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previous: steve anderson recapped my 1970 vibrochamp and put... -- 5/12/2000 11:25 AM

Re: vibrochamp

5/12/2000 6:26 PM
MBSetzer	Re: vibrochamp I looked at the instructions for the Torres champ tweedizing kit and was not impressed with the circuit on paper. I did notice that it was only a very slight move in the tweed direction, but did appear to be a completely reversible mod. There are many ways to make a champ louder, and most players will like them better louder. If it sounds better to you then I would say enjoy your improvement for a while before further modifications. I'm a real champhead, maybe someday I'll be able to post some of my various ideas on a website, I have not listened to the Torres kit circuit or I would be able to give a more worthwhile opinion. This is an outstanding vibrato when working as stock, but this particular vib method can be almost inaudible when the amp is highly overdriven, lots of other amps have more vib consistency between clean & overdrive. If you do not get a full, lush, pulsating vibrato when playing clean, then that part of the circuit might need a bit of attention. When everything is OK, and you like to overdrive a lot, start with the vib at an appropriate intensity setting for moderate modulation of your clean tone, then overdrive by turning up the guitar, amp, pedal, or all of the above. Most amps (including VC) soak away power during the vib cycle, but this amp has less effect as you overdrive it so there is less overall loss (because the effect is so weak when the amp is cranked) until the note starts to fade down to the clean range, where you then hear the vib come in at the setting you had previously dialed in. To me it makes it seem more like the walls are shaking for some other reason than vibrato, and that's pretty good for such a small amp. Did I mention I like to play through a 2x12 cabinet with 8inch speakers wired parallel for 4ohms? Surprisingly to some, the characteristics of the preamp 12AX7 will have a moderate effect on the vib performance. The average performance of the second triode within the preamp tube will give the expected vib, if a preamp triode which draws more current than average is put into the stock circuit, the vib will be less prominent at the same settings. Using low-gain (higher current) preamp tubes like 12AT7 or 12AU7 can give good amp tones, but then you may not have any vib effect even if the vib tube is still a stock 12AX7. Likewise substituting other tubes than 12AX7 for the vib tube will usually not be as good for vib either. There are three levels of vib removal for experimentation. Simplest, just set the intensity for zero. More like a plain champ would then next be just remove the vib tube (2nd 12AX7 away from the input jack). This is really no different circuit-wise than just setting it for zero, but it does leave a little more voltage for the remaining tubes when it is absent. Finally with the tube removed you could go one further and disconnect the lead from the vib area to the cathode (pin 8) of the first 12AX7. Insulate this lead well from the chassis in case a tube is reinserted to the vib socket, it would then be fairly hot & could do some damage if shorted. All three of these ways will not sound much different, but they are easy experiments to try. Be careful, of course. Hope this helps, Mike

5/12/2000 6:26 PM

MBSetzer

Re: vibrochamp

I looked at the instructions for the Torres champ *tweedizing* kit and was not impressed with the circuit on paper. I did notice that it was only a very slight move in the tweed direction, but did appear to be a completely reversible mod.

There are many ways to make a champ louder, and most players will like them better louder. If it sounds better to you then I would say enjoy your improvement for a while before further modifications.

I'm a real champhead, maybe someday I'll be able to post some of my various ideas on a website, I have not listened to the Torres kit circuit or I would be able to give a more worthwhile opinion.

This is an outstanding vibrato when working as stock, but this particular vib method can be almost inaudible when the amp is highly overdriven, lots of other amps have more vib consistency between clean & overdrive. If you do not get a full, lush, pulsating vibrato when playing clean, then that part of the circuit might need a bit of attention.

When everything is OK, and you like to overdrive a lot, start with the vib at an appropriate intensity setting for moderate modulation of your clean tone, then overdrive by turning up the guitar, amp, pedal, or all of the above. Most amps (including VC) soak away power during the vib cycle, but this amp has less effect as you overdrive it so there is less overall loss (because the effect is so weak when the amp is cranked) until the note starts to fade down to the clean range, where you then hear the vib come in at the setting you had previously dialed in. To me it makes it seem more like the walls are shaking for some other reason than vibrato, and that's pretty good for such a small amp. Did I mention I like to play through a 2x12 cabinet with 8inch speakers wired parallel for 4ohms? ;-)

Surprisingly to some, the characteristics of the preamp 12AX7 will have a moderate effect on the vib performance. The *average* performance of the second triode within the preamp tube will give the expected vib, if a preamp triode which draws more current than average is put into the stock circuit, the vib will be less prominent at the same settings. Using low-gain (higher current) preamp tubes like 12AT7 or 12AU7 can give good amp tones, but then you may not have any vib effect even if the vib tube is still a stock 12AX7. Likewise substituting other tubes than 12AX7 for the vib tube will usually not be as good for vib either.

There are three levels of vib removal for experimentation. Simplest, just set the intensity for zero. More like a plain champ would then next be just remove the vib tube (2nd 12AX7 away from the input jack). This is really no different circuit-wise than just setting it for zero, but it does leave a little more voltage for the remaining tubes when it is absent. Finally with the tube removed you could go one further and disconnect the lead from the vib area to the cathode (pin 8) of the first 12AX7. Insulate this lead well from the chassis in case a tube is reinserted to the vib socket, it would then be fairly hot & could do some damage if shorted. All three of these ways will not sound much different, but they are easy experiments to try. Be careful, of course.

Hope this helps,
Mike

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