And Now for Something Completely Different- new "British" Project to begin shortly

[TelZilla]

OK, this may be a little premature, but I got some stuff in the mail, and just couldn't wait to start a "my new amp" thread.

Got a box from Mojo, and inside was the beautemous combo below. Tasty...

So here's the general plan:

~Matchless Spitfire circuit (2x12ax7 pre, 2xEL84 power, GZ34 recto, vol/tone/master)
~Warehouse Green Beret Speaker (Greenback clone)
~Marshall 1974x ("18 watt")style combo cab- red tolex, cane grill

I don't have all the parts yet, but that picture made me salivate, and I wanted to share my sickness with my fellow addicts.

I'm going to be drilling the chassis meself, and tolexing too, so I expect this will take me forever. I was going to build the cab too, but I found a dude who would do one for $145 shipped, so I figured I could delay my introduction to woodworking. Hopefully the thing will be good. I think it's lap jointed, but hey, it was cheep.

Anyway, stay tuned for the usual series of dumba55 questions and laughable mistakes!

PS-I'm already dreaming of this thing and my 5e3 run in stereo, and maybe the 5f1 too in tri-eo or whatever it's really called. Oh lord, it will be good.

[marshman]

Why master vol?

[TelZilla]

Originally Posted by marshman

Why master vol?

Why not? Are you with the tweed police?

1. That's what the circuit of the Matchless Spitfire calls for
2. I have 2 non-master amps (5e3 and 5F1), and I'm interested to try something different
3. If I hate it, I'll take it out

[celeste]

Cool build, and above all have lots of fun.

[marshman]

Tweed Police--good one!

Naah, I was just wonderin'...a few years spent hangin out at other forums where Master Volume is a dirty word had me wonderin' thasall.

I have 1 real MV guitar amp and one real non-MV gitar amp, and I like the tone of the non-MV amp better, but my skills with the vol knob are not yet sufficient to gig with it, I gotta have me some footswitchable crunchiness. I'm not all that familiar with the Matchless amps--is it one of those deals where the MV is removed from the circuit when dimed?

I'd still love to be able to play such that all I need is a 20wattish Champ.

And so far, despite the much higher likelihood of death by electrocution, I still fear the woodworking much more than the electronics in an amp-building project. Guys with the right tools can knock out a cab in no time flat for a fistful o' dollars, but I'd need a forest and a chest of tools to do it right.

Enjoy the project!



Tweed Police, indeed!

[ThermionicScott]

I'm here to make a citizen's arrest...












Nah, this is going to be awesome. From the schematic, it looks like a really simple, straightforward tone machine! I don't have much experience with 2xEL84 type amps, but if the thought of building in a fixed-/cathode-bias switch had occurred to you, it's most convenient to build those in from the get-go.

- Scott

[TelZilla]

Originally Posted by Scott S

Nah, this is going to be awesome. From the schematic, it looks like a really simple, straightforward tone machine! I don't have much experience with 2xEL84 type amps, but if the thought of building in a fixed-/cathode-bias switch had occurred to you, it's most convenient to build those in from the get-go.

- Scott

Hmmm- I had thought mostly about a switch for tube/solid state recto, but that might be interesting too. Got a schematic or anything that might point out the general architecture?

[JohnnyCrash]

Originally Posted by TelZilla

Hmmm- I had thought mostly about a switch for tube/solid state recto, but that might be interesting too. Got a schematic or anything that might point out the general architecture?

IDK how much sag you'll notice. The higher voltages when in SS on the other hand may make more noticeable headroom differences.

As far as fixed versus cathode biasing - a DPDT switch should be enough to:

Fixed bias: ground the EL84 cathodes, pull the 220k grid leaks from ground and apply negative bias voltage to them instead.

Cathode bias: put the cathodes on their 120ohm/25uF instead of ground (grounded when in fixed), and ground the 220k grid leaks instead of feed them the neg bias voltage.

In the end it depends on the sound you're looking for. I'd stick with tube rect and cathode biased for a meaner amp at lower volumes, but with a MV I tend to prefer fixed bias, SS rect, huge filtered machines. Why? Master volumes give you control over gain, but not overall response - which I personally like for high gain pre's with big bottomed power sections - I like finding the sweet spot between the MV and the Pre with a chasm of Bass below it. Lower watt amps on the other hand have nicer touch dynamics and cathode bypass lowers headroom while a tube rect gives it some more give-and-take when finding sweetspots on the volume knob.

