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Marsh P2000T hybrid preamp....Should I modify??

First, I'd like to say how much I've enjoyed reading and learning about high end audio on this site!!

In regards to my question, I am seriously thinking that a modification of the Marsh P2000T is in order. My system consist of a Pioneer Elite PDR-19RW CD player/recorder, Marsh P2000T preamp, Marsh A400s amp, and Magnepan 1.6's.

After reading in this forum about microphonics, I can say that this preamp has a problem in that area. Another issue is that I can only turn the volume control up to about 11:00 or the blue LED on the A400s starts blinking!! It does get relatively loud. I got this preamp as a demo from Audio Advisor for $975, so I could afford a modification. I am thinking that I would send it to Underwood HiFi for the mods. The mod talks about reducing microphonics and lowering the gain from 23dB to 14dB. Those 2 items address problems that I've mentioned earlier.

BTW, I will be replacing the Elite CD player/recorder with a Music Hall CD-25, also modified , either by Underwood or Sound Odyssey. Thanks for your time and thoughts on this matter!!
128x128pummill
pummill's avatar
pummill OP
34 posts
 
Well, as a follow up, I HAVE sent my Marsh P2000t preamp in for modification at Underwood Audio. I should have it back in a few weeks and will give my reactions and results as they become available!!
dimitry
83 posts
 
I have ordered a pair of mono 100K series attenuators from Gold Point. I will report on the effect of these instead of the Marsh's balance and volume dual Alps pots.
pummill's avatar
pummill OP
34 posts
 
Dimitry,

Can you give me some input on the inverted polarity of the P2000T output. The manual says this:

"The output signal is inverted polarity to the source signal, you may need to change the polarity of both left and right speakers cables to get correct program polarity"

Do I really need to hook my speakers up + to - and - to +??
mattybumpkin
590 posts
 
Yes,

If nothing else in your system inverts polarity. In my system, my cd player and amp both invert polarity, so they cancel each other out and I hook my speakers up normally (+ to +, etc.)

Regards,
dimitry
83 posts
 
Well, polarity is a complex issue. Some people are sensitive to it, some are not. In a well recorded material, where relative polarity of all tracks is maintained, inverted polarity at playback is heard as lack of ambiance and pace in the mid-bass.

However, most material is not recorded in such a fashion. Often different tracks have different polarity and final polarity of the master is either "in-phase" or "out-of-phase" with the original event.

Therefore, since polarity is essentially random on most recorded material, it is not really necessary to maintain it on playback.

However, for those rare records and CDs that are recorded in constant and correct polarity it is nice to have it right on playback.

So, I do hook my speakers backwards, as per Marsh's manual. Since their manual is the first manual for a tube product that never mentions the word "tube" it is remarkable that they decided to include the relatively exotic topic of polarity into it.

I wrote to Marsh, that since their manual excludes instructions on how to change the tubes entirely, they should expect customers to start returning them in about a year, complaining of lack of air and drive.
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