tremolos... 5G9, 5E9 and 5F11!

[bruno]

Ok I'm sort of addicted to understanding tweed tube tremolos, but I could use a little help here...

http://www.kbapps.com/audio/schematics/tubeamps/fender/images/tremolux5e9a.gif
http://www.charlestonarea.com/Fender_Super_Reverb/FenderSchematics/tremolux5g9.gif
http://www.charlestonarea.com/Fender_Super_Reverb/FenderSchematics/vibrolux5f11.gif

On the 5f11 the oscillator seems to go directly to the output from the plate!

On the the 5e9 the tremolo is located around the phase inverter.

On the 5G9 the tremolo seems to be the later bias modulated tremolo that fender went on to use in the brownfaces, with a cathode follower buffer.

What's does this translate to in terms of tremolo effect on the amp?

[sluckey]

On the 5f11 the oscillator seems to go directly to the output from the plate!

Not quite. The trem signal leaves the oscillator plate, passes thru a coupling cap to the depth pot. The negative bias voltage is applied to the other end of the depth pot. The bias voltage and trem signal leave the wiper of the depth pot and continue on to the output tube grid resistors.

The 5F11 is very, very close to the Princeton Reverb trem, maybe even identical.

On the the 5e9 the tremolo is located around the phase inverter.

OK.

On the 5G9 the tremolo seems to be the later bias modulated tremolo that fender went on to use in the brownfaces, with a cathode follower buffer.

OK. This is just like the 5F11, but with the added cathode follower. Works the same.

What's does this translate to in terms of tremolo effect on the amp?

Trem effect is simply amplitude modulation of the instrument signal. You can do the same thing manually by varying the volume control up and down. The farther you turn the volume control the more intense (depth) the effect. How fast you vary the volume equates to speed or rate.

All the simple trem circuits like the ones you linked do the same thing. It's just different ways to skin a cat.

[tubesornothing]

I have had trem on both the PI and on power tube bias (non-roach types like you have posted).  They sound very close to me.  I was forced to use a CF for one of them (I think the bias one), because the target circuit would load down the trem circuit too much, turning it from a nice sine wave to a sharp triangle on top and sine on the bottom.  This was giving too much put-put at higher intensities.

I found it quite easy to experiment with the placement and configurations of the trems.  My biggest challenge was getting enough voltage swing for my circuit.  CF plus a high B+ fixed that problem.

[tubeswell]

The 5F11 is very, very close to the Princeton Reverb trem, maybe even identical.

... or to a brown Princeton (with a few different component values) but uses a different envelope for the LFO.

What tubesornothing said about a CF. I find the 2 stage trem with the CF has a more intense hypnotic quality and is not as 'noisy' as a single triode LFO. If you build an AC coupled CF stage, it produces different effects - still very nice. I did this on a recent 5F6something with 6G9B trem, because I found the cathode voltage in the follower stage was too high for the h-k insulation. Using an AC coupled follower allowed me to manipulate the cathode voltages a bit more easily. (But that's another story). I have built a 5G9 and I think it is one of the nicest of the tweed era amps.

[bruno]

Thanks for the replies! The guys from 65 amps, have a tremolo on their latest amp that appears to tremolo as the notes decay... rather than right as you play! I guess I'm trying to tweak one of these so that it'll give me something similar to that, I'm a little unsure, where to begin.

[topbrent]

Don't forget about the Vibro-Champ style tremolo.

It too, is a bias wiggle trem.  However, it wiggles the bias of a preamp tube cathode, not effecting the power tubes.

Wonderful trem in my opinion.

http://www.el34world.com/charts/Schematics/fender/VIBRO_CHAMP_AA764.pdf

[HotBluePlates]

The guys from 65 amps, have a tremolo on their latest amp that appears to tremolo as the notes decay... rather than right as you play! I guess I'm trying to tweak one of these so that it'll give me something similar to that, I'm a little unsure, where to begin.

Really? Sounds like the opposite of the folks who build the Hoffman AB763 board with a 6L6 amp and are working to increase the trem strength.

It seems to me that the trem signal is probably just too small and doesn't give a noticeable effect against tube bias until the note decays and the dry signal weakens.