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Old 14th July 2012, 12:20 AM   #11
kevinkr is offline kevinkr  United States
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Old 14th July 2012, 12:40 AM   #12
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Are any of the amps tube amps? Are you planning on driving all the amps all the time, or just drive the amp with the speaker connected?
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Old 14th July 2012, 01:49 AM   #13
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Are any of the amps tube amps? Are you planning on driving all the amps all the time, or just drive the amp with the speaker connected?
yea 2 or marshall 78 and 79' JMP's which have been modded to the moon and back... the other is a soldano SLO, and last is a fender supersonic which has been modded for cleans. all are tube amps

I want to be able to switch between the 4 amps via footswitch, but only use 1 cabinet on stage. so all would be connected at one time, but only one will be playing at a time. I already have an ABCD box to toggle the guitar input from amp to amp, but they are set to 4 different cabinets with 4 different sets of speakers... so its kind of impossible to do that stage setup...
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Old 14th July 2012, 02:39 AM   #14
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yea 2 or marshall 78 and 79' JMP's which have been modded to the moon and back... the other is a soldano SLO, and last is a fender supersonic which has been modded for cleans. all are tube amps

I want to be able to switch between the 4 amps via footswitch, but only use 1 cabinet on stage. so all would be connected at one time, but only one will be playing at a time. I already have an ABCD box to toggle the guitar input from amp to amp, but they are set to 4 different cabinets with 4 different sets of speakers... so its kind of impossible to do that stage setup...
How many watts are these amps? What is the impedance of your speaker cabinet?

What kind of ABCD box? Does it connect to only one amp at a time? Or, can you play through more than one amp at once.

The problem I see is that tube amps want a resistive load near their nominal load impedance when they are not connected to a speaker. If you play into an amp without some kind of load, it could fail suddenly.

You really should have a box that not only connects one amp to the speaker while connecting the others to load resistors, but also switches the guitar to the amp that has the speaker connected. A significant problem is that it's a bad idea to have guitar switching and speaker switching in the same box. You would have to run all the speaker cables up to your pedal board and back again. Bad idea. Better to have a box on your pedal board that connects the guitar signal to the correct amp and also controls another box behind the speaker that selects which amp is connected to the speaker. Logic inside the pedal board box controls the speaker switching box via a cable.
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Old 14th July 2012, 03:05 AM   #15
Phalanx is offline Phalanx  United States
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How many watts are these amps? What is the impedance of your speaker cabinet?

What kind of ABCD box? Does it connect to only one amp at a time? Or, can you play through more than one amp at once.

The problem I see is that tube amps want a resistive load near their nominal load impedance when they are not connected to a speaker. If you play into an amp without some kind of load, it could fail suddenly.

You really should have a box that not only connects one amp to the speaker while connecting the others to load resistors, but also switches the guitar to the amp that has the speaker connected. A significant problem is that it's a bad idea to have guitar switching and speaker switching in the same box. You would have to run all the speaker cables up to your pedal board and back again. Bad idea. Better to have a box on your pedal board that connects the guitar signal to the correct amp and also controls another box behind the speaker that selects which amp is connected to the speaker. Logic inside the pedal board box controls the speaker switching box via a cable.
the abcd box is 1 guitar input, 4 output, and only 1 output at a time... I built it, so its just a couple 3pdt's, a few 1/4 inch, a 2.1mm dc jack and 4 led's... its basic as hell, but its true bypass so it sounds great.

the cabinet is 16 ohms, however each amp can be switched to have 4 ohm, 8 ohm or 16 ohm output. I tend to stay at 16. I would like the pedal to output 16 ohms as well.

as for all in one box I figured it would be bad to have it in the same box but it was merely something to try and attempt... the only thing absolutely necessary is the 4 way toggle between the 4 amps... at this point hoping it would be simply a pedal that I could have 4 switches to 4 LED's, so that each one cancels out the previous one when stomped.
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Old 14th July 2012, 04:15 AM   #16
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Connecting 4 amps to one box is an invitation to ground hum. And that's just on the input side. All kinds of strange things can happen when you try to connect the speaker grounds together. How many watts are these amps?

So in your ABCD box you can just push one switch and it automatically cancels the one already selected? I'd like to see that schematic.

To make this work well you will need four DPDT relays that can handle the current of the speakers (that's why I need to know how many watts). The grounds of the amps' speaker outputs will be isolated. On the input side the outputs to the amps need to be transformer isolated so there won't be any hum problems. There is a project like this a Geofex.
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Old 14th July 2012, 04:15 AM   #17
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the abcd box is 1 guitar input, 4 output, and only 1 output at a time... I built it, so its just a couple 3pdt's, a few 1/4 inch, a 2.1mm dc jack and 4 led's... its basic as hell, but its true bypass so it sounds great.

the cabinet is 16 ohms, however each amp can be switched to have 4 ohm, 8 ohm or 16 ohm output. I tend to stay at 16. I would like the pedal to output 16 ohms as well.

as for all in one box I figured it would be bad to have it in the same box but it was merely something to try and attempt... the only thing absolutely necessary is the 4 way toggle between the 4 amps... at this point hoping it would be simply a pedal that I could have 4 switches to 4 LED's, so that each one cancels out the previous one when stomped.
in addition to above each amp is 100 watts...
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Old 15th July 2012, 01:00 AM   #18
Phalanx is offline Phalanx  United States
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There is a project like this a Geofex.
hey I searched all over geofex... where is this thing... I cant find it anywhere...
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Old 15th July 2012, 01:07 AM   #19
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I found this. this is pretty much what I want to build except I need it to be able to switch between 4 heads and at will instead of in series.

http://www.ebay.com/itm/Radial-Toneb...item2572c0dcc3
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Old 16th July 2012, 03:48 AM   #20
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hey I searched all over geofex... where is this thing... I cant find it anywhere...
Go to GeoFex, select FX Projects on the left menu, then Hum Free Splitter/A/B/Y Box. There are a couple of other similar projects. The idea would have to be expanded for 4 amps.

The thing on Ebay is the right idea for two amps. Not sure if the grounds are isolated between the two amps. Did you notice they suggest you locate the unit close to the amps to minimize the length of speaker cords and use a remote footswitch. But then the guitar signal has to run back and forth to the pedal board.
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