Adding filament bias and output caps
Author: Ale Moglia
"A mistake is always forgivable, rarely excusable and always unacceptable. " (Robert Fripp)
01a Preamp Build: UV-201a version – step 1
This is what I managed to do with a couple of hours at the workshop. Time is gold for me these days. Quick drilling and fitting the main components. You can’t get a smaller preamp than this one. It’s quite packed:
Planning the layout before drilling
Back panel with all connectors (supply and signal)
Inside the preamp
Close look at the gyrator boards
UV4 sockets with rubber dampers
Fitting a pair of brass base UV201a
Next, soldering. Yay, just looking forward to my favourite part of the build process
01a Preamp Build: UV-201a version – layout
Just playing with the layout a bit. The gyrator boards, the UV4 sockets and the Rod Coleman regulators. All in a tiny aluminium box:
26 DHT preamp Gen3
Using the Gyrator PCB board:
JFET Buffer
Fall 2016
End of summer is here, and for some the beginning of the building season. Well, not for me am afraid. My parental duties and work are keeping me very busy these days. I don’t have the free time I used to have before (I guess I’m not the only one on this so won’t rant on it). Today, building DIY audio gear is a matter of a well planned and negotiated free-time that worths more than gold to me. Well, that’s the way it goes. Anyhow, I picked up my daughter from nursery yesterday and on the way back I was faced with this beautiful landscape. I guess nature give us some gifts from time to time, you just happen to be on the right place at the right time:
Standing on the middle of the street with the pram was a bit dangerous so had to park my daughter on the side whilst I managed to take this picture. Time ago, I’d have taken probably a long time to take this snapshot, but now it was as quick as a bank robbery. Just take the phone out and shoot – you can’t take your time when you have a crying toddler on the pram!
A tail of buffers
I think I have spent far too much time designing, building and testing preamplifier, perhaps more than amplifiers lately. I don’t know why. I guess I fell in love with the preamps and their contribution to sound overall. Who knows, who cares.
SMD soldering for gyrator PCB
I have a new microscope for SMD soldering. If you want your gyrator PCB with a presoldered BF862, now it’s possible!
Running
A common theme of our age, run. We keep running, but not physically only. Our minds are constantly interrupted, like an CPU IO interrupt. Well, sort of. You get the gist. We run from home to work, from there to here, from here to nowhere. The reality is though, we are always on the move. Do we really like that? Hey, probably no, but that’s the way things work these days.
I have a hectic life myself, no doubt. As so probably you. Either way, the most precious moments in life – at least in the XXI century – is to unwind, stop and enjoy a bit of the slow movement. Slowly put the needle on that record, slowly sit down on your comfy sofa and slowly pour that single malt.
The rest is your imagination that I will so much struggle to put into words
Ale
Playing
UV4 PTFE sockets
Looking to build a new 01a Gen2 preamp shortly. This time will be for the rare UV-201a valves. They need a special socket UV4 rather than the usual UX4. See width difference of both filament pins. In the UV4 all pins have same size as below:
Weather they have brass or bakelite bases, the new UV4 sockets produced by Luciano Bandozzi (Jakeband) are of supreme quality. I highly recommend them:
I already reviewed these and you can see more info here. I hope to post some pictures of the new preamp shortly
SiC MOSFET Follower Driver
How many more times
Led Zeppelin wrote a fantastic song on their first album: how many more times. You may not be a rock fan, but hey: what a great song. How many more times do I want to get back to this “slew rate” theme? I don’t know, as much as I have to. Plenty of comments out there of bad designs with wimpy drivers attempting to take the 300B/2A3 or even 45 valves to full tilt with disappointing results. Either way, they always blame the valves.
I came back to revisit the driving of capacitive loads effectively as I’m working on a new 4P1L PSE amplifier. Slowly, but getting there. Previously I looked at adding a buffer to the 01a preamp as a result of slew rate limitations found in Tony’s implementation of this preamp.
