Coherent RTZ Grounding Box Review

Good posts macca.👍

Obviously anyone with a vested interest producing / selling BMU's (or any other product for that matter) is going to shout said products praises from the roof top.

I would also be interested in perusing any measurements that may be available.

On a more subjective note , a friend recently brought his commercial BMU round as he was keen for me to hear the sonic benefits potentially available to me on my system with Pre and Power connected via an Isotek Titan II conditioner.

We spent quite some time running through variations of connectivity from individual componants to combinations to full system.
After the fat lady had finished her last aria we both agreed that the performance of Pre and more notably Power was more veiled
less extended and with diminished dynamism via the BMU as apposed to the Titan II.

Less clear cut was connectivity to sources were the BMU exhibited more of a different presentation as opposed to a better one.

Interestingly my friend having re-evaluated the BMU in his own system is now also running his sources via his BMU and the rest via a conditioner to mains wall socket.

YMMV IMHO etc etc.

That's how I've been using mine since it was built. It's what worked here. Proved a bit more today.

The thing is an amp is refreshing its own power supply from the reservoir capacitors on every cycle- it's the charge in the caps that is powering the thing - so even if there was some problem with the mains it isn't going to manifest itself via the amplifier.

I did have good results with a Belkin mains block years ago. Not with the amp plugged into it, as that was worse,  but with the cd player and pre-amp running off it there was a noticeable subjective improvement. When I had that thing everyone who came round, totally unprompted, would say that sound was fantastic - even civilians - even my mother!

In truth it was not, there were still many issues with the sound I was not happy with, not would any serious enthusiast be. But it added a certain something in the midrange that really made the sound involving compared to when it was out of circuit. I concluded that it must be some sort of pleasant colouration, a degraded sound that was nevertheless more enjoyable to listen to. But I don't know for sure and the thing died when I accidentally left it plugged in when they came round to change the leccy meter. And Belkin don't make them anymore. 

I can ask Nick to do some measurements- he’s got test kit coming out of his ears.

One thing- at the last Yorkshire club meet we tried Nick’s new regenerator power supply for AC motor turntables. It produces a very pure sine wave and frequency can be adjusted too- idea behind that being you can easily adjust speed on the likes of a Lenco between 33 and 45, easily, and as it’s regulated speed will stay absolutely steady. Clever bit of kit, and weirdly means you can leave a 401 on 33 but still adjust the speed to 45 without turning the selector switch.

This made a large improvement to all the TT’s it was tried on, so that would appear to suggest that crap on the mains certainly affects the motor.

Ali, and that wasn't raw mains, it had been using a big Isotek regenerator.

I think the thing with these units is that you should hear a problem that needs to be solved. Some are looking for a problem that may or may not exist. I did try the NVA BMU and it did improve things in certain areas while I felt the sound hardened up a bit. Different kit maybe different result. Tempted to try the mini BMU as the flying lead makes it more adaptable and maybe the big BMU is overkill in many circumstances.

Mini BMU looks like a very good value product. £225 on HFS and it’s more easily accommodated with the trailing socket. Price compares very well with the smallest airlink product and that one only has a singke inlet. Plus I’m guessing you will get the usual 30:day trial.

For F#ck sake, all grounds are connected together internally on the back panel of any amp, what the actual F#ck can adding another wire from this point and back to it again do but offer further loop area for receiving more airborne radiation to pollute the gnd even more. It's just a parallel loop of wire FFS.



Krell pre-amp, one single signal wire from each rca socket to the main board and then the white wires are the shared chassis gnd from all the rca sockets and the xlrs (the xlrs get one each because that complies with the wiring spec for xlr sockets. )

this is just utter nonsense.

This may highlight met lack of technical knowledge but it's been on my mind for a few days so:

WHAT IF the ground box somehow absorbs the RF around the system (if that's a thing) and uses the ground of the system (via the cable) to get rid of it. So dispersion via the systems ground rather than removing RF from the system

What if we've been looking at this all wrong?

Just a thought based on NO technical knowledge at all.

Similar thoughts crossed my mind.

Maybe it's a diode rectifier that goes nowhere?

100 watts into 8 ohms but at 1% THD+N which is not really an acceptable level of distortion, for me, anyway. The blue lights come on at 25 watts, I've never lit them up in domestic use, not even on peaks.

Yes I would like a go on those Hypex amps just out of curiosity, on paper they are close to perfection yet with Sh#t-loads of power. I just have an unreasonable prejudice against class D.


My new speakers will be even more efficient than the current ones so no real need for more power.