Everyone is different, so you might as well put both switches in so you can play with all the options - put em somewhere hidden from the front panel... flipping rectifiers or bias methods on accident while the amp is running will not be too fun, plus if you don't like them and tear them out, it won't leave visible holes :)

[TelZilla]

Originally Posted by JohnnyCrash

IDK how much sag you'll notice. The higher voltages when in SS on the other hand may make more noticeable headroom differences.

As far as fixed versus cathode biasing - a DPDT switch should be enough to:

Fixed bias: ground the EL84 cathodes, pull the 220k grid leaks from ground and apply negative bias voltage to them instead.

Cathode bias: put the cathodes on their 120ohm/25uF instead of ground (grounded when in fixed), and ground the 220k grid leaks instead of feed them the neg bias voltage.

In the end it depends on the sound you're looking for. I'd stick with tube rect and cathode biased for a meaner amp at lower volumes, but with a MV I tend to prefer fixed bias, SS rect, huge filtered machines. Why? Master volumes give you control over gain, but not overall response - which I personally like for high gain pre's with big bottomed power sections - I like finding the sweet spot between the MV and the Pre with a chasm of Bass below it. Lower watt amps on the other hand have nicer touch dynamics and cathode bypass lowers headroom while a tube rect gives it some more give-and-take when finding sweetspots on the volume knob.

Everyone is different, so you might as well put both switches in so you can play with all the options - put em somewhere hidden from the front panel... flipping rectifiers or bias methods on accident while the amp is running will not be too fun, plus if you don't like them and tear them out, it won't leave visible holes :)

Ahh, an amp project starting and a post from J Crash- not bad for a Monday morning.

Lots to chew on there, JC. Let me respond , and see if any questions result:

As far as mean amps at a low volume, I've got a 5e3 and a 5F1, so I think I've got that covered (open G+tele+jumpered 5e3 with all 3 knobs halfway=heaven). Theoretically, this is going to be my "clean amp", but I'm not going to be playing super duper clean. "Bold as Love" is about as clean as I need.

As far as building in mods, I'm sort of of two minds: on one hand, I'm all for flexibility, and to have the bias option and the recto option would be cool. On the other, I'm sort of thinking I might just get it going "stock" before adding additional gew-gaws. On the other other hand, it would probably be easier to put in the stuff while I'm figuiring out a tidy layout as opposed to cramming sh1t in after the fact. So we'll see.

I have all my tolexing/grillclothing time to contemplate. No rush on this one.

A did want to ask for a little clarification on this sentence:
Master volumes give you control over gain, but not overall response - which I personally like for high gain pre's with big bottomed power sections - I like finding the sweet spot between the MV and the Pre with a chasm of Bass below it.

What do you mean by "overall response"? Are you talking about a lack of dynamics (e.g., my 5e3 can clean up just by hitting the strings softer)? Also, I don't think I'd call this a high gain pre- only 2 12AX7's in the pre. A Matchless Lighning has 3, and it's still no metal amp.

Anyway, thanks for the reply. This should be fun...

[JohnnyCrash]

Originally Posted by TelZilla

A did want to ask for a little clarification on this sentence:
Master volumes give you control over gain, but not overall response - which I personally like for high gain pre's with big bottomed power sections - I like finding the sweet spot between the MV and the Pre with a chasm of Bass below it.

What do you mean by "overall response"? Are you talking about a lack of dynamics (e.g., my 5e3 can clean up just by hitting the strings softer)? Also, I don't think I'd call this a high gain pre- only 2 12AX7's in the pre. A Matchless Lighning has 3, and it's still no metal amp.

Anyway, thanks for the reply. This should be fun...

In generalities, preamp gain reigned in by a master volume still does have some dynamics and response. What I mean is that the on-the-edge sound is more dynamic on amps running closer to full-open on the volume.

You can do this with MV amps by cranking the Master and slowly turning up the Pre/Gain - it makes them essentially non-MV in that way.

