Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: plexi50 on April 29, 2012, 09:38:01 pm

Title: Mid Scoop
Post by: plexi50 on April 29, 2012, 09:38:01 pm

I have a 1969 Fender Pro reverb that has no mid pot. I changed the bass pot resistor from 6.8k to 22k to get a more scooped mid.
Did i go in the right direction? My brain quit working 4 hours ago. Can i hear a difference? Dont know that either!  :l2:

Title: Re: Mid Scoop
Post by: TubeGeek on April 29, 2012, 09:43:12 pm

22k will give full mids, wouldn't 6k8 be more scooped?

Title: Re: Mid Scoop
Post by: bigsbybender on April 29, 2012, 09:47:03 pm

TubeGeek is right.  22K will shunt less mids to ground, You'll probably notice some gain increase and more mids.

Maybe try 2.2k, 2.7k, 3.3k or 5k.

j.

Title: Re: Mid Scoop
Post by: TubeGeek on April 29, 2012, 09:54:07 pm

Temporarily wire up a 25k pot to find the sweet spot and then install a resistor of the pot value you like. Easiest way to do it.

Title: Re: Mid Scoop
Post by: plexi50 on April 29, 2012, 10:17:02 pm

Great idea on the temp pot. Thanks guys. I was thinking i might be going the wrong way

Title: Re: Mid Scoop
Post by: tubeswell on April 30, 2012, 03:05:19 am

And if you want chime on top of the mid scoop (once you've got the tone stack sorted), add a 100pF bright cap to the vol pot input-to-wiper.

Title: Re: Mid Scoop
Post by: Ed_Chambley on May 01, 2012, 11:17:36 pm

I have installed a 3 way switch with different values.  6k8, 3.3k and 1.5.  Switch it to whatever I am in the mood for.

Title: Re: Mid Scoop
Post by: plexi50 on May 02, 2012, 07:15:05 pm

I wound up putting a 50KL pot mounted to the rear of the amp in the extension speaker out jack that was missing.
Now getting used to it being mounted on the rear of the amp is another story