30 March 2012

Laney Build Clips


So I've been on the nightshift stopping the Gremlins from getting wet and eating after midnight before climbing up inside your TV's.

One night before I went off to work I decided to record a clip of the amp. I haven't mastered this art yet, so I took a picture of what I ended up with. An SM58 slung over my cab, going into a cheap iUSB audio in/out for my mac, and I recorded directly into garageband with zero effects. The photo shows the settings used for the later half of the clip. You can hear me playing sloppy (sloppier than usual anyway) throughout. Mainly because at the start I'm messing with my guitar volume and then other nonsense while worrying about being late for work.

Guitar I used was my Japanese Charvel Pro Mod.

29 March 2012

Let me introduce you to Swirley Shirley!

Here is a little something that I am going to be putting together over the next few months.

I got the body from Out of this swirled. I looked at it on the website for a good while and then just bought it as I noticed they are closing down and I didn't want to miss out.

This is going to be a more rock oriented guitar as my others are very metal so this will be a nice change.

Its American Red Alder and I am planning to pair it with a Kramer classic replacement neck with the beak style headstock.

The neck will be a single piece of flame maple with black dots for fret markets.

I will probably grab a set of custom Bulldogs for this also as there isn't really much else on the market that appeals to me or is good value for money.

I have also decided to load this with a Kahler trem which is going to be another new experience for me as i've strictly used hardtails & FR type trems in the past.

I am just about to pack the body up to send it off for clear coating and hopefully I will have decided on the neck spec and have it on the way by the time I get the body back.

InMadOut Transformers - Soldano Replacements.

This post is a follow on from the heavily modded SLO post which can be found here.

I had a few reasons for choosing these transformers. The main one being that I am building this amp around a dual KT88 Power section and these transformers are perfectly specced for the application.

These were made to order and had a very short lead time of around 10 days which is another fantastic reason to use these.

There was a bit of the impregnation resin on one of the endbells which I cleaned off but it also took a bit of the black paint off too so i'm possibly going to dissasemble these and spray them matte black.

The power transformer is an absolute beast!

So now all that i'm waiting on for this build is the chassis & a headshell that I am getting custom made.

Hopefully there will be more posts soon.

22 March 2012

Last of the Laney Issues...

So last issue in the Laney has been solved. It needed the use of an oscilloscope but it got fixed in the end. Cheers to JPF Amps in London for help fault finding this last bit. The problem was that when the Middle pot was turned to 0 (wiper to ground) a rather noisy hum came through the speakers. Quite loud. This turned out to be caused by the impedance of the wire to the Master Volume wiper forming a resonant circuit with the grid capacitance of the gain stage it was fed into.

The solution was a grid stopper. Grid stoppers are awesome. They protect against various nastiness in amplifiers. The SLO uses large value ones around 470Kohm, but they can be as little as 10Kohm. I went for 15K here at the suggestion of Frank at JPF. Problem solved.

Here is an artists impression of a grid stopper preventing bad things happening to the grid of a gain stage.

The original pots I used turned out to be shockingly poor. I used the Bourns pots available from Tubetown.de. TubeTown sell a lot of great stuff and are super reliable and helpful. The Bourns pots are also kind of expensive, but the Alphas are more robust. I prefer CTS in general but they seem hard to locate in certain values. In the end I went right over the top and got hold of some Clarostat mil-spec conductive plastic 2Watt pots. This meant I had to redo the tone stack board... here is version 2!

You can see an extra hole I popped in before I realised I could get away doing it neatly with just 2 turrets and some bus wire. The wiring needs to be tidied up, and some grid stoppers added, and then hopefully this will come gigging with me! Fingers crossed!

7 March 2012

5150 / 6505 IEC Installation

Here are a few good reasons why an IEC socket is a good thing...

LOOK AT THAT! The mains chord has actually pulled out of the grommet that is meant to hold it in place. The grommet no longer actually holds the cable steady enough at all. The strain of anything pulling on the chord is being taken by the LIVE wire soldered to the fuse holder, and the SAFETY EARTH soldered to the chassis.

The yellow/green wire (Earth) should be longer than the Live and Neutral wires so that in the event of any cores of the mains cable breaking inside the chassis (Say for example some Goomba comes and yanks that cable so hard it breaks at the solder connection, probably at the live wire) the safety earth will always be the last thing attached or at least be the last core to break off.

The other issue I have with the 6505 at least... is this plug adapter.

