Early vs. Mid. vs Late 5E3 Amps?

[srolfeca]

As previously noted, capacitors are +/- 20% at best, resistors +/- 10%, and parts were subject to availability and price, and there was no "one" transformer to rule them all. Also, the carbon composition resistors used in the 1950s are notorious for drift. Add to that that household voltage back then was <115V and today is >120V, and the B+ voltages can vary as well. Leo was notorious for making in-process changes, leading the VP/GM Forrest White to put a stop to that emphatically when techs couldn't get voltages to spec because Leo made a change.

Some kits and clones use a 12AY7 as V1, some use a 12AX7. These will sound different.

All 5E3 amps suffer from the same symptoms of: noisy; poor grounding; uneven frequency response (lows 2x highs); short power tube life due to 96% bias; and early cutoff distortion.

Several of these can be easily fixed with simple tweaks that don't alter the famous 5E3 'sound'.

When I build a 5E3, I use some MIL-Spec 1% resistors; most are 5%, and I don't use carbon comp. I also measure every cap and resistor for values before and after soldering them to the board, and use high temp/high voltage MIL-Spec wire and cable.

Back to the B+ thingy and so-called "period correct transformers." I call it "marketing BS". A "period correct transformer" would be one designed for 110VAC input and B+ in the low 300s. Plug that baby into your 122VAC outlet and your B+ will be way too high. What you want is a tranny designed for 120VAC input and about 330-ish VDC on the plates. A modern 5E3 tranny will likely see closer to 400V, as srolfeca noted above. Every 12AX7 triode, 6V6 pentode, 5E3 power and output transformer will have slightly different behavioral characteristics.

To get a modern-built 5E3, use proper grounding techniques (reduces hum 50% or greater), a 12AY7 or 12AX7 with no cathode bypass on V2a, 470Ω/2W screen grid resistors, larger cathode resistor on 6V6s (<90%), proper 5Y3GT, proper standby switch, reduce the stage 1 coupling caps from 0.1µF to something a bit more reasonable, such as 0.02µF (YMMV). The result is a 5E3 that has reduced hum, no 'farting out', longer tube life and doesn't go into cutoff distortion at Volume 2, but more like 4 to 6.

Bruce’s Mission PT’s are wound that way- a pragmatic approach to modern AC power distribution.

I also used a Hoffman eyelet board instead of the period correct eyelet board.

Aside from being nicer to build on, Hoffman’s careful rearrangement of a few component locations reduces the amount of power supply hum, without changing the overdrive characteristics and other factors that we value. My 5E3 is almost silent with everything dimed and a guitar plugged into the input.

 

[gabasa]

B+ voltages, changes in AC outlet voltages over the years, component differences.... they've all been discussed a lot.

Within all this, there have been output transformer changes that would have profoundly changed the sounds of the amps from the mid '50s to the early '60s. They would have trended from bassier to noticeably clearer and brighter over the years, on average. When I put a 50246 into one of my two Harvard builds, with no exaggeration, they sounded like two completely different amps.

 

[cobaltu]

B+ voltages, changes in AC outlet voltages over the years, component differences.... they've all been discussed a lot.

Within all this, there have been output transformer changes that would have profoundly changed the sounds of the amps from the mid '50s to the early '60s. They would have trended from bassier to noticeably clearer and brighter over the years, on average. When I put a 50246 into one of my two Harvard builds, with no exaggeration, they sounded like two completely different amps.

Not to dredge-up this slightly older thread - but what transformer was in the other Harvard (the non 50246)?
How was the sound different?

I'm curious beacause I've been thinking about putting a 108 style transformer in Mojo-ish 5e3 build.

 

[gabasa]

The Harvard with the 50246 had a looser, deeper sound that started to remind me of the sound of my 5E3.

The other Harvard had a 125A1A style of output transformer. It had a tighter bass response and more extended high end. I kept the 125A1A in it because it made the amp sound more unique within my little collection.

I just put a 50246-style transformer into my 5E3 build to replace the 50246 that was in there. The new one is from Pacific Audio Magnetics and it sounds incredible in that amp. I've completely converted my amp collection to Pacific OTs because I like them so much. I can highly, highly recommend this OT for your 5E3. They also make a 108 style of OT, as well as 125A1A.

Soursound has a great page on their website that describes the differences.

Fwiw, I always stayed away from the 108 because of the plastic bobbin. I'm sure it's just fine ... I have to get over the mental hurdle.

 

[mrfitz98]

And if we were measuring with objective equipment...because our brains make $#!+ up.

Sensory perception.

Our brains selectively receive and process information from our senses in a very efficient, yet VERY subjective, manner. They even invent data that isn't there, either because there is a hole in our experience or simply because we WANT to. It's how something "smaller than a breadbox" still beats out much larger supercomputers.

