Common, Rare, Odd, & Obscure Amplifier Poker

[highfigh]

It's not HiFi, but it's an oddball and it's old. It's an Oahu lap steel amp from before 1940, as far as I have found but have never seen a schematic, read anything about it or seen another exactly like it. The 1940 and later models have an octal socket in the chassis for a harness that connects to the field coil speaker, to enable removing the chassis without the speaker (unlike mine). It uses a #80 rectifier, 6C8G dual triode, 6Q7G Duplex diode and 6L6G output tube. SE Class A, all original KenRad tubes and absolutely nothing had been replaced, although the 6C8G and 6Q7G had been swapped and the rectifier didn't work. I suspect these were the reasons it was covered and left in a closet, unused.

I posted a few other photos in the "Let's see them axes" thread here, too. I re-capped it completely (all of the caps were wax and paper/foil), found some #80 rectifiers on ebay and fired it up a couple of nights ago- sounds better than I though it would and has some balls.

 

[GordonW]

Bogen E-8 - one of the few amps ever built using two different output tubes in push-pull:

Ah, one of the 6AD7/6F6 push-pull amps, huh?

The paraphase splitter triode is contained within the 6AD7, and feeds the grid of the 6F6 to make a push-pull pair... the 6AD7 has the other "6F6 equivalent" beam power pentode section within itself.

http://www.nj7p.org/Tube4.php?tube=6Ad7G

Regards,
Gordon.

 

[ke4mcl]

i had the MI350 (mcintosh 350 watt tube monoblock) from mission contrrol used during the apollo space program. paid $700 for it from a space junk dealer

i came to grips with the fact i'd never be able to afford a second one at their real going rate so swapped it for a c22 and an mc240.

 

[ke4mcl]

golana,

your link aviation amp reminds me of another pre-stereo era dual channel amp i have. it seems that dual channel amps where made for driving pen recorders. to the average joe they look just like a stereo audio amp but stereo didnt exist yet.

 

[jaymanaa]

Wow..I have a simular Masco at my storage so I have no picture of it...
A 78 turntable/changer is mounted to the top and it has two microphone inputs. I recapped it a while back/plays good..more of a Western Electric inspired design..and with around 525+ volts of B+ driving p-p 6L6GA's!!
And I have the same maggie as you too..an AMP182!!

I biamped some large horns with that Maggie, and in true Maggie form, it was pretty darn unbeleivable. The single ended 6V6s were especially nice driving some 511Bs with 902 drivers.

 

[golana]

golana,

your link aviation amp reminds me of another pre-stereo era dual channel amp i have. it seems that dual channel amps where made for driving pen recorders. to the average joe they look just like a stereo audio amp but stereo didnt exist yet.

Do you mean the 6v6? I believe there was stereo in '55, which is the 6l6.
They are both Link models, adding to my confusion. Also, wouldn't stereo, just be
two channel? You know for some reason, that is sounding bad as I write it. Thanks, Mike

 

[radioactive]

time for me to post some of mine i guess.first the exclusive fairchild 260 mated with the 248 preamp.

second is my pr of george gott g50d amplifiers.

 

[radioactive]

this not a amplifier but a rare electrovoice preamp

 

[Steve O]

Altec A323B

PP 6L6G for about 20W. Early Peerless transformers. Switchable radio or mike/phono input. Feedback type bass tone control. Strange multi-position treble control that also doubles as phono equalization HF roll-of. Sounds remarkably good considering age.

 

[WopOnTour]

This is definately my "rarest" amp
1959 Fender Bassman 5F6-A :thmbsp:
2x5881 in push pull + four 10" Jensens
Definately "worn & weathered" it's a vintage tone monster and still all 100% original which is near impossible to find these days.
(I bring it up on the variac for 24 hrs prior to use)
I guess technically it's more of a tube audio source? :scratch2:

WOT

 

[diamondsouled]

This is definately my "rarest" amp
1959 Fender Bassman 5F6-A :thmbsp:
2x5881 in push pull + four 10" Jensens
Definately "worn & weathered" it's a vintage tone monster and still all 100% original
(I bring it up on the variac for 24 hrs prior to use)
I guess technically it's more of a tube audio source? :scratch2:

WOT

Boy that one has sure been around the block! I'd take out those nasty, old and leaky Astron coupling caps and replace them with orange drops, then toss the Astrons. By the way when is garbage day at your place? ;^)

Lar

 

[SpruceMoose]

i have a PACO SA40, but i will have to dig it out to get a pic.

 

[WopOnTour]

Boy that one has sure been around the block! I'd take out those nasty, old and leaky Astron coupling caps and replace them with orange drops, then toss the Astrons. By the way when is garbage day at your place? ;^)

Lar

Dude, no can do.
Believe it or not this is actually a valuable collector's piece and an early example of one of rarest most desirable guitar amplifiers in existence. It's considered the nirvana of vintage guitar "tone" and the Astrons are a big part of the mystique.There have been books written about this amp and Leo Fender's development of the 5F6A circuit.(and the controversial copy ala Jim Marshall in the early 60s) In fact Fender still builds it as a "reissue" some 50+ years later.

