Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: firemedic on September 12, 2010, 06:18:25 pm

Title: Reducing gain
Post by: firemedic on September 12, 2010, 06:18:25 pm

What would be the better method of bleeding off a little gain, while preserving tone? A resistor in series or bleeding to ground? Or does it not make a difference?

Title: Re: Reducing gain
Post by: kagliostro on September 12, 2010, 06:22:31 pm

decrease the plate resistor

read this thread

http://www.el34world.com/Forum/index.php?topic=10019.0

Kagliostro

Title: Re: Reducing gain
Post by: zendragon63 on September 12, 2010, 08:04:20 pm

Like kagliostro says, reducing the plate resistor reduces the voltage swing. However, if you like the way that stage is currently biased, you can also split load the Rp. The more tonally astute can weigh in though I don't notice the change in tone as I do using a voltage divider to ground that is more common. Regards

dennis

Title: Re: Reducing gain
Post by: tubesornothing on September 12, 2010, 08:32:45 pm

Every decision has its compromises

Decreasing the plate resistor will decrease gain, but it will allow the preceeding stage to overdrive the stage easier.  Sometimes a problem, sometimes not.

A resistor in series will have to be a big resistor (like 300k and up) and can introduce noise.

A voltage divider works (series and resistor to ground).  It tends to be the easiest and tonally transparent.

Title: Re: Reducing gain
Post by: kagliostro on September 13, 2010, 02:54:44 am

You can split load with two resistors

I've also seen this circuit implementation with a switch to have different gain

also few ones uses a fixed resistor and a pot (connecting the cap to the wiper)

or can use a voltage divider

BUT

Quote

Every decision has its compromises

try more and select which one you prefer

Kagliostro