Just finished the digital tracer project uTracer V3. Did some further tests this morning, now with my favourite DHT: 4P1L.
Started with a well known bias point for triode-strapped operation:
uTracer up and running
After a stupid mistake which blew the PIC, I finished today my version of the uTracer. A quick trace of an CX-226 RCA Radiotron can be seen below. This is an incredible digital tester. I need to test it properly and do some comparisons against my analogue tracer, but as everyone would expect,the digital tracer has superior capabilities in terms of data manipulation and representation.
Highly recommended. Ronald provides a sterling service and specially when I damaged the PIC and send me a replacement at no cost!
More to come shortly…
Unknown pleasures record shop
A great record shop in Edinburgh. Highly recommended. Came out with some Thelonious Monk LPs. Even brewdog house is 5 min away. Enjoyed a 14% ale so can’t get better than this!
Tonearm adjusted
Raised arm board flushed to the plinth so VTA and arm position was optimised. Great sound indeed 🙂
Joy time
Listening to Mingus Band. It sounds really nice on the Lenco turntable!
4-65A SE Amp: first tweaks
As discussed previously, I replaced the gyrator’s polypropylene caps with better ones I had at hand which are 1uF 450Vdc Mundorf Mcap EVO Silver Gold Oil Cap (EVOSGO-080). I should look at lower value. A 220nF or even 100nF one should provide a 1Hz -3dB point with the 4M7 resistor. Anyway, the sound is a tad better in the bass I would say. Nice upgrade but should listen to it more to find what other changes has this capacitor made to the amp:
Replacing the capacitors
Mu-follower gyrator boards finished
Lenco turntable (Part II)
Great thing about bank holiday weekends is that you have more time to work on your projects! At least I had this time round.
After doing the initial calibration to the Lenco idler mechanism, I got the turntable finally assembled on the new plinth. It runs very quiet and smoothly despite having not dampened the idler wheeler as recommended in the Lenco Heaven forum. I need to look into it but so far the turntable runs really quiet.
The arm board is a bit lower than it needs to probably. I can adjust the VTA with the micrometer but I should look at raising it to allow the arm to be rotated to the right for best placement. The micrometer is preventing this to happen. Will refine later.
GL75 now on its final place
Audiomods tonearm
First test
Clearaudio virtuoso cartridge
Ok, impressions so far after all this work then. I did many upgrades this time to my system so it is hard to quantify which part contributed the most to the sound improvement. Overall tone and clarity has improved. I suppose that the heavy plinth makes a big difference to the bass clarity. The overall tone improvement and detail is quite likely to be the Audiomods tone arm as well as using the Clearaudio Virtuoso Wood MM cartridge that Tony kindly give me to try.
Lenco turntable (part I)
A rare occasion in my hi-fi life is too see me switching from electronics to basic mechanics. I’m not either good with woodworking or mechanics :). Either way, the GL75 rebuild is coming along quite fast. I sealed the original arm holes in the top plate and painted it yesterday. Today, I spent all morning waxing the plinth. The afternoon was devoted to rebuilding the Lenco turntable mechanism and testing the re-lubed motor and spindle. I still need to do further calibration, but so far so good.
Here are some pictures of the building steps:
plinth and arm
top plate ready for paint
painted top plate
waxed plinth
Barry French’s 26 DHT preamp
26 DHT Preamp (by Barry French)
After owning several high quality pre-amps & modifying some of them to some degree or another, I decided to have a go at building a top quality unit, so here goes first I needed to build the power supplies for filaments & B+ in a separate case, I already had some idea of the look & design that I wanted to follow, so I sourced the following components from these suppliers:
4-65a SE Amp: output valve
One of the output 4-65a was actually a military JAN-8165. Wanted to test a pair of them but in the rush of building the amp I ended up with a mixed of the two. Not an orthodox approach buy who cares! After playing the amp extensively for a couple of weeks I noticed that this valve droped anode current after 1hour or more of playing. Anode current could go down by 10-15mA. Perhaps it has to do with the pin oxidation, but I also suspected on the filament regulator due to the heavy current required on this. The regulator heatsink gets really hot as you can imagine so I was already blaming on the regulator FET before I even suspected on this output valve.
A simple test was to replace this valve by a new NOS 4-65a. I did that and surprised to find that the filament regulator wasn’t to blame. The 4-65a SE filament stayed rock solid at 100mA after 1h30m of fantastic music. Yes, the bass of this SE is unique. It exceeded everything I previously listened to. Is the 46 driver in filament bias? Not sure yet, but hey ho. What an amp!