Colossal wrote:heisthl wrote:It would seem to me that JB needs an amp tech who can correct some of the amps in his set up so every amp is the same and can all plug into the same source using the 3 prong cords without issues.
Hi Henry,
Thanks for weighing in on this thread. I've seen some photos of Joe's rig and he has everything plugged into a Monster (brand name) power supply and conditioner. I haven't seen any phase switches on the other 3 amps in his arsenal (the Carol Ann/Van Weelden, the Two Rock, or the Jubilee) although that doesn't mean they aren't modded that way (just haven't seen any closeups). He doesn't have anything like the Morley Hum Eliminator in his rack setup so perhaps it's all done with phase switching and as JB points out, painstaking work. From what I've read from others who have been around his rig though, they say it is very quiet and hum free. JB seems quite gear savvy.
Regards,
Dave
The main phase issues he has are not related to power phase, but signal phase. The output of amps such as as the CA with a built efx loop are out of phase with the input. The Marshall style amps are in phase. A phase reversal speaker cable cures any issues here.
He also uses a combination of ground lifted signal cables (ground only connected at one end) and 3 pin to 2 pin power plug converters.
Lets just back up first of all. Your wall supply has a live and a neutral. US code (most Countries are similar) requires that the neutral is kept at ground potential and not floating at any voltage . The neutral should only be connected to ground at one point, that is in the distrubution panel. Code also requires a seperate ground (earth) cable that is independant to the neutral. Similar requirements extend to certain electrical equipment, including amplifiers. They must have a seperate safety ground connection and wire . For the hobby builders out there always use a completely seperate chassis connection as close as possible to the power inlet for the safety ground, don't share it with other grounds. Also avoid the use of power phase switching on any new equipment. That was useful back in the days when ungrounded 2 pin power plugs could be inserted the wrong way around. All old amps can and really should be rewired and converted to 3 pin power connectors and the power phase switch circuit disabled. The only thing between you and 120V on your guitar strings is a 30+ year old capacitor......not good.
It is vitally important never to compromise the ground protection circuit of any piece of electrical equipment that is not double insulated (tube amps in general are not). There are a mixture of AC and DC voltages inside a tube amp that can kill you. Having no seperate uninteruptable dedicated ground circuit is dangerous. Safety ground returns using the signal cables alone are not adequate electrically and can be interuptable if someone pulls a cable out. Bottom line....be very careful with the use of 3 to 2 pin adapters.
It is possible however to have a multi amp rig with lots of off board processors etc without ever having to break a safety ground.
First off you should get a piece of paper and draw out all the equpiment and their interconnections. The only way you can do this effectively is to see it visually. It is a fair assumption that every input and output signal connection for a piece of equipment will have a common ground. Some rack processors have signal ground lifts that will help minimise the number of ground lifted cables needed.
The idea is to minimise the number of signal ground returns between each piece to just one and to break any loop between two pieces. So put an 'X' on every input or output where you want to break the ground. Count the number of cables with an 'X' and get the soldering iron out....
A ground lift cable is made by desoldering and insulating the ground at just one end of the cable.
A fair amount of experimentation is still required, but drawing it out on paper really helps a lot to make some logic of it all.
Other points to note.
1. Always connect all pieces to the same power source. Most multi-amp/effects rigs will not take you close to maximum current capacity from one outlet, even at 120V.
2. Always use a power conditioner as your power distribution point.
3. Always keep power cables as short as possible.
4. Don't allow the metal work of two pieces of equipment (such as amps) to touch.
5. When using more than one piece of rack equpiment, always use a rack and ensure the pieces are bolted in tight using all 4 mounting points.
6. Keep signal cables clear of power cables, especially in racks. You don't want to spend all that time getting rid of your ground loops only to induce a whole load of hum back in there making you think there are still loop issues.
7. If you use a pedal board, use a good quality AC - DC adapter and power supply, ideally with independant isolated 9V outputs. Watch out for ground loops in pedal boards, they can be a pain in themselves.
8. Don't use the same wall supply as heavy current demand equipment such as stage lights, PA power amp racks, beer pumps etc....
9. The use of a transformer isolator such as the Ebtech units does work, but bear in mind that the transformer isolated output is attenuated about -3dB from the non-isolated side and it does affect the tone. However, they work as a last ditch method when all else fails.
10. Finally, always uses good quality signal cables and heavy duty power cables.
Good luck.
Regards,
Alan Phillips
Carol-Ann Amps
