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Author Topic: Rogue preamp/Emotiva amp mismatch?  (Read 8504 times)

bmwr75

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Rogue preamp/Emotiva amp mismatch?
« on: December 30, 2010, 09:52:42 AM »
Hooked up a Rogue 66 tube preamp (output impedance = 650 Ohms) to an Emotiva XPA-2 solid state amp (input impedance = 23.5k ohms) today. Have a very noticeable hum coming thru the 100 db efficient Klipsch speakers. When I switch the preamp off, the hum goes away.

Do I have a gain or impedance mismatch causing the hum?

The preamp was previously connected to a Dynaco ST70 in the same location and the hum was not noticeable.
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bmwr75

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Re: Rogue preamp/Emotiva amp mismatch?
« Reply #1 on: December 30, 2010, 02:22:55 PM »
Nevermind.  I found this thread on impedance matching.  Seems my noise problem lies elsewhere.

http://www.audiokarma.org/forums/showthread.php?t=289288
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Offline schwarcw

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Re: Rogue preamp/Emotiva amp mismatch?
« Reply #2 on: December 30, 2010, 11:36:47 PM »
Hmmmmm!  I wonder what's up with that???  The preamp sounded fine yesterday.  Have you put the Emotiva in another setup to see if the hum is in the amp?
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Carl

Offline F1nut

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Re: Rogue preamp/Emotiva amp mismatch?
« Reply #3 on: December 30, 2010, 11:39:43 PM »
I think your Rogue is trying to tell you something. The question is, are you listening?
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bmwr75

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Re: Rogue preamp/Emotiva amp mismatch?
« Reply #4 on: January 01, 2011, 10:19:52 AM »
Quote from: F1nut on December 30, 2010, 11:39:43 PM
I think your Rogue is trying to tell you something. The question is, are you listening?

F1 nut,

Enlighten me.  What do you think might be going on?

Scott
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Offline Zoot Horn

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Re: Rogue preamp/Emotiva amp mismatch?
« Reply #5 on: January 01, 2011, 10:45:05 AM »
jumping in kinda late,, but have you tried another amp in the mix?
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bmwr75

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Re: Rogue preamp/Emotiva amp mismatch?
« Reply #6 on: January 01, 2011, 12:12:32 PM »
Today I tried a different preamp in this system, a vintage Marantz 3200, and the noise went away.

Reconnected the Rogue 66 preamp today to the Emotiva amp.  Lifted the ground on the preamp, no change in the noise.  Lifted the ground on the amp, no change in noise.  

FYI, this doesn't sound like a 60 Hz hum to me.  It is a much higher frequency.  In fact, it is coming from the midrange or tweeter horns (not the woofers) on these Klipsch KLF-20 speakers, which are 100 dB efficient.

When I hit the Mute button on the preamp, the system goes dead quiet.  Another weird thing.....with no signal to the preamp, I can turn the volume knob to maximum and the noise attenuates as the knob is rotated and nearly disappears when the volume knob is at maximum.

So, my conclusion is the problem is in the preamp, or there is just a great lack of synergy between the Rogue 66 pre and the Emotiva XPA-2 amp when driving very efficient speakers.  Way too high a noise floor.......
« Last Edit: January 01, 2011, 12:14:47 PM by bmwr75 »
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Offline F1nut

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Re: Rogue preamp/Emotiva amp mismatch?
« Reply #7 on: January 01, 2011, 06:29:31 PM »
Quote from: bmwr75 on January 01, 2011, 10:19:52 AM
   
F1 nut,

Enlighten me.  What do you think might be going on?

Scott

I think it's time to change the tubes.

On another note...Emo, really?
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bmwr75

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Re: Rogue preamp/Emotiva amp mismatch?
« Reply #8 on: January 01, 2011, 06:34:05 PM »
Quote from: F1nut on January 01, 2011, 06:29:31 PM
Quote from: bmwr75 on January 01, 2011, 10:19:52 AM
   
F1 nut,

Enlighten me.  What do you think might be going on?

Scott

I think it's time to change the tubes.

On another note...Emo, really?


Did change the tubes.....had no effect.

What is your first hand experience with Emotiva amps?
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Offline F1nut

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Re: Rogue preamp/Emotiva amp mismatch?
« Reply #9 on: January 02, 2011, 02:47:29 AM »
Ah so, I must have missed that. Hmmmmm......in that case it would seem you have two pieces that don't like each other. It happens. A few years back I bought a very nice tube pre amp that didn't like one of my CDP's or vice versa...anyway, the CDP wasn't going anywhere, so the pre amp made a hasty exit.

I have friends with first hand experience, who's ears I trust enough to know all I need to know about those products.
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Offline Falcon

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Re: Rogue preamp/Emotiva amp mismatch?
« Reply #10 on: January 02, 2011, 08:18:52 PM »
Hey Scott, if the Emo is not working out for you,  give me a call..
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Offline thuffman03

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Re: Rogue preamp/Emotiva amp mismatch?
« Reply #11 on: January 06, 2011, 02:33:41 PM »
The Rogue and the Emotiva must have a "Error Type 101: Mismatch Error"
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