The Fourteen31

Most of us have the luxury of living in a world where the overall power of an amp is a secondary concern. Performance venues are less and less reliant on massive backlines and more geared to controlled PA support. If an amp sounds great, stick a mic in on that speaker and run it through FOH. If it’s too loud, mic it off stage.

 

What this means for me is that it’s really all about tone. It is about asking “what is the fundamental character of an amp and how can that be captured and maximized?”

 

After building the 45 I became infatuated by the very different sound of an old off-model Silvertone combo amp – the Silvertone 1431.

This amp is the little brother of the 1432 and a close cousin of the 1482/1484, and because this was a “budget” amp, variants of the same amp were made by valco, airline and all of the other likely suspects. It has the same rough and ready sound that has made these amps the darlings of garage rockers and hipsters, but something caught my ear about the 1431 as unique – almost a chimey “vox-like” quality. 

It’s an odd duck. The original had a 6×5 rectifier, a 6v6gt power tube and a 6au6 preamp tube. The originals came with a 6″ or an 8″ speaker based on surviving examples. 

Silvertones are a study in contradiction. They generally used the cheapest production materials and techniques around, which at times held them back and at other times really contributed to their signature sonic quality. The speaker was a drawback making the 1431 sound thin and weak.  The transformers, on the other hand, while technically “undersized” seem to make the power tube compress and overdrive in a very musical way.

Because of it’s 6au6 pentode preamp, this amp doesn’t have the inherent roaring overdrive of a champ, but it’s far more musical in its cleans with a tone that just loves single coils. Strats and teles sound like heaven through this. P90’s scream.

Just about the time I heard this amp for the first time, I had stumbled upon an old Roberts reel-to-reel unit that was in disrepair, but had some wonderful transformers that would work perfectly for this build. I was able to source the vintage transformers from that unit, and then match them with a collection of new and vintage parts to pull together just about everything I would need for the build.

I ordered a chassis and got to work.  

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Laying out the front panel was nice and easy. I like a clean interface with only the essentials. 

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I wired up the heaters and started planning the layout:Image

I decided on a 6X4 rectifier, which is electronically identical to the 6×5 but was a cool little glass 7 pin tube like the 6au6.

The circuit was all laid out vintage style on tagboard:

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F&T electrolytics, Orange Drops throughout and carbon comp resistors in the signal path. I was really happy with that layout and it makes for a nice quiet ride.

Here’s the Vintage OT all prepped and ready to go:

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After getting the amp up and running, I spent some time tuning the tone control for a wider sweep and more responsive interaction with the overall gain of the amp. I ended up with something very close to the passive tone stack on a fender 5F2A (which has long been one of my favorite amps), built a head cab for it and set about testing different speakers.

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The layout in the head is dead simple and clean. 

The tiny speakers in the original amps made for some “unique” sounds, but really held the amp back in my opinion. This circuit has so much more to give with the proper speaker compliment. 

My first thought was to go with a 10″ Alnico speaker. I have some old stock Eminence Alnico blue 10’s, one of which will never leave my Princeton Reverb, so I tested the amp with one of these in an open back cab. Sounded good, but still missing something. I switched over to a 12″ Mojotone BV25M in an open back cab. I finally decided on a slightly oversized (but shallow) closed back 12″ cab which gives the amp enough bass presence without getting woofy or boomy. It now had everything I liked about the character of the original, but louder and with more authority. The Chime was still there, the harmonic complexity of the 6AU6 was still there, and the 6V6 was able to really fill out and bloom.

The speaker cab is built out of hand finger-jointed pine with a 4 point baffle like an old Fender tweed which gives the speaker the perfect amount of resonance. At 22″ x 22″ It’s slightly smaller than a tweed bassman and lighter than you would expect. 

I couldn’t be happier with how this one came out.

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Ladies and Gents, the Fourteen31.

 

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