EF86 Modern Classic tones

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Bieworm
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Re: EF86 Modern Classic tones

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With the stupid MV on 10 you won’t hear it’s there. But use shielded wires to implement it.
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Re: EF86 Modern Classic tones

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AleS wrote:
Sat 01/14/23 7:46 am
Thanks both for your input and expertise! I've seen that MV often implemented as either a or a click to turn push pull on/off pot, which should mean the original character can still be there. As Josh mentions, it's such an easy add on that I recon I'd just have it there to begin with and see how much use it gets, most chassis have multiple pot holes anyway and I'd probably wait before ordering a faceplate until I'm happy with what I've got.

Another pair of schematics I've started looking at are the EF86 Lite 2P and the Trinity TC15, both of which again use the EF86 and tweak the power amp into a Voxy direction: files/JMPGuitars_18W_EF86_Lite_2P_Schematic.pdf | https://www.trinityamps.com/wp-content/ ... tic-v9.pdf

Josh, out of curiosity - looking at the EF86 Lite 2P, I see the infamous 220k grid resistors are there - any specific reason why? Did the amp come out better suited for a slightly more headroomy vibe or is that implementation of EF86 preamp saturating more than a regular 18w, thus needing less power tube push?
The Lite 2P is the single preamp tube version of the EF86 Xtra. I forgot I posted that one lol. All the values are based on best tone and performance for the tube. That's a great circuit. You can use it as channel 1 of a 2 channel amp if you want.

I'm not sure why grid resistors would be infamous?
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Re: EF86 Modern Classic tones

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JMPGuitars wrote:
Sat 01/14/23 11:06 am
You can use it as channel 1 of a 2 channel amp if you want.
That's definitely looking like a good option, though I might adopt the matchless-style rotary tone control
I'm not sure why grid resistors would be infamous?
A few searches on the forum suggest some people definitely don't like how 220k lessen power tube saturation and "weaken" the sound by reducing distortion vs stock 470's - understandably not everyone's cup of tea, but a successful choice in many designs and definitely, at least on paper, one that aligns best with my goal :)
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Re: EF86 Modern Classic tones

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AleS wrote:
Sat 01/14/23 4:14 pm
JMPGuitars wrote:
Sat 01/14/23 11:06 am
You can use it as channel 1 of a 2 channel amp if you want.
That's definitely looking like a good option, though I might adopt the matchless-style rotary tone control
I'm not sure why grid resistors would be infamous?
A few searches on the forum suggest some people definitely don't like how 220k lessen power tube saturation and "weaken" the sound by reducing distortion vs stock 470's - understandably not everyone's cup of tea, but a successful choice in many designs and definitely, at least on paper, one that aligns best with my goal :)
Use whatever tone knob floats your boat. 😉 If you do the fancy rotary and don't like it, you can remove it and save it for something else. For that section, I typically do the tone knob components on the knobs, so the board isn't effected really if you change it up.

Ohhh, you meant 220K on the power tube grid reference resistors. Do the 470Ks and the 1M pot. Figure out what you like best if you find yourself staying in a specific point on the pot.

In the docs, I do the 220K on the power tubes with an EF86 preamp, because that's how the Vox style stuff here was done in the past. You can try 220K, 330K, stick with 470K, or do as I mentioned previously. It doesn't matter. Tweak to YOUR taste, and let everybody else have their own opinions.
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Re: EF86 Modern Classic tones

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JMPGuitars wrote:
Sat 01/14/23 4:54 pm
Use whatever tone knob floats your boat. 😉 If you do the fancy rotary and don't like it, you can remove it and save it for something else. For that section, I typically do the tone knob components on the knobs, so the board isn't effected really if you change it up.
Great point about making sure the components are off the turret board, and one I'll keep in mind when looking for layouts. The rotary job looks good to me as removing the lower frequencies and the chimey end should also allow for a slightly cleaner sound for full jangle :)

Quite a few layouts do have the tone off board, including that of Steve Luckey's dual lite which I'm pretty set to use: https://sluckeyamps.com/dual_lite/dual_lite.pdf

What I like about it is that it offers two different flavours while keeping the parts count low. I will however repopulate the schematic, tweaking a few values and target voltages that should work well with more standard transformers (his design's starting point is repurposing an old Hammond amp transformers). The Lite IIb, EF86 Lite 2P and Trinity TC15 will be what I'll look to adopt from.
Ohhh, you meant 220K on the power tube grid reference resistors. Do the 470Ks and the 1M pot. Figure out what you like best if you find yourself staying in a specific point on the pot.

