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Tube amp modding

/ Conrad Johnson LP70 / LP140

Moving up the CJ tube line (MV50, Premier 11A, now a pair of LP140 mono blocks) with solid state interludes, I have continued to enjoy the sound with improved micro-dynamics, detail and sound stage.

Having shelled out quite a bit to improve the cabling and power and before circling back to upgrade the source and DAC - or implement DEQX to double the function of room correction and DAC upgrade - in the near future, I wonder if fellow tube amp owners can recommend any more tweaks, including mods to the amp.

Implemented tweaks on my LP140s so far:
-line stage 6922 tubes upgraded to Amperex Philips Orange Globe late 60s, Herbies tube damper.
-output stage tubes 6550 upgraded to KT120
-stock power cords to Audience powerChord SE
-AC fuse to HiFi Tuning Supreme with WA Quantum chip (am considering the modern ones like Audio Magic Super Fuse, SR Red, Audio Horizons Platinum Reference). Note: there are 3 full size fuses inside the unit, besides the large rail fuse -accessible from the back- that has probably no audio fuse alternative. I plan to replace the internal fuses too, not with the top line but maybe Furutechs that sound pretty neutral and balanced.
-isolation: Black Diamond Racing pucks on BDR shelf (works in my system almost as good as the Stillpoint ultra SS).

So far the list of easy tweaks with out the need to send them in. Anything else I should consider?

Now for the surgical tweaks:
-as for caps that contributes a lot to the sonic signature (as well as everything in the power path), I haven't thought hard about having the coupling caps changed as they are CJ proprietary and said to be very good, although I would suspect that the new gen (e.g. VCap CuTF) may be worth a try, anyone had experience with them?
Other caps upgrades/bypass: each power supply filter capacitor gets its own bypass (Teflon?).
-what about replacing resistors in the line stage?
-RCA jacks: those on the LP140 look decent enough or should I envisage upgrading to Cardas alternatives?
-IEC socket to Furutech?
-have not thought of inserting Bybee purifiers as there seems not to be a consensus speaking for them.

As for comments, I hope not to get those "can not be measured, must be snake oil" type remarks, I trust empirical findings. Thanks!
128x128jazzonthehudson
4 responses Add your response
jazzonthehudson's avatar
jazzonthehudson OP
277 posts
 
Anybody tried a really expensive set of 6922 or equivalent on it/them (LP70/LP140) and noticed big difference?

/Plasmatech: well that's the plan, just a bit hesitant as it will take at least 300h before I hear the real beauty, will burn them in else where.

/Geoffkait: thanks for the tip to help remedy EMI. Is 0.004" thick enough?
Will try the cork and hope that there is enough room to lift up the board.

Audience use a dark sheet (non conductive) in their power conditioners, I strongly presume for the same reason. Do you happen to know where I can buy them?

/Jafant: I had powerChord e so thought it was the logical upgrade path. I was thinking about TWL 7+
jafant
18,767 posts
 
Jazz-

very cool project. I love CJ gear. You are off to a great start. The Audience power cord is a nice touch- sonic match for CJ gear- IMO. Keep us posted and happy listening!
geoffkait's avatar
geoffkait
23,365 posts
 
Isolate the transformer with cork and wrap the transformer with mu metal. Isolate the circuit boards using small squares of cork where the screws hold the circuit boards to the chassis.
plasmatech
77 posts
 
I have the VCap CUTF in my tube amp, and they do make a significant improvement. A more textured organic midrange, but no loss of detail, in fact, possibly more, with more layers of information. Add to that a big jump in dynamics. Without a doubt, the best cap I have heard in the coupling cap position. Also, add some of the Eichman or good WBT low mass binding posts.
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