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Stephen, have you thought about sticking a EF86 circuit in place of the normal channel of the sIII? I have found I use the TMB more than the normal channel (or have it jumpered) wondered if we could get a voxish tone out of the amp. There is an EF86 variation circuit that I got from 18Watt.com with various component values but nothing regarding the tone circuit, would a single tone pot work OK with an EF86?

Nigel

I have thought about it, but not pursued it yet. Here's some stuff to think about:




Just add the tone stack Volume controls of the sIII after Cc (Coupling cap).

I wondered if this would sound Voxy with the Marshall PI?

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Yes, that's the diagram I was looking at. Steven suggested Mark Durhams Varja schematic and I am looking at the moment at combining the EF86 channel of that with the sIII TMB PI and output circuits. Don't know what the sound will be like but worth the experiment and I do have a Mullard EF86 awaiting a home
Nigel

If you were going to try Mark's Vajra, just do the EF86, dont change the Tone/Vol control. I think the Vajra EF86 channel controls are like the original 18 normal channel.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

can we some how add a ef86 to nigels phoenix desgin. for a vox tone ..

Here's another (if slightly self serving) idea. Why not build the TMB channel like the sIII One and add the EF86 channel to it. You could do it on a Trinity 18 chassis. If you don't want to bother with a footswitch boost, just put it on a DPDT toggle. That should leave plenty of room for the EF86. You'd also end up with a really versatile amp. The new chassis has plenty of room for the extra tube.

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Richard Johnson
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Playing an insturment doesn't make you a musician, listening does

I have decided to do the Vajra as is for the moment, it looks like an interesting design and I feel I owe it to Mark to do his amp justice.
Nigel

Alright, first of all hello to everyone on the forum! I'm another tube amp newbie and slowly building a combo sIII.

I've also been pondering about this EF86 normal channel modification. Last night I even made a test layout based on a schematic / layout drawing from the 18 Watt downloads section. I tried to make it so that there would be no need to modify the stock sIII board by adding turrets... but I'm not sure if it's even half correct as this is only my second amp build ever.

What do you guys think - is this of any use? Or if it's rubbish, perhaps we could together come up with a proper sIII EF86 mod?

I could at least do the layout drawing part.

OK, I'll play. I think the cap between the vol and tone after the coupling cap should be 470pf and the Vol should be 500K-A, you are right pins 7 and 2 go to ground. I might try this tomorrow in my sIII combo.
Nigel

Yes, it looks good except the 470p cap as Nigel pointed out. Which EF86 component values did you choose? Not Vajra anyway.

You might leave the Tone section of this channel as stock sIII though.

Good job working this out. Once it's on paper, it all looks clear!

In fact, on our new chassis, one of the extra socket holes could be for an EF86 switched option if you could find a place for the components.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Thanks for your comments Nigel and Stephen!

You are right about volume pot and the 470pf cap. I fixed those in the layout above and also changed the Cc / Cs to more Voxish values. The original component values were from the link below... no idea what amp they are based on though.

http://www.18watt.com/modules.php?name=Downloads&d_op=getit&lid=156

About the EF86 pins 2-7 - since this is just the internal shield, I take it would be fine to connect it to terminal strip center lug. No need to run it all the way to the bus ground, right?

-Antti (very happy)

Antti,

You could go to the centre lug, it would work. But if you get hum, be prepared to move them to the pre ground.*

*Personally, I'd do it that way from the start. Star grounding.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I know many people love the Normal Channel of the sIII, but what has been presented here is an option for some who want to experiment.
Antti started this so maybe he has a pic already and some comments.

Based on the sound of the EF86 on the TC15, an EF86 is a good option on the 18 watt. Not that it needs more grind/crunch/distortion. So, if you have a chassis with an extra hole in it, you can easily add the EF86 and make the modification. Or punch the hole yourself. Difficulty would depend if you want the Tone Contour rotary switch like in the TC-15 or a tone conttrol as on the 18 watt. The easiest is the Tone control.

People talk about old and new EF86, but I've only heard the old ones so I would use the schematic from the TC-15. I'll try to draw up a layout for an easy EF86 mod, with Tone Control and you can try it out if you want to.



Of course doing this mod will leave you with an extra Triode...

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Stephen
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Not just here, but does everyone see a huge switch to EF-86 's. Seems like everyone is now designing the 86's, very cool.
Not to mention the great sound.
Jac

Yeah, they seem to be coming on strong lately. They do sound good if you get a good one.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

the 86 tube is the one thing I haven't bought yet. What constitutes a "good" one and where do you find one? And how much?
Thanks,
Jac

Look for an Amperex/Philips Made in Holland/Germany NOS . You should pay $20 or less. I got 2 'used' Rogers for $21 . They were made in Holland.

The other ones I looked for were the Telefunken.

The TC-15 I built used an old Rogers from an old SE amp I had kicking around.

The 'sarg' has EF86s, you could try him.

I hear you should stay away from the new ones but I've never tried them.

Of course, you could always score a MULLARD!

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Jac, I called Matchless the other week to see what they recommend. Dario-miniwatt, also from Holland.

Thanks, James and Coco

Doc Phil on 18-watt said to go after a brand called Valvo. There inexpensive, (right now) and even score mullards under that brand, so we'll see. So I'll look for the Roger's and the Valvo. Those Dario's seem a little high priced .
In the meantime I ordered an EH and Svetlana. Just to have something on hand Hopefully they're not microphonic.
I let everyone know, once I use them, how they turn out.
There's another point though Stephen, those "rings" you have around the 86. Are you including them in the kit or tell me where to get them?
Jac

The rings I had on hand. Got them from lbet who got them somewhere I cant recall. If I could find a cost effective source for them, I'd include them. but for now, no.
I'll check with lbet to see where he got them and then I'll corner the market !

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps