reverb - player?

[shooter]

I’m using this schematic for reference;
 http://el34world.com/charts/Schematics/files/fender/Fender_Vibrolux-Reverb-AA964-schematic.pdf

my main question as a non-player; If I’m plugged into vibrato channel, turn off/down the Reverb, (not looking at the trem part for discussion), do I *hear*/*play* basically the same as plugging into the normal channel, since both have nearly identical pre-TS circuits?

Other question, It appears with the ½ tube on the reverb channel you can’t *jump* both channels, why have 2?  Maybe the 1st answer answers this?
thanks

[sluckey]

They basically sound the same, but not quite. As part of the VIB channel reverb circuit, the dry signal gets knocked down by a 3.3M/220K voltage divider 15:1. Then an additional triode is used to make up that 15:1 loss. So, it will always sound slightly different from the NOR channel.

That's right. You can't jump the two channels because the signal will be out of phase and do some unpleasant sounding cancellation. The resulting sound is very thin sounding. But Fender two channel amps was never about 'jumping' the channels. It was about providing a separate preamp so two guitarist could play thru one amp. Or maybe one guitar and a mic.

[HotBluePlates]

They basically sound the same, but not quite. As part of the VIB channel reverb circuit, the dry signal gets knocked down by a 3.3M/220K voltage divider 15:1. Then an additional triode is used to make up that 15:1 loss. So, it will always sound slightly different from the NOR channel. ...

And the gain boost of the additional triode exceeds the 15:1 loss from the mix network, so the reverb channel always has a slightly gainy-er sound than the normal channel.

For this reason alone, non-reverb versions of some blackface amps (Deluxe vs Deluxe Reverb, and Princeton vs Princeton Reverb) command much lower prices on the vintage market.

However, aside from how soon distortion occurs, the non-reverb amps/channels have a very similar sound to the reverb amps/channels. As you noted, everything other than that reverb makeup gain stage is identical.

[shooter]

Thanks guys.

never about 'jumping' the channels. It was about providing a separate preamp so two guitarist could play thru one amp

Doesn't phase cancellation come into play here also?

[eleventeen]

You'd "never" hear it from two separate guitar-signal sources.

[sluckey]

Doesn't phase cancellation come into play here also?

How could it? There is absolutely no correlation between the phase of one instrument and the phase of another instrument. Think about it a moment. 

[shooter]

Think about it a moment

That's how I get in trouble , But here's my *thought* process; 2 of us are playing "A" (440Hz) ad-infinitum, we're in unison........swap humans for sig-gen.......outta phase by 180.....thin sound.  Now I did consider normal *analog* variations of 2 humans, so I *hear* in my *minds ear* something like cross faded A's

[sluckey]

The two guitars are totally nonsynchronous. How can they possibly be exactly in phase or exactly 180° out of phase. Sure, they may cross phases occasionally but unless you can find a way to synchronize the two they will never be locked in phase.

The only way to insure that the two signals are totally coherent will be to apply the SAME signal to the input of both preamps. (This is called jumping the channels). Now you have a situation where if you combine the two signals at the output of the preamps, they will either be in phase and add to each other if they both go through an even or odd number of inversions, ***or*** they will be 180° out of phase and subtract (cancel) each other if one goes through an even number of inversions while the other goes through an odd number of inversions.

[PRR]

> 2 of us are playing  ... we're in unison....

Did you pluck at the same instant? (Sub milli-second accuracy.)

Are you perfectly in unison? (Never in my experience.)

Both Pitch and amplitude decay?

One guitar two paths is always in unison with itself.

Two strings (much less two guys on two guitars) will be "in unison" only in passing. (If one is 440.000 and the other is 440.100, 1/3rd cent pitch error, they will cross through unison and every 10 seconds, though at different amplitude each passing.)

[shooter]

Once again, thanks!  I do get  how single source phase cancels, 2 guitar player however is *new* to me.
Last night random chance, one of my musician friends called, way past my bedtime, artists, , so I asked; "as long as you woke me up..."  He had done exactly what I'm trying to understand, had EVEN used the fender vibrolux!  His comment was; "you absolutely do hear cross fading", to the point they drug out another amp for the recording session.
So my *take-away* , try and design my next build with both channels in-phase for both jumping and playing.
again, thanks for dragging me to the water

[HotBluePlates]

Once again, thanks!  I do get  how single source phase cancels, 2 guitar player however is *new* to me.
Last night random chance, one of my musician friends called, way past my bedtime, artists, , so I asked; "as long as you woke me up..."  He had done exactly what I'm trying to understand, had EVEN used the fender vibrolux!  His comment was; "you absolutely do hear cross fading", to the point they drug out another amp for the recording session.

I don't believe your friend; if it actually is happening as he describes, it is absolutely not due to opposite-polarity channels.

It's no different than 2 singers singing the same note. You're telling me if one of them moves a few feet away (whatever is 1/2 wavelength for the sung pitch) that both their voices will disappear?? It's plainly obvious when you think of practical situations.

There's only way for "cross-fading" to happen is due to shared cathode resistors among channels. This is the only plausible way for a large signal in one channel to upset the volume in the other channel.

But if the guitarists use similar sounds, play similar parts on the same part of the instrument, they'll always fight each other to be heard, single-amp or no.

[shooter]

But if the guitarists use similar sounds, play similar parts on the same part of the instrument, they'll always fight each other to be heard, single-amp or no.

It's all *over my pay-grade* musically, all I got was they had a sound guy set-up inside and old factory, originally 1 amp, one player, player 2 shows up, they plug in, and sound guys says listen, player 2 gets own amp, sound guy and players happy.
I'm in the pencil whip state of a 2 channel, it will be "in-phase"
thanks much

[sluckey]

You can prevent these kinds of issues by installing a single input jack.   

[Willabe]

 

[shooter]

You can prevent these kinds of issues by installing a single input jack

I have yet to build a 2jacker
But.. I do want my next build a 2jacker, since I'm using pencil instead of Crayola, I can erase lots til I get close, then I can color

I do wanna minimize pitfalls though, I'll be askin about signal spiting and combining next, but i'll sit in the corner and read more 1st