JoaMat

Sorry for your second failure. After my own failures I've been like gun-shy dog – haven’t touched the Circlotron project for a year. But there must be a way to get the Circlotron safe even for the common DIYers, mustn’t it?

Thanks for the information. I have made some attempts with the Circlotron. Blown both PSUs and outputs. Small black fragments all over the place. Seems that things easily might get wrong and then both PSU and output are effected.

@Tinkerer,Sorry for your accident. Did something broke on the output board?

Has anyone tried the low voltage supplies on the HV boards with AMB’s Sigma 78/79 regulators? I think it would be a simple and not very expensive improvement.

I run my mini Dynalo at +/-20 volts. AMB voltage regulators, positive 10K and 133K, negative 10k and 160K resistors.

https://tubedepot.com/ - Claim they match up to 9 tubes for free??? Also have Philips Miniwatt metal base tubes.

Nice! 18.5 mA through output transistors? Nearly 2.5 W each.

I had 0.1uF wima in mind, but i'is to low?

I guess the 35uF electrolytic are on the board for some reason – why?

I'm going to feed ducks, sometime.

Brainstorm - Output transistor on bottom side and the other components on the top. There are some 300V and even 400V sot-23 devices.

not possible, I am several hours ahead of you Americans

You don’t want the male pins be exposed with voltage on them. Imagine your 2 years old grandchild about to explore the world and found the exposed kV pins. IMO it’s not necessary to separate filament wires from the others.

Yes, that’s copper clad. I’ve a CNC machine. Nice opportunity to learn have to use it. I’m not ready to mill aluminum yet.

don't hold it for to long, it might get old

I think it might be possible to squeeze in a digital attenuator in Mini Dynalo. ATtiny85 is in the middle of the breadboard, lots of space for it in the box. Need some 5 volt supply as well.

Right, no volume control - also the way it should be.

I said a few days ago that I’ve given up Attiny85 as controller for the digital attenuator. I’ve done some additional attempts today and it turns out to work all right. I really like that little thing. Can’t be more minimalistic..? Regarding pops/clicks I think I've to give up. Seems to be to complicated for me to solve.

Very nice indeed! And two boxes - that's the way it should be!

Got Kerry’s VolumeController to work. Wasn’t that difficult when I just figured out the output pins for the digital attenuator. Compiles much faster and uses much less memory than my firmware. Nice display, like the relay indicators!

Thanks guys. Found a post at diyAudio by Russ White. Mr. White said the problem was easily addressed by some change in the firmware. Well, I think this will be a real challenge for me…. will give it try though.

Have been struggling with controller for the digital attenuator. Finally the Arduino Pro Mini works OK, both with rotary encoder and with potentiometer. I’ve also tried the little Attiny85 but it didn’t worked with both relay banks so I’ve given that up. Power supply is to get an idea of current requirements for the attenuator. I’ve pops when relays are switching between 7/8, 15/16, 31/32, 63/64 and 127/128 “bit”. At AMB’s forum the pops are discussed and I guess I’ve to live with that??

Sort guld. Very nice.

Congratulations!

Have made some progress programming both Arduino Pro Mini and ATtiny85. My impression is that using 7 relays with 0.5 dB steps is sufficient and the eighth relay mostly contributes to more silent silence. Opinions from folks that have experience from digital attenuators are welcome.