Hoffman Amplifiers Tube Amplifier Forum

Other Stuff => Effects => Topic started by: alathIN on January 08, 2019, 09:05:41 am

Title: Ground Loop Solution?
Post by: alathIN on January 08, 2019, 09:05:41 am

It seems that a chronic problem with standalone effects units like the Fender reverb etc is the possibility to ground loops between the amp and the effect via the patch cable(s).
I was looking up various strategies for dealing with ground loops and wondered if anyone had ever tried using 1:1 isolation transformers at the effect output (when the instrument plugs directly in to the effect) or the effect output and input (when the effect is being used in a loop).
https://www.ebay.com/itm/10pcs-Audio-Transformers-600-600-Europe-1-1-EI14-Isolation-Transformer-Ringing/372428915842?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3Dff6c9fba432247a4b7eea7b0f9b3362e%26pid%3D100675%26rk%3D5%26rkt%3D15%26sd%3D113513215878%26itm%3D372428915842&_trksid=p2481888.c100675.m4236&_trkparms=pageci%3A1cdd48ac-1356-11e9-a2d3-74dbd180e49a%7Cparentrq%3A2dfa80ee1680ac1f5f4d28a1fffda93e%7Ciid%3A1

These transformers are readily available and inexpensive.
They do have some resistance (135 ohms for the ones linked above).
My sense is this could be an issue for the signal coming out of an instrument, but it seems like a signal that's been amplified should be able to tolerate this.
This seems to be fairly common practice in audiophile world, just wondering if there is any particular reason it's not widely adopted among the guitar amp crowd.

Title: Re: Ground Loop Solution?
Post by: jojokeo on January 22, 2019, 06:40:05 pm

There isn't an issue with ground loops on most simple guitar>effects board>amplifier situations. Using a separate Fender Reverb unit still should not present a problem? But if there's a unit without a normal grounded plug it should be replaced/fitted with one. Those reverb units weren't meant to be inserted into a send/return effects loop if that is what you were implying? If all equipment is grounded properly you should not have any loop issues. But if you were running several amps at a time then you likely would have issues between everything and why the need for a ground lift and an isolation transformer on ONE of them. The Radial Big Shot ABY has one built into it for these situations. But using the isolation transformers do come with a price to the tone in these situations. A remedy is to use a simple buffer circuit going into it which lifts the blanket off the negatively sounding amp/channel.