'50s Epiphone EA-35.....cool story

[Geezer]

My 82 year old Dad (living in the hills of West Virginia) called me with this.................
he loves to go to yard sales & find old junk. I told him to be on the lookout for anything with tubes in it.
He called this morning & said he thought he had found something I might like. He described it to me, then asked if I wanted it.
I sez "maybe, but don't pay too much for it.....let me do some research & see what it's worth".
He sez "too late, I already bought it".
Uh, oh....."how much?" sez I.
"Five bucks" was his reply  :o   "I figured it was worth at least that much."

$5 is the price the guy had on it. Dad asked "is this tag right?"
The guy said "I just want to get it out of here.....been lookin' at it too long......"

Turns out the guy has had it in his closet for 30+ years. He said he put it away after his band played their last gig. His brother was in the band with him, & died suddenly that very night after the gig. He never played music again.

Dad told him that I was an amp lover & that it would be well taken care of....he was pleased & said "perfect! Hope he enjoys it."

I don't have it in my hands yet (may be several weeks) but Dad says it has a 5Y3, 2x 6V6's & one other tube he can't read, but I suspect it's an octal, as he said it's about the same size as the other tubes. Also, the speaker is a Jenson Alnico "Special Design"....Dad thinks it's around 10".

Thanks Dad!  :-*

[Geezer]

Oh yeah.........the next thing I asked Dad (after he told me how much he paid) was "Did you ask him where the guitar is!??"

He didn't, but I said if he went back by there today, stop in & ask!

[jhadhar65]

That's extremely cool!  You have an 82 year old dad that can still get around and enjoy life.  He can even call you on the phone and talk to you.  Be very thankful for that.

And the amp sounds good, too.

[billcreller]

Isn't the EA 35 the same as one version of the Gibson GA8 ??  I seem to remember using a schematic from an Epi to work on my GA8T.  Mine had EL84s, but there was a 6V6 version too.

[bluesbear]

The EL84 version was from the early to mid '60's. You know how Gibson was about changing things. There may have been 4 or 5 incarnations over a 20 year period... and that doesn't count any possible Herb Sunshine/Nat Daniels versions predating the Gibson connection.
Dave

[tubenit]

I had a EA-35T Devon tremolo. It had 6BQ5 (EL84's). It was a nice amp. It was given to me free. Traded it for a Music Man RD-50


I think it's incredibly cool that your dad picked that amp up for you!!

With respect, Tubenit

[Tiny_Daddy]

There was lots of good tube stuff in West Virginia. Way back in them hills. I used to buy stuff from Hicks Radio and Sodaro's (I called it Solder-o's) in Charleston and repaired bunches of old radios and other things. I went into Sodaro's a few years ago to visit the owner and was surprised that Vincent still looked the same - but it was his son. I didn't want anything to do with the hot-chassis amps that were the rage at the time.

[Platefire]

De Geezer

Kool Story, thanks! Your blessed you Dad takes an interest in your hobby enough to do that. My dad is 94, lives by himself and still drives. Plate

[jrmintz]

So you're actually Da Geezer, Jr.?  ;D

I miss my dad...

[Shrapnel]

Miss my dad too.

and had he not thought I was ever going to use the stuff, had a bunch of old tubes and a tube tester (and myself at the time) probably would still have them...   So much for forward thinking. LOL...

Anyway, I'm glad your dad is still alive and kickin' AND is in an area rich with tube booty. I wish I could say the same... this area people think only in "idealistic collectors value," as if they had some high value stash inside, when something shows up for sale.

Stopped by a yard sale the other day, and was looking at a stand-alone phono player... RCA, IIRC... Examining it it had the makings of a small wasp nest, as if it had been stored out in a shed for a few recent years. The lady wanted $50.00 for it.. it had maybe 2-EL84s and maybe one or two other tubes in it as far as I could tell, with a RCA phono jack for an output or input (Can't remember now, slept since then.) Gave me this story of some collector (or dealer) coming along offering her way less, and when she wouldn't sell, told her not to let it go for any less that $50.00. She claimed it still worked too. Too much for my blood, especially if I decided to cannibalize it.

[jhadhar65]

>...it had maybe 2-EL84s and maybe one or two other tubes in it...

You could easily get your money back if those are RCA 6BQ5's.  I'd go in half with you just to get the two power tubes if you want.  You can have the rest, which may include some RCA 12A_7 types.  If you're interested, PM me so we don't hijack the thread any worse.

[Geezer]

It's "in the house"!

It's a '59, and is the exact same (the schem is inside the cab) as a GA-8 Gibsonette (schem link below)....double SE.

http://www.schematicheaven.com/gibsonamps/gibsonette.pdf

The cab & chassis are way cool. The cab is covered in a cream "polka-dot" tolex, & the grill cloth is gold sparkle with the intact Epiphone badge still there. Original metal & bakelite handle still there & in great shape.

