Sub Query...

[icehockeyboy]

If a sub is used, taking the feed off speaker terminals/ amp, does it affect impedance at all?

And I recall when I had a Lyngdorf amp, the very nice folk at REL made me up a special lead to use with it as it was Class D, so would using the REL with a, and I quote ‘fully digital amp’ mean I needed to use the ‘special’ cable again?

[Pigmy Pony]

I would imagine impedance would only be affected if using a passive sub, I don't think a powered sub would make any difference. My BK XLS200 is connected this way, along with a pair of Celestion 5s, and the amp (Amptastic Mini-1) seems perfectly happy :)

[icehockeyboy]

Thanks Steve, I think a call to REL re the cable is necessary.

[Mr.Ian]

From what I have read you need to take care if you use one sub from both speaker terminals with most class d amps. See rel Web site

https://rel.net/connect-rel-class-d-gear/

[icehockeyboy]

From what I have read you need to take care if you use one sub from both speaker terminals with most class d amps. See rel Web site

https://rel.net/connect-rel-class-d-gear/

Thanks for that.

They told me not to connect the black wire.

[Discopants]

I run a Lyngdorf TDAI3400 with a REL stentor III. The Lyngdorf dealer reccomended running rca to the sub for me. There is also the option to use XLR, but I have a short run and the sub is in the same power socket. With the DSP there is no need to pick up from the speaker terminals. The sub and monitors integration is seamless. [emoji41]

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[icehockeyboy]

I run a Lyngdorf TDAI3400 with a REL stentor III. The Lyngdorf dealer reccomended running rca to the sub for me. There is also the option to use XLR, but I have a short run and the sub is in the same power socket. With the DSP there is no need to pick up from the speaker terminals. The sub and monitors integration is seamless. [emoji41]

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My Quake only offers phono (low level) input, and neutrick for high.

And as there is no other option coming out of the stereo amp, other than using the high level option, that’s what I’ve had to do, however, as pointed out earlier, it’s a digital amp, so , as REL recomend, the black wire is not connected, but, the Quake isn’t outputting any audio.

It worked perfectly a month or two back when connected to an analogue amp, so, any thoughts?

[Mr.Ian]

these are the steps I would do, at your own risk of course, but seems sound based on REL guidance below

0. increase crossover frequency on sub so you can hear more frequencies
1. check fuses in sub and sub mains plug
2. test sub high level input with another amp
3. test sub low level input with another preamp pr source direct to sub, ( use vol control on sub, keep it low to start)
4 run an rca cable from unused source input on amp to low level input on sub ( turn low level input vol on sub down to zero)
5 touch/wire the high level black lead on a number of different screw points on amplifer case, probably one closest to mains input
6 phone Rel

https://relsupport.zendesk.com/hc/en-us/categories/115000818247-How-To-Connect-My-REL

[icehockeyboy]

Already did 6, 5, 1 and 0
Re 4, surely I’d need an output from the amp, not an input?

[Mr.Ian]

Option 4 "the lead is only being used to join the earth's. But based on what you have tried it sounds like the sub may have died. I would jump to 2or 3 depending on what gear you have available, I think some subs have a 3.5mm headphone type socket input for phones and music players but a 3.5mm to rca adapter would work too for testing the low level input

[icehockeyboy]

Yes, it does have a 3.5 mm input, I was going to try that yesterday but gave up

[Mr.Ian]

Run a lead from your phone to the 3.5mm input see if that gives any sound

[icehockeyboy]

The sub is working, used the 3.5 mm input,guess I’ll make up a longer cable utilising the 3.5 mm plug end into the sub, and bare wire from the amp/speaker end.

[Mr.Ian]

I would try to run to rca input earth on amp myself

[icehockeyboy]

I would try to run to rca input earth on amp myself

Can you clarify why?
There seems to be no problem with earth hums or anything of a similar nature....?

[Mr.Ian]

Read the rel guidance they say connecting lve and earth to the speaker termains may break the sub amplifier because most digital amps use a use a different voltage level for ground.

[Sherwood]

On a related note, does anyone know of a small(ish) sub that can take a digital (spdif) input? This would overcome the grounding problem with many digital amps, many of which have a digital output.

[Mr.Ian]

Digital out is usually fixed volume

[icehockeyboy]

Read the rel guidance they say connecting lve and earth to the speaker termains may break the sub amplifier because most digital amps use a use a different voltage level for ground.

Is that only REL-evant (sorry, couldn’t resist that!) if I use the hi level connection that has a neutrik at the sub end, and bare wire for amp/speaker connection?

[icehockeyboy]

Interesting to see this is a 3 way thing involving folk from Nottingham!

[Mr.Ian]

I think it would apply to anything connected between the sub and the the amp speaker terminals.

[icehockeyboy]

I think it would apply to anything connected between the sub and the the amp speaker terminals.


But what would it do?
Would it damage the sub, or amp?

As I said nothing was humming, or behaving oddly, the only thing, which might have been purely coincidental, was that my iPad would not pair with the amp via Bluetooth.
To make sure I disconnected the sub, re booted everything, and when I powered it all up again, they paired, like I say, that may be purely coincidental.

[Mr.Ian]

This is what rel say on the subject

Here’s where Class D amps get weird (not all, but about 90% exhibit the anomaly I will describe next). The Black speaker terminals on the rear of your amp traditionally, and by electrical convention, mean Earth Ground. Zero ohms, zero Hz. Ground. But with most Class D amps, that Black-colored speaker terminal* is no longer ground. Worse, it actually references to a positive voltage that is significant. We consistently measure 10-15 volts ABOVE ground. In practical terms, if your REL were mistakenly connected to a Class D amp or receiver the input of the REL would eventually be burned out because it would be pulling 15 volts through a circuit designed to see zero voltage. Over some period of time—months or a few years, this unwelcome voltage will burn out the front end of your REL.

[icehockeyboy]

Hi Ian,
I’ve been on the phone to REL numerous times this week, and I gleaned from day 1 that If I’m using the hi level input, the black wire should not be attached in the normal way, however if an earth hum was present, to attach it to the amp chassis, so I’ve been through this scenario, and at this stage it was where I got no audio output from the sub.

But inputting via what they term the PC input, which is a 3.5 mm mini jack, I got audio, with no earth hum at all.

But despite everything sounding great, am I likely to encounter problems?

[icehockeyboy]

No one seems to be able to sort this problem, even REL say they’d have to talk to their place in the USA.

[Lawrence001]

I went through a very similar experience to you with a Rel Quake and Tripath amp, followed the instructions to no avail. I think I used a ground from somewhere into the RCA and the speaker red outputs to the high level inputs. Can't remember if I got no sound or a bad hum but I called it a day before I risked blowing the amp.

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