Single Channel 5e3

[gsr]

Hello,

I just completed my first scratch build. A 5e3 modified to single input channel. I found the concept on old threads in which Bruce was describing "split cathodes," and "stagger tuning." Hasserl posted an idea involving "blending" the split cathodes with a pot. The attached schematic is my interpretation. The amp sounds great, but differentiation on the blend pot is very subtle. While I may add a tone control after the volume, I would like to wring out a little more variation from the cathodes if possible first. I would greatly appreciate it if any of the many knowledgeable people here would care to take a look and advise.

Thanks, gsr

[cminor9]

I have experimented with this several times.

I have tried a LOT of the methods you have outlined. Bruce Collins posted one of his old schematics here in a similar thread and it was really helpful in generating some ideas. What I ended up with was basically an internally jumpered 5E3 (referencing how people will sometimes jumper the channels on a 5E3 with a patch cable).

I outlined the mod at tdpri.com, here: Tweed Deluxe Volume/Tone control mod - Telecaster Guitar Forum

What I like is that you can dial in a stock 5E3 tone, but also get something with a bit more sizzle. The only thing I lost is the channel interactivity (which did nothing for me).

[gsr]

Cminor9,

So the difference mainly seems to be, you are using the two volumes to blend the cathodes. Correct? Mine is set up like a "balance" control. Is the difference one of your volumes is tied to the tone control? Would tweaking some values improve anything for mine short of rewiring to two volumes and tone?

Thanks

[gsr]

A thought just came to mind. What would the effect be if the "Cathode Blend" pot was before the coupling caps?

[Bruce / Mission Amps]

Blender circuit

Try this instead:

[cminor9]

Cminor9,

So the difference mainly seems to be, you are using the two volumes to blend the cathodes. Correct? Mine is set up like a "balance" control. Is the difference one of your volumes is tied to the tone control? Would tweaking some values improve anything for mine short of rewiring to two volumes and tone?

Thanks

I am not blending the cathodes. I am blending the differently tuned triodes.

the tone control doesn't affect the volume, but it definitely has more effect on one channel just like a stock 5E3.

Personally, I don't think two tone controls are necessary. The first vol pot is the one I have set up more stock (more bassy). If I turn that up and the second vol pot down, it's pretty stock. I use it as a way to dial in some fatness

[cminor9]

Try this instead:

far be it from me to question your obviously superior knowledge, and you have helped me a lot...but why would you rather blend the cathodes? To me it seems like you need to make a more significant mod to the circuit (like adding another pot). You don't need a blend pot if you have two volume controls that you can use to blend with.

The mod I recommended doesn't add anything to the control panel, and it keeps the amp fairly stock (no holes to drill, and you can always dial in a classic 5E3 tone no matter how crazy you get with the other channel). It's basically hard-wiring a patch cable across the two channels. The fact that the two channels are tuned differently and that the cathodes are split is just a matter of preference.

Just wondering...

[RWood]

gsr,

I really like this idea of blended, mis-matched triodes. It's something I will try on a similar build that uses 6L6s (like a one-channel 5E5 pro).

Putting the Blend pot before the couplers would result in DC voltage on the pot, so that won't work. Bruce's version looks good except I think he meant for the couplers to come straight off the plates, not from the tops of the plate load resistors.

Another thing you could try if the different values you've shown here don't get you enough variation is to mis-match those plate loads. You could go 120K or even 150k on one, 81K on the other. that might be too radical, but that, in conjunction with the cathode resistor, will set the bias of the tubes farther apart and perhaps give you a wider swing between the tones.

You could also come out of the gate with a mismatched tube like a 12DW7 and drastically alter the characteristics, but I think I'd only resort to that after exhausting the possibilites with the 12AY7 or 12AX7.


RWood

[Bruce / Mission Amps]

The method I illustrated is exactly how I meant to do it.
I think you guys have the cathode and the plates mixed up in my artwork.
I promise your balance/blender control doesn't work very well to get what you want...
trust me, I've tried a bunch of circuits like this.

The output signal in mine comes from the plate of each stagger tuned triode... plate coupled.
The DC from the plates is blocked by the capacitors and the actual mixing occurs across the two, fixed value 220K to 270K mixing resistors... the blending occurs by sending part or all of one channel to ground before the mixing resistor.
With the linear 500K to 1Meg BLEND pot in the center position both channels are only mildly attenuated and most of the signal from the two stagger tuned stages goes right to the mixing resistors and onto the common volume control.
it is a very simple circuit....
You can do anything you want.... this is a way to do it with three pots that I know works 'cause I've done it.
Blender, Volume and Tone.

[cminor9]

The method I illustrated is exactly how I meant to do it.
I think you guys have the cathode and the plates mixed up in my artwork.

yeah, I didn't pay close attention. I had a different mod on the brain, looked at yours, and didn't really *see* it.

So that makes sense to me now that I have paid attention to the drawing, but I guess I still wonder why this is more effective? Is it because you are cutting one triode as you boost the other triode?

[Bruce / Mission Amps]

yeah, I didn't pay close attention. I had a different mod on the brain, looked at yours, and didn't really *see* it.

So that makes sense to me now that I have paid attention to the drawing, but I guess I still wonder why this is more effective? Is it because you are cutting one triode as you boost the other triode?

Yes.. well sort of... you are not boosting anything but actually sending the unwanted portion of your mix to ground on one side while the two 220K-270K resistors keeps the "wanted" channel's signal from going to ground.
The net effect is that it sounds like you are blending the two together...
There is attenuation to both channels but there is a lot of available signal to mess with that is almost unusable anyhow so the whole thing just ends up kind of working pretty good.
What I drew there the second time is actually very similar in all respects to my old Bluestone 16-18 watt 6V6 amp....

[gsr]

Bruce,

I implemented your "Blend" control and it works much better. I plan to add the tone control tonight. The only thing I need to clarify is, does the b+ still connect to the junction of the 100k plate resistors? So far, I have only altered my scheme after the coupling caps. I have left the 100ks as they were. Is this correct? Sorry to bug.

Thanks, gsr

[CitizenCain]

Is the blend control using one of the blender pots like Stew-Mac sells?

Our unique linear-taper pots controls the signal mix from two pickups or sources, panning from one source to another, with both signals full at the center detent.

STEWMAC.COM : Blend Pots

[gsr]

I am just using a 500k linear cts pot. At half way it is a little bit louder than at either end, but the circuit Bruce from Mission Amps kindly shared works well. You hear pretty much all one triode when all the way ccw-fading to both in the center position-fading to the other triode when all the way clockwise. My attempt at the start of the thread apparently did not attenuate one triode as the wiper was moved to the other triode. It makes sense, I wasn't sending it to ground. I'm on the big learning curve.

Afaik, those blender pots you refer to are used on mods on strats. I remember coming across them when my son was building a "David Gilmour Black Strat."

[CitizenCain]

Yeah, I used one of those Stew-Mac blenders when I modded a friend's guitar. Did away with the pickup selector and replaced it with the blender.

Seemed like it would work great in Bruce's circuit, I just wondered if it would hold up to the voltage. It sounds like the regular linear pot is working out OK for you though.

I'm really intrigued by this mod.