Chassis is chrome w/ 2x inputs, VOLUME (that's it!), fuse, switch & fender-type jewel lite.

Tubes are (1) RCA Blackplate 12AX7, (2) RCA Smoked Glass (Blk plt?) 6V6-GT, and an RCA 5Y3.

The circuit is a basket case.....sometime long ago, someone tried to replace the caps (the replacements are ~30 years old or older & the originals are in the bottom of the cab) & some resistors with a very cold solder gun. That's OK....I'll enjoy putting it back to spec!
The 2-prong cord is toast, was gonna replace it with a grounded anyway.

The speaker is a Jenson 10J11 "Special design" dated 51st week of 1958.

Can't wait to get it up & running to see what she sounds like.
I'll post some pics ASAP....prob tomorrow.

DG

[FYL]

Cool amp. great find.

double SE

Actually it's a crude form of push-pull using a self-splitter.

 

[Geezer]

Actually it's a crude form of push-pull using a self-splitter.

So the 470Ω on the input grid of the 2nd 6V6 is the "self splitter"? Everything else looks straight parallel to me......what am I missing? :icon_scratch:

[tubenit]

I was looking for a picture of something else yesterday and stumbled on the picture of the Epiphone EA-35T Devon tremolo amp I had.  Definitely wished I had NOT gotten rid of it. 

It was given free to me. Reportedly, the guy that owned it was in a high school band with the guy who was later Willie Nelson's harmonica player at one point.

The amp exterior was in perfect shape when I got it. I plugged it in & it worked after it had been sitting for 20 yrs. Knowing nothing about "vintage" value, I built an oak cabinet to replace the greyish tolexed cab but left everything else original. In the picture, you can see that the grill cloth and suitcase handle still looked excellent.

This was my 1st tube amp. The guitar with it was a Fender Squire Bullit that I built a maple body for.

With respect, Tubenit

[Geezer]

No pics yet, but this is what mine looks like>>>>>>>>>>

[FYL]

So the 470Ω on the input grid of the 2nd 6V6 is the "self splitter"? Everything else looks straight parallel to me......what am I missing? :icon_scratch:

Gibson made zillions of variations around the same amp. Early Gibsonette amps used a self-splitter, hence my remark, but the schematics show a peculiar PSE, so you're not missing anything.

[tubenit]

DaGeezer,

I think it's an incredibly cool thing your dad did for you! Nice to have a dad who celebrates your passion for music!

With respect,Tubenit

EDIT: changed to match DaGeezer's more legible schematic. Thanks!

[Geezer]

The ?? resistor in the B+ rail is a 500R/10W.

Here's a scan of the original schematic (with some touchups of missing stuff from the disintegrating edges)

[66merc]

Hey folks,

Sorry to drag up an old thread but I was casually searching self-split info and saw this.

I understand that this scheme is actually not self-split but I don't understand what the 470 ohm resistor does for the parallel SE design.  Anybody know?

Thanks

[kagliostro]

Very nice score Geezer

Kagliostro

[Pleximan]

Yeah cool story & nice score.

It’s a single ended with paralleled 6v6 tubes
The 470 is a grid stopper. I believe for paralleled
tubes it’s just as effective to have the grid stopper on
just one of the tubes

You got to think like a manufacturer.
It’s cheaper to use just one resistor.
You don’t get anything extra when one will do.

[66merc]

Thanks, Plexi.  I just wasn't sure since most of the designs I have seen, such as the Angela super single ended amp, use them on both tubes.  But, as you point out, they arent making a thousand of them.

[HotBluePlates]

The earlier model Gibsonette, which would probably be the same thing as an earlier EA-35, is the self-split version.

Notice the OT is push-pull, as the plates go to opposite ends of the OT. In Geezer's newer amp, both plates feed the same side of the OT, making that amp parallel SE.

Also note there is no phase inverter, and the non-driven tube has its grid connected to ground. The output stage is cathode biased, which in this example is very important. You could describe the output stage as "cathode coupled." The cathode resistor has no bypass cap, so the absolute voltage across it varies with the a.c. signal applied to the driven tube. Since the non-driven tube has its grid held at a steady 0v, the grid-cathode voltage of this tube is varied by the non-bypassed a.c. signal across the cathode resistor. This is how it receives a drive signal, and fills in the other half of the push-pull signal.

If the gain of the effective "cathode follower" of the driven 6V6 were unity, we'd get a pretty balanced output signal. But the a.c. across the cathode resistor will be somewhat less than the drive signal to the driven 6V6's grid. So the cathode-coupled 6V6 has a smaller effective drive signal, balance is not perfect and the maximum output power for a given level of distortion is reduced.

But so what? Epiphone (Gibson) gets most of the output power attainable anyway, and saves the cost of a phase inverter tube (or interstage transformer) and associated parts. It also performs well enough for the student/non-pro price point it was designed to meet.

