BHK250 buzz


#1

I received my new BHK250 from Underwood HiFi on Wednesday, 12/28/2016.

I previously was using an Anthem P2 for all my 2 channel listening; now traded in to allow the BHK250 purchase. All equipment and cables are identical to what I was using with the Anthem amp; the only difference being now the BHK250 is in the mix!

Power is from a dedicated 20amp outlet to which a PSA Powerplant P3 is connected. I have front-end digital equipment (PSA Directstream, Auralic Aries, DirecTV Genie box, Anthem D2 pre/pro, Opportunity BDP-83) connected to the regenerated circuits and the BHK250 and a Richard Gray Power Conditioner to the HC circuits. The RGPC houses additional inputs of my 5.1 equipment in the same room, and network switches power.

This was the setup with the Anthem in place as well and speakers were dead silent with all 2 channel equipment on!

I immediately noticed a harsh buzz from both speakers when I fired up the BHKs from the get-go. After much reading and numerous permutations of isolating the suspected equipment (PSA DirectStream and its interaction with the BHK250), I have the following setup observations:

  1. 20amp line to which the PSA PP3 is connected; PSA BHK 250 into the HC circuit: silent with PP3 switched on and amp off; obviously harsh buzz with amp’s main back switch on, worsened in magnitude when front switch also turned on. Only connection here with amp is with PP3 and speakers

  2. to see the effect on music, I first connected the Directstream to one of the PP3’s regenerated circuits; connection to amp via XLRs. Initially, without any input into the Directstream, I turned on the Directstream and once it cycled through there was a faint buzz through the speakers (amp is off presently); I turned on the back switch of the amp with a slight increase in intensity of the buzz noted; with the front switch engaged on the BHK250’s, marked increase in the magnitude of the buzz (audible five feet or so from the speakers’ front). Powered everything down and changed the fire-up sequence: amp on first with slight buzz with back switch on, magnitude increased with front switch on, even higher magnitude once power up to DirectStream completed. I powered everything down and connected the Aries to the Directstream via USB using Jitterbug; power to Aries fed from PP3 regenerated circuit plug immediately below the Directstream (same outlet). Aries on first no buzz; Directstream on next with same previous observations and same again with turning on the amp. The buzz clearly audible at listening position. Music played streaming via Aries from my NAS and it was glorious! Clearly audible buzz continues between tracks…annoying!

  3. Attempts at remedy: it seemed to me that the interactions between the DirectStream and BHK250 were the culprits and everything pointed to a ground loop issue.

Current setup: 20amp line to which the PSA PP3 is connected; PSA DirectStream into same regenerated circuit via a HUM X; PSA BHK250 into the HC circuit via a second HUMX. All other connections are the same as per previously cited observations. Dead silence with firing up in sequence: PP3, the Aries, the DirectStream after full cycle (dead silence!), BHK250 back switch on (dead silence!). When the tube input is switched on via the front switch on the BHK250 and full cycling completed, an same, obvious buzz from both speakers is heard, however markedly lower in intensity from previous…audible faintly to about 1 foot from both speakers (from all three drivers of the Focal Scala Utopias)

The music is gorgeous indeed…significantly improved low-end, marked improvement in soundstage and just overall more engaging in both soft and complex passages. Cannot hear the buzz from my listening position any longer!

As this is my first foray into tubes, is this normal tubes behavior. If not, I am open to suggestions from the community.

Thanks is advance for dissecting through my observations and any assistance…

Cheers

Chirag


#2

Tubes typically do not buzz, although on occasion they can be faulty.

While you are noting an issue with the amp and the DS, I suspect the DirecTV cable ground as the culprit, although DirecTV is getting better at grounding their antennas at the panel ground when installing the system - this helps eliminate voltage potential.

Have you tried lifting the ground on the amp and/or the DS?

Have you tried disconnecting everything tied in any fashion to the DirecTV equipment?

You must play electric guitar/keyboard if you have multiple Hum X lying around. (As I recall, they are good only for pretty low current. You do not want to plug an amp into one as it will choke off the current supply.)


#3

Thank you for your insights Elk.

The new DirecTV Genie devices in my home have a wireless connection to a central hub located strategically so it can communicate with the four Genies I have throughout the house. The only two “cables” exiting the small Genie box is HDMI going directly into one of the D2’s inputs and the power supply (to PP3 regen plug). There is no longer a coax cable in the vicinity. I have removed any such cables from the vicinity of any of my audio or video equipment. I will check but I suspect there is a coax coming into the previously-mentioned hub so as to allow the system to receive the actual satellite signals.

