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Harmonic Tremolo in a pedal?

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8/30/2000 4:29 PM
Deltablues	Harmonic Tremolo in a pedal? Does anyone make a pedal that emulates the tremolo/phasing effect of "Harmonic Tremolo" that is found in the Brown era Fender amps like the Pro?

8/30/2000 6:16 PM

Matthew Springer

Not as far as I know since this is an effect that modulates the bias current to the power tubes (ala Vibroverb). It would need to be built into the power amp section. You can get a pretty good approximation (so they tell me) using trem pedals with "soft" settings ala Fulltone Supatrem.

One pedal brand many people swear by is the Lovetone trem panner (forget the name). check out Lovetone's website. (no I don't own any personally)

Personally, I like the Blackface stutter type more. Especially with heavy flanger.

8/30/2000 9:53 PM

Quoting from this link:

http://www.stompboxology.com/gazette.htm

quote:
" Vol. 4, No. 4 – Mo’ Trem’lo – $14.95
Despite six 'designer' tremolos through the Cookbook alone, tremolo remains king of the undiscovered effects. This issue shows you why, with a detailed examination of tube-amp tremolo, plus plans for five 'designer' tremolo stompboxes. Tremolo-Matic X is a solid-state embodiment of the “3-tube” tremolo/vibrato found in classic amps; but goes the amps one better by making both halves of the effect variable. Tremolo-Matic XI features an oscillator whose rate varies under control of a secondary oscillator. We're keeping Tremolo-Matic XII a surprise, but can say that it opens the door to a previously unheard category of sounds. The projects conclude with primo B-mods of Tremolo-Matic and Pan Tremolo-Matic, both simplified and adapted to 9V operation without losing their original performance. All five projects feature trim-free oscillators and are built on uncommitted circuit boards; four of the five are single-9V boxes; all power-on with plug insertion. Beginner’s View takes you step-by-step through TM10’s function and assembly; plus a few surprises."

The $14.95 buys you the schem, probably worth it as opposed to the R & D time you'd spend.

8/31/2000 1:27 PM

Hi guys,
I may be sticking my neck out here, but from my read, the "brown era" tremelo doesn't really mess with the bias/power amp. It's simply a dual triode configured as an oscillator into a cathode follower buffer, so as not to load down the next triode stage which is a "symmetric modulator," or phase splitter. This stage feeds a dual triode frequency divider/mixer stage. Overall, the circuit requires 2.5 12AX7's.

This is easily built as a pedal, (mine has a pretty big footprint.) I actually put this together to A/B sound test some of my other oscillator-based circuits by, kinda as a "gold standard".

Also, consider putting in a wet/dry mixer beforehand to give depth of effect. If you put in a feedback loop between the wet/dry paths, you can also get some cool stuff happening.

I've been thinking about doing this up as a SS unit, by modifying Kevin O Conner's wide range tremelo circuit as outlined in his Tonnes of Tone. He also has an excellent explanation and includes some component value mods on pg 6-42 of The Ultimate Tone, Vol. 2.
Cya,
Jon

9/1/2000 3:44 PM
Matthew Springer	After looking at the spec again of the amp in question, I'd have to agree. The Vibroverb actually does mess with the bias, though. That one would be tough to build. Jon, How does it sound?

9/1/2000 9:26 PM

Hi Matthew,

My 'brownface' trem pedal has the oscillator waveform "feel" of a Vibrochamp or an original Ampeg Jet (I have one of the latter)...to my ear a lot nicer than the LDR coupled oscillators. I have a '68 Blackfaced Deluxe Reverb, and several original Ampeg Gemini's; this pedal is way more musical. In the brownface, what's nice is you can hear the shifting between the bass and treble in addition to the amplitide modulation. Still not the vibrato that's in my Magnatones (mono in a 410 and stereo in a 280) but nice.

Doing these oscillator based circuits as free-standing pedals required getting gain levels correct and lots of attention to lead dress and shielding. Parasitics were also a bit of a drag initially. Overall, I feel they'r worth doing as I don't care too much for most of the SS trems/vibratos I've tried.

Even though O'Connor's SS trem circuit is clean and straightforward, it doesn't have the "feel" of a tube circuit. I'm sure in the right hands, this too can be tweaked; I'm just so much more comfortable with tubes.

In reviewing the Vibroverb schematics, I see there was the 6G16 which did have the trem circuit tie into the bias supply. I don't have one of these, I believe my Traynor Guitar Mate Reverb III has a trem tied to the bias supply (been a while since I was in there, don't have the schematic readily available) on a pair of EL84's; this is a very pronounced pulsatile amplitude modulation. Looks like the Vibroverb AA763 (blackface?) had the usual LDR setup.

See ya,
Jon

9/9/2000 2:39 PM
Corwin	Is it possible to modify the circuit of the brownface tremolo to use smaller value pots instead of 10M RA and 4M RA?

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