VDS Posted July 6, 2021 Author Share Posted July 6, 2021 I assume the cable is XLR at one end and RCA at the other (IOW, no additional connectors added to an otherwise three wire cable). This probably is not the problem, but have you measured whether the pin 1 and pin 3 on the XLR side side of the cable are electrically tied together ? yes, no additional adapters attached to cables. checking pin 1 and 3, with a ohm meter? Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted July 6, 2021 Share Posted July 6, 2021 38 minutes ago, VDS said: But that make sense right, your literally creating a gap in signal chain, or am i off base? Wondering if the connection to the high frequency amp causes problem, or just doesnt allow problem to get to the speakers? You have only eliminated the Pass as the source of the noise at this point so you don’t know for sure if you have broken the ground loop between xilica and amp or just not allowing the noise to be heard. To properly complete the troubleshooting you should reconnect the Pass amp to the xilica and disconnect the interconnects to the Xilica’s Input. If noise stops you have issues between pre-amp and xilica. If the noise persist you have now proved the interconnects or ground loop between xilica and Pass is your problem. Quote Link to comment Share on other sites More sharing options...
Chris A Posted July 6, 2021 Share Posted July 6, 2021 46 minutes ago, VDS said: This looks very similar to my "hiss" noise issue before installing the ISO-MAX (i.e., same frequencies at ~1500, 2000, 3000, 4500 and 6000 Hz), however, I don't remember seeing such large SPL spikes. Chris Quote Link to comment Share on other sites More sharing options...
VDS Posted July 6, 2021 Author Share Posted July 6, 2021 7 minutes ago, mikebse2a3 said: If noise stops you have issues between pre-amp and xilica Noise continues when preamp to Xilica cable is disconnected. Quote Link to comment Share on other sites More sharing options...
VDS Posted July 6, 2021 Author Share Posted July 6, 2021 7 minutes ago, Chris A said: This looks very similar to my "hiss" noise issue before installing the ISO-MAX (i.e., same frequencies at ~1500, 3000, 4500 and 6000 Hz), however, I don't remember seeing such large SPL spikes. Chris If you solved similar problem with the Jensen isolator I’m seeing that as the most likely solution at the moment. its not loud, but audible during slow passages of solo piano music, between song, etc. And it’s a very annoying frequency for my ears! Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted July 6, 2021 Share Posted July 6, 2021 1 minute ago, VDS said: Noise continues when preamp to Xilica cable is disconnected. This indicates you have a ground loop between Xilica and Pass in which case the best solution in my opinion is the ISO-MAX Chris linked to previously.. These are Input Transformer Isolators and the cable should be kept very short between the ISO-MAX and the Pass amplifier. 2 Quote Link to comment Share on other sites More sharing options...
Chris A Posted July 6, 2021 Share Posted July 6, 2021 I do hear those frequencies quite well. I would characterize what I heard before the ISO-MAX as hiss that was barely audible from the listening position, but audible when I put my ear next to the K-402 horn mouth. Chris Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted July 6, 2021 Share Posted July 6, 2021 Max cable length 3ft and if feasible I suggest less. 1 1 Quote Link to comment Share on other sites More sharing options...
VDS Posted July 6, 2021 Author Share Posted July 6, 2021 this is somewhat noticeable at listening position, and the frequency is so annoying, like a super high speed dentist’s drill in your ear! I have 2 experienced people, at least, suggesting the Jensen isolator. Unless anybody can think of anything else I think I’ll try that. once again I’m so thankful for all the help and knowledge I’ve received from this forum! Really you guys are great! Thanks, Ted Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted July 6, 2021 Share Posted July 6, 2021 Also note for maximum noise rejection the recommendation about adapter cable configuration… miketn Quote Link to comment Share on other sites More sharing options...
babadono Posted July 6, 2021 Share Posted July 6, 2021 ^Yes this. Pin 1 of XLR should NOT be jumpered to pin 3 at the XLR end. An ohm meter will not tell you this, you have to visually inspect. This is with a shielded twisted pair cable. If your XLR to RCA cables are just 1 conductor and shield like a normal RCA cable then all bets are off. My mentor at Jensen transformers...."you must always think about where the current wants to flow" Quote Link to comment Share on other sites More sharing options...