It's HUGE and you HAVE to use it because under there is a 2 Pin European style plug with no fuse, that you can't remove from the amp because the mains cable is fixed. This makes it really annoying to carry your amp around and even if you use a flight case, you always have this brick attached to your amp.

Most techs are probably gonna charge you a bunch of doubloons to fit an IEC but it's a quickish job and will save you a lot of hassle and potential death.

Step 1: Get rid of the grommet and cut the mains lead leaving enough wire on the fuse holder, voltage switch and earth to go back to the IEC. (Not really major surgery!)

Step 2: Best way to make a hole for the IEC is with a sheet metal punch. These are expensive, but if you can borrow one (like me) then its cool. A tech should probably have one for doing stuff like this. I removed the fuse holder because it was in the way simply by unsoldering the wire going to the mains switch from the back of it. You line up the cutting side of the punch and then assemble it again, and use a wrench to tighten that big nut which in turn pulls the cutting part through the metal. BEAST!

Step 3: Get your IEC socket, mark the holes for mounting it, drill em out.

Step 4: Install the IEC and wire it up making sure you get the wires back on the correct pins! This IEC would have stuck out a tiny bit at the top and bottom of the chassis where the metal curves around. For this reason it was mounted at a slight angle so it could be fixed in a solid fashion with no bits sticking out to snag on anything.

And thats it! Throw that massive old mains plug away and get a nice kettle lead. Stop worrying about the Live wire breaking because a Goomba yanked on it. Don't let a tech tell you that doing this is a major operation. Actually... to be fair... if you try and do this with a drill and a file instead of a punch, it IS a major operation and you'll get metal filings in your amp... so screw that!

3 March 2012

Last Witness

So... I've been messing about with the Last Witness 6505.
You can check out Last Witness by CLICKING HERE

The first cool thing about this amp, is the 'Witness' on the front.

My man Sykes brought this to me for an Adjustable Bias mod. Here is the 'before' shot. That little resistor is going to get sliced out of there, and then we'll bang in a trimpot and another fixed resistor. The trim pot allows the bias voltage to be adjustable, while the fixed resistor acts as a safety device. These amps are biased notoriously cold and this is a pretty common mod.

This is it. Job done. The trim pot and resistor are joined in a way that stops a total break in the circuit should the wiper in the pot become disconnected. This means that the bias voltage won't vanish and your valves won't fry. It's a bit awkward to get in there, but you just need to be careful and use insulated tools, and watch your fingers. That big black tube is a high power resistor, and it has the plate voltage across it... which will make your hair stand on end if you touch it!

Now... another thing we found with this amp, was a bad valve. This valve has in turn blow one of the 100ohm screen grid resistors. After finding this some more surgery was needed.

100ohm is pretty low in value for a screen grid resistor, and since we've got the bias mod, changing to a more usual value of 470ohm for 6L6 valve types was definitely a good idea. We could even go up to 1Kohm but 470ohm should be cool. I also spotted the amp was running set for 220/230v, I'm guessing the switch was knocked at some point. If you stick ~240v into an amp set for 220v, you're going to get higher than expected voltages inside the amp. When you consider that some mains in the UK can be 250v (the legal maximum) you can imagine the problems this might lead to! Well maybe you can't... but be honest... doesn't look good does it? So putting the switch back to 240v and using 470ohm screen grid resistors with the adjustable bias, means this amp should be running a bit smoother and sounding like mini atom bombs are going off all over the strings on the axe whacked into it! Peace

2 March 2012

Laney... Down to the Ground

So.. here are some more photos.

Originally this amp was made using a system of ground 'nodes' strung together to the bus running through the middle of the preamp board.

After I proved the amp would switch on and work, I decided to convert this to something closer to a star system, but one that still included nodes based on the ground connections of the filter capacitors. The valve wizard website has a great PDF on grounding. Imagine being called 'Merlin'? Pretty cool eh? I have a friend who has the surname Wizard. I say friend, I don't like him that much but he has a cool surname (He's alright actually... I guess).

Comparing the two photos you can see the divided ground bus. Eventually individual wires connect the filter caps to a 'star' ground.

The input jack has a small cap to ground attached to it, which creates a low resistance path to ground for radio goblins carried along the shield of the instrument cable.

Put short... this is all that 'special sauce' that stops the hum gremlins getting wet or being fed after midnight.

Some of those wires in the photos are still temporary, and will get fixed when the pots are upgraded to Clarostat 2Watt Conductive Plastic mil spec types. This keeps the other kinds of Gremlins as cute Mogwais.