In an A-B test, our brains focus on, and actively enhance, differences between the amps. It's our brain's shorthand in sorting identifiable information. Our brains make these differences seem larger than they actually are.

But once we go above a certain threshold of test amps, our brains "work smarter, not harder". Instead of looking for identifiable differences between a half dozen or so amps, it flips a switch and starts focusing on and enhancing the similarities. Our brains make these similarities seem larger than they actually are.

Any two or three 5E3s will sound different from another, but a room-full of 5E3s will all sound pretty much the same (ignoring the high probability of at least one outlier).

And, for more bias... It is impossible to A-B compare sound with your ears. We can think they sound alike, or different, but it is not a "direct" comparison because it is done one after the other. We can "like" one more than the other, but without advanced spectrum analysis it is impossible to pinpoint the difference. "Smoother," "More Raw," are just terms we've created to inaccurately describe sounds we like more or less.

 

[Ricky D.]

I built a Mission 5E3 kit in 2007. It’s my only amp. The circuit adheres to the original 5e3 schematic. It has the big brass plate behind the panel for grounding. With no instrument plugged in, it is silent at any control setting.

Bruce encouraged me to build it with no modifications and get to know it before considering any changes to the original circuit, and that’s what I did.

This thread reminds me of all the PAF threads, people trying to duplicate the original. Problem is, there is no one original. Too many production variations. Like my dad used to say, “If you don’t know where you are going, it doesn’t matter which way you go.”

 

[gabasa]

And, for more bias... It is impossible to A-B compare sound with your ears. We can think they sound alike, or different, but it is not a "direct" comparison because it is done one after the other. We can "like" one more than the other, but without advanced spectrum analysis it is impossible to pinpoint the difference. "Smoother," "More Raw," are just terms we've created to inaccurately describe sounds we like more or less.

If you like one amp vastly better than another and could pick it out blindfolded in 100% of cases, and one was distinctly better sounding to you over and over again, (for example, one was clearer and one was more muted), would you change your mind on which amp you prefer based on a spectrum analysis?

Personally I'd say that our ears and playing experiences trump everything, and that it is easy to hear differences between amps if the listening tests are seconds apart and the differences are plainly apparent. Even better, double-blind so that you have no chance of picking the "upgraded" amp.

I understand the trap we've all fallen into, but if you do AB tests enough times, there are differences to be heard in some occassions.

 

[gabasa]

I built a Mission 5E3 kit in 2007. It’s my only amp. The circuit adheres to the original 5e3 schematic. It has the big brass plate behind the panel for grounding. With no instrument plugged in, it is silent at any control setting.

Bruce encouraged me to build it with no modifications and get to know it before considering any changes to the original circuit, and that’s what I did.

This thread reminds me of all the PAF threads, people trying to duplicate the original. Problem is, there is no one original. Too many production variations. Like my dad used to say, “If you don’t know where you are going, it doesn’t matter which way you go.”

I try to duplicate the original circuits, but I don't try to duplicate the construction of components. For example, I don't feel the need to have tin foil/mylar or aluminum foil/mylar coupling caps.

I get what you mean though. For example, the tweed Deluxe and tweed Harvard amps used three different OTs, and they were quite different sounding from one another. The 50246 and 125A1A are *very* different sounding!

 

[mrfitz98]

If you like one amp vastly better than another and could pick it out blindfolded in 100% of cases, and one was distinctly better sounding to you over and over again, (for example, one was clearer and one was more muted), would you change your mind on which amp you prefer based on a spectrum analysis?

Personally I'd say that our ears and playing experiences trump everything, and that it is easy to hear differences between amps if the listening tests are seconds apart and the differences are plainly apparent. Even better, double-blind so that you have no chance of picking the "upgraded" amp.

I understand the trap we've all fallen into, but if you do AB tests enough times, there are differences to be heard in some occassions.

Sure, my point was just that we like what we like. If I run an amp and like it, and then run an identical amp and don't like it, it just means I like the one I like. There are so many variables (like every component) in a tube amp that duplicating one is generally pointless. The same circuit, with the same components and tubes can get really stinkin' close though. This forum (and probably a bunch of other places) are full of stories from folks who found "the ONE."

 

[Ricky D.]

I try to duplicate the original circuits, but I don't try to duplicate the construction of components. For example, I don't feel the need to have tin foil/mylar or aluminum foil/mylar coupling caps.

I get what you mean though. For example, the tweed Deluxe and tweed Harvard amps used three different OTs, and they were quite different sounding from one another. The 50246 and 125A1A are *very* different sounding!

I left all the component selections to Bruce at Mission. I built the chassis kit, got a Mojo cabinet on EBay, and got a Weber alnico Sig 12. It sounds exactly like Cropper on “The Great Memphis Sound of the Mar Keys”. I guess all the individual deviations summed out to something close enough.