Working on the write up, but I guess it’s time to show off the results of the latest mod!
Big shout out to
@Guidostrunk for the cosmetic work... stealth black just looks perfect on this amp.
I have been low on time lately and have not been able to get photos organized quite yet but here is the summary of what has been done to the LP.
Bit of backstory...Sam and I have been working on modding the LP for a few months now with his original idea of upgrading the caps to Elna Silmic II's to see what kind of improvement it could bring. Many swaps later their remained the issue of a sub-par volume pot with low-mid level channel imbalance. Then the discussion turned to how to fix it.
Well, how hard could it be to swap out a volume pot, right?
Turns out that it is not terribly difficult to do so, but the pot we chose to use is the Alps RK27, sort of industry standard volume pot that is quite a bit larger than the stock knock off version.
Original thought was...maybe it could fit into the stock location, but after a few measurements it became clear that the Alps was too large, both in length and in height of the shaft. Turns out the Alps is wider than it is tall, and rotated 90 degrees, it fits perfectly between the stock pot location and the adjacent components to the left of it (such as in the picture above, but turned) So I went to work desoldering the OG pot and getting the board cleaned up for testing.
Couple issues to overcome:
- Determine the pin-map of the stock daughter board to the main circuit board, which of course was unique.
- Second test had me coming to terms with the fact that their really was not enough room in the case to apply my own daughter board at that I was going to have to just go direct from Alps to board.
- The new placement meant that the stock faceplate was going to have to have a new hole drilled.
The third problem was solved by
@Guidostrunk . He filled in the original hole location and drilled and bored out the new one. He also went above and beyond with the finish paint work. Sanding the stock plate, painting, wet sanding, painting, clear coating...he did it all and it turned out fantastic and a great match for the original LP finish. Gone are all text and symbols, but I never needed those in the first place and prefer the murdered out look! The stock volume knob was usable with the new setup, but the larger one I ended up going with just felt a bit nicer. I like the larger diameter and knurled edge.
Knob
Number 1 and 2 were solved together and ended with me testing a number of difference resistance Alps pots to "try all possibilities" of attenuation. The stock pot is a 50K resistance pot. My finally settlement was for the same. I tried 10k and 100k. 10k sounded great with a little more low end, but also sound leakage at the lowest volume. The 100k also sounds great and provides a very smooth rotation to listening level, but ramps up quickly from 10-11, so back to the 50k which basically follows the stock pots profile and has me listening at 11 or so unless its late and quiet and then its much lower.
Here is one of the original test fits showing the tangle of cables and basically the proof of concept.
In this image I parted a Kimber PBJ cable for the wiring, but the gauge was way too big and became a problem removing the wires for further testing. I switched to some silver 24 gauge wire that was much easier to work with in the final iteration.
Here is the stock hole vs. the new hole and vol pot location. The Alps housing had to be glued to the board for a nice secure feel. Also realized at this point that the new hole had to be dished out like the stock location so that the threaded section would come through the front plate.
So how does it sound is the most obvious question. Good, very good is the answer. With the 10k pot, I never quite got to 0 volume, but it was very faint like whispers in your ear...but these whispers were very nicely balanced. The 100K pot allows to full 0 volume, but also retains a hint of channel imbalance at the whisper level. The 50K pot is just right! Tight volume matching, smooth attenuation and a really nice overall upgrade.
I hesitated to show this off since I currently I do not have a lot of bandwidth to offer this as an upgrade service like the cap upgrade (cap upgrade I can still do). But I have also alluded to this often and wanted to show that its possible, and does make an improvement. I also was directed that perhaps we could try and Alps RK09, compact volume pot, but I could not locate a 4-gang unit. I am sure they exist, but they might be special order parts from Alps.
Give me a few months to finish my home move and get school squared away and I will be able to some upgrades for folks at a slow pace. The upgrade involves the removal and replacement of the volume pot, but also some fairly heavy cosmetic work to finish off the product.
I am glad I took this on, and really love the new feel of the volume pot and the new improved sound.
If anyone is inclined to take this one, I can provide answers to any questions you would have, just let me know!
