andrewsrea
Well-known member
A friend of mine has been on a quest for the tone of a loud Fender Black panel amp, at about 70dB of real volume. Think of a Vibroverb or Super Reverb on '4' to '7'. We have tried pedals, master volume mods, speakers, expensive attenuators and various amps. Nothing got close to the nuance of a guitar into an amp, which is punishing a nice speaker at loud volumes. Big sounding without being overtly distorted.
He asked me to make a Tube Screamer with much less fizz, only a dash of mid-hump at 728Hz, a modicum of compression, which bloomed when the guitar is played hard and lots of 'level' on the back end to drive a tube amp. His platform is a Fender Super Champ XT.
A simple mod to the PedalPCB 'Little Green Scream Machine' got wickedly close. It sounded stellar at low volumes on my 1965 80w Twin circuit though a 4x12 cab with Celestion Super Lead 80's, as well as genuine in the Champ XT.
He named it 'Cornstarch' as he said it acts as in a way which binds the guitar tones.
Here are the mods:
1.) C2 changed from a 1U to a .33, to reduce frequencies below a guitar's fundamental notes.
2.) C4 from a 47n to a 220n, which shifts the 'Gain' frequency into the lower mid-range and greatly reducing the mid-hump.
3.) 'Drive' potentiometer from a A500K to A250K, which lowers overall gain range and provides more precision settings. It also limits the opamp to 'edge of breakup'.
4.) R19 from a 10K to 12K, resulting in less AC signal being leaked to ground via the Vref.
5.) R10 from a 1K to a 1K5, bumping the gain in the tone circuit a pinch.
6.) R15 from a 15K to 20K, shifting the output impedance up and sending a little less output to ground, providing more signal over longer cable lengths.
7.) The clipping circuit is switchable between 'no clip' and a 'red-green led pair' for slightly asymmetrical clipping. 'no clip' is punchy and the leds add a little
8.) Opamp socketed. RC4558 is what my friend chose. OPA1678, OPA2134 and LM833 all allowed more cut for muddy amps (like my Tweed Champ). A MC1458
thickened up sterile sounding solid state amps.
It can get grindy at full gain, without sounding buried in compression or sounding like the parallel 'clean note' (part and parcel of a soft-clipping circuit) is too forward. I really like this pedal and found it much more useful than a standard TS. I will be building myself one sometime later this year (when I clear my bench of amp work).
He asked me to make a Tube Screamer with much less fizz, only a dash of mid-hump at 728Hz, a modicum of compression, which bloomed when the guitar is played hard and lots of 'level' on the back end to drive a tube amp. His platform is a Fender Super Champ XT.
A simple mod to the PedalPCB 'Little Green Scream Machine' got wickedly close. It sounded stellar at low volumes on my 1965 80w Twin circuit though a 4x12 cab with Celestion Super Lead 80's, as well as genuine in the Champ XT.
He named it 'Cornstarch' as he said it acts as in a way which binds the guitar tones.
Here are the mods:
1.) C2 changed from a 1U to a .33, to reduce frequencies below a guitar's fundamental notes.
2.) C4 from a 47n to a 220n, which shifts the 'Gain' frequency into the lower mid-range and greatly reducing the mid-hump.
3.) 'Drive' potentiometer from a A500K to A250K, which lowers overall gain range and provides more precision settings. It also limits the opamp to 'edge of breakup'.
4.) R19 from a 10K to 12K, resulting in less AC signal being leaked to ground via the Vref.
5.) R10 from a 1K to a 1K5, bumping the gain in the tone circuit a pinch.
6.) R15 from a 15K to 20K, shifting the output impedance up and sending a little less output to ground, providing more signal over longer cable lengths.
7.) The clipping circuit is switchable between 'no clip' and a 'red-green led pair' for slightly asymmetrical clipping. 'no clip' is punchy and the leds add a little
8.) Opamp socketed. RC4558 is what my friend chose. OPA1678, OPA2134 and LM833 all allowed more cut for muddy amps (like my Tweed Champ). A MC1458
thickened up sterile sounding solid state amps.
It can get grindy at full gain, without sounding buried in compression or sounding like the parallel 'clean note' (part and parcel of a soft-clipping circuit) is too forward. I really like this pedal and found it much more useful than a standard TS. I will be building myself one sometime later this year (when I clear my bench of amp work).