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Post subject: Help Needed with BDRI Effects Loop Issue.
Posted: Sat Sep 07, 2013 12:24 pm
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Hello out there from Paisley, Scotland. I have a Blues Deluxe Reissue which I am very happy with following a recent visit to the guys at Flynn Amps in Glasgow. I have a problem with the FX Loop though which I'm finding to difficult to diagnose. It goes a bit like this - the amp is recently serviced with good quality pre amp tubes in full working order and new TAD 6L6WGC-STR output tubes. I run the following pedals before the input (Boss TU3, Barber Tone Press, EHX Nano Small Stone, OCD, Signa Drive, Timmy, Dano Cool Cat Tremolo and Ernie Ball 25k volume pedal) and am happy with the way they all work with each other and the amp. In the loop I have been running a Boss DD7, DD5, RV5 and TC Hall of Fame and this is where the problem of significant and unworkable hum/hiss is raising its head. The amp is very quiet without the loop engaged but unbearable when it's on - whether the FX loop pedals are engaged with a daisy chain or batteries.

I had been running a Diago daisy chain for all pedals which I thought was the root cause of a ground loop but having tried batteries in the pedals in the loop the hum and hiss remain - but not when I connect the send and return with a patch cable. All of my patch cables are high quality and in full working order having tested each. The amp is very quiet without pedals in the FX loop and remains so when I run all 12 of the pedals in to the input at the front of the amp. It still sounds good this way but I'd much rather be using the delay and reverb in the loop after the preamp.

Before I go and spend money on a decent power source (which I probably will anyway) does anyone out there have any idea why the hum is persisting if it's not a grounding issue - do the batteries rule this out? Having spent so much on putting my rig together and being so pleased with the preamp sound I'm desperate to find a solution.

Thank you for any help/views offered!


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Post subject: Re: Help Needed with BDRI Effects Loop Issue.
Posted: Sat Sep 07, 2013 1:09 pm
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hi and welcome to the forum , now hows it gaun :D im in wishaw just outside motherwell , as for your amp , do you get the hum if you plug your pedal output into the main input of the amp ? cheers
Alan

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Post subject: Re: Help Needed with BDRI Effects Loop Issue.
Posted: Sat Sep 07, 2013 1:14 pm
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Thanks for getting back to me mate. The hiss and hum sounds aren't an issue at all plugging my pedal board straight into the input. It's only an issue when pedals are hooked up to the FX loop. A patch cable from send to return sees the amp stay quiet.


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Post subject: Re: Help Needed with BDRI Effects Loop Issue.
Posted: Sat Sep 07, 2013 1:23 pm
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Thanks for the welcome to the forum too - I've been a regular visitor for some time and now need to draw on some collective wisdom and experience...

Cheers,

Steve.


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Post subject: Re: Help Needed with BDRI Effects Loop Issue.
Posted: Sat Sep 07, 2013 1:37 pm
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Like you say, running the pedals on batteries eliminates a possible grounding problem. Have you tried connecting one pedal at a time into the effects loop to check if there's one pedal that causes the problem?

I'd also try connecting the pedals in a different order, see if that makes a difference. It's possible that one pedal's output level or impedance may not be ideal for the next pedal in the chain. If that's the case then you may have to start looking at some kind of buffer circuit between the pedals.

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Post subject: Re: Help Needed with BDRI Effects Loop Issue.
Posted: Sat Sep 07, 2013 2:24 pm
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Right, I've rechecked my preamp tubes - JJ EC803S V1, Gold Lion 12ax7 V2 and Sovtek 12ax7 LPS V3 and they're all good. I dropped in an EH 12at7 that I have in the PI position and that didn't solve it either. I also tried a 12spx7 Mesa I have for V1 and it's supposed to be very low noise. None of these changes did a great deal and switching off the lights and computer in the room didn't either. It could be an issue with the power in the room I'm in but it still is a distinctly quiet amp with everything plugged into the front end.

I've copied this over from another forum to see if it chimes with anyone:

"Some amp's effects loops, like my PV Bravo don't have any circuitry for the effects loop, its just an insertion point of the existing amp circuitry. I looked at the schemo for yer amp (Hot Rod Deluxe), the effects send goes thru an op amp IC. From your detailed description, my best guess is that it is bad. It may have failed on its own, or possibly someone before you damaged it by hooking it up incorrectly. It is possible that it could be one of the caps in the op amp's circuit, or something else maybe. Before giving up I would clean that jack just in case its causing some sort of ground loop...?"

I cleaned the sockets too but that made no odds. I also popped a buffer I have (T1me) on at the end of my chain in the loop and it sounded great but didn't take away the hiss increase... A spend on an isolated power unit is looking inevitable but I'm still not convinced on the grounding front.

Thanks for your help with this - it's much appreciated.


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Post subject: Re: Help Needed with BDRI Effects Loop Issue.
Posted: Sat Sep 07, 2013 3:26 pm
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If the hum's still there with batteries then I really don't think an isolated PSU will cure the problem. Remember, running your pedals on batteries is just about the most isolated power supply you can get!

Many years ago I damaged the effect return IC of a Fender Pro 185 by sending way too much voltage through the effects loop, it should be a cheap and easy repair if that's where the problem lies. Did you try connecting in the pedals one by one and changing the order they're connected?

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Post subject: Re: Help Needed with BDRI Effects Loop Issue.
Posted: Sat Sep 07, 2013 4:01 pm
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I hadn't isolated each pedal using a battery to do so and the solution has been found in one of the Boss delay pedals introducing hum and hiss to the line. It's now pretty much as quiet with the FX loop in use as it was without it earlier. If you're ever up Glasgow way there's a drink or two waiting for you! :D

Much obliged mate,

Steve.


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Post subject: Re: Help Needed with BDRI Effects Loop Issue.
Posted: Sat Sep 07, 2013 4:18 pm
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And the slide guitar on Fly Me to the Moon is cracking too...


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Post subject: Re: Help Needed with BDRI Effects Loop Issue.
Posted: Sat Sep 07, 2013 4:51 pm
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Hooray! I'm helping!

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Post subject: Re: Help Needed with BDRI Effects Loop Issue.
Posted: Sun Sep 08, 2013 12:19 am
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hi Steve , glad you got it sorted mate , cheers
Alan

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Post subject: Re: Help Needed with BDRI Effects Loop Issue.
Posted: Mon Sep 09, 2013 10:34 am
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Nice one guys.

Cheers!


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