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Albert Einstein's 6B4G Amp - A Gift from friends at Princeton

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Posted on November 14, 2011 at 23:44:44
Jim Doyle
Audiophile

Posts: 1180
Location: Medford, MA
Joined: July 8, 2001
 This was forwarded to me from someone who found the article and wants to build it.

It's interesting... It's using 6B4G's (DHT) in 1949 when there'd be plenty of 6L6's or 807s from the war - so this was a deliberate choice by the designer! The rest is pretty sensible: gain, then phase split then a differential amp doing the driving with some more gain. No global feedback.

A quick PSUD run whos this power supply is feeding 390V at about 140mA load.

Eminently buildable with off-the-shelf transformers!

This looks like about 13-15W Class AB1. Einstein was probably listening to mono recordings, who knows what he used for speakers.

-- Jim

 

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'Gotta love the parts PRICES, best of all !!, posted on November 15, 2011 at 00:56:34
drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005
 Man,

We, (my Mom, Dad, older brother and I) lived only ten miles from Princeton, and I was entering Kindergarten. Dad used 6L6s back then, a yuccy-sounding Karlson on one wall, and a soffit mounted glorious-sounding 604B Altec coax on the other. Actually, the 604B was in 1952.

Was this the same guy who made bagels ??


Jeff Medwin

 

75¢ for a 1940's 6SN7!, posted on November 15, 2011 at 07:55:57
FenderLover
 Double wow on those prices.

 

RE: Albert Einstein's 6B4G Amp - A Gift from friends at Princeton, posted on November 15, 2011 at 09:46:17
R. Mercure
Audiophile

Posts: 450
Location: Central Appalachian Mountains
Joined: April 25, 2008
 Around 1996-7 I acquired several hundred issues of magazines such as Radio and Television Engineering and others that were oriented at an audience from the highest reader of the old Popular Electronics (as it was in the 1960s) up to professional engineers. Most of these magazines covered the time period of 1947 - 1956, almost a decade (I was born in early 1954) and even then the DHT, vs., heater triode vs., BPT debate (including the UL "semi-triode") was going hot and heavy - this time period pretty well covered the introduction of Williamson's and much of Baxandahl's early works. So here we are more or less 75 years later still pretty much arguing the same old stuff. Folks, I've lived in Virginia most of my life and this reminds me of nothing so much as the continual rehash of the "Civil War, or "the War of Northern Agression," or "the War to end Southern Treason" whatever you want to call it (I favor the last)!
If you can tell a major difference with triodes, no matter how warmed, then that's what you like. To me the inefficiency isn't work the marginal cost and I like BPTs for general audio and instrument amplifiers while I hate pentodes for instrument use but like then for general audio. I also think that chocolate tastes just like much of the dung it looks like, along with coffee ("hot black water") but I'm enjoying a "cuppa" tea as I write and love the taste - and even more the aroma - or vanilla. I hope I've made my point (still have most of my top hair as I approach 58 so you might not notice it).

Rob
"Monoblocks" = "monoblockheads" - it's "monaural amplifier"; "power output tubes" not "power tubes" & "patch cords" not "interconnects!" "Passive preamp(lifier) is oxymoronic!

 

BPT?? , posted on November 15, 2011 at 09:55:40
SteveBrown
Audiophile

Posts: 2454
Location: Portland, OR
Joined: November 14, 2002
 Sorry, my decoder ring is missing.

 

beam power tube?--NT--, posted on November 15, 2011 at 10:35:55
elblanco
Audiophile

Posts: 3486
Joined: August 20, 2004
 kh

 

Relative costs: Back then, pair of output tubes half the cost of output TX, posted on November 15, 2011 at 11:02:15
Jim Doyle
Audiophile

Posts: 1180
Location: Medford, MA
Joined: July 8, 2001
 That's what struck me!

Back then, the pair of output tubes ($5) would be more than the power
transformer! But, half the price of the output transformers.