[PRR]

> saves the cost of a phase inverter tube

Also the P-P OT is a fraction the size (and cost) of a similar SE OT.

[HotBluePlates]

What I don't get is why Gibson/Epiphone devolved from self-split to parallel SE. I looked up mid- and late-50's catalogs, and the output power claimed is essentially the same (at 8-9w) for each version.

[moonbird]

Geezer --

Did you ever get this one up and running? I have been interested in this architecture for a while. Though it might be fun to "play" with the output a bit. Maybe run one tube ultralinear and the other pentode. Or "tune" each output for a different tone. Goofy stuff like that. I was going to get a Edcor OT that has the ultralinear tap.

[Platefire]

My Dad passed away a little over a month ago. Sure do miss him and I sure enjoyed the story about your Dad going ahead and picking up the Epi for $5.00 bucks. I sure would fix that one up top shelf and hold on to that one forever. My Dad thought it was interesting about my tube amp hobby but he was never one to go to flea markets, garage sells or thrift shops. I would allways tell him about my searches and he would inquire rather I found anything. He was an old fisherman, I was cleaning out his garage today and found his old fishing hat complete with fishing lures attached, his old Zebco 808 reel/rod, minnow bucket, stringer and two of his old pipes he use to smoke.

I'll also be interested in following your progress on getting the Epi up and running. Platefire   

[CraigB]

My Dad passed away a little over a month ago. Sure do miss him and I sure enjoyed the story about your Dad going ahead and picking up the Epi for $5.00 bucks. I sure would fix that one up top shelf and hold on to that one forever. My Dad thought it was interesting about my tube amp hobby but he was never one to go to flea markets, garage sells or thrift shops. I would allways tell him about my searches and he would inquire rather I found anything. He was an old fisherman, I was cleaning out his garage today and found his old fishing hat complete with fishing lures attached, his old Zebco 808 reel/rod, minnow bucket, stringer and two of his old pipes he use to smoke.

I'll also be interested in following your progress on getting the Epi up and running. Platefire   

Sorry to hear that Platefire.  My sympathies to you and your family.

[PRR]

> devolved from self-split to parallel SE.

The wiring may be a shade simpler (or not).

PSE has better voltage gain. At least twice; enuff to notice.

> output power claimed is essentially the same (at 8-9w) for each version.

It's all Class A. Power is ideally 50% of Pdiss (40% in real life). The self-split "could" reduce THD at medium powers but tends to rise fast at full power; anyway there's no THD numbers in those catalogs, right?

The OT "should" be bigger for PSE..... but Honda "should" not have put the EVAP in a mud-trap under the floor, nor used thin plastic for ABS. And Honda generally "cares" more about their machines than Gibson's luthiers did about those electrical accessories. Or maybe fat SE OTs became a glut on the market.

[moonbird]

PRR --

Is there a way to make one of the output tubes MORE likely to distort than the other? How could that "gap" be expanded / contracted? I like on the edge distortion -- if it can be done it might finally be what I have been looking for. thx much!!

[moonbird]

PRR -

The OT "should" be bigger for PSE.....

By this you mean higher wattage -- right?

PSE needs an impedence that is half of the target impedence for one tube -- is that right?

thanks

[moonbird]

My Dad passed away a little over a month ago ...

Platefire --

I have heard that losing a father is one of the toughest things a son must face -- I would have to agree. Lost my Dad in 04 due to complications after open-heart surgery. Hope you can find solace in the good times you had together ....

[HotBluePlates]

PRR -

The OT "should" be bigger for PSE.....

By this you mean higher wattage -- right?

No.

Transformers couple the primary to the secondary on the basis of magnetic flux. Current flowing through a wire sets up a magnetic field around the wire. In a push-pull transformer, the d.c. used to idle the output tubes is fed from the center-tap, and flows in opposite directions out to either end of the primary. the two fields set up as a result tend to cancel each other out.

The amount of flux the OT can handle is determined by the size of the core. SE transformers must handle not only the flux due to useful power signal being transferred to the secondary, but also the flux due to d.c. passing through the primary to idle the tubes. Therefore the core must be larger to handle the same output power, because the core's capability is being used up to handle the unbalanced d.c.

Look at two Hammond transformers, the 1640SEA (SE) and the 1645 (PP). Both transformer claim 30w of power handling. The 1645 weighs 4.5 pounds, and the 1640SEA is 11 pounds. The wieght difference is almost entirely due to the larger core required for a SE transformer.

So, the self-split design should be able to have a smaller, lighter (and cheaper) OT. The parallel SE operation should require double the unbalanced d.c. of typical single-tube SE, meaning twice as big an OT. But no one said Gibson spent the money for a bigger OT. It just means the power level/bandwidth of the resulting amp might be constricted.