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Guys .. some of you may remember that I built a Lightning head with added ef86 channel about six months back. I've finally built another one and it sounds GREAT! Here's a link to some pics:
http://www.18watt.com/modules.php?set_a ... _album.php
It's not hard to add this channel, and the Westlabs trannies can handle the extra current draw. The comment I've had from people that have played it is that "it sounds like two amps in the one package" .. and I agree with them.

Regards

Barry M

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Barry M

Nice build Barry. Looks very nice indeed. What schematic did you use for the EF86 channel? Was it Vox, Matchless or ?? Can you post it in case someone wants to add that channel?
If you have any details (layout , schematic) , I'd be happy to post them here.

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

Stephen .. you've got email! Essentially I used the old Vox AC15 values and Richie's 5e3 tone circuit (from the 18watt forum). I'm really happy with how it came up ..

Regards

Barry M

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Barry M

Wondering why you chose the design? What do you like about that channel sound?

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

I guess I wanted to do something a little different than the DC-30 and figured a Vox ef86 type preamp would work well, given that the power section of the Lightning & Vox AC15 are very similar. Furthermore, a few others over at the 18watt forum had done this with 18watt power amps; some going with the Vox preamp ef86 resistor/cap values and others using the DC-30 values. Initially when I built my first Lightning/ef86 amp, I was running a 22k resistor on the B+, with connection into the other side of the PI. The ef86 channel seemed to be a bit "buzzy" at high gain settings, so I connected it to the other side of the PI (same as Lightning channel). The voltage divider had the effect of dumping some gain and solved the buzz problem, but the ef86 channel had no real growl to it when driven. It was too clean. So, I connected it back to the other side of the PI and measured the B+ voltage after the 22k resistor - it measured around 360v, which I figured was too high. So, I put a 68k resistor there, which dropped the voltage to just less than 300v .. which made all the difference (no buzz but lots of gain). I went with Richie's 5e3 tone stack mod, mainly coz I've used it successfully on many 18watters and really like the tone sweep from the single tone control. I got a few guys to play it and got great feedback on the design .. so I've left it that way.

Firstly, the comment I've had from everyone that's played it, is that the two channels are VERY different - like two amps in the one package! Secondly, the variation in tone that is possible on the ef86 channel is astounding - the "cleans" are sweet, melodic and rich (in contrast to the crispness of the Lightning channel). At the other end of the scale, the ef86 has a sweet sustaining (slightly compressed) distortion (not at all "grainy" or harsh) .. it kinda reminds me of Brian May's tone.
But, more than anything, its the contrast between the two channels that works real well here - both are great in their own way ..

Hope this information is helpful ..

Regards


Barry M

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Barry M