


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Post subject: Re: Twin Reissue questions
Posted: Tue Jul 10, 2012 2:45 pm
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evets618 wrote:
Removing two power tubes (going from 85 watts to about 40) will not allow a Twin Reverb to be "cranked" in an apartment or small room any more than using full power.
Cutting the power in half DOES NOT reduce the loudness by half.
To do that, the power must be reduced by a factor of 10, i.e., from 85 watts to 8.5 watts, which is still plenty loud in a small room.


+1

Time for a Vibrochamp, methinks.

Arjay

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