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AUDIO FORUMS >> General Discussion and Support >> Decware MLB with new tubes - has hum
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Message started by Rivieraranch on 10/18/07 at 23:59:16

Title: Decware MLB with new tubes - has hum
Post by Rivieraranch on 10/18/07 at 23:59:16

I ordered some new tubes from Jim McShane, 3 Sovtek 6N1P's for the Decware MLB that I purchased from an ebay auction. I am using a new Sovtek 5Y3GT rectifier that came with the unit. The tubes I bought from Mcshane arrived today. I connected the MLB to my CD player, plugged in my Sennheiser HD580's and turned on the MLB. I hear more hum than I thought I would. The music sounds beautiful, though. Is this normal? The sticker under the unit states that it was manufactured in June 2003.

Title: Re: Decware MLB with new tubes - has hum
Post by Yoda on 10/20/07 at 03:38:30

Unplug your cdp inputs, plug in Headphones and turn on unit. See if hum level has changed. If so, then perhaps a ground loop issue. Location of your mlb or other tube gear for that matter next to other magnetic fields could induce noise as well. Try it in a different location, on a different circuit, etc. did you swap the rectifier?

I have a csp2, but my cd is actually a dvd player that when connected to my tv, induces minor hum on the system. Usually I don't care until I want to listen to headphones which tell all, so I then unplug the video.

Matt

Title: Re: Decware MLB with new tubes - has hum
Post by Rivieraranch on 10/20/07 at 14:32:29

I changed the rectifier, and ran different sets of tubes. I changed the interconnects, and have moved the unit to a fairly neutral place on top of a speaker stand. I turned it on without a source connected and it still hums. I plan on making an amp stand using a piece of wood screwed into the bottom the the speaker stand. As it is the unit is resting on the rubber bumpers on the speaker stand's top plate.

Title: Re: Decware MLB with new tubes - has hum
Post by Rivieraranch on 11/03/07 at 01:43:52

Back to the factory it goes for a good once over. It was packaged and sent out this afternoon. I can hardly wait until its speedy return!

How lonely its MDF stand looks. When the unit returns I will be making a stand for it using that platform and some moulding on the sides, then painting it black.

Title: Re: Decware MLB with new tubes - has hum
Post by Rivieraranch on 11/10/07 at 15:03:51

Steve called on Tuesday, the same day he received the amplifier. I was very surprised; I am not used to such a high level of customer service. He would check it out.

Friday Steve's assistant called; the amp is ready, with some new capacitors, new volume control (N/C)and some updates (very reasonable). I paid over the phone and they shipped the amp that afternoon.

All is well.

Title: Re: Decware MLB with new tubes - has hum
Post by Rivieraranch on 04/11/08 at 03:27:00

I began using the amp at my office and for some reason I do not notice any bothersome hum. Go figure.