In the docs, I do the 220K on the power tubes with an EF86 preamp, because that's how the Vox style stuff here was done in the past. You can try 220K, 330K, stick with 470K, or do as I mentioned previously. It doesn't matter. Tweak to YOUR taste, and let everybody else have their own opinions.
Just to clear this one in my head - in order to make the value of the PT grid ref resistors effectively variable as you say, would I need a dual gang pot MV or would the 1M single gang wired as a variable resistor work as well?

Either way it's such a simple addition that it seems worthwhile, especially if that means I can effectively have both values available. It should also be somewhat "educational" by making the difference between the two variants tonally audible. More in general, I like the idea of going for a nice, simple design like this as it should make it clearer how tweaks and mods change the character of the amp, probably in a more straight forward way than a more complex design would.
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Re: EF86 Modern Classic tones

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Bieworm wrote:
Sat 01/14/23 8:00 am
With the stupid MV on 10 you won’t hear it’s there. But use shielded wires to implement it.
Will keep that in mind. Am I right in assuming the ground to which the PT grid ref resistors connect to would be an appropriate place to connect the shield?
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Re: EF86 Modern Classic tones

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AleS wrote:
Sat 01/14/23 5:33 pm
Bieworm wrote:
Sat 01/14/23 8:00 am
With the stupid MV on 10 you won’t hear it’s there. But use shielded wires to implement it.
Will keep that in mind. Am I right in assuming the ground to which the PT grid ref resistors connect to would be an appropriate place to connect the shield?
No, connect the shield to the back of the pot.
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Re: EF86 Modern Classic tones

Post by Bieworm »

JMPGuitars wrote:
Sat 01/14/23 6:31 pm
AleS wrote:
Sat 01/14/23 5:33 pm
Bieworm wrote:
Sat 01/14/23 8:00 am
With the stupid MV on 10 you won’t hear it’s there. But use shielded wires to implement it.
Will keep that in mind. Am I right in assuming the ground to which the PT grid ref resistors connect to would be an appropriate place to connect the shield?
No, connect the shield to the back of the pot.
+1 on that! I always do this. But for best results in not ruining your pots you should follow this procedure:
1. Turn pot fully clockwise. In case you burn the carbon strip it’s only on the far end side, where the wiper almost never comes.
2. Sand the back of the pot with a rough grid paper
3. Apply a drop of solder on the back of the pot
4. Solder the shield to that spot while holding it down with a needle nose plier or flat head screwdriver. This helps to do it in one (short) time, to avoid overheating the pot.
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Re: EF86 Modern Classic tones

Post by AleS »

More thank you's to both :)

Currently comparing values and voltages and a bit puzzled looking at this TC15 schematic from Trinity: https://www.trinityamps.com/wp-content/ ... tic-v9.pdf

Checking voltages at the EL84s, this reads 242V at the control grid and 384V at the plate - is this a typo and should assume g2 is probably 342?
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Re: EF86 Modern Classic tones

Post by JMPGuitars »

AleS wrote:
Sun 01/15/23 1:55 pm
More thank you's to both :)

Currently comparing values and voltages and a bit puzzled looking at this TC15 schematic from Trinity: https://www.trinityamps.com/wp-content/ ... tic-v9.pdf

Checking voltages at the EL84s, this reads 242V at the control grid and 384V at the plate - is this a typo and should assume g2 is probably 342?
You're reading it wrong. That says 242V at SCREEN grid, and 384V at plate. Plate voltage should be higher than screen voltage, but that's a lot bigger difference than I normally see. Not that there's anything wrong with that, if that's their goal, there may be a reason or sound they like. 🤷
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