Vox with Fender channels?

[roseblood11]

I would like to hear your thoughts about this concept:

Originally, I planned to build a '63 AC30TB.
I already bought the transformers and a chassis and I made a combo enclosure for 1*12 (Celestion Blue Alnico) and 1*10 (Weber Blue Pup). I'll definitely build the vintage AC30 top boost channel, phase inverter and power amp
But I'm not the biggest fan of the Vox normal and vibrato channels. So I thought: Why not add one more preamp tube and replace those channels with a 6g3 Brownface Deluxe bright channel and a Brownface/Blonde Harmonic Tremolo channel with full TMB tonestack?

Is this a good idea?

It would be more versatile, because of three tonestacks with different voicings. And the 6g3 channel could add more gain and distortion, especially if I don't use a split load plate resistor at the second triode. And 6g3 normal channel and Vox top boost channel would be in phase, a real plus when the channels are bridged

[Dave]

I think it sounds like a fine idea. It's just the sort of thing I like to do... Marrying different circuits together. That harmonic tremolo takes four gain stages to work and it can be very finicky. Three things I have done to make it work a little better/stronger... 1. At the output of the vibrato circuit, add the low pass filter from the Vox version (or some variation thereof). (On the schematic, it looks like a chain of capacitors with resistors to ground at each link of the chain. It helps filter out the low frequency oscillations that tend to find their way into the audio range. That will allow you to play around with the circuit and the frequency response. 2. Use an LED on the cathode of the oscillator tube. It will give you a lot deeper oscillations and works great (as long as you use the low pass filter I mentioned before). 3. Study the vibrato circuit and the way that it delivers certain frequency ranges to one stage and the other ranges to the other stage. Then use a DPDT switch to switch out/switch in the corresponding capacitors. Then, for the price of 4 stages, you get a vibrato circuit and a tremolo circuit at the flip of a switch.


Have fun with it.



Dave

[HotBluePlates]

... I'm not the biggest fan of the Vox ... vibrato channels. So I thought: Why not ... replace ... with ... a Brownface/Blonde Harmonic Tremolo channel ...

This is really the same thing as Vox' vibrato channel.

Except the "harmonic trem" works a little funky because Vox completely ripped off Wurlitzer's vibrato circuit (while being somewhat out of reach in the UK), but Fender had to be more careful about infringing Wurlitzer's US patent.  Whatever is cool about Fender's circuit is an accident of not-copying Wurlitzer's circuit closely enough to get actual vibrato.

Sure you can exchange one wobble-channel for another wobble-channel if you like.

... I'm not the biggest fan of the Vox normal ... channels. So I thought: Why not ... replace ... with a 6g3 Brownface Deluxe bright channel ...

... the 6g3 channel could add more gain and distortion, especially if I don't use a split load plate resistor at the second triode. ...

EL84s have a smaller bias voltage than 6V6, and so are driven harder with a smaller signal.  This fact alone will lead to "louder/more-distorted/faster" when you're driving EL84s with the brown Deluxe preamp.

An AC30 is LOUD when it is distorting (I've got a couple of them, including a 1963 AC30).  The power tubes are the first place in the circuit that distorts, same as for the 6G3 Deluxe.  Except the AC30 is producing about double the output power when it is distorting.  If you're excited to get amp-distortion with your build, do you have an attenuator?  Or at least a place where you can play louder than most clubs allow bands to play these days?. Because the 6G3 Deluxe also distorts first at its power tubes, after making max clean power output (got a 1962 Deluxe here as well).

[dwinstonwood]

At home, I use a Weber MiniMass attenuator with my single channel (EF86) AC15, and my 6G3.

So, I must be hearing the power tube distortion that HotBluePlates describes. And, it's an awesome sound!