This particular unit has been appraised at ~$16K "as is". (it's actually an early 59 model assembled in Nov 1958) Therefore altering the original circuit, housing, speakers, wiring, ANYTHING in almost anyway will potentially affect it's sound and significantly affect it's value. (Believe me if I could ditch that old frayed away leather handle I would!) But it rolls around in a wheeled road case for the most part.

I regularly measure the DC passed by those old Astrons in the output coupling positions and believe it or not they are still <5mA.(I dont trust them either but my hands are tied!)Then I use a Bob Parker "Blue" ESR meter to check the electrolytics "in circuit".

I'm actually designing/building a matching tweed variac for it, complete with isolation transformer, digital voltmeter/ammeter, current alarm, PTC and fast-blow fusing, and CL-90 thermistor soft-start so I can "exercise" it regularly in safety and maintain the original circuit.(I also plan to "distress" the old matching tweed sheet I found on eBay for the variac so they look "right" LOL)
WOT
PS> My wife says I never throw ANYTHING out, so I guess you're SOL!

 

[marty59]

This is definately my "rarest" amp
1959 Fender Bassman 5F6-A :thmbsp:
2x5881 in push pull + four 10" Jensens
Definately "worn & weathered" it's a vintage tone monster and still all 100% original
(I bring it up on the variac for 24 hrs prior to use)
I guess technically it's more of a tube audio source? :scratch2:

WOT

Very nice!...I can understand you liking the tone and not wanting to recap but your amp will live happier with fresh in spec components...just make sure the electrolytics don't start to blister on the positive side or start getting warm...and some of those resistors are drifting out of spec too...and no spark show inside that rectifier tube!! Continue to be careful with it and enjoy...but it's just a matter of time.....

 

[marty59]

I've worked on a few of those and as long as those Astrons are ok I'd leave 'em in there. I can understand your point about the value...enjoy it!

 

[soundmotor]

Therefore altering the original circuit, housing, speakers, wiring, ANYTHING in almost anyway will potentially affect it's sound and significantly affect it's value.

Yep. A friend builds & repairs guitars & amps for a living. The stories he has told me about letting the mojo out are quite frankly, amazing.

 

[gearhound]

If those Astron coupling caps ARE bad.....and need to be replaced.....while the Sprague Orange caps will work fine.....paper-in-oil caps.....will probably get you closer.....to the amps original sound.
Tube Depot sells Sprague Vitiman Q's.....or you could go on flea-bay.....and find some nice deals on other paper-in-oil caps.....including NOS and Russian.
Good luck!


Steve

 

[kcin]

Here's one you don't see much: A Futterman H3 Output Transformerless Amp (OTL). This one is rare as it has the very inexpensive but wonderful 6FW5 sweep tubes in it which are cheap and plentiful.

Kcin

 

[zenith2134]

For me, that Futterman is the pick of the litter so far. :thmbsp:

 

[diamondsouled]

Dude, no can do.
Believe it or not this is actually a valuable collector's piece and an early example of one of rarest most desirable guitar amplifiers in existence. It's considered the nirvana of vintage guitar "tone" and the Astrons are a big part of the mystique.There have been books written about this amp and Leo Fender's development of the 5F6A circuit.(and the controversial copy ala Jim Marshall in the early 60s) In fact Fender still builds it as a "reissue" some 50+ years later.

This particular unit has been appraised at ~$16K "as is". (it's actually an early 59 model assembled in Nov 1958) Therefore altering the original circuit, housing, speakers, wiring, ANYTHING in almost anyway will potentially affect it's sound and significantly affect it's value. (Believe me if I could ditch that old frayed away leather handle I would!) But it rolls around in a wheeled road case for the most part.

I regularly measure the DC passed by those old Astrons in the output coupling positions and believe it or not they are still <5mA.(I dont trust them either but my hands are tied!)Then I use a Bob Parker "Blue" ESR meter to check the electrolytics "in circuit".

I'm actually designing/building a matching tweed variac for it, complete with isolation transformer, digital voltmeter/ammeter, current alarm, PTC and fast-blow fusing, and CL-90 thermistor soft-start so I can "exercise" it regularly in safety and maintain the original circuit.(I also plan to "distress" the old matching tweed sheet I found on eBay for the variac so they look "right" LOL)
WOT
PS> My wife says I never throw ANYTHING out, so I guess you're SOL!

He, he. Yup don't touch that beauty, lol. I were only joking.:yes:

It always kinda surprises me when I see Mustards or Astrons going for big $$$$ on that auction site, even if they are pulls. Thing is the tone they produce is unique.

I have a late 60's Traynor YBA-1A amp that has Mustard caps in it and I'm not touching them unless it's absolutely necessary.

There is a guy out there who makes repros of vintage caps and he does a real pro job on them.

I've heard that if you take your vintage amp to Torres or some of the other places for repair that they will yank out all the vintage caps but keep them and sell them on the sly.

Where did you pick up the tweed?

Lar

P.S. I'm another one of those folk who rarely throws things away. My basement is a testimony to this, good thing I don't have a garage as well I'm sure it would be full too. Only thing I get rid of is packing material. Even then I take it over to the recycling depot were they have a drop off for such stuff so it can be reused.