babadono Posted July 6, 2021 Share Posted July 6, 2021 @VDS If you are going to order from Jensen, do yourself a favor and get some "dummy plugs". They'll be an extra $10 or $15. Invaluable in troubleshooting this kind of stuff. Quote Link to comment Share on other sites More sharing options...
babadono Posted July 6, 2021 Share Posted July 6, 2021 1 hour ago, mikebse2a3 said: This indicates you have a ground loop between Xilica and Pass in which case the best solution in my opinion is the ISO-MAX Chris linked to previously.. These are Input Transformer Isolators and the cable should be kept very short between the ISO-MAX and the Pass amplifier. Both the Pass Amp and Xilica have 3 prong AC plugs...Just as a short term test put a cheater on one of them. @VDS Quote Link to comment Share on other sites More sharing options...
VDS Posted July 6, 2021 Author Share Posted July 6, 2021 3 minutes ago, babadono said: Both the Pass Amp and Xilica have 3 prong AC plugs...Just as a short term test put a cheater on one of them. @VDS @babadono dummy plugs? cheater, you mean those adapters for ungrounded outlets? Is that what people call “lifting” the ground to test for ground loop problems? is there a simple way for me to buy the right cables? Until now I’ve never bought a xlr cable. “Need “xlr cables for dummies” explanation. thanks, Ted Quote Link to comment Share on other sites More sharing options...
VDS Posted July 6, 2021 Author Share Posted July 6, 2021 Any opinions on 3 conductor shielded xlr cables? Good brands to look for? Quote Link to comment Share on other sites More sharing options...
VDS Posted July 6, 2021 Author Share Posted July 6, 2021 This is the cable I’m currently using. i mean it says “superior construction” ! Maybe not so superior? Quote Link to comment Share on other sites More sharing options...
babadono Posted July 6, 2021 Share Posted July 6, 2021 yes "dummy plugs" I've got a call into Jensen, they're going to get back to me whether these are available anymore. They were never on their website. You can make you own if need be. How to build is on page 107 of the doc: https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf And yes as a temporary test with just the Xilica and Pass amp connected "lift" the ground on one. I think I would try the Pass Amp first since the Xilica is balanced "Pro" gear. I just use Monoprice for RCA to XLR cables, Rugged, inexpensive and built properly. Especially if you are only going 6 feet or less. Of course the sky is the limit as far as cables go. Quote Link to comment Share on other sites More sharing options...
babadono Posted July 6, 2021 Share Posted July 6, 2021 1 minute ago, VDS said: This is the cable I’m currently using. i mean it says “superior construction” ! Maybe not so superior? only one conductor + shield? The ONLY choice the inter chassis current has in this case is to flow down the shield with the signal ground current. Not ideal. Quote Link to comment Share on other sites More sharing options...
VDS Posted July 6, 2021 Author Share Posted July 6, 2021 “Of course the sky is the limit as far as cables go.“ That’s the problem with this crazy audio stuff, the sky is always the limit! I’ll check out Monoprice. I’m also talking to a guy at Blue Jeans Cable, they seem like a high value brand. I use their rca interconnects. and I’ll try lifting the ground thanks. Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted July 6, 2021 Share Posted July 6, 2021 As @babadono said looks like monoprice has reasonable cable options for XLR to RCA cables just stay less than 3ft Lengths on the output side of the ISO-MAX PI-2XX . NOTE: If you are going with the Jensen ISO-MAX and don’t have XLR to XLR cables you might want to pickup some from them to help get free shipping if you decide to order from Monoprice. https://www.monoprice.com/product?p_id=4783&gclid=EAIaIQobChMI5P2HsszP8QIVFv_jBx1mTQ6iEAQYBSABEgLhS_D_BwE Quote Link to comment Share on other sites More sharing options...
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