Single channel 5E3

[Blindog]

I posted this question in the conversions sub forum but no takers Thought I would try the the tweed gurus here

I converted a Zenith phonograph to (more or less) a 5E3 circuit. Schematic:http://music-electronics-forum.com/a...6&d=1221592514

Some changes: 6J5 to a 12AY7, and rewired the 12AX7 to 5E3 cathodyne.

I found a post by Bruce Collins about a single channel 5E3 where he talks about stagger tuning the 2 halves. I understand all that but I'm having trouble seeing how it it all connects together. Here is link: http://music-electronics-forum.com/s...75&postcount=1

does anyone have a schematic of this setup, or can someone explain it to my dense head?

Thanks!

Mark

[hasserl]

Well, it would be best to let Bruce explain it himself, and he frequents here so he probably will. But in the meantime, my interpretation of what he meant is, design a single channel amp around the 5E3 Bright channel, so I suggest looking at the tweed Tremelux for how to wire up the Vol/Tone control. Now you've got two triodes at the input, so wire the input to the grid of both triodes, then tune the triodes differently by using different cathode resistor/bypass cap combinations. Use a typical Fender 1k5 cathode resistor along with a 4.7 to 22 uf bypass cap (you decide), then wire up the other triode with a 2k7 cathode resistor w/ a .68 bypass cap. Now you'll have to use some type of switching system to choose between the two triodes. Bruce suggests using a switch between the cathode resistors and ground to open up the circuit to turn the unwanted triode Off, and close the circuit for the triode you want On. Then you'll have to use some mixing resistors before the Volume control to isolate the two triodes.

I don't know if that helps or not. Sometimes it's better to view these things thru a schematic so you can see what's going on.

What I think might be interesting is to go with the stagger tuned triodes, but leave both cathode circuits closed to ground so they are both On all the time. Then use say a 250k linear pot before the volume control to choose one or the other, or a blend of the two, in whatever amounts you choose. Wire each triode circuit to either side of the pot and take the wiper out to the Volume control input. With the pot centered you would get a 50/50 blend of both circuits, as you turned the pot clockwise or counterclockwise from center position you would get more of one circuit than the other. Heck, if one was set up real bassy and one side very trebly, this would work in place of the Tone control.

[Marc]

You can also look at the Tweed Harvard schematic you'll see it basically is the 5E3 with a single channel. It sounds much like the 5E3 even with the 10" speaker.
Marc

[hasserl]

You can also look at the Tweed Harvard schematic you'll see it basically is the 5E3 with a single channel. It sounds much like the 5E3 even with the 10" speaker.
Marc

Ahh, yes, the Harvard is what I was thinking of when I posted Tremolux in my post above. The Harvard is a good example to work from.

[Blindog]

Thanks for the replys guys.

hasserl, that does make more sense now. I was just a bit confused as to where the grid and plate of the other half went. I had my ideas, just wanted to be sure. If you look at my schematic, I think I have my Volume and Tone wired like the bright channel of the 5E3 already, no? I agree with you about mixing in the other half and leaving it on all the time, especially since I 'm out of real estate for another pot!. Though a mini toggle would be cool also. I still would like to see it in a schematic (pretty please Bruce) Marc, I'll check out that tweed Harvard schem...thanks for the info.

Mark

[Blindog]

I checked out the Harvard. That's kind of how I have it now (just one triode).
What I'm really after is utilizing the other half of the 12AY7 so I can still get some of the vibe that 5E3 has (the channel interaction) That's why Bruce's idea is appealing to me, if I can get my brain around it!

Mark

[tubeswell]

I have found out by painful experiment, that the road to complicated things can just lead you back to simple things.

Why not try set the two tridoes in v1 up so that they can either be run in parallel or separately jumpered together with different cathode/plate combinations?

[Blindog]

Now that makes sense! So you are saying maybe a switch to togglethe unused half parallel (with shared cathode as is right?) and another to switch in a different cathode bias cap/resistor combo? I wouldn't have to add another bypass cap or mixer resistor, correct? Just add anothe 100k plate resistor? Thanks!

Mark

[hasserl]

I looked at your schematic, I don't see where you'd get the "extra" triode.

[Blindog]

In my OP I noted that I changed the 6J5 to a 12AY7. Haven't had time to redraw the schematic...sorry 'bout that!

Mark

[hasserl]

In my OP I noted that I changed the 6J5 to a 12AY7. Haven't had time to redraw the schematic...sorry 'bout that!

Mark

Oh, I missed that. That's what happens when you skim thru things instead of taking the time to really read them.

[Bruce / Mission Amps]

The 6V6 SOULKICKER

By rote memory, here's a quick sketch of my old 1994 (hard to believe it was that long ago) 6V6 Soulkicker amp.
Where I put variable values for parts.... is where "you" tune your own amp to taste.
The cathode switch, on the bottom of the other triode, is so you can engage it as you want.
If you allow different values for the plate load resistor, coupling .01uF to .1uF cap and the .68uF to 22uF cathode bypass cap (and or 1k5 to 2k7 cathode biasing resistor) on the switched triode, you can stagger tune these preamp so it sounds like two different preamp stages mixing/running into one driver and power stage.
If you want a little more channel isolation, use a 220K resistor after each coupling cap before the volume control.
Also, with the addition of 220K to 270K mixing resistors, you can later put a little 360pF to 1000pf cap across one of the 220K mixing resistors to get a little more high end sizzle grit into the mix, with respect to one stage over the other. Again, tune the switched preamp triode to taste...
As drawn, you can wire the volume and tone control like a brownface Deluxe or the other way around, like a tweed 5E3 Deluxe but use a 500K audio pot.
I preferred a 1M a volume pot wired as a brownface Deluxe in the Soulkicker amps...

[Blindog]

Bruce, thanks a million. Sometimes I just need to see it to understand it. I just hate to leave that other half of the 12AY7 hangin' there unused in my project. Dumb question: Am I connecting the 2 grids of the 12AY7 together? It's not drawn, just want to be sure. I'll get to working on this and report back!

Thanks again,

Mark

[Bruce / Mission Amps]

Bruce, thanks a million. Sometimes I just need to see it to understand it. I just hate to leave that other half of the 12AY7 hangin' there unused in my project. Dumb question: Am I connecting the 2 grids of the 12AY7 together? It's not drawn, just want to be sure. I'll get to working on this and report back!

Thanks again,

Mark

Ah... oops, yes. I just assumed you knew that.
I made a change to a new file to show you a different way to mix the two channels together as I mentioned in a previous thread....

[Blindog]

Thanks Bruce. I just wanted to be sure you were not doing anything other than tying them together. Thanks for the help!

Mark