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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
kkm
124 posts
 
Your microphonics might be related to the particular tube you are using, it might be cheaper to try different tubes first before modifying if that is your major concern. I've tried the Tung Sol brand with success on this pre. Also there are some tube sleeves that help with microphonics like Herbie's or Pearl's, there are others. Good luck.
pummill's avatar
pummill OP
34 posts
 
Thanks Kkm, and I think that some good isolation of the preamp would also help in this area.

Will the lowering of the gain from 23dB to 14dB help with the problem of limited volume knob range. I have read that it is not a good thing to have such a limited range. Anything over 11:00 starts the lights on my amp to start going out!!
rwwear
2,851 posts
 
Lowering the gain should help. It sounds like you are overloading the amp.
pummill's avatar
pummill OP
34 posts
 
Thanks Rwwear. The modification that I'm thinking about at Underwood is said to put this preamp in-line with those costing $4 - $5k. Here is a full detailed list of mods at Underwood...I'm thinking of going for it!!

http://www.underwoodhifi.com/mod_marsh.html
dimitry
83 posts
 
I have done simple modifications on this preamp myself. First, change stock feet to "superspike" type or equivalent. Take a 1" by 0.25" aluminum bar and bond it with marine epoxy to the underside of the top cover in the long direction. Then buy a pair of HAL-O damping instruments from Herbie's Audio Labs and put them on a pair of Tung-Sol D-getter NOS 5687, which you can get for under $100 per dozen on Ebay. Finally, put on a VPI Magic Brick at the rear middle of the top cover.

Voila - no more microphonics. The preamp is silent up to -10db attenuation. I have installed a -60 to - 10 db switched attenuator and silver contact selector switches, which I highly recommend. Really good ones are available from www.goldpt.com. Apparently the guy will give you custom 24-step attenuator if you tell him the range you want.

The service you cite looks good and comprehensive, but should include the attenuator for best performance. I consider this Marsh preamp the best line circuit available today. It is made to a price point and can be improved with better parts.
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