How can I flatten the "midrange hump" on a tube screamer ??

[ChrisGS]

Hi Everybody ,
This is my first post...I was reading a few different Tube Screamer articles on the web , and I decided to start experimenting .

The pedal in question is a Maxon OD808 , which as I understand isn't exactly an 808 schematic , but closer to a TS10 . Anyway , as is I like the smoothness of the distortion quality , but I wish the pedal had a more natural EQ .

I changed the .047uf cap at the input of the op-amp to the recomended .1uf cap for increased bass , and I think it did increase some bass but the pedal still has the "midrange hump".

I'd like to try some things to get a more natural EQ...Are there any things that can be done to "fix" the midrange hump ?

Thanks for any advice ,
Chris .

[MetalGod]

From my experiences with TS-808s and SD-1s I'd say its the 0.047uF cap from the non-inverting input of the 4558 that needs to be altered to get rid of the midrange hump. 

Try a 0.1uF cap and you should be good to go.

[donald stringer]

http://www.muzique.com/lab/fatt.htm This article should be of interest to you.

[R.G.]

See "The Technology of the Tube Screamer" at GEO for why it's got a hump. Then un-restrict it, using the article as a guide.

[JHS]

Maybe a twin-T filter between the stages would be helpful, or raising the lows and highs, or a mid-trimpot wired like in the Barber DD.
There are a lot of other ways to reduce the mids. The best way to start is to build a clone on a breadboard (w/o buffers and the front end booster stage) and to try out every mod.

JHS

[markm]

The best way to start is to build a clone on a breadboard (w/o buffers and the front end booster stage) and to try out every mod.
JHS

Question?
What is the benefit without the buffers on the circuit?
Are they neccessary to have? I have been thinking of building one w/out the buffers but was wondering what effect it would have.

[Seljer]

Question?
What is the benefit without the buffers on the circuit?
Are they neccessary to have? I have been thinking of building one w/out the buffers but was wondering what effect it would have.

well the TubeReamer over on runoffgroove took them out and still works pretty well. I'm not sure if the input one has a huge effect but doesn't that output buffer do some magic in regarding how well it drives your amp?

[Urso]

Try this (inspired by the Full-Drive 2):


Tested on an Ibanez TS808 RI, and it sounds *very* good

[ChrisGS]

Hi Everybody ,
Thanks for all of the replies...Of course some of the answers lead me to new questions ...Such as , what's a twin T filter ,and is there a schematic around for a DirectDrive ? (I did not know that it is in the Tubescreamer family)

Also , I changed the .047 cap that connects to the chip (pin 2 ?) with a .1 cap , and I believe that it did help the bass ( One of the mods listed in the Technology of the Tube Screamer) but I was wondering if there is a point where increasing the size of the cap may muddy -up the sound.

And also , I like that article link for the frequency cut-off for the input cap , and the Fulldrive 2 schematic .

Thanks again for all the help ,
Chris.

[ubersam]

See "The Technology of the Tube Screamer" at GEO for why it's got a hump. Then un-restrict it, using the article as a guide.

Thanks for that article R.G. I refered to that article when I modded my buddy's TS9, it also got me started on my first DIY FX project.

Anyway, since I changed the resistor in the highpass filter to 1.5k, for more gain, I changed the cap to .22uf to bring the knee to 321Hz. I've brought it down to 193Hz and I think that was too muddy for my taste, specially at higher gain settings. I did the calculations the hard way, by hand, not knowing that there is an easier method here -> http://www.muzique.com/schem/filter.htm, thanks to Mr. Jack Orman.