Anyone tried an 18w Lite with Vox cut instead of tone control?

[Jennings]

Anyone tried building an 18w lite type amp but substituted the tone control for a Vox-style cut control?  I'm tempted to mod my 18w self build, but wonder whether anyone's tried it and thinks it's a rubbish idea or not! 

My idea was that in a lot of amps I tend to have tone controls all full open, and control the treble/bass response mostly with the presence/cut control.

[sluckey]

I have a cut control on my dual lite amp. I also have the 18W Lite IIB tone control. Works fine and very easy to remove if you don't like it.

     http://sluckeyamps.com/dual_lite/dual_lite.pdf

[Jennings]

Wow, thanks for the heads-up on that one Steve!  I actually have a load of room on the board and chassis of my 18w build, so I might just turn it into a slightly bigger project and have the dual setup you've described! 

I already have a spare noval valve base drill in the chassis, just need a few more face plate holes (no big sweat) and I can site the channel switch where my second (low) input drill currently is.

Do you think I'll be able to stick with an EZ81 rectifier, or is it wise to go for the 5Y3 or even a GZ34?

[sluckey]

EZ81 will be fine. I only used a 5Y3 because the donor PT I used had a 5V winding. The channel switch is just a standard DPDT (ON-ON) type. Circuit board is surprisingly small and everything fits a 12-1/2" x 6-1/2" chassis with plenty of room to spare. You only need about 1" board space to add the EF86 components to an existing board. Here's the project with pics of my amp.

BTW, this is one of my favorites.

     http://sluckeyamps.com/dual_lite/dual_lite.htm

[Jennings]

Well I'm sold on the plan  

I need to grab a few parts, not least a couple of EF86 (this will be my first time of trying EF86s, bar playing the odd vintage combo years back) but I've got most bits to hand.

[Jennings]

Quick question...the 33k on pin 9 of the EF86 going to the channel switch...that's not grounded in the layout, is it?  Just tied to a floating post for connecting to the switch wire, right?

[sluckey]

Correct, the 33K resistor is not grounded. It's mounted to an insulated turret standoff. There is a ground lug at the base of that turret standoff that is used to connect a couple of the EF86 pins to chassis ground. The layout drawing doesn't clearly show this but I think the actual photo shows it better.

[Jennings]

Update:  Well I decided to follow the dual lite approach, and added the extra circuitry.  Slightly different layout, as I already had the 18w layout largely in place.  Although I renewed a lot of those components too while I was there.  I've used a few different cap values also, but it's largely the same.  Anyway...currently I get main power after flicking the power switch, but not a sausage after turning the stand by on (the donor 18w already had a standby stitch, so I retained it).  The EZ81 is known good...but to be sure I tested it on my Sencore tester.  I therefore decided to check the voltages, starting at the EZ81...all seemed ball park OK until I got to pin 3...almost nothing!  I mean like mV.  Weird!  What ball park voltage should I be expect coming out of the EZ81?  I tried a few ore good valves and also replaced the socket just in case of duff contacts...still mV only.  I'm sure I'll work it out soon, but it's stuck currently! 

[sluckey]

You should expect +340 to +350 VDC on pin 3 of the EZ81 when the standby switch is in operate mode. Pins 1 and 7 should be about 275 to 300 VAC, and across pins 4 to 5 you should have 6.3 VAC.

[Jennings]

August Update!  Finally got to knuckling down and completing the project!

I took my 18w clone, which was installed in a ply 1x12" cab with Weber 12A125A, and reworked the additional parts of the Dual Lite design into the existing layout.  Luckily I had a spare hole punched in the chassis anyway for the additional EF86, and enough room on the original 18w board for the other components.  I also had plenty of chassis front panel space for the additional holes and controls with almost no drilling. 

I did deviate slightly from sluckey's Dual Lite design...I retained the 18w amp's EZ81 rectifier, and I used the original AC15's filter cap values...just because I like the feel of low filtered amps.

After a period of work, summer holidays and head scratching with a wiring issue that was eluding me, I finally finished building and trouble shooting, and I've reinstalled in the cab.  It's my new favourite amp!!!  Both channels give a nice range of sounds, with plenty of flavours to suit styles, different guitars and volume settings.  Thanks to sluckey for the suggestion, for sharing the layouts and design, and for the assistance with the build questions.  I'm over the moon with the way it's turned out, and it's so much better than my original idea when I started the thread.  Hope you enjoy the couple of completed pics, and mid-build gut shot to show how I was fitting the parts and additional valve into the existing build.  Oh, and my paired up components to account for values I didn't have!  Haha!!!  Now all I need to get round to doing is working up some kind of control panel rather than the Dymo labelling!

[sluckey]

Good job! Sharp looking cab too. I use a Dymo label printer too. I'm fond of black on clear tape.

[dude]

I too love 18 watt amps and often they can be overly bright, I have a cut control on two of my 18 watter's and it helps control a strat's top end.


I like a 5Y3 too, a lot of O35 Hammond reverb chassis are perfect for 18 Watt Lites. Lately, the prices are climbing crazy on ebay but I guess when you think about it though you get the chassis, PT, OT, rectifier tube and all the other sockets. it's perfect for a lite. You might want to add a 2 watt bleeding resistor on the power supply. Didn't see it on you bd, drains the voltage fast when working on the amp. I once got Zapped with 340 volts working on an old BF Bassman head, I even shorted the filter but they have a memory. Voltage went in one arm out the other, right through my heart, probably the closest I came to death. After I got zapped, I checked the cap, 340v, so I put a bleeder in all my amps that don't have one.


take care,
al


al

[Jennings]

Thanks guys!  I'm really pleased with the results...though I can't claim the glory myself for the cab!  That's the work of a guy called Chris that's recommended by a well known UK home-build amp kit supplier!  Most of my amps now reside in cabs from him.  Good point on the bleeder resistors and amp safety...I did get a belt late one night from an old 60s Bassman head I was working.  That taught me to go easy on the wine when working on amps!  I'm very careful these days!