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AUDIO FORUMS >> General Discussion and Support >> Amp low speaker output jumper vs SQ
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Message started by qaztar on 08/14/21 at 17:28:03

Title: Amp low speaker output jumper vs SQ
Post by qaztar on 08/14/21 at 17:28:03

I'm considering adding a REL sub (or two) in line with my SE84UFO25 speaker outputs (high level; also coupled to Lii speakers) and think I'll need only one sub if the speaker output low terminals are at the same potential, e.g. jumpered. I did a sound check with and without a jumper and found without such the sound is more musical, whereas with the jumper this is less the case. Now I'm at a point in which I'm not sure which is prefereable. I found a forum thread (https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1609863726) in which 'CDN', also incorporating a REL sub, was advised by 'Geno / Steve?' to jumper the Rachel's low outputs to eliminate hum. But what about the effect on SQ when jumpering the two output transformer low windings together? Any sage advice on doing this with a SE84 series amps (even without a sub)?

Thanks,
Tim

Title: Re: Amp low speaker output jumper vs SQ
Post by kulafu on 08/15/21 at 21:42:14

Greetings. Just to clarify, is your Rel hooked up to the UFO25th using the hi level without having to jumper? I also am planning on using my T7 to my incoming UFO25th. Thanks.

Title: Re: Amp low speaker output jumper vs SQ
Post by qaztar on 08/16/21 at 21:43:05

I haven't purchased any RELs yet but, yes, the intent would be to use the high level inputs connected to the amps speaker outputs; seems it would track the best. Just not sure if I'd need one or two RELs based on the RELs user manual connection instructions. I'm having a hard time explaining the SQ change with and without the jumper; would first like to get to the bottom of that before proceeding with any REL(s). Who knows-- perhaps a REL could be connected without the low reference wire and without the amp jumper. I'll also ping on REL -- perhaps they've been asked before about Decware amps (though none are listed on their site). In any case, I'll post here if I find out anything more.

Title: Re: Amp low speaker output jumper vs SQ
Post by kulafu on 08/17/21 at 00:00:49

Thanks. I appreciate it when you find out.
bob

Title: Re: Amp low speaker output jumper vs SQ
Post by Geno on 08/17/21 at 01:29:05

Guys,

Attached is a link that explains the high level connection. The diagram shows how to wire it at the amp speaker terminals.

https://relsupport.zendesk.com/hc/en-us/articles/115004486987-What-is-a-High-Level-Connection-

Hum will most likely be present. It was with my T5. To stop the hum, run a single piece of wire between the two negative speaker terminals.

Title: Re: Amp low speaker output jumper vs SQ
Post by qaztar on 08/17/21 at 17:49:15

The reason has been found for the change in SQ vs amp low output jumpering. I don't mean for this to become a speaker cable review, but I've been using the Mapleshade double helix cables (wires), which claim to be uni-directional. Jumpering the amp side low outputs appears to cause them to lose musicality (airiness, fullness) and, after extended listening, even seems to introduce a bit of fatigue; certainly not my preference. The good news is that when I changed over to the ZSTYX cables (with jumper installed) everything I'm used to and like returned. Note that when I removed the jumper using the ZSTYX cables the sound did seem to became more neutral (but non-fatiguing); somewhat less preferable-- I realize I'm listening off axis, and room acoustics, my hearing, and perhaps some personnel bias are factors, but that's what it seems like. As such, I think I'll continue with the plan to test one REL T/9X with the amp low outputs jumpered as Geno suggests. Should be interesting!

Title: Re: Amp low speaker output jumper vs SQ
Post by kulafu on 08/17/21 at 19:24:07

Thanks for the additional clarification. I am guessing this is unique to the Decware amps? As I dont have a problem with my current amp. I will keep this in mind when I get mine. qaztar, thank you for bringing this up!
Bob

Title: Re: Amp low speaker output jumper vs SQ
Post by Lin on 08/17/21 at 21:13:07

SE84UFO
This circuit features a floating output-stage that makes it possible to bridge the amp into mono without any loss of fidelity.

Title: Re: Amp low speaker output jumper vs SQ
Post by qaztar on 01/14/23 at 17:50:03

Just an update. Since my last post there were a couple system changes (I just realized the most recent signature is also applied to older posts). First, after changing from the Lii Crystal 10 to Silver 10 drivers (in the 'Origin' cabinets), the REL T9 sub was turned off as it was just "too much". But after readjusting the sub crossover/amplitude - not so bad - I used it regularly. I then went to a new DAC; big step up in SQ. Finally I migrated to my present speakers (Coherent Audio 15's) and found the sub detracted, no matter the adjustments, from their qualities. So the sub was out. Then back to the Mapleshade wires (my favorite), no jumper, and now just enjoying the music. Note that I did retain my Zrock2 but normally have it bypassed. For recordings a bit bass shy, by design or b/c of my system, I can always enable—a great option to have without any smear, etc. It remains a mystery why there was an apparent (but slight) SQ difference between the SE84UFO25 output low terminals jumpered vs not jumpered when using the VSTYX cables (amazing how little things like this are even noticeable), but that’s okay—only a minor data point in case somebody else experiences it.
Tim