Keith Hilton
From:
248 Laurel Road Ozark, Missouri 65721
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Posted 15 Aug 2022 9:22 am |
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I made a new electronic isolation box for my own personal use, and thought I would ask if there is a need for this type of box. I know the world is full of all types of direct boxes, and isolation boxes, both passive and active. I might add, 99.999% of them coming from China.
The reason for building the box was for "me" using two amplifiers. Yes, two amplifiers can be used "sometimes" without problems. I can assure you problems can happen when running two amps. The number one issue is a ground loop noise due to the fact that different amps have different ground potentials. The difference in ground potential is usually the most when using a solid state amp with a tube amp. The second big issue when using two amps, is the input impedance of each amp. Most people simply "Y" the signal. For example: I tried using a Trace Elliot bass amp with an Evans amp. The signal was "Y" to the two amps, and the input of the Trace Elliot bass amp sucked most of the signal away from the Evans amp. I had to turn the volume up to extreme level on the Evans amp to even get an acceptable signal. I lost tone quality hooking up the two amps. The issues happened even though the "Y" signal to the two amps came from my Hilton pedal, which is a line level signal. I would assume the problems would even be more with the low level output signal of an old pot pedal.
To solve the above two issues, I built a box that fed the "Y" signal to two separate Operational Amplifier chips. Each amplifier chip had a gain knob. Which helped solve the two separate input impedance problems. With the input signal split, I sent one signal out to a 1/4 inch output jack. The other leg of the "Y" signal I sent through a isolation transformer, then out to a 1/4 inch output jack. Care was taken, in the selection and arrangement of parts, to make sure the isolation transformer did not color the signal. The isolation transformer separated the ground of one of the "Y" outputs from the other output, thus solving the ground loop issue.
The box worked in testing, but then I realized their "might be" a need for a XLR output. If someone would want to send the isolation transformer leg of the signal to a PA, then a XLR output would be needed. If the XLR and 1/4 inch output of the isolation transformer were connected in a Y---and a amp plus a PA was hooked up together, the two original issues could happen. Most newer amps have a XLR output, so maybe a XLR output on the box is not needed.
The box could be used just as an isolation box with one line out. The box could also be used as a pre-amp boost since each op-amp chip has gain.
It needs to be understood that a simple isolation transformer will not solve all noise. Single coil pickups act like an antenna picking up all kinds of noise. Also, ground loops can happen in powered devices between the guitar and the amp. Ground loops can also happen in the building wall receptacle. A plumber might have hooked one of the grounds to a water pipe.
I have two questions: Is there a need for the box? Is there something that needs to be added to the box, or something that needs to be changed?
I need to mention one other thing the box will not solve. If you hook up two amplifiers, make sure the speakers of each amp are in phase. If the speakers are out of phase it sounds terrible! |
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