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Old August 8th, 2009, 06:31 PM   #1 (permalink)
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Narrowed it down to an EVJ to Lite II 18 watt conversion

In my quest to get more headroom on the cheap, I've been all over the Internet looking for solutions. Here's the situation:

I play in a small/medium (200 people) church in our praise and worship band. I'm using a MIM Tele with a stock bridge pu and a GFS 'bucker in the neck. I play through a Digitech RP250 which then goes into an Epi Valve Jr. which is hooked up to a homemade cab with a used Eminence Lady Luck speaker. The 5W is better through the 12" speaker, but I want more clean.

I found these guys and they have two options I'm looking at, the Baby Will 18 watt conversion for the EVJ and the Superlite.

http://guitaramplifierpcbs.com/liteiib.aspx

I like the Baby Will, but want to do a hand wired version on a fiber board. I also found a layout for the fiber board here: http://www.silvatone.bravepages.com/...20II/Build.htm

The components seem to be all the same between the PCB version and the fiber board one. I can do this conversion for about $150, providing I don't screw things up too badly.

Questions: 1.) Is this a plausible job?
2.) How does the 18 watt compare to the 5E3 in terms of tone, headroom, etc.?

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Old August 8th, 2009, 07:03 PM   #2 (permalink)
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Originally Posted by Southpaw Tele View Post
In my quest to get more headroom on the cheap, I've been all over the Internet looking for solutions. Here's the situation:

I play in a small/medium (200 people) church in our praise and worship band. I'm using a MIM Tele with a stock bridge pu and a GFS 'bucker in the neck. I play through a Digitech RP250 which then goes into an Epi Valve Jr. which is hooked up to a homemade cab with a used Eminence Lady Luck speaker. The 5W is better through the 12" speaker, but I want more clean.

I found these guys and they have two options I'm looking at, the Baby Will 18 watt conversion for the EVJ and the Superlite.

http://guitaramplifierpcbs.com/liteiib.aspx

I like the Baby Will, but want to do a hand wired version on a fiber board. I also found a layout for the fiber board here: http://www.silvatone.bravepages.com/...20II/Build.htm

The components seem to be all the same between the PCB version and the fiber board one. I can do this conversion for about $150, providing I don't screw things up too badly.

Questions: 1.) Is this a plausible job?
2.) How does the 18 watt compare to the 5E3 in terms of tone, headroom, etc.?


1. You'd have to replace the VJr PT and OT with a set suitable for the voltage and current (PT) and push-pull EL84 pairs (OT) - transformers are expensive parts. You might be able to reuse some guts/parts for some of the other stuff.

2. I'd go with the Superlite. With other Lites you have few options for controlling volume when you inch it up for overdrive. You can't use a MV (unless you cascade the preamp instead of parallel it, then place a 500k or 1M pot between stages), VVR's can't be used -IF- you run into the common "18w buzz" problem, and PPIMV's don't really do much in such a small circuit (some folks call them).

The Superlite cascades one half of the preamp tube into the next (which is where the Gain control is placed). Afterwards it uses a plate-fed tonestack (which is where the Master Volume is placed). So Gain, Volume, and TMB tone controls always help :)

--

1. Is it a plausible job?
YES. Many people have converted EVJr's to 18w type amps.

SOCKETS/CHASSIS WORK:
You will have to drill the chassis for another EL84 and 12AX7 socket. If you go with a Superlite, you'll also have to drill the chassis for the added tone controls.

If it were up to me, I'd NOT use the existing socket holes (maybe use them for cap cans? see below). I'd move them farther back. It'll be easier to work on inside if you move the sockets.

INSIDE WORK:
I'd go with external cap cans for the filter caps, since there will be limited space inside the chassis.

I've used Turretboards.com's small universal turretboard (7" by 2.5") in smaller chassis where I didn't want to bother with drilling/staking my own board (I took a gut shot of one of my 18w Lite builds with this board if you want to see about how big it is).

You may need terminal strips or other smaller boards to get everything in there right.

--

2. How does the 18 watt compare to the 5E3 in terms of tone, headroom, etc.?

VOLUME:
It breaks up a little later on the dial than the 5E3, but is essentially about as loud.

If you want a tad more headroom, you could easily put a negative feedback loop into the PI's unused side (pretty much just a resistor from the output jack to the ground PI cap).

SOUND:
It has a more Marshall type of midrange and is MUCH smoother in the bass department (not all flabby/muddy like the 5E3).

The bass is even better if you go with solid state rectifiers (PLUS those tiny 1N4007 diodes also save more chassis room than using a tube rectifier and socket), and a larger filter cap in the first spot, with a giant EL84 cathode bypass cap (2200uF).

Also if you go with the Superlite TMB you'll have more toneshaping options.

Sounds like a lot, but its about the same trouble as converting a SE 5w into a PP 18w.

As always, BE CAREFUL. Read up on discharging caps and understand how and why this can be dangerous.
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Old August 8th, 2009, 07:08 PM   #3 (permalink)
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Here's a thread with some photos of my 18w Lite (actually a cascaded 18w Stout) where you can see how big that universal board is inside the chassis (compared to the tube sockets, knobs, etc - hopefully that can give you an idea of scale/size):

http://www.tdpri.com/forum/shock-bro...ml#post1970627
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Old August 8th, 2009, 07:38 PM   #4 (permalink)
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Johnny, I was hoping you'd chime in on this one, due to your knowledge base.

