Time to upgrade my pre-amplifier (again) and is perfect timing to go back to 4P1L. The Siberian preamp had a fantastic bass response and detail.
Here is the new filament raw supply. It has split bobbin transformers, schottky rectifier bridge and input choke LC filter stage. It also has a CM choke and EPCOS electrolytic capacitors:
Power supply ready
Input chokes
Chokes and capacitor bank
Schottky Rectifier Bridge plus snubber
Building the power supply
Dead quiet at 16V output and 550mA which is the load used by 4P1L starved filaments in parallel with filament bias.
Soon to build the preamp!
Interesting Ale!
Did you find the cm choke Connection to be better than the “ordinary” Connection +
Best regards Vegard
ps 50’s on their way this week
Hi Vegard,
The common mode choke is simply a dual bobin in a ferrite ring. I have it for preventative measures as never had any mains noise issues (touching wood now)
I still need to build the power supply, expand the SSHV regulator by adding a proper heatsink as will run it rather hot and build new transformer and socket units for the preamp. A long way to go still
My Shuguang SG-50 were lost on the post so bad luck. Had to fight to get my money back from the seller/courier. Anyway, when get yours will trace them. It’s been a long time since I fired up the tracer
Hope they arrive safely so please ensure accordingly!
cheers
Ale
Hello Ale !
I am using the Siberian for a year now and it is time to upgrade !
Will the LL1660/18ma a good match with the 4P1L ? I have a pair
in my stash !!
Best regards Martin.
Hi Martin,
4P1L is best run at least 20mA, however for low level signal as in a line-stage you can get away with the 18mA. I always loved the gyrator sound, but transformer coupled is a great choice to try indeed!
Looking at the starved filament curves I’d suggest you try any of the two options:
(If=550mA)
1. Ia=18mA, Vak=130V, Vgk-8V or Rf=14 ohms
2. Ia=18mA, Vak=155V, Vgk-10V or Rf=18 ohms
Let me know how you get on.
Cheers,
Ale
Are you going to use the Coleman regulators, or do all LC filtering?
Hi Scott,
I will use Rod’s regulators
Ale
Hi Ale
I have a 46 linestage with filament supply similar to yours, choke input with Lundhal Chokes feeding to Rod Colemen supply.
I would like to build the 4P1L linestages based on your circuit, except, I will with a LCLC power supply instead of shunt reg, as I am not good at building that stuff.
I have a question on the 4P1L filament supply. jUST WANT TO CONFIRM, YOU HAVE 16V going into the coleman reg?
thanks
Sridhar
Hi Sridhar,
Nice, you’re as crazy as I’m after building a 46 in filament bias. I use it as the room heating during winter time!
The HT supply based on LCLC should be good providing you implement the right level of filtering.
The Coleman regulators use 16V input to achieve the filament bias requirements.
Keep me posted on your progress and keen to read your thoughts about 46 vs 4P1L. Both are on my top five of best DHTs!
cheers
Ale
Hi Ale
I am few steps behind you, I used the choke input and colemen reg for the 46, but punted on filament bias and went with regular RC for the cathode bias. I am going to use filament bias for the 4P1L.
I plan to use teflon sockets as they help with microphonics for this stage, I use yamamoto, which are pretty expensive, do you have happen to have another source for loctak teflon sockets?
btw, if you have a an email address, I can send you my latest work – 811A in pure class A2 using a mosfet source follower. The thing sounds awesome – max power 12w at 1KHz
I will be getting the coleman regs soon
will keep you updated on the build
thanks
sridhar
Sridhar,
I forgot to reply this after sending my email. Regarding the sockets, the best options I can recommend are:
1. Custom-made loctal by Jakeband in Italy:
http://www.bartola.co.uk/valves/2012/12/03/teflon-sockets-loctal-and-ux5/
2. NOS ceramic sockets from Russian. you have to search in eBay, they don’t come very often but are superb:
http://www.bartola.co.uk/valves/2013/01/09/4p1l-ceramic-socket/
cheers
Ale
May I ask how you describe the effect of this no-compromise raw supply ? Currently I use Rod’s norml CRC raw supply, but yours is far more $$$ and wffort, which I will follow if this has a noticable impact….
Hi Frank
The filament supply has a noticeable impact on the overall sound. I prefer a choke input (LCLC). The selection and quality of components is also key. For the transformer I use a custom made split bobbin transformer with outer screening in copper. This minimises the noise coupled from the mains as interwinding cap is minimised. The chokes I used are Lundahl and the output caps are EPCOS series.
There is plenty of info regarding these filament supplies on the DIYAudio forum or you can also ask Rod Coleman for advice. He may be able to help depending on availability.
Thanks
ALe