Choke/resistor switch?

[dehughes]

I have a question nearly exactly along these lines....

I'm looking to build a 6G6-B-ish amp with a pair of 5881s and was going to install a switch to select either a choke or a large resistor, and was wondering what value I should choose. The choke I'm using has a DC resistance of 80 ohms (according to the manufacturer...Mercury Magnetics....it's their stock Blonde Bassman choke), so I'm wondering what value of resistor I should install as the option. Any recommendations? I don't want to drop the voltages so much as just have the option of the feel of either a choke or a resistor. My instincts say somewhere in the 160 to 320 ohm range, but I figure you guys with more experience and knowledge might have a better recommendation.

Thanks.

[Enzo]

But that is exactly what we have been talking about. Did you read the whole thread?

[dehughes]

But that is exactly what we have been talking about. Did you read the whole thread?

Yes I did, and I noticed that the majority of the discussion has been focused on the filtering aspects of the Choke/Resistor issue, which, while being informative, doesn't speak to the feel/tone aspect of choosing one or the other. Nor does it answer the question of whether one can indeed install a resistor in place of a choke, given both have the same DC resistance, and still have the amp function in a "proper" manner. Nor does it answer the question of why on, say, Dumble mod forums why people are installing this "Robben Ford mod" which switches in a 330 ohm resistor in place of the choke and using that value instead of a value more close to that of the choke's actual DC resistance, especially given that they don't install a switching mechanism to change the fixed bias (assuming then that the bias doesn't shift too much then in that circuit when the R is in place of the choke?).

Those are the questions floating about in my mind that weren't answered even in re-reading the threads. Sure, techy information regarding the differences is helpful, but I'm looking for a methodology or principle that would let me know what value range of R should be installed in order to keep the amp as a whole in balance and functioning "properly" and the tubes biased relatively in range, while still allowing for the sonic/vibey/textural affect of a resistor in the choke's stead. Perhaps the answer is "Put in a R with the same DC resistance as your choke", but I think not, being as I've never seen this in any of the schematics where people have actually installed choke/resistor switches, this then leading me to think that one is best to not just install a R with the same DC resistance value as their choke.

My thoughts then are: "Do they raise the R value higher than the choke's DC resistance in order to up the filtering effect yet not too high so as to drop excessive voltages?" "If so, how does one determine this value a priori, being as I don't have the amp built and am still in the design stages?" "Is there a point that one should not drop below in terms of R values in a given circuit so as to not have too little filtering from that R?" You know, stuff along those lines, stuff a non-engineer, semi-newbie builder would think.

Thanks.

[Bruce / Mission Amps]

Just leave the 20H choke in place and install 500 to 15K power resistor in series with the choke but before your screen supply filter cap.
Put a SPDT toggle in parallel with the choke and the power resistor.
Let the common lug of the switch go to the junction of the power resistor and the choke.
Then you can switch the resistance or the choke in an out at will by bypassing one or the other.
If you use a SPDT with center OFF, you hear what it sounds like with both the resistor and the choke.

[dehughes]

Just leave the 20H choke in place and install 500 to 15K power resistor in series with the choke but before your screen supply filter cap.
Put a SPDT toggle in parallel with the choke and the power resistor.
Let the common lug of the switch go to the junction of the power resistor and the choke.
Then you can switch the resistance or the choke in an out at will by bypassing one or the other.
If you use a SPDT with center OFF, you hear what it sounds like with both the resistor and the choke.

Now THAT's a clever idea.... Such switching (choke/resistor/both) could be accomplished with a switch like this, yes?

http://www.tubesandmore.com/scripts/...XP?item=P-H496

What would be the sonic/feel benefits of both the choke and resistor in series? This would almost certainly throw off the bias setting, yes?