Regenerator and my CJ monoblocks

[AnotherJohnson]

Today I brought the CJ LP275Ms to the ARC system that’s running off the PS Audio P12.

I carefully replaced the REF 75SE, switching to SE.

I used the CJ power cords, my usual interconnects, my usual speaker cables.

I unplugged the REF75SE from the P12 and plugged one monoblock into each of the high current outlets.

This was an unhappy combination. Hum started building in, and triggered the breaker on the P12 (not the fuse).

I turned the P12 off, reinstalled the REF75 SE as the system amp, and audio Nirvana returned.

This is what I’m listening to.

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It is a very believable, very smooth and relaxing, performance.

As for the LP275Ms, every time I move them there is hum to be dealt with. They’re great in my outbuilding system at the other house, but I’ll bet I’m in for a day or two of troubleshooting if I want to use them here.

[Joe Appierto]

Just out of curiosity, do you have your cable system hooked-up to the preamp? I've found with the 11A, the 140 and the CA200 there were hum problems. I eliminated the hum when I installed a cheater plug on the 11A and the 140. I then bought an inexpensive isolation transformer which I plugged in between the incoming cable and the leads going to my set-top-box and the second lead going to the modem/router. Without the use of the cheater plug the hum disappeared.

Anecdotal I know but what else do we have to work with? Plus I've never had a regenerator in the system so I don't know, if at all, if it enters into the equation.

[AnotherJohnson]

I won’t use a cheater plug, but neither will I give a sermon on it.

The XLRs from the preamp to the REF75 were removed from the preamp. The SE MacKenzies were installed from the preamp to the LP275Ms with attention to both seating and routing.

Speaker cables from the REF75 to the F228Bes were removed at the speakers. Short runs of my bespoke cables were used as always to hook the LP275Ms up to the speakers. Care in both seating and routing again.

Power cords were CJ hospital style.

Further experiments showed the hum to be present when plugged directly into the wall on duplex outlets on a common ground bar.

If a cheater plug fixes this, it will not bring me a warm and fuzzy feeling. Maybe I’ll try that.

No trouble with Krell, Levinson, McIntosh, ARC, Cambridge Audio, Marantz, or even Prima Luna amps on these same circuits.

I understand why guys throw up their hands and buy McIntosh.

[AnotherJohnson]

If by cable system you meant video/data feed, the answer is no. Nothing but a handful of long proven 2 channel audio.

The ND8006 gets its feed from WiFi, but I haven’t turned it on today.

And what’s ailing the LP275Ms isn’t bothering anything else.

I’m going to set it up on a table with a set of PSB Alpha A/Vs and figure it out … later.

It’s self selecting out of my system.

[Joe Appierto]

If by cable system you meant video/data feed, the answer is no.

Yes, that's what I meant and it was consistently the culprit for me. Sorry I wasn't any help.

[AnotherJohnson]

I can see where that could be an issue, and I appreciated it once I recognized it .

I don’t know what it is about these monoblocks, but they seem to talk to each other through the house wiring. Seriously.

When I first got these amps as replacements for my Krells, the hum was exasperating. JF’s advice was to forget about my separate 20 amp circuits and instead to just plug everything into the same plug via a power strip. That did work. I’m going to try it here.

I would have thought the P12 would meet this criterion. But the hum was worse when the P12 was the power source compared to duplex outlets on a common ground bar, but on opposite sides of the room. It grew, and it flipped the P12 off. The P12 thought that something wasn’t right. Unplugging the monoblocks and plugging in the REF75, and all was exceptionally well.

[admin]

The fact that the amp is throwing the breaker is concerning for overload. Not sure what the peak load draw is during start up for the LP275M's is but it should not throw the breaker. I find it surprising that it would draw so much current that the P12 faults.

It sounds like a ground loop issue. I also recommend disconnecting any coaxial cable inputs as those a notorious for causing ground loops. I also share your hesitancy in using a cheater plug.

If you have some RCA ground loop isolation connectors, I would also try to identify which components the ground loop is being introduced. it could be further up stream from the amp.

[AnotherJohnson]

The fact that the amp is throwing the breaker is concerning for overload. Not sure what the peak load draw is during start up for the LP275M's is but it should not throw the breaker. I find it surprising that it would draw so much current that the P12 faults.

It is not tripping the house breaker.

It is not tripping the breaker internal to the P12 until the hum builds. The hum is unstable. I think the two LP275MS and house wiring form a tank circuit.

It sounds like a ground loop issue. I also recommend disconnecting any coaxial cable inputs as those a notorious for causing ground loops. I also share your hesitancy in using a cheater plug.

Of course it’s a ground loop. And unstable at that. I don’t use bnc or other similar coaxial connector’s. With CJ you are forced into RCA which is also coaxial.

If you have some RCA ground loop isolation connectors, I would also try to identify which components the ground loop is being introduced. it could be further up stream from the amp.

It’s not upstream… it’s in between. This is a ground loop problem that CJ understands (for trouble shooting, not for permanently fixing). I’m going to follow JF’s path. It will lead to a solution… but it worries me when I go to sell these. It makes me think I need to deliver them and set them up before taking anyone’s money.