If I were to guess - the assembly of the 6L6 was probably highly
automated early on - with tooling design specifically to crank out this
tube accurately in high volume at lower prices, to facilitate sales volume
of more affordable products..

The 6B4 - however, I bet was still subject to hand assembly, keeping the price high... Maybe (we dont know!) the early 6L6 didnt last long in circuit, so perhaps the earlier generation of DHTs was thought to be better solely because of it's longevity in the socket. Who knows!


-- Jim

 

RE: Albert Einstein's 6B4G Amp - A Gift from friends at Princeton, posted on November 15, 2011 at 11:03:07
Tre'
Industry Professional

Posts: 17302
Location: So. Cal.
Joined: February 9, 2002




I've built countless amps, SE and PP, with BPT's in UL, and triode connected.

To me a DHTs are worlds better and the plate curves (and resulting dynamic characteristic curve) prove it.

A very linear DHT (45,2a3,300b) working in Class A will produce very little harmonic distortion compared to BPT, even if the BPT is triode strapped.

"If you can tell a major difference with triodes, no matter how warmed, then that's what you like"

It is what I like but I believe only because of lack of distortion.


Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: beam power tube?--NT--, posted on November 15, 2011 at 11:22:17
SteveBrown
Audiophile

Posts: 2454
Location: Portland, OR
Joined: November 14, 2002
 Thanks, I was trying to make it into bipolar transistor... but I think that would commonly be BJT.

 

RE: Albert Einstein's 6B4G Amp - A Gift from friends at Princeton, posted on November 15, 2011 at 12:07:54
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 "If you can tell a major difference with triodes, no matter how warmed, then that's what you like. To me the inefficiency isn't work the marginal cost and I like BPTs for general audio and instrument amplifiers while I hate pentodes for instrument use but like then for general audio."


If you think about what a pentode is,its nothing more than a triode with an extra element to increase or accelerate the flow of electrons.Fundamentally,most pentodes are incorrectly run according to original manufacture data.Screens need regulation and lower SG voltage with respect to the plate.In my experience,this gives the amp more depth and clarity. BTW,I agree with your post 100%
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: 'Gotta love the parts PRICES, best of all !!, posted on November 15, 2011 at 14:56:52
Paul Joppa
Industry Professional

Posts: 7296
Location: Seattle, WA
Joined: April 23, 2001
 Dude! I lived in Dutch Neck around 1961. Remember the PJ&B?

 

RE: Albert Einstein's 6B4G Amp - A Gift from friends at Princeton, posted on November 15, 2011 at 16:12:38
SteveBrown
Audiophile

Posts: 2454
Location: Portland, OR
Joined: November 14, 2002
 Interesting too that all the tubes including the DHT's share the same heater winding. I wonder what the hum level was like - I know the PP arrangement will kill some of it, but I've used 300B in PP and AC can still exhibit a fair amount of hum.

 

RE: Albert Einstein's 6B4G Amp - A Gift from friends at Princeton, posted on November 15, 2011 at 18:38:29
CharleyW
Audiophile

Posts: 361
Location: Arlington, Texas
Joined: November 21, 2002
 Check out the link.

 

RE: Albert Einstein's 6B4G Amp - A Gift from friends at Princeton, posted on November 16, 2011 at 08:53:07
Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000
 45 and 2A3 linear? You bet. 300B? Not nearly as good. Even Harvey Rosenberg unambiguously stated that the 300B puts on a show.

BTW, triode strapped 6V6 family tubes are damned good.


Eli D.

 

RE: Albert Einstein's 6B4G Amp - A Gift from friends at Princeton, posted on November 16, 2011 at 09:13:17
Tre'
Industry Professional

Posts: 17302
Location: So. Cal.
Joined: February 9, 2002

You're right. The 300b is not as linear as the 45 or 2a3 but much more linear than a triode strapped 6v6 based on the curves I've seen.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

6v6 triode curves, posted on November 16, 2011 at 09:17:21
Tre'
Industry Professional

Posts: 17302
Location: So. Cal.
Joined: February 9, 2002

.
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: 'Gotta love the parts PRICES, best of all !!, posted on November 16, 2011 at 10:09:12
drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005
 Nope, sorry. But I knew there was something about you I liked!!