As I mentioned, the buzz was not present whatsoever with the same setup with the Anthem amp; it was present with just the amp connect to the PP3 and speakers and everything else disconnected from the equipment and power. I will disconnect the coax in the central hub and see if the issue disappears.

The Hum X suggestion was from a previous PSAudio forum discussion on troubleshooting hum. The specs on the Hum X show max current allowable at 6 amps. It certainly works to completely eliminate the buzz until I turn on the tube input stage of the BHK250. But I understand your point that electricity is weird in its manners!

More to follow…


#4

I experienced the same problem. Tried all the “typical” trouble shooting methods. I finally bought a PS Audio power cord and pulled the ground (they screw out). Solved the problem unless I crank up the multi wave on my P10 beyond 3. Not happy about the solution, small but real electrical short risk, but it works. I think the BHK is 60 hz buzz prone but can’t prove it. Neither of the two previous amps Parasound A21 and ATI) in my setup buzzed.


#5
cvpatel said As I mentioned, the buzz was not present whatsoever with the same setup with the Anthem amp; it was present with just the amp connect to the PP3 and speakers and everything else disconnected from the equipment and power.
I misunderstood, I did not understand that only the amp was connected to the PP3 and speakers; everything else is completed disconnected.

I can’t imagine the main Genie being connected to coax makes any difference when there is only a wireless connection to the little Genie connected to the audio system.

As you get a hum with only the PP3 and the amp connected, something else is happening than a ground loop. Just to be sure, I would try plugging the amp directly into the wall, and separately lifting the ground. If the noise is still present, it must be the amp itself.


#6

Elk

Elk

I did as you suggested: straight into the 20amp wall plug with the amp with only speakers connected. No buzz with back switch on, but buzz with front switch cycled on from both speakers (all drivers). The buzz is definitely fainter (but still audible to about 1 foot from speakers) when I added the Hum X between the wall plug and amp cord; again with nothing but speakers attached to the amp.

BTW, I got a cheater plug from HomeDepot and tried the same setup as above with the same results; this time, no decrease in the buzz as I did with the Hum X in the circuit; I believe the Hum X must be benefitting slightly, but not eliminating the issue.

It seems I have the same issue as amsco15 but I believe I am protected from a short with the Hum X.

When all is said and done, listening at all levels of volumes across different inputs into the DAC still results in bliss emanating from the Focals!

I have re-done my setup as in the original post am am indeed smiling from ear-to-ear; the only slight annoyance is the knowledge of the buzz if I were to walk up to the speakers in between tracks…alas!

Should I play along as is or are there other options to try? Have the tubes themselves being an issue been ruled out? Will this perhaps change with further break-in? I estimate about 75 hours of use since Wednesday with the first two days essentially on 24/7.

Would love to hear any insights from Paul &/or BHK

Cheers

Chirag


#7

I do not think you have aground issue. You may have slightly noisy tubes. I suggest giving PS Audio a call in the morning.

Others may have ideas for you as well.


#8
Elk said I do not think you have aground issue. You may have slightly noisy tubes. I suggest giving PS Audio a call in the morning.

Others may have ideas for you as well.

I had similar problems with my previous preamp. I got an uneven sizzling sound in one channel. The tubes should clearly be checked out.

#9

Not long after taking delivery of my BHK-300’s - I had a similar sizzling noise issue appear on the left channel. Then after a short period of time the output started to drop down on said channel with the right channel louder… P S Audio sent me a new set of tubes and normal service resumed…


#10

Definitely worth checking the tubes, although I would be more suspicious of them if it was only one channel. My BHK250 is pretty darn quiet, although my speakers are of average sensitivity. Are the Focals highly sensitive (would not expect them to be)?


#11

Thank you all for your ideas. I will get on the horn with PSAudio and discuss the situation and hopefully will be sent replacement tubes. Will follow with an update thereafter

Joyous New Year

Chirag


#12

UPDATE

I received a brand new replacement BHK250 from PSAudio to be assured that the hum was not a result of some more global input stage issue with the previous amp. Indeed the same caliber of hum is also present with the replacement. I have gone straight into a dedicated 20A plug with the amp only connected to the speakers with no other devices. Turning on the amp with the rear-panel switch produces no hum; as soon as the blinking front panel cycling is complete and the light is solid (input-stage active) there is the hum. The exact same occurs when I have my PowerPlant P3 into the 20A and only the BHK250 into the non-regen plug. I suspect this is the nature of the BHK250.

Most crucially, the music is glorious and I suspect to continue to improve as break-in matures…

Cheers

Chirag