Separate names with a comma.
Discussion in 'Shock Brother's DIY Amps' started by theprofessor, Feb 2, 2019.
hmm see below
You're right, good eye... those small upgrades and updates are all potentially useful.
Adjustable bias -- a very useful, convenient way to help you set your amp to run 'best.' Not a mod to the original sound, but a modern way to avoid having to replace resistors to set the all-important power tube bias to save your tubes and get the best sound.
Rectifier diodes -- these are simply protection against possible tube failure damaging your circuit. Easy, minor, and definitely will not alter the sound.
The 470R 'screen resistors' from pin 4 to 6 on the power tubes are an 'update' that adds protection and may improve the overdrive tone.
If I'm seeing right, the 1.5K control grid resistors connect to the 220 K either way. Recall pin 6 in inactive in these tubes, so that lug is just a tie point. Tying it to pin 6 is probably more physically stable than hanging it in the air.
Ok, think I’ve got the gist. But I cannot see from the updated layout what kind of diodes are used and the pins to connect them to. Can you shade some light?
i am ordering some missing parts and I will start a new tread on my build. Hopefully it wont look too amateurish.
For the diodes, and in fact all the items we discussed, you can hunt up good info on Rob Robinette's amazing pages, especially on 5e3 and 5f6a mods.
Rob's pages explain all of those tweaks and are immensely useful to any amp builder.
Thanks guys. I have been reading alot on his website. I didnt think those mods were compatible with different amps. I guess I have a lot to learn.
Well I'm not not doing that again! That is, I'm always doing this:
I added the 1Ω 1% tolerance resistors to the power tube sockets between pin 1 (which is tied together with pin 8) and ground. I have tried other ways of taking bias measurements, and this is by far the easiest. Get your plate voltages in DCV from pin 3 on each power tube socket, then measure across the 1Ω resistor (from one end of the resistor to the other) in DCV, which will give you a negative number but which will be identical to the plate current in mA as a positive number.
Best $1 component addition to any fixed bias circuit!
Agreed! I ordered 20 of them from Doug Hoffman, just to have them on hand for this very purpose.
You said it, Prof. And of course I agree with @D'tar . Best simple mod in the universe.
I don't do this (yet), but I know a guy that does. Get a red sharpie. When all soldering is complete on a turret (or eyelet), and checked, then add a red dot.
That's a really good idea. Thanks! It's easy to lose track, especially when there are a lot fairly close together, and they're not laid out in a linear fashion.
I do this on a paper layout... I use different color pens for different steps. As I lay out all the components and jumpers, I mark the length of the wire or component, then mark each solder joint as it's done as well. Adds a little time to the front end, but has spared me untold hours of troubleshooting on the back end!
I use the transparency in DIYLC. Everything processed is set to 10%. Things you forgot pop out.