I was raised in Trenton, NJ, and in 1958 moved to Bucks County, PA.

Cheers,

Jeff Medwin

 

RE: Albert Einstein's 6B4G Amp - A Gift from friends at Princeton, posted on November 16, 2011 at 19:58:01
zacster
Audiophile

Posts: 2179
Location: NYC
Joined: November 22, 2003
 At least I have something in common with him, other than my brain of course!

PP 6B4G makes a nice sounding amp.

 

PJ&B, posted on November 19, 2011 at 21:20:52
Gary B.
Audiophile

Posts: 76
Location: No. Cal.
Joined: January 9, 2000
 Also known as the "dinky". I lived in Princeton Junction when I was a kid in the 60s and used to flatten pennies on the train tracks.
Certainly a small world.
---Gary

 

RE: Albert Einstein's 6B4G Amp - A Gift from friends at Princeton, posted on November 22, 2011 at 13:40:24
UFO
Audiophile

Posts: 148
Joined: November 19, 2011
 Thanks for that, very interesting read.

Is there a picture of the amplifiers case anywhere?

 

RE: Relative costs: Back then, pair of output tubes half the cost of output TX, posted on November 22, 2011 at 21:08:00
BofService
Audiophile

Posts: 741
Location: Atlanta
Joined: February 28, 2003
 I think that the speaker he was driving IS important to our understanding of the design. How can we assess the design choices without at least knowing the efficiency of the speaker? Based on the number of stages I'm guessing that "clarity" was not of particular value, while it was important to have a lot of "drive". (Granted I have not assessed the operating points, gain, etc.)

 

What's interesting about these curves..., posted on November 23, 2011 at 16:43:39
JJ Triode
Audiophile

Posts: 716
Location: Northwest
Joined: December 2, 2004
 Is how linear (evenly spaced) they remain as the grid voltage becomes positive. It suggests an ability to perform well in class A2 or AB2, at least on transients, as I understand it (anyone please correct me if mistaken.)

I wonder what other common pentodes or beam tetrodes, triode-connected, share this property? Usually the plate curves are plotted only for Vg = 0 and negative values.

 

RE: What's interesting about these curves..., posted on November 24, 2011 at 20:07:44
Tre'
Industry Professional

Posts: 17302
Location: So. Cal.
Joined: February 9, 2002
 "Usually the plate curves are plotted only for Vg = 0 and negative values."

Yes. It's nice to see what the tube would do into A2.

"....Is how linear (evenly spaced) they remain as the grid voltage becomes positive."

I guess there is "evenly spaced" and then there is "evenly spaced".

Compared to the 300b curves shown in my post, I don't see ANYTHING evenly spaced in the triode 6v6 curves.

The space between 0 and -5 is smaller than the space between 0 and +5 or the space between -5 and -10.

Then the space between -10 and -15 is smaller still with the space between +5 and +10 almost right but then the space between +10 and +15 is tiny.

Compare that to the 300b curve. The spacing between any two adjacent grid lines are all pretty much the same all the way across the board.

Do you see what I'm seeing?

Tre'

Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: What's interesting about these curves..., posted on November 25, 2011 at 12:31:04
PakProtector
Audiophile

Posts: 12365
Joined: May 14, 2002
 That which you're noticing about the 6V6 is most likely an artist's aritfact. Nothing I've seen shows triode curves bunching up as grid voltage increases( along with gm ). Now the guy drawing from the 570( or what ever RCA used at the time ), is quite capable of bunching up the grid lines where ever he wants...
cheers,
Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

 

RE: What's interesting about these curves..., posted on November 25, 2011 at 13:22:30
Tre'
Industry Professional

Posts: 17302
Location: So. Cal.
Joined: February 9, 2002
 What about bunching up as the grid becomes more negative?

I think that is normal for all but the most linear tubes.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

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