Audible hiss from KEF KC62 when using its line output

[davybyrne]

I'm getting significant hiss from my KEF Q1 Meta mains when a KEF KC62 is in the signal chain in a 2.1 nearfield desktop setup.

Signal chain:
Mac Studio → (USB-C) → MOTU M2 → (RCA out) → KC62 Line In → KC62 Line Out → (RCA) → 3e Audio A7 (volume knob bypassed) → KEF Q1 Meta

Volume is controlled by the M2. I bought the KC62 specifically to use its high-pass filter in this setup. Crossover is set to 80 Hz, high-pass filter to 100 Hz, though none of the knobs or switches on the KC62 seem to affect the noise.

With no signal playing, there's a loud, constant hiss from the Q1 Metas. For reference, it's noticeably louder than the hiss from a pair of JBL 305P Mk IIs, which are well known for that. (Side note: I have a UMIK-1 and REW — if there's a reliable way to measure this, I'd be interested to know.)

If I remove the KC62 from the signal chain and go MOTU M2 TRS out → 3e Audio A7 directly (using the M2's RCA out for the sub only), the mains are dead silent. No hiss at all. I also tested M2 RCA out → 3e Audio A7 RCA in without the sub, just to rule out the RCA connection and cables. Still silent.

So the hiss only appears when the KC62's line-level passthrough is in the chain.

The retailer insists there's nothing wrong, saying I'll always have "audible THD when no signal is present as not all devices like the KEF sub have an auto mute." But nothing else in my chain uses auto-mute and none of it produces audible hiss.

As a separate issue, both this unit and a previous KC62 from the same retailer also have an internal mechanical buzz/rattle audible with only the power cord connected — no inputs or outputs attached at all.

Anyone have experience with the KC62's line-level passthrough adding noise? Is this a known limitation, or does it point to a defective unit? The retailer is trying to charge me restocking and shipping fees, so if there's something I'm doing wrong or a better way to document the problem, I'm all ears.

 

[staticV3]

Subwoofer Plate Amps are notorious for introducing hiss to their Satellite Line outs, as maintaining signal fidelity right next to the beefy Sub Amp is tricky and also just not a big priority.

What you can try is turning down the 3e and KEF volume knobs, then turning up the Motu to compensate, that might put some more distance between the Satellite signal and the KC62 noise floor.

If that doesn't help, then you may have to look into Passive attenuators or External DSP Crossovers like the 2x4HD or Audient ORIA Mini.

 

[Kal Rubinson]

You might try

So the hiss only appears when the KC62's line-level passthrough is in the chain.

Is that, also, the only time you are using the 3e Audio A7 with the volume knob bypassed? With that amp at full gain, it is amplifying the residual noise in the KC62 cruelly. Very few devices will not be revealed as noisy when subjected to such an audio magnifying glass.

I suggest you experiment with turning the gain down in the 3a amp until the noise is at a reasonably tolerable level and then properly re-balance the levels of the rest of the system.

 

[davybyrne]

Subwoofer Plate Amps are notorious for introducing hiss to their Satellite Line outs

I was afraid you'd say something like that. Of course, if I'm going to use a 2x4HD, I don't think there's good reason to stick with the KC62, right? I might as well get a REL or Rythmik or SVS and save myself some money. Heck, for nearfield, I could get a pair of REL Tzeros plus a miniDSP 2x4HD and still save a couple hundred bucks compared to the KC62.

I'll give the volume adjustments a shot, thanks for that and the other suggestions!

 

[davybyrne]

You might try

Is that, also, the only time you are using the 3e Audio A7 with the volume knob bypassed? With that amp at full gain, it is amplifying the residual noise in the KC62 cruelly. Very few devices will not be revealed as noisy when subjected to such an audio magnifying glass.

I suggest you experiment with turning the gain down in the 3a amp until the noise is at a reasonably tolerable level and then properly re-balance the levels of the rest of the system.

No, I have had the 3e audio A7 volume bypass enabled in both configurations I've described. When fed directly by the MOTU M2 (whether TRS or RCA) there's no noise whether the volume bypass is enabled or the 3e audio A7's volume knob is cranked to the max.

 

[Kal Rubinson]

No, I have had the 3e audio A7 volume bypass enabled in both configurations I've described. When fed directly by the MOTU M2 (whether TRS or RCA) there's no noise whether the volume bypass is enabled or the 3e audio A7's volume knob is cranked to the max.

Whether it is an inherently noisy design, is encumbering noise in your set-up or is defective, it is the noise in the KC62 that is being amplified. Short of replacing it, the audible noise can be ameliorated by lowering the gain in the amp.

 

[davybyrne]

Whether it is an inherently noisy design, is encumbering noise in your set-up or is defective, it is the noise in the KC62 that is being amplified. Short of replacing it, the audible noise can be ameliorated by lowering the gain in the amp.