On replacing the PT: It looks like I can reuse the Version 3 PT from the EVJ, according to the Baby Will site. Is this a "barely gonna make it" solution or should I indeed go with a new PT. The OT needs replacing, of course.

Based on your comments about the Super lite, I think I'll go that route. I heard some samples on Youtube and they sound fantastic.

On cap cans: let me make sure I have this straight - cap cans are for the filter caps and allow more room in the chassis? Kind of like adding a closet to the outside of a house?

I appreciate your thoughts on this one! I got hooked on this amp tweaking stuff with the Bitmo mods (which aren't really much) and thought this would be a great next step. Muchos Gracias!
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Old August 8th, 2009, 07:39 PM   #5 (permalink)
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I just had a thought after I hit submit. Is the PT change suggestion for the Superlite or any 18 watt lite mod, in general?
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Old August 8th, 2009, 09:03 PM   #6 (permalink)
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It depends.

1. If the PT has enough current for two EL84's and two 12AX7's, it'd work.
2. If the voltage aint quite right, there's a few things you can do.

Voltage too low, will mean lower output and a bit more overdrive early on (it'll sound "browner").

Voltage too high, we can lower it a few different ways.

--

Does the PT have any specs on it? Do you have any info on the PT from Epiphone? All the VJR schematic shows is voltages (325 rectified is fine), not current/draw specs.

PLATE CURRENT:
Check tube data sheets for 12AX7's and EL34's.

1. The JJ EL84 spec sheets show 48mA plate current. Times two EL84's means 96mA.

2. 12AX7's show about 1.2mA each. Times two (2.4mA), plus the EL84's 96mA means 98.4mA minimum high voltage current required from a PT.

HEATER CURRENT:
1. The JJ EL84 spec sheets show 0.76mA plate current. Times two EL84's means 1.52mA.

2. 12AX7's show about 0.3mA each. Times two (0.6mA), plus the EL84's 1.52mA means 2.12mA minimum heater current required from a PT.

You always want to err on the side of more current available than draw you'll be expecting.

--

I know the EVJr uses a bridge rectifier on both the high voltage AND the heater tap, so you're likely dealing with a very inefficient PT. Using normal old rectifiers might result in LESS efficiency. So I'd stick with the Bridge rectification if you're going to chane this PT.

Edit:
I just checked the 'net and it looks like several people have rebuilt 18w amps into their Epi's, keeping the stock PT. There's gotta be some info on the rectifier situation and the PT's specs... but apparently its safe to use.
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Old August 9th, 2009, 01:36 AM   #7 (permalink)
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Okay, I'm getting a free education here, thanks!

I've been pouring over the stock schematic of the EVJ and some annotated pics on sewatt.com. It also looks like the Super Lite uses the bridged rectifier (according to the schematic on the site). I'm starting to wonder if I should just buy their 30 buck PCB, but I like the idea of using the eyelet board. Again, thanks for the tips and free advice.
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Old August 9th, 2009, 04:30 AM   #8 (permalink)
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Originally Posted by Southpaw Tele View Post
Okay, I'm getting a free education here, thanks!

I've been pouring over the stock schematic of the EVJ and some annotated pics on sewatt.com. It also looks like the Super Lite uses the bridged rectifier (according to the schematic on the site). I'm starting to wonder if I should just buy their 30 buck PCB, but I like the idea of using the eyelet board. Again, thanks for the tips and free advice.


Don't be afraid of PCB.

Most PCB's are labelled (whether that's for the assembly people or repair folks IDK), which is really cool. For building it becomes a connect the dots/color by number kind of project.

A lot of PCB's have thick boards, and thick copper leads. Even so, some hand built PTP/turretboard amps have smaller copper wires than some PCB's traces! Put it this way - your computer you're using right now is PCB construction (so too are practically all DMV, business/office, government, movie/art/recording computers - solid performance, no?).

Jacks and pots mounted to the board are obviously not cool, but if you're going DIY you can chassis mount them and make leads to the board.

When it comes to compact builds/designs, there are some I'd actually prefer were PCB for space issues... I could fit a ton into a small chassis. The new Vox Night Train is so small, yet loud and versatile (15 watts, TMB, Gain/Master) - you couldn't do something that small without PCB... after a ton of builds, I've come to appreciate PCB's perhaps for some of my own future builds (boards and etching materials are available at most electronics shops).

Plus, in this case, PCB might make the build a LOT easier.
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Old August 9th, 2009, 10:18 AM   #9 (permalink)
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Okie dokie, I'm going PCB for this one as I get acquainted more with tearing these suckers apart. Here's a quick shot of the Bitmo modded combo with my first homemade extension cab (pine, with birch ply baffle, vinyl bought from a fabric store for covering, and Mojotone hardware and grill cloth. Not pretty, but does the job).

During the build: Name:  Cab build 1.jpeg
Views: 315
Size:  10.2 KB

After completion: Name:  cab build 2.jpeg
Views: 282
Size:  10.5 KB

Crappy pics courtesy of my LG cell phone, so apologies are in order. Also, you can see my Tele (named "Steve" peeking into the shot).
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