Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Underwood on November 29, 2011, 12:51:29 pm

Title: 100K resistor on tremolo speed pot
Post by: Underwood on November 29, 2011, 12:51:29 pm

 I have a brown Bandmaster and was wondering what does the 100K resistor do on the tremolo speed pot? Does changing it do anything to it? Also, what does the resistor going to the speaker out exactly do? Does it affect the load on the OT? The impedance of the 3 speakers is 2.6 and the OT is 4 ohms.  Was wondering if the resistor had anything to do with the overall impedance of the speakers. Otherwise I hear the the 2.6 load is fine with the 4 ohm OT.   THANKS

Title: Re: 100K resistor on tremolo speed pot
Post by: chocopower on November 29, 2011, 01:38:24 pm

I´m not a pro, but i think the 100k resistor in the speed pot, set a minimun speed for the tremolo when you dial the pot to cero.

The other one (10k), is the NFB loop resistor, who set the signal quantity going into the NFB circuit.

In this forum, take for sure, someone is gonna give you a better explication. :help:

Title: Re: 100K resistor on tremolo speed pot
Post by: Leevi on November 30, 2011, 01:39:59 pm

Quote

Does it affect the load on the OT?

Theoretically yes but according to Kirchhoff's current law most of the current goes through the speaker
and a minor part to the feedback loop so in practice it does not affect the load.
/Leevi

Title: Re: 100K resistor on tremolo speed pot
Post by: sluckey on November 30, 2011, 01:53:23 pm

Quote

what does the 100K resistor do on the tremolo speed pot?

It prevents the speed pot from being able to go all the way to ground when the speed is set to 10 (max CW). If the speed pot was directly connected to ground then the tremolo oscillator would die whenever you set the speed to max.

The 100K is needed but the value ain't critical. I would not go lower, but a bigger resistor just means that the fastest trem speed would be slower.