Got my 6BC8's - think about UA 175A

[jhaible]

[quote author="toby"]hi jhabile,

any prototype, progress yet? or any interesting varimu based discoveries?[/quote]


Hi Toby,

oh no, I'm thinking in weeks, not days, for something like that.

Maybe I'll hook up the variable gm stage alone, just to see how the VCA function works, before I build the whole thing.

What I've done meanwhile, is buying more tube sockets, and an OB2 for the 108V shunt regulation. What a surprise: I had expected a small glow lamp, but this is a full fledged tube (and not cheap either).

I've also made a simulation of the amplifier section, and unlike the LA2's amplifier this one seems to do very nice soft clipping. If I can trust the simulation, that is. I saw that for large input signals (only speaking of the amp, not the variable gm stage), the grid of the 12BH7 is going positive (in simulation) long before the output saturates. No idea (a) if the simulation is anywhere near reality for this condition, and (b) if the 12BH7 allows significant grid current. Seems to run rather close to its limits in this circuit anyway!

JH.

 

[toby]

might make the pcbs over the weekend for mine, but still waiting to order some transformers.

i email you the schematic i've been working on if i get it finnished this week.

what software are you using to simulate circuits?

 

[jhaible]

[quote author="toby"]might make the pcbs over the weekend for mine, but still waiting to order some transformers.

i email you the schematic i've been working on if i get it finnished this week.

what software are you using to simulate circuits?[/quote]

PSpice

JH.

 

[jhaible]

Here I am again, working on the UA175 - like variable mu compressor.

Wait - I better start a new thread with the right question in the subject line.

JH.