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[Luke Geis]

The patriotic theme seems to be in your plate feeds. Is this a B1270 build?

[Bob Leonard]

What is a B1270.

[Luke Geis]

http://www.kbapps.com/audio/schematics/tubeamps/fender/princetonreverbb1270.php

It's another schematic for the same amp that use AA1164 and AA764 schematic nomenclature. The AA764 uses a GZ34 while the other schematics call for a 5U4. The AB1270 is the same as the B1270 and are CBS era amps as is the AA764.

The B1270 / AB1270 is the same between both the silverface and blackface models. The B1270 is as far as I can tell, nearly identical to the AA1164 with the exception of a couple small tweaks like a 2000pf cap on the reverb return and bigger capacitors on the tremolo power supply.

When I think of Princetons with reverb and tremolo, I think of the B1270. Mostly because it is both CBS and transition years related, and was the same in both the silverface and blackface models. I guess the AA1164 would likely be the one people gravitate towards because it was pre CBS.

[Stephen Kirby]

Here is the 18 watt TMB Marshall clone I built! Not quite done with it in this shot. Was waiting on a couple more parts.

Why do people hang parts in these things with no strain relief?  Particularly when they're in love with carbon comp resistors?  Martin Marrietta figured out all this stuff in the '50s.  At least this doesn't have any backwraps, which I've seen in "boutique" amp builds on line.

[Luke Geis]

There are a lot of build procedures I did that go against best practices. The resistors and caps should all have a little swoop in each lead for expansion and contraction and that isn't even the worst of it. The Heater wires should be laid in to come down over the top more like Bob's leads do in his build. Despite not going with what is considered " best practices ", this thing is dead quiet and it doesn't get hot enough to really be of concern for extraction and contraction.

Looking at many of the Hiwatt amps as an example, he went against best practices a lot, but made the cleanest looking amps there are. What has been found, and believe me I studied a bit on this, is that as long as the lead dress and component layout is clean and to some sort of standard, problems are usually sparse. In my case I have proper grounding, and my lead dress is pretty good. I have the noisy stuff tucked away in the corners and coiled tightly, the output transformer leads are braided and laid to go perpendicular to as many other components as possible. Along with that all my leads are essentially 90* perpendicular to others, or laid in nice clean lines.

My gripe with this particular kit was the width of the turrets. They were a little far apart and as can be seen, I had to shortcut a few components. Doing a proper relief on most of the parts would have been impossible as the leads were only just long enough to span the board. As much as I would love to do a military grade build, it also isn't as clean looking as people who spend $2,000 plus on these things want them to be. The majority of turret and eyelet board builds are running the leads as straight and geometrically as can be it seems. It looks better and doesn't appear to be problematic. I have no backwraps in my build and spent a great deal of time forging what was essentially a custom layout into a fairly small chassis. What I can say from my limited experience, is that it is not as easy as it seems to build an amp that follows all the best practices and looks like a million bucks too.

[Bob Leonard]

http://www.kbapps.com/audio/schematics/tubeamps/fender/princetonreverbb1270.php

It's another schematic for the same amp that use AA1164 and AA764 schematic nomenclature. The AA764 uses a GZ34 while the other schematics call for a 5U4. The AB1270 is the same as the B1270 and are CBS era amps as is the AA764.

The B1270 / AB1270 is the same between both the silverface and blackface models. The B1270 is as far as I can tell, nearly identical to the AA1164 with the exception of a couple small tweaks like a 2000pf cap on the reverb return and bigger capacitors on the tremolo power supply.

When I think of Princetons with reverb and tremolo, I think of the B1270. Mostly because it is both CBS and transition years related, and was the same in both the silverface and blackface models. I guess the AA1164 would likely be the one people gravitate towards because it was pre CBS.

Schematics didn't enter my mind when I read your question. I was thinking more like "What type of amp is this. Maybe a Portaflex I've never heard of."

The amps I build aren't from kits. I generally use Leo's late 50 early 60's schematics and my own values for the tone stacks, etc..

The patriotic signature can be found in the B+ wiring to the different sections of the amp.

[Craig Hauber]

Why do people hang parts in these things with no strain relief?  Particularly when they're in love with carbon comp resistors?  Martin Marrietta figured out all this stuff in the '50s.  At least this doesn't have any backwraps, which I've seen in "boutique" amp builds on line.

So somewhere between nuclear power plants and monorails Martin Marrietta built amps?

What's a backwrap? (I've done wire-wrap boards in the past?)

And why aren't circuit boards used for this?

[Stephen Kirby]

So somewhere between nuclear power plants and monorails Martin Marrietta built amps?

What's a backwrap? (I've done wire-wrap boards in the past?)

And why aren't circuit boards used for this?

Martin Marrietta wrote the book on hardwire workmanship standards.  Later translated in to Military Standards such as Mil-Std-454 and the high rel Mil-Std-2000 (which I contributed to).

A backwrap is when a wire or lead dress bends backwards against the direction it's wrapped around a terminal.  Such strains leading to fractured solder connections.

In the early days of tube electronics and audio amplifiers, circuit boards were expensive and not terribly robust.  Because through hole plating didn't exist, eyelets were often swaged into circuit boards.  Sometimes circuit board materials were used to support swaged in turret terminals such as the amp build shown.  But this was more expensive than for example Fender's practice of swaging eyelets into what was essentially oil soaked cardboard.

Because all modern technology is intrinsically inferior to the way they did things in the '60s, pretty much all high end boutique amplifiers are built using the same 1950's technology.   

Of course circuit board technology has advanced since the '60s.  Higher temperature laminates and lower expansion glass cloths.  Plating technology and metallurgy.  Not to mention very consistent electronic behavior.  The few boutique folks who avail themselves of the improved performance of circuit boards over manually hardwired circuits (like my Fuchs ODS) are shamed in internet communities for "going cheap".

[Ned Ward]

When circuit boards are done right, like Mesa, Soldano and a few others, or Barber and other pedal makers, it can be good sounding and not blasphemy. It just takes a few Fenders with pc boards with tube sockets to tar and feather them all.

[Bob Leonard]

Amen brother Ned. Not as much fun changing values or components though.

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