Please Help Me Understand?

[The Ballzz]

Please help me understand what is going on here?

Twin-5E8-A-Inputs jpeg.jpg

Let's first look at the upper channel inputs. Obviously there are no grid stoppers, only grid leaks. My take on the inputs is that if I plug into input #1, it parallels the grid leaks to ground for an overall effective 500kΩ grid leak and also sends input to both triodes of the 12AY7. Moving to the right, we have two plate load resistors coming from the DC power node. Then just to the right, there are two more 100K that I assume are effectively "mixing" resistors to "mix" the signal produced by those two triodes. Then onward through the .02-600 coupling cap and volume pots to the 270K resistors that I assume to also be "mixing" resistors to "mix" the two channels together, before entering the driver stage of the cathode follower tube. Am I correct so far? What confuses me a bit is what is actually happening and being accomplished by the interaction of those four 100K resistors, especially when driving both triodes in parallel from input #1?

Next, can I assume that the only way to actually "plug into" both channels and access both grids of each channel simultaneously is to use a "Y" cord or all parallel box arrangement, plugged into the #1 input of each channel? It also appears that if I do this, I'll end up with an effective grid leak vale of 250K? This 250K seems a bit low for an input grid leak, but am I missing something here?

My eventual proposed goal here is to have the input drive the grids of all four triodes, from just two jacks. One jack to access just both grids of the two triodes of one channel and the other jack to access both channels. I do not intend to ever drive only one triode at any time. It seems that in addition to having an already low resistance grid leak/input impedance, there will also be a fairly substantial drop in signal strength of approximately -3db for each parallel connection? One thing I'm wondering is if to best accomplish my goal, I may need to re-calculate the grid leak values and possibly even add grid stops of 68K or 33K for each channel, although that would seem to drop the signal level even more?

Please help me understand what is actually going on here and the feasibility of what I'm proposing to accomplish. I'm going to guess that for initial testing purposes, it may be best to go ahead and wire up one input jack and simply play around with grid leak values? I'm extrapolating that this one input, paralleled to all four triode grids may want to see either a single 1M or 500K grid leak?

Thanks Folks,
Gene

[clarkleach]

It seems like you have a handle on what's going on there. It's just a matter of figuring out the jack/switching arrangement. I would add grid stop resistors. There's not a whole lot of advantage to running parallel triodes. You'll get some gain boost and less noise.

[The Ballzz]

It seems like you have a handle on what's going on there. It's just a matter of figuring out the jack/switching arrangement. I would add grid stop resistors. There's not a whole lot of advantage to running parallel triodes. You'll get some gain boost and less noise.

Thanks for that. I think I've got my input figured out, but will likely need to play with the "grid leak" value. And "some gain boost and less noise" sure sounds like a big win-win to me!

Thanks Again,
Gene

[thetragichero]

parallel triodes giving "some gain boost and less noise" is compared to a single triode
if you're looking for gain boost cascading one of those triodes into the other would wipe the floor with the parallel triodes
that being said i have used the old "4 hole" trick with a single input build and enjoyed it

[Shockway]

I'm beginning to evaluate the Japn drawing of SSS-002 and am drawing out the schematic. I am hoping to understand:

What Mr Dumble was accomplishing when he connected the Plate voltage at V2A directly to the Grid of V2B ?

Shockway-D3S2-NoDecoupleCap.pdf

[thetragichero]

dc-coupled cathode follower to drive the tone stack

[sluckey]

I'm beginning to evaluate the Japn drawing of SSS-002 and am drawing out the schematic. I am hoping to understand:

What Mr Dumble was accomplishing when he connected the Plate voltage at V2A directly to the Grid of V2B ?

Your schematic has errors. V2B cannot possibly work because the cathode has no dc path to ground.

[Shockway]

Thanks, Guys. I watched Uncle Doug's video on Cathode Followers. Much appreciation.