Dear hifi & tube enthusiasts,
after 10 months project time and lot’s of patience in regards getting all components, I’m pleased to showcase this pretty unique (high end) diy tube mono project. I’ve them now playing the last 3 weeks and quiet impressed 
All have started with my beloved japanese magazine: PX4 - Fascination 113 von Koreeda Shigeharu (Stereo Sound Japan, Vol. 113 - 2024). As I still have my old PX4 (orig. Marconi’s, unfortunately not good measured value anymore) and love this one of the oldest Triode, I also thought about last year to get the new Lowther PX4, but after I saw the design it was not something I liked for those very special tubes (even the tried me to sell their first badge for less thank €9k)’.
So i asked in our special german forum if one of our tube gurus would support me and to build it (also I forced my demand for pcb-free build). So I was lucky to got support from one of the most experienced tube gurus I’ve ever met and usually he doesn’t do any builds for anyone, only mentoring (his age: 76). He also creates his own tube designs and only Single Ended Triode, even builds his own transformers - perfect in my case
After he saw Koreeda’s design he was curious and already found too many weaknesses in his opinion (design flaws). But he was also very, very curious about this very unique sowther parafeed transformer and impact to the overall sound, as he never heard about it.
So we created over several weeks complete components list and the plan was from the beginning to use only best components (Lundahl, Sowther, Vishay/Dale/Caddocks with lowest tolerance, WBT connector, DACT mono poti’s etc). Also only using Emission Labs 5U4g-Mesh rectifier and EML PX4-Mesh and my tube guru als had direct dialog with Jac van de Walle (Mr. EML) and he also provided some technical aspects we should consider. Also was interesting to see why he created the paper of Marconi’s PX4 misunderstanding 
I learned a lot as an ^audiophile and I’m now much more relaxed about all our crazy tuning rabbit-hole we think is necessary (silver soldering, esoteric cables …). My key learnings in regards of tube gear:
- it’s all about highly precise, stable voltage & very low resistor tolerance - this is also where Parafeed-magic is happening
- my tube guru was very impressed and he is now rebuilding his GM70 with Parafeed, of course with handmade transformers
- BTW: we are talking about a 2x6 watt’s output power (optimal working point: 3-5 Watt)
Price components only (incl. tubes and cabinets - for 2 monos): ~€7.500 (incl. EU-VAT)
(original Japanese Kore3da’s PX4 Monos was €20k in total - ordering price for EU customers)
Finale design:
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SOWTER 8983 Parafeed & SOWTER 8982 Plate Choke , Lundahl LL1673 10H, custom toroidal 370v audio grade (double windings for all heating voltages), mundorf tube cap 600v, Mundorf MCap Supreme SilverGold …
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Tubes: EML 5U4G-Mesh (orig: 5Z4P), EML PX4-Mesh, EC86 (orig: EF86), Yamamoto tube sockets
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Tube rolling not easy possible, due very sensitive voltage/resistor matching and would need resistor change, also no auto-bias (pcb-free was my main demand!). Also original Marconi PX4 specs are not optimal, therefore EML PX4 (Mesh plate) changed them to more optimal specs (Lowther is using them as well)
If somone wants to have the schematics, let me know (not complicated, but high voltage and only for experienced tube builders).
How they sound?
- First to clarify: if they can play “loud” with ~2x 6 Watt? Oh yes, at least on my 96db Cube Audio’s I was listening with moderate-loud level (DACT-poti position at 8 from 24)
- As I’d already experienced wich my much older PX4 DIY-build: they tubes have something I didn’t hear so far from any of the GM70/2a3/300b. They combine many of those 3 mentioned tubes into one: holographic & warmth like a 300B, authority & dynamic like a GM70 and transparenccy like 2a3
- So they have now around ~150h playtime and tonality is even getting better and my AN 300b Meishu is jealously sitting turned-off right next to it
I found my perfect match for full-range speakers. I’ve not tried them to my YG Acoustics Carmel 3, but will do soon.
Cheers & happy listening, Gerald
. Bravo! Gorgeous and such a very interesting project, what an awesome audio adventure! I Love it 