My response was a bit off the cuff, general, and fueled by a lack of sleep, but I think you understand what I meant. Over-using Pre/Gain can make for a tastey sound, but for more of that give and take, a light touch on the Pre/Gain and a heavy dose of Master Volume works well.

A 5E3 is a primitive beast and can start overdriving very early on the dial. Some folks call their cleans "warm" others "gritty" and yet others "there is no cleans at decent volumes." This build should have more cleans for sure.

I'm a heavy music junkie, so I like more preamp gain than most folks :)

[TelZilla]

Originally Posted by JohnnyCrash

As far as fixed versus cathode biasing - a DPDT switch should be enough to:

Fixed bias: ground the EL84 cathodes, pull the 220k grid leaks from ground and apply negative bias voltage to them instead.

Cathode bias: put the cathodes on their 120ohm/25uF instead of ground (grounded when in fixed), and ground the 220k grid leaks instead of feed them the neg bias voltage.

OK, I'm sort of turning this over in my branium...

So this is for fixed, non adjustable bias right? So I don't need a bias pot in there anywhere?

Also, I know I should know by now what "apply negative bias voltage to them" means, but I can't remember.

[JohnnyCrash]

Originally Posted by TelZilla

OK, I'm sort of turning this over in my branium...

So this is for fixed, non adjustable bias right? So I don't need a bias pot in there anywhere?

Also, I know I should know by now what "apply negative bias voltage to them" means, but I can't remember.

I would make it adjustable. Only difference between fixed and fixed-adjustable is a trimpot instead of a fixed resistor.

The bias supply is negative voltage. Setting it up for fixed, adjustable - then setting bias at the trimpot will be fine. Your bias should stay put even after changing bias modes. By the way, I'm sure you already know, but the cathode/fixed bias switch should only be flipped when the amp is off.

[Tele-Dave]

Originally Posted by JohnnyCrash

By the way, I'm sure you already know, but the cathode/fixed bias switch should only be flipped when the amp is off.

Except on the 4th of July!!!!

[RodeoTex]

Well the tech talk got way over my head before I even saw this thread but I did want to congratulate on you tolex/grille choices.
I'll still be watching, still trying to learn something.

[JohnnyCrash]

Originally Posted by Tele-Dave

Except on the 4th of July!!!!

HAHAHA

I'll bring the hotdogs and gasoline, you bring the beer :)

[ThermionicScott]

Originally Posted by JohnnyCrash

By the way, I'm sure you already know, but the cathode/fixed bias switch should only be flipped when the amp is off.

Now ya tell me!

- Scott

[TelZilla]

Originally Posted by JohnnyCrash

By the way, I'm sure you already know, but the cathode/fixed bias switch should only be flipped when the amp is off.

What if I just flip it really fast?


Joking, only joking.

[TelZilla]

OK, I got a big box in the mail yestiddy from Tubesandmore, containing an aluminum chassis, 2 trannies, and a bunch of little electronic bits.

I've never used an aluminum chassis before- very light!

I have a question about mounting the PT. It's a giant honking Hammond thing (way heavier than the Weber one I've got in my 5e3), and currently has the adaptors on it to be mounted as a stand up:


I'm a little concerned about mounting it to my little 13.5"x5"x2" Aluminum chassis, which will be oriented like a Tweed / Marshall combo chassis. Any chance it will tear out the aluminum or anything?

I thought about cutting a big hole in the chassis and mounting it "flat", but I don't expect to have a ton of room in the box, what with a choke and an OT and maybe a SS/Tube Recto switch, etc.

I thought about cutting some kind of metal "straps" that I could put inside the chassis across the span between the PT screws, but I'm not sure that would do anything.

Maybe I can build a small shelf inside the cab to support the thing?

Since the Cab is gonna be 24" wide, mounting the chassis will be interesting anyway.

God help me, I do love it so...

[celeste]

Yeah, stress fracture can be a problem in aluminum. I use automotive "body washers". Big washer 1 1/4- 1 1/2" OD, 1/4-5/16" IDspreads the force out over a greater area and stabilizes the stress riser (the hole edge).

[ThermionicScott]

Get a piece of aluminum "angle iron" at the hardware store, cut a piece as long as your chassis, and mount it inside the chassis with two of the transformer bolts through it. That'll strengthen things nicely without adding much weight.

- Scott