AC15 & 30 - fattening up the tone in trem mode

[pdf64]

Dunno if this is old news, but from http://www.voxac30.org.uk/vox_ac30_vibrato_gl.html

“some years later that it was realised the shorting capacitor could be moved to the tonally thinner side of the modulator to produce the very same Tremolo effect, but now with the fuller signal allowed to remain. This modification doesn't appear to have been documented in the List of Changes but was quietly introduced in all JMI product with a Vib/Trem channel by 1964.

One can demonstrate the two different 'tones' of the Vib/Trem channel. With the footswitch in the off position, use the Vib/Trem switch with a guitar or other audio running. You will hear a change in tone as you switch from Vibrato to Tremolo setting. If you have an early amp the audio will become noticably thinner, if you have a later amp the audio you will hear a slight reduction in high frequency.“

I’ve not tried it, but it makes sense.
It’s just that there’s been a few AC15 builds here, and they might be able to sound even better.

[sluckey]

After reading this I drew up a simple mod to switch between fat trem, vibrato, and thin trem. Some of you guys that have recently built an AC15 may want to give this a try. Heck, there may even be some useful tones available. If my AC15 was on the bench I'd give it a try. Easy to do and undo. Just need a .1µF cap and a SPDT with center off switch. About $5 for the parts from AES.

[pdf64]

Nice!
Only need one C22, inserted between the switch and circuit common 
A couple of 10M anti pop resistors on the switch might be useful.

[sluckey]

10M resistors is probably a good idea, even for the original circuit. I can't recall if the original switch pops or not. I just left the switch in VIB mode because I did not like the trem. This thread probably explains why. 

[sluckey]

Only need one C22, inserted between the switch and circuit common 

Duh! Didn't even think about that.

[shooter]

 
took me a minute, maybe 2, or 3.  got hung-up on "circuit common" so I ignored it til the bulb lite 

[AlNewman]

That's interesting.  I've never played an ac-15, but I think as a first build I might like to try it.  Would it look more like this then, with 1 cap and the pop resistors?

[dwinstonwood]

took me a minute, maybe 2, or 3.  got hung-up on "circuit common" so I ignored it til the bulb lite 

It took me more than a few minutes to see that one cap between the switch and common (ground) works the same way as two between the switch and the two signal paths. 

[sluckey]

That's interesting.  I've never played an ac-15, but I think as a first build I might like to try it.  Would it look more like this then, with 1 cap and the pop resistors?

I think the resistors should be across the switch contacts.

[AlNewman]

That's interesting.  I've never played an ac-15, but I think as a first build I might like to try it.  Would it look more like this then, with 1 cap and the pop resistors?

I think the resistors should be across the switch contacts.

Ok, gotcha.  Thanks