Ah ha! It looks like my cathode voltage is swinging wildly with the input signal. It idles at 45V to bias the toobs but when you apply signal it jumps up by 90V so I've definitely bozo'd the layout there. I want to get this damn thing working so I can try building an amp using the gothik ring layout method as it looks totally hot.

Ah ha! x2.

I totally screwed up the bias! I used a 470K resistor when really it should have been a 470R or something
At idle it will have been dissipating a whopping 0.01W

What's this then?

Tag board arranged around the sockets



If its done right you can have real short signal paths. Apparently you can make very high gain amps that are pretty quiet using this as very little crosses over the heater wires and what does it at right angles so it doesnt induct! I can see this working nicely with some elevated heaters to further push the induction down. Itching to try it!

There are some pretty gratuitous map upskirts here using this method for the AX84 october.
http://smg.photobucket.com/albums/v673/ ... er%200002/

Ah, i see, it is basically just point-to-point, but specifically always with the tubes between the terminal strips?

I drew up an AC30 variant that way once, but never built it. After repairing something that used the basic terminal strips i was turned off to them: it can be a royal ballpain to get components out, after they have been put in, especially if the components have been put in properly with the leads bent around and all.

Some day i will probably point-to-point something, but eyelet/turretboards are just so easy to work on, i am in no hurry to ditch them right now.

Thats the one. Ideally you want to keep the B+ and grounds on one side and the signals on the other but it doesnt make a huge difference.
The real advantage is you havent got many flying leads to fuck things up with. I've been lucky with that so far but its only a matter of time before an underside wire causes me some pain I could start using turrets and keep it all up top of course. The other advantage is not having to drill and swage a board which is a pain in the ass. I wouldnt want to make a 3 channel amp with switching bells and whistles this way but I think I'm done with switchers for the time being.

that is spiffy sir.

Indeed. I'm sure my first attempt wont end up that neat haha.

Ghetto solutions

Damn shop not having any 5W resistors...

It lives! (sort of)

Heres a quick vid


Description:

So I have the power amp and power scaling working on the AR-20 now. In this video I'm only running through a single gain stage with no tone stack or tone shaping. What you're hearing is the phase inverter and power tubes distorting.

The dial I'm fiddling with is the power scaling circuit.
its running at about half a watt at the start of the video and this gets gradually cranked to full beans which is about 20W give or take a few. On full it was shaking the bench ;)

Thing has just a tiny bit of low end, eh?

Well thats what P90s in B will do for ya haha

That and for sure, being tuned to X flat.

My memory is not good and i am too lazy to read back a few pages: which power scaling method are you using?

Using a power mosfet as a voltage stabiliser

Oh why didnt I pay attention to antek transformers earlier? Their power trannys are ludicrously powerful and cheap! International shipping rate is great too!
I'm itching to finish this build now so I can get on with planning and building something with 2 (maybe 4) KT90s! A pair of them into a 4K primary will give me something like 90-100W with 500V on the plates and 300V on the screens! I already have an appropriately rated OT too....

Clean channel now fully works
tres creamy

Filth channel lives. It oscillates when the gain and volume are maxed so I need to add a snubber somewhere. Sounds pretty damn filthy with buckers and its do a nice indie sound with my strat. Just the NFB loop and switching to do now

Low quality photography off the port bow sir

Less shitty photos off the starboard cap'n

That is some kind of hot shit.

How do those turrets work? Do you use a nut, or do you thread the holes in the board and screw them directly in?