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Decware MLB with new tubes - has hum (Read 3215 times)
Rivieraranch
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Decware MLB with new tubes - has hum
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.
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DECWARE CSP2+, TABOO MK III; SE84CKC; HR1; TRAPEZIUM DESKTOP SPEAKERS; TECHNICS SL1200MK5 turntable; Ah! Njoe Tjoeb CD player; MARANTZ 2226B, 2216B receivers; SENNHEISER HD-580 headphones
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Yoda
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I ride!

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Re: Decware MLB with new tubes - has hum
Reply #1 - 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
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Decware HDT-Alt tuning, Hagtech Cymbals
Hagerman: Chime Gold DAC; Castanet Line Stage; Cornet II, Piccolo, Thorens TD160 w/ Rega Rb300; Oracle Alexandria II TT, Mayware F4 arm w/Soundsmith-Denon dl-103, Yamaha T-1 Tuner
Many fostex experiments....
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Rivieraranch
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Posts: 1274
Re: Decware MLB with new tubes - has hum
Reply #2 - 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.
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DECWARE CSP2+, TABOO MK III; SE84CKC; HR1; TRAPEZIUM DESKTOP SPEAKERS; TECHNICS SL1200MK5 turntable; Ah! Njoe Tjoeb CD player; MARANTZ 2226B, 2216B receivers; SENNHEISER HD-580 headphones
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Rivieraranch
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Posts: 1274
Re: Decware MLB with new tubes - has hum
Reply #3 - 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.
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« Last Edit: 11/04/07 at 15:47:47 by Rivieraranch »  

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DECWARE CSP2+, TABOO MK III; SE84CKC; HR1; TRAPEZIUM DESKTOP SPEAKERS; TECHNICS SL1200MK5 turntable; Ah! Njoe Tjoeb CD player; MARANTZ 2226B, 2216B receivers; SENNHEISER HD-580 headphones
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Rivieraranch
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Re: Decware MLB with new tubes - has hum
Reply #4 - 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.
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DECWARE CSP2+, TABOO MK III; SE84CKC; HR1; TRAPEZIUM DESKTOP SPEAKERS; TECHNICS SL1200MK5 turntable; Ah! Njoe Tjoeb CD player; MARANTZ 2226B, 2216B receivers; SENNHEISER HD-580 headphones
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Rivieraranch
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Posts: 1274
Re: Decware MLB with new tubes - has hum
Reply #5 - 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.
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DECWARE CSP2+, TABOO MK III; SE84CKC; HR1; TRAPEZIUM DESKTOP SPEAKERS; TECHNICS SL1200MK5 turntable; Ah! Njoe Tjoeb CD player; MARANTZ 2226B, 2216B receivers; SENNHEISER HD-580 headphones
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