Teach me about phasing issues while jumping plexi channels

[Digital Jams]

So why do so many people internally jumpering these? Are they looking for that extra tonal choice or they just dig that?

Seems easier just to plug in and go.

 

[RoccaforteAmps]

jumpers are for skipping rope!

 

[RoccaforteAmps]

So why do so many people internally jumpering these? Are they looking for that extra tonal choice or they just dig that?

Seems easier just to plug in and go.

You can internally link the channels without any attenuation.
I have two models that come this way.

The attenuation from jack jumping comes from resistors (grid stop, and grid leak) that are mounted on the input jacks.
Doug

 

[Greazygeo]

I hate jumping channels.

FWIW, I can actually hear something happening when going into the high input, but turning up channel 2 volume. It seems to add compression although I am not using the input...

All mine are that way too.

 

[Greazygeo]

So why do so many people internally jumpering these? Are they looking for that extra tonal choice or they just dig that?

Seems easier just to plug in and go.

It does allow you to add some low end content to the signal. I don't see how guys can run CH II up past 9:00....way too much muddiness. I've never understood the channel jumpering myself.

 

[Digital Jams]

So why do so many people internally jumpering these? Are they looking for that extra tonal choice or they just dig that?

Seems easier just to plug in and go.

You can internally link the channels without any attenuation.
I have two models that come this way.

The attenuation from jack jumping comes from resistors (grid stop, and grid leak) that are mounted on the input jacks.
Doug

HA!!!

That makes sense.

Glad I asked the question, thanks guys as I have learned alot

 

[RoccaforteAmps]

BTW, many years ago I was told
that Hendrix didn't have the channels jumped.
What they did was internally link all 4 inputs
together so he could plug into one, and then
run three separate cables to three other heads.
I *think theres a picture somewhere this
and you can see all 4 inputs are being used.
If the amp was stock, this wouldn't work.

 

[Anonymous]

turn up both volumes but plug into vol 1 upper left. run head at 16 0hms into an 8 ohm cab for the goods.

 

[Digital Jams]

turn up both volumes but plug into vol 1 upper left. run head at 16 0hms into an 8 ohm cab for the goods.

and how long would the OT last while doing this?

 

[Greazygeo]

turn up both volumes but plug into vol 1 upper left. run head at 16 0hms into an 8 ohm cab for the goods.

and how long would the OT last while doing this?

I do the opposite....my heads are set to 8 running a 16 ohm cab. I've done it that way forever.

 

[killertone]

I guess I am in the minority here but I like jumping the channels on my Metro 50 watt plexi. Like George said, I don't run Ch 2 any higher than 9 o'clock because of the muddy bass issue but when mixed correctly the 2 channels are pure fucking . Super tight bottom end.

 

[Digital Jams]

turn up both volumes but plug into vol 1 upper left. run head at 16 0hms into an 8 ohm cab for the goods.

and how long would the OT last while doing this?

I do the opposite....my heads are set to 8 running a 16 ohm cab. I've done it that way forever.

Yeah that I know will work, I am thinking I am being screwed with

 

[Anonymous]

Im not bsing you dj. 16 into 16 is the best but 8 ohm head in to 16 ohm cab makes for higher resistance on the output of the amp because of the higher ohmage on the cab. equals not good. 16 into 8 is actually safer. reason i mentioned it, i have jtm 45 clone that is the original. it has one speaker output wired to 16 ohms like the original jtm 45. the amps is twice as ballsy 16 into 8. i wouldnt go wire a 8 ohm cab its not that much difference. just go 16 - 16

 

[steve_k]

So when plugging into ch1 high sens and then jumpering from ch1 low to ch2 high sens I hear you have to watch out for phase issues, what exactly should I hear when this happens?

Yeah I know I am going to get slapped for this, sorry but I am used to high gain switchers still

There are no phasing issues like one might find running two separate amps. These inputs only route signal through, one, two or both circuits, so it s not going through any gain stages, phase inverting stages, etc. One thing you won't find is any additional gain or separation of signal or delay. All it does is blend the bright circuit of input one with the attenuated circuit in input two. I jump the inputs on my 78 Super Bass and it softens the bite and attack with input 1. I am sending my Super Bass to Dave Friedman for some work and make it a little more "user" friendly.

Steve

 

[ratter]

16 into 8 is actually safer.

I'm no tech, but that's exactly the opposite of what I've always been told, and done.

Example:

When matching amplifiers to loudspeakers, the output impedance of the amplifier should match that of the loudspeakers as accurately as possible, to ensure that the amplifier is able to deliver its maximum rated power. If the speaker impedance is lower than that of the amplifier's output impedance, the amplifier will be forced to work too hard, which will cause overheating and possibly failure. If the amplifier has an overload protection circuit built-in, this may operate and shut down the amplifier, either partially or completely.

If, on the other hand, the speaker impedance is significantly higher than the amplifier's output impedance, the amplifier will be unable to deliver its full power rating, but should in all other respects work normally. Taking an example, if an amplifier with an output impedance of 4(omega) is connected to an 8(omega) loudspeaker, the maximum power available will be half the rated power of the amplifier. Never run valve amplifiers without a speaker connected, as damage may result. This does not apply when using solid state amps, however.