[AnotherJohnson]

If I’d not gone through this in every new installation with the LP275MS, I’d be more concerned. Its just part of the tuition. If it hadn’t occurred right from the factory refurbishment and if it hadn’t gone completely away in my outbuilding listening room, I’d suspect a bad ground connection.

But honestly, when I watch how turning off one amp affects the bias LEDs on the other, I can’t help but think there is something “synergistic” going on, most of it may be good.

[AnotherJohnson]

The hum does not sound like classic motorboating, which would suggest a power tube.

But it is worse on the P12, which does not like it, than without the P12.

More next week after I’ve gotten to the bottom of it.

[AnotherJohnson]

FWIW, they rode down here in style, as passengers on the back seat of my 1794 trim Tundra. Smooth road.

Lifted from floor to cart. Placed gently on the nice leather seat. Moved to a cart. Then carefully put in place with a soft landing. They worked perfectly on removal from the other system. Installation of cables and power cords were carefully done to avoid proximity to other cords and cables.

I am going to test tubes if the low hanging fruit (JF’s advice on the single outlet) or cheater plugs () don’t get it.

[roberto]

Hola, I'm going to chime a little bit.
1) try the amps without any input cables. Just the power amps. Are both humming? Yes?, the problem is the neutral wired in one of the power amps. Because all CJ products, they can be used on 240V or 120.
2) NO hum? Connect the preamp without any input cables. Just the output cables to the power amps. Is there hum? Yes? Wrong polarity in the power transformer.
3) No hum? connect just the first input and listen. Yes? The hum is coming from that component...and so.

[AnotherJohnson]

I’ll add this kabuki dance to my list.

But right now, my dance card is full.

I’ve always suspected something akin to your door number 1. Would that go away by putting everything in the system on the same power strip?

The LP275Ms have been playing very nicely single ended with the LS28 SE in the other location.

[admin]

Another way to rule out a "before amp" component causing a ground loop besides running it without inputs is to either use a ground loop isolator connector or simply connect your phone via 3.5mm to RCA jack. Just another way to narrow the problem.

[Big Dog RJ]

I've had similar issues when using the Prem8A's, VTL 700's, Manley Ref350's and the LP140m.
Talking with Ed at time and Eve Anne Manley, both recommended:
A high grade single AC outlet (10A to 15A more than adequate for domestic audio).
A thick 10awg line, wired directly to AC mains board with a dedicated CB.
For the audio system: the use of a high grade power board with 8 outlets (Nordost Qbase 8), all components including electrostats are plugged into this single power board having one common ground.

With CJ monoblocks, there are no filters, gadgets, bells or whistles, very simple design and very high current on initial draw... this can cause hums if the AC mains supply is inadequate. In your case the PS Audio regen unit is ok with the REF75SE simply because it's nothing compared to the mighty LP275M's ! No chance!

Although the REF75SE is very pretty up close & personal, when comparing the LP275M's side by side... boy does that REF75SE look small... the power supplies are much smaller than one LP275m, and when you have two... she'll blow anything!

Initially back in home town, I had four dedicated AC lines for the system. Two separate lines just for the monoblocks, another separate line for the preamps, and another line for all source gear. This did cause hums every now and then and so I ended up using just two lines, one for the amps and one for the other gear.

In Melbourne, due to electrical regulations and not having the need to go over 10A, just a single AC mains line was all that's needed. 110% quiet! No noise, no nothing, absolutely silence! In fact, that's the first thing many people comment on over again, how extremely quiet the system is, and they want to know my config. Keep it simple maties!

Cheers, RJ

[Wildcat]

Reach out to TJ at PS Audio--he's helped me a bit in the past, and has been there a few years. Even if it's not a problem with the P12, TJ or the other techs might have a few ideas of their own. They welcome audiophiles to call in, even if not purchasing a product.

[AnotherJohnson]

There are some good folks at PS Audio. Helpful and friendly.
The P12 is fine. It is smart enough to recognize that the hum, which is without a doubt, originating in the way CJ handles ground, isn’t right.

I’ll probably have it sorted out tomorrow. I’ve scheduled the time for tomorrow morning.

[Wildcat]

I'd love one of their regens myself but it will be a while. I haven't been back there since 2018, and I don't know if they've yet resumed visits since COVID hit.

[AnotherJohnson]

I'd love one of their regens myself but it will be a while. I haven't been back there since 2018, and I don't know if they've yet resumed visits since COVID hit.

There is another P12 on the inventory at The Music Room as I write this $3199 with remote and a year left on warranty.

I love mine.

[Wildcat]

I'll get one, one of these years! Fun fact--at 2019's AXPONA, a lot of exhibitors were stopping into PS Audio's room and asking if they had any of the regenerators for sale. The power in the Renaissance Schaumburg hotel was suffering quite a bit during the show! I think next time, they should load up a couple pallets of regenerators (all three sizes) and sell 'em right there.