My 5F6A head build

[LeonC]

I haven't built anything in the Fender vein for a while and I've always had the itch to have a '59 Bassman style amp. But these days, I can't really get away with that kind of volume anywhere I play...and space on stage is typically at a premium at the little joints I play (and unfortunately weight is gradually becoming more of a concern as well). so I was thinking of building the amp as a head. I recently built a cab that has both as 2x10 and 1x12 baffle, which I really like, so I figured I could use that cab. Also, I had an extra chassis from a recent Supro-type project. It's a little small but could be made to work...and I already had a head cab that I could mount it in.

So I set about planning out the layout. I decided to make it a lot like the original...but not identical. For one...why would I want a ground reversal switch? I see all the repro chassis are made with this, like the original...but it seems like a useless waste of space. And as space was at a premium, I decided to move the fuse to the bottom of the chassis, where there is a bit more room. I also decided to get rid of the dog-house and mount the filter caps on the board...and try to ground them with the sections of circuit that they serve.

I also figured that a multi-tap output transformer would be of more utility to me than four-RCA-hole speaker output in the original design/layout. So I got to work. Ordered transformers from Magnetic Components (Classictone.net) and designed the control panel and placed an order with Sandy @ Precision Design in IN. (Chassis came from Terry @ Seaside.)

[img1296]http://www.chalnick.org/LeonsGear/Fende ... build1.jpg[/img]

[img1296]http://www.chalnick.org/LeonsGear/Fende ... build4.jpg[/img]

[img1296]http://www.chalnick.org/LeonsGear/Fende ... build7.jpg[/img]

[img1296]http://www.chalnick.org/LeonsGear/Fende ... build5.jpg[/img]

I should have taken some shots of the circuit board before I laid it out...but...oops Anyway, here it is filled up. I'm using a 15K bias resistor with a 50K trim pot.

[img1296]http://www.chalnick.org/LeonsGear/Fende ... /works.jpg[/img]

That was version 1. Sounds real good, very much what I was hoping for...you get those big, bold gorgeous Fender cleans but a bit tweedier than blackface...with a bit o grit as you edge it up past 1:00 or so. Between 2:00 and wide open, it starts sounding more like my old tweed Harvard...but massive. You never get a great deal of gain, more like mild classic-rock crunch.

All good...but man...this is one loud amp! And I missed the sweetness, softer-edged sound and responsiveness that I'm accustomed to from my cathode-biased amps (which is mostly what I use). So I decided to mod it with a switch that enables you to flip between cathode and fixed bias. So when you want to go cathode-bias, you must take the pair of 220K resistors coming of the PI and send them to ground. The bias supply circuit needs to be disconnected. The power tube cathodes must go to the bias resistor (and cap) and then to ground rather than going directly to ground. You can do all this with a DPDT switch--you can see the switch in the last photo.

I decided to mount it between the rectifier and first 6L6. Got this done last night. Works like a charm. I can hear the value of both settings but I suspect I'll be playing it cathode-biased most of the time. It takes on a somewhat more responsive, softer-edged vibe that's a bit easier on the ears; mine at any rate.

Well, only had time to demo it over the weekend before I got the cathode-bias switch in there. But I'm diggin it; sounds good to me in both modes. Sure can hear the early Marshall roots. Mostly Les Paul in this demo, but I've got a section with my Thorn R/S (strat type guitar) near the end.

Also, I didn't realize until afterwards it was biased really cold; I've subsequently reset the fixed bias to about 32mA and it sounds/feels much better there, IMO. Finally...I tried playing it through one of my combos that's loaded with a pair of 10" greenback. MAN!!! Fantastic sound. Like them even better than the golds with this amp. They attenuate the real high freqs in a very musical way, and are much less efficient...so for my needs, they're a better choice.

I'll do another clip with the new stuff soon. But for now...

http://www.youtube.com/watch?v=FHY2uPlDlI0

[xtian]

Very cool, Leon!

I find it really rewarding, after three years of building amps, to be able to improvise on a theme instead of just paint by numbers, as you've done here.

[LeonC]

Thanks! Yeah, that's exactly how I feel. The tried and true stock designs are usually great and often suit the needs of many...but it's so liberating to have progressed to a point where you can get in there make some adjustments that tailor the basic design to your particular needs.

[LeonC]

BTW, here's a shot of the head in the cab. It's a mashup of Supro-style mounting/construction (but I'm using inset-nuts and machine screws rather than wood-screws ) with mid-50s two-tone Gibson aesthetics, LOL.

[img1296]http://www.chalnick.org/LeonsGear/Fende ... /above.jpg[/img]

[billyz]

I really dig the cosmetic design of your cabinet. Especially the curves and the two tone. The gold piping adds . Who did the logo manufacture , may I ask ?

[LeonC]

I really dig the cosmetic design of your cabinet. Especially the curves and the two tone. The gold piping adds . Who did the logo manufacture , may I ask ?

Thanks man. I had Sandy @ Precision Design in IN do the faceplate and she did my "Tonester" badge too. She's great to work with, fast, and reasonable.

Took me a while to figure out how Gibson's cab makers did the tolex around the corners so that there's no visible seam...you do it by folding the front edge over the side and then slicing with a razor down the side, cutting off the excess. If you're right up on it and you look real close, you can see the cut..but from a few feet back...damn near invisible

[img1296]http://www.chalnick.org/LeonsGear/Fende ... _angle.jpg[/img]

[roadkingbluzs]

Matching speaker cab, please! Very, very, nice.

[LeonC]

Yeah, got it.

[img1296]http://www.chalnick.org/LeonsGear/Cabs/2x10_front.jpg[/img]
[img1296]http://www.chalnick.org/LeonsGear/Cabs/2x10_rear.jpg[/img]

That's the cab I'm using in the video at the bottom of the original post in this thread.

[roadkingbluzs]

Dang...you good. SWEEET!! Thank you

[RB]

Sounds great and I love the aesthetics - very classy and classic vibe.
Just a great job!

Regards Randy

[LeonC]

Thanks gents. It'll get the acid test tonight--gigging with the band. Looking forward to it.

[ToneMerc]

Sweet looking, sounds meets art.

TM

[martin manning]

Looks great Leon!

[cbass]

Looks sweet! I'm scared of tolex I'm afraid I'll glue it over my face and suffocate or something worse.

[LeonC]

Thanks guys.

cbass--I'm just using that white tolex glue that CED and Mojotone sell. Stuff is really easy to deal with, FWIW. The best stuff though, IMO, is this similar white, rubbery glue called Wilsonart H2O...but I can't find it around here anywhere. The was even easier to use (and worked better, IMO) than the mojo/ced stuff.

Played this amp with the band last night. Unfortunately, we had a keyboard player subbing for our regular guy. Showed up w/o any sound reinforcement so he was blaring away through the PA all night. It was a constant battle. Uggh...but from what I could hear of it, the amp sounded great. I'll be trying it again next week...