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Tech: Amp question

Raptor 18 Oct 08 - 08:38 AM
GUEST,Gene 18 Oct 08 - 12:10 PM
treewind 18 Oct 08 - 01:59 PM
Richard Bridge 18 Oct 08 - 07:33 PM
Raptor 21 Oct 08 - 06:07 PM
GUEST,popstudioguitar 31 Oct 08 - 09:08 AM
JohnInKansas 31 Oct 08 - 06:36 PM
John J 01 Nov 08 - 07:41 AM
Mooh 01 Nov 08 - 08:16 AM
Raptor 01 Nov 08 - 04:52 PM
Bernard 01 Nov 08 - 06:33 PM
Sandy Mc Lean 01 Nov 08 - 07:40 PM
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Subject: Tech: Amp question
From: Raptor
Date: 18 Oct 08 - 08:38 AM

I just bought an amp at a garage sale with a 12" speaker and 2 tubes in it the faceplate is gone and I don't know what it is.

I does say Pine Electronics on it somewhere as well as Made in Canada.

Any Ideas?

Raptor


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Subject: RE: Tech: Amp question
From: GUEST,Gene
Date: 18 Oct 08 - 12:10 PM

YOU MIGHT FIND MORE INFO AT:

http://www.fenderbronco.com/id14.html


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Subject: RE: Tech: Amp question
From: treewind
Date: 18 Oct 08 - 01:59 PM

http://www.fenderbronco.com/id14.html
Search that page for Pine - which suggests you should try googling for PEPCO too

A.


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Subject: RE: Tech: Amp question
From: Richard Bridge
Date: 18 Oct 08 - 07:33 PM

There was a DA Pine who built amps in Dartford Kent UK until about 20 years ago - but that would make the "made in Canada" label unlikely.


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Subject: RE: Tech: Amp question
From: Raptor
Date: 21 Oct 08 - 06:07 PM

Its on that page you linked to. It's called the arc 801.


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Subject: RE: Tech: Amp question
From: GUEST,popstudioguitar
Date: 31 Oct 08 - 09:08 AM

You can find more info at
http://sites.google.com/site/pepcotubeampinfo/


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Subject: RE: Tech: Amp question
From: JohnInKansas
Date: 31 Oct 08 - 06:36 PM

The "two tube" description suggests a pretty "primitive" amp; but the discussion at one of the links indicates later dates of production than a "just two tubes" circuit would suggest, and indicates that one of the "tubes" might be a 12AX7 which was, in fact "two tubes in one" with two separate plates and a separate and independent grid for each of the two plates, allowing the tube to function as a "two channel" or even "two stage" amp. So the "two tubes" may function as at least three gain channels/stages.

Early to late 60s amps most likely would have used the two sides of a 12AX7 as a "push-pull" amplifier stage with one channel boosting the signal while it's on the "plus" side of the cycle, and the other during the "minus" side, but this arrangement usually used a center-tapped output transformer with each channel from the tube driving "one end of the wire" into the output xfmr.

Note that the amp cited as using this tube may not be yours(?).

A possibly pertinenent question would be whether you need/want information to "make useful," or are mainly interested in finding "provenance" for the amp as a "collectible."

If you intend to try to use the amp, the note by a couple of posters regarding common absence of a (power) transformer in amps from this builder should be noted. Some amps in this era just connected the line power directly thru a rectifier with "dropping resistors" and capacitors to get the DC voltages needed inside. A "fault" in the wiring could cause the user to "glow 'till the fuse blows" so the apparently common practice of adding an "isolation transformer" (and a smaller than "wall-circuit-value" fuse) to the power side might be worth some consideration.

John


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Subject: RE: Tech: Amp question
From: John J
Date: 01 Nov 08 - 07:41 AM

It's a long time ago since I used these but I recall the 12AX7 / ECC83 as being a twin triode for low frequency (AF) applications. It wouldn't be used as an output device - not for anything other than very low power (headphone output), more likely use is in a pre-amp stage.

John


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Subject: RE: Tech: Amp question
From: Mooh
Date: 01 Nov 08 - 08:16 AM

Raptor..The folks over at the Canadian Guitar Forum may have some additional expertise. www.guitarscanada.com

Peace, Mooh.


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Subject: RE: Tech: Amp question
From: Raptor
Date: 01 Nov 08 - 04:52 PM

Thanks folks


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Subject: RE: Tech: Amp question
From: Bernard
Date: 01 Nov 08 - 06:33 PM

Output valves in push-pull amps were usually EL84 (15w) or EL34/KT66 (50w). The Vox AC30 used four EL84s in dual push-pull, self-biasing configuration, and the AC100 used a similar setup with four EL34s.

ECC83/12AX7 were usually used as pre-amp valves, and had a tendency to go 'microphonic' - if you tapped them, you'd hear it through the loudspeaker. Quite handy for acoustic feedback...


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Subject: RE: Tech: Amp question
From: Sandy Mc Lean
Date: 01 Nov 08 - 07:40 PM

or 50L6 (8 pin base with key slot.)


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