Yes, definitely. Sorry if it seemed I was contradicting you but you're absolutely right. I meant only to remark upon how quiet everything else in the system is despite generally being much lower cost equipment than the KC62. I take @staticV3's (and perhaps your) point that subwoofer plate amplifiers are hard to make quiet.

I've tried a range of volume settings on the 3e audio A7 and am able to reduce the noise to the Q1 Metas but not to the point that I'd prefer. Also, when I do get the noise down close to an acceptable level, I no longer have enough usable range from the MOTU M2's volume control. With the M2 cranked to the top there are many tracks I listen to commonly that barely achieve 80dB peaks at 1 meter.

 

[Kal Rubinson]

I've tried a range of volume settings on the 3e audio A7 and am able to reduce the noise to the Q1 Metas but not to the point that I'd prefer. Also, when I do get the noise down close to an acceptable level, I no longer have enough usable range from the MOTU M2's volume control. With the M2 cranked to the top there are many tracks I listen to commonly that barely achieve 80dB peaks at 1 meter.

Understood. Unfortunate configuration constraint.

 

[3125b]

Not uncommon.
The cheapest option is to return the KC62, sell your amp and get an Aiyima A20 instead.
That amp has a high-pass for the mains and a sub-out for under 200€.
It allows you a proper crossover to limit the excursion of the 2-way coaxials.
What sub you should be getting is up to you, the SVS SB-1000 would be a good option for example (flat and extended FR, not too large, reasonably priced).

 

[Kal Rubinson]

Not uncommon.
.................................................................... get an Aiyima A20 instead.
That amp has a high-pass for the mains and a sub-out for under 200€.
It allows you a proper crossover to limit the excursion of the 2-way coaxials.

Agreed.

What sub you should be getting is up to you, the SVS SB-1000 would be a good option for example (flat and extended FR, not too large, reasonably priced).

Yes but he already owns the KC62 and it will no longer contribute any relevant noise.

 

[davybyrne]

Not uncommon.
The cheapest option is to return the KC62, sell your amp and get an Aiyima A20 instead.
That amp has a high-pass for the mains and a sub-out for under 200€.
It allows you a proper crossover to limit the excursion of the 2-way coaxials.
What sub you should be getting is up to you, the SVS SB-1000 would be a good option for example (flat and extended FR, not too large, reasonably priced).

It's an interesting idea. I considered the Aiyima A20 but ended up with the 3e audio A7 since I was expecting to be able to use the KC62's crossover. I'm leaning toward a miniDSP 2x4HD as that'll give me more flexibility than the fairly limited range of options the A20 offers with its 12dB/octave HPF and fixed 200Hz LPF at 24dB/octave.

I'm definitely getting rid of the KC62 sub, though. I just can't get a reasonable listening volume without tripping all over its noise floor.

 

[davybyrne]

For posterity: I picked up an SVS 3000 Micro. While it doesn't have a high pass filter, it does have RCA input from a preamp and RCA output for the mains, just like the KC62. In the exact configuration that produced significant (unacceptable to me) hiss the SVS 3000 Micro is dead silent. Not to mention the SVS 3000 Micro is less than half the reatail price of the KC62.

Mac Studio → (USB-C) → MOTU M2 → (RCA out) → SVS 3000 Micro Line In → SVS 3000 Micro Line Out → (RCA) → 3e Audio A7 (volume knob bypassed) → KEF Q1 Meta

 

[Kal Rubinson]

it does have RCA input from a preamp and RCA output for the mains, just like the KC62

Not just like the KC92. The output from the SVS is connected directly to the input and not actively processed. That means it has no high-pass filter and all the bass will be going to the amp and the Q1 (as well as to the sub). How will you implement the LPF?

 

[davybyrne]

Not just like the KC92. The output from the SVS is connected directly to the input and not actively processed. That means it has no high-pass filter and all the bass will be going to the amp and the Q1 (as well as to the sub). How will you implement the LPF?

You know, that's a good point. I guess it's not apples-to-apples if the SVS doesn't actually touch the signal that's going out to the mains.

The SVS does have an LPF, which I'm still experimenting with but currently have at 80Hz. I think you meant to ask how I will implement the HPF. I have a miniDSP 2x4 HD on order and intend to use that for the LPF, HPF and room correction.

 

[Kal Rubinson]

I think you meant to ask how I will implement the HPF. I have a miniDSP 2x4 HD on order and intend to use that for the LPF, HPF and room correction.

Yes, I did. The miniDSP is ideal for this short of an alternative with REQ.

 

[Andysu]

its the lousy amps , or avr that has lousy signal to noise ratio , its not the speakers producing hiss , its the amps or avr that is producing the hiss