Parallel Inputs On V1 w/o Switch Just Using Jacks Possible?

[rp]

On my 5C8 I like to put the two inputs on V2 (cathode biased not grid leak) to better use than having both the same and I couldn't be bothered w/ the typical hi-lo set up. Is there a way just using the isolated switched Cliff jacks to do this? I'm using the normal jacks switched to ground when nothing's plugged in, that's the difficulty, how to keep one side from grounding the other if I want to parallel.

[Jana]

One thing you could do is run the ground connection from each input switch connection to the tip contact connection of a third jack. Then, on that third jack, run the switch contact to ground. That way you can plug into either (or both) of the original jacks and when you do, it breaks the connection to ground. Plugging into the third jack sends the signal to both of the original inputs (unless something is plugged into those jacks).

See the older Sunn Model T schematic for a schematic of a "Both In" arrangement.

[rp]

One thing you could do is run the ground connection from each input switch connection to the tip contact connection of a third jack.

No holes allowed. I have to do it with just the two jacks. I could add a volume pot with a push pull switch, simple SPST, but I can't work it out w/ that either. Hopefully I'm just not seeing it, but I think it can't be done.

A small guitar pull pot with DPDT I think could do it but I hate working w/ those things and I hate them in amps.

[Jana]

Okay, no holes allowed.

[rp]

Is it really that simple? I think it is

[Jana]

I hope you weren't expecting me to think up something complicated!

[Leo_Gnardo]

Bububububut.... if you plug into #1, signal is shorted to ground. If you plug one instrument into #1 and another into #2, assuming they're normally wired passive guitar/bass/whatever then if one player dials down to zero, it kills off the other instrument - a "feature" I found on a Lafayette kit amp my very first college band used to use for practice sessions.

I know that amp was in another thread, recently resurrected, and it's a beaut, simply outstanding build rp!

[Jana]

If you plug into A, it lifts the ground from the contact and the signal just goes into tube A and B is grounded out.

If you plug into B, it lifts the ground entirely and the signal goes into both A and B tubes.

If you plug into both of them, each jack goes to its respective tube.

[Leo_Gnardo]

If you plug into A, it lifts the ground from the contact and the signal just goes into tube A and B is grounded out.

If you plug into B, it lifts the ground entirely and the signal goes into both A and B tubes.

If you plug into both of them, each jack goes to its respective tube.

OK I get it now. (gotta imagine solid line turning into dotted "grid" line...) Thanx for the explication Jana!

[Jana]

I'm pretty good at imagifying things. It's good you check up on me and keep me honest--sometimes I imagine myself in a parallel universe and, let me tell you, things are a lot different there. For one thing, there are a lot of cute puppies. And transistors haven't been invented and probably never will be.

[Leo_Gnardo]

sometimes I imagine myself in a parallel universe and, let me tell you, things are a lot different there. For one thing, there are a lot of cute puppies.

I dunno Jana, my parallel universe is a lotta snow & a thermometer that hasn't seen above freezing for a long while. No fewer than 8 deer ransacking my neighbors' bird feeder - again - not 8 tiny reindeer either. Another - 94 year old neighbor who needs nearly constant attention. Plus an orange + white cat that manages to aim his cat stink spritzer precisely between my door and its frame. Oh RATS that's no parallel hell, it's all for real. Puppies would be a relief.

I'm working on a Tesla-coil based solution for the cat. If you see one streaking thru the stratosphere - that would be him. Most cats I like. This one, not so much. He's a bully, a mooch, and obnoxious to the max. Planning for a landing in North Korea. MMmmm good!

[Deric]

Double post..... F.

[Deric]

Like this?

http://mhuss.com/18watt/schematics/18wattLite2b.gif

[rp]

Leo, thanks for making me feel better, seems simple enough but start adding in the 1M grid loads resistors and jack switches and you need to start firing up at least a few brain cells.

I've been drawing it out with Cliff jacks and got to where Deric's Huss's drawing got me, though I did it a little more complicated w/ the switches and 1Megs - which is why I'm not an engineer.

Question, are we sure here (Huss's drawing) that in parallel each input is seeing a 1M grid load? I also have 33K grid series resistors right at the socket so I'm pretty sure they are out of the switching.

BTW, I tried paralleling w/ an external jumper cable a la Marshall just to hear the effect: Gnarly, a 6SC7 paralleled is some thick freight train.

Re-doing the inputs is going to be tonight's PITA task.

[rp]

hmm, something's not right. I did Deric's wiring, or I think I did. I get weak gain on the single input, I get correct sounding boosted paralleled gain on the parallel input ok but it sounds off, too bright.

I tested the resistances inserting a cable plug, I get 500K on the grid load when in parallel, and 1meg when in single. The series grid resistors show up correct (I actually have one at 10K other at 33K). I also tested continuity and the jack switches are working properly.

Why the single input should have weak gain is very very odd, when plugged into it the switches disconnect it completely from the parallel jack.

Any idea what's up w/ the single input jack? Is Deric's drawing wrong, if so how to correct for the 500K grid load that should be 1meg? I'm thinking one of the 1megs should go across a jack switch?