VTA-SP-14 Hum

Hi all. I have the SP-14 preamp custom built by Roy himself with all the best parts. It has the Mundorf caps on one output channel and the KY's on the other. I have a multi amp set up that includes the VTA-120 power amp. I have a noticeable audible buzz from the speakers on all amps except the VTA-120. I'm thinking it's about at 120hz or so as it's not a 60hz hum. I have changed cables, outlets for the power source etc..., re-routed audio cables to no avail. I have hooked this amp to a Sony ES55 power amp, a Transcendent Sound OTL tube amp, a Harmon Kardon and a Heathkit power amp with the same results with all. I have even taken everything to a different room but the results are still the same. A low level (more a buzz than a hum) that is clearly noticeable. My speakers are Klipsh with an spl of around 95db but in the other room using some speakers in the 85db range the buzz is still present. Roy supplies Tung-Sol 6SN7's which are fine but I have changed them out for some vintage Sylvania 6SN7's from the 50's (clearly Superior). The noise level is the same regardless of which tubes I use. What puzzles me is why the VTA-120 has no noise at all but all other amps do. I wouldn't think the SP-14 is designed to be "perfectly" matched to the VTA-120 amp and nothing else. Could it possibly be the rectifier tube that's causing the issue? I'm using the supplied one provided by Roy. Anyone with a possible solution would be of great help.

Thanks,
Leigh

Hi Leigh,

When I build mine I also had a buzz issue. In my case I was able to track it done to a missing ground connection.
Since you do not have the issue with all you amps, you can try to run a ground wire from the SP 14 to the amp and see if it goes away.

Best

Michael

Thanks Michael/ Bob.

Bob. I did what you mentioned about the cheater plugs on "all" 3 prong plugs and it "has" made a difference for the better. There is still a buzzing in the speakers though, but not quite as much. I have a considerable amount of equipment running off a dedicated 80 amp "pony" panel (4 separate 20 amp outlets), so I wouldn't be surprised if there is interference somewhere in the chain. I'm also using two "Monster Power" line conditioners in my set up. I wonder sometimes whether these things do more damage than good. Lot's of controversy from what I've read online. The buzz may be something I have to get used too, until I can strip the wall and rewire everything. Thanks guys, for your help.

Leigh

Bob.

Thanks for the info. I tried the cheater plugs and at first I thought that helped somewhat, but on removing them for comparison I notice now that there was no real improvement. I took the Monster line conditioners out of the system and plugged all "three prong" components into the same outlet. No change. After reading online I went out and purchased a ground loop isolator and installed it between the SP-14 outputs and the second amp. The hum was magnified 10 fold. I actually bought two of them in case I needed a second in the future. Both produced massive hum. They were from "The Source" here in Canada. Radio Shack in the States. Now I'm really miffed! And again, on the VTA-ST 120 I don't here hum at all. I even swapped the cables between the outputs on the SP-14 and no change so I know the preamp isn't the issue.

definitely some sort of ground problem. At one time I had a customer who found out his house wiring was at fault !!
Since the preamp was dead quiet here and is quiet when playing thru your ST120, there is obviously something wrong with the grounding connections of the other amps.
Those types of problems are extremely difficult to figure out . . .

tubes4hifi wrote:definitely some sort of ground problem.   At one time I had a customer who found out his house wiring was at fault !!

Just curious, what was the problem with your customers house wiring? Was the customer able to fix it?

I can't remember, it's posted somewhere on this forum