Dusty Old Amp - 1963 Symphonic - tube rectified - 2 watts (edit: AND circuit diagram)

In my efforts to get caught up with this list I've taken on a couple of tasks... one is to provide some info on a couple of recent gear purchases.

One of my favourite new toys is this 1963 Symphonic MA-7. Its got all the original tubes (!) including the MIJ 12AX7, 50L6 power tube, and the 35Z5 rectifier. This little beauty also has the stock Jensen alnico 6" speaker, and is wired to take an extension cab. Two inputs. Most of these kinds of amps were sans power transformer - just like the old AC/DC radios of the era, but this one has a PT (good because you are not subjected to potential shock by line voltage). It was made in Montreal, Canada. It came with extra New Old Stock RCA 50L6 and 35Z5 tubes and a JBL speaker to replace the Jensen, and I bought it from a nice old dude here in Winnipeg, who got it a year ago from an estate sale. Because its such low power, you can get some nice overdrive sag and clipping by cranking the volume - not much change in volume after 5, but the tone gets nice and warm. Here are some photos (cell phone pics, sorry for the quality):


Love the suitcase handle.









Point to point wiring, no printed circuit boards here!
Its got some hash in the output, which will need some TLC.

Ok, I've got to ask, what does 'She's a crypto-speciated, quasi-conjugal adjunct' mean?

I think it's a reference to a SF short story....

You are the first to ask.

Its a quote from one of the better short stories I've ever read. Yes, its SCIFI, one of my weaknesses. That and historical fiction (just finished reading the 20 books of the Aubrey-Maturin series for the 3rd time).

Story is set in the 50's. Its about a gal who attends one of the lead characters. He is smart enough to realize that she is not of "this world". Beautiful to the point of caracature, loyal, smart. The protagonists' description of this woman is that as a crypto-species, as she's not quite human, more like an exagerrated human, but that notwithstanding he's not sure just what she is. Then again, she's loyal beyond all comprehension - my take is that the hero knows that he has hit the jackpot, to have a this kind of conjugal mate eg, quasi-spouse.

Struck a chord with me, as that seems to fit my spouse's description on her better days.

That's my story and I'm sticking to it. Will try to find the author and story name if you have any interest. Highly recommended.

Cheers 'A', I've got one of those at home as well (spouse not valve amp).

These old amps are quite something, easy to repair being point to point.
The lower wattage do break up quite nicely.
Here's a tiny one I've had for a while. Elpico, probably a kit from way back.
It's about 3/5 watts, never tested the output as yet but sounds ok cranked up to full power through a 2x12
Looks real funny sitting on top of a 4x12 cab but does sound fine.
A dreaded fag packet to gauge the size.



Here's a Selmer that is very unusual.
It's a point to point wired transistor amp but incorporates a massive output transformer.
It's just gone in for a full checkover.






It's fantastic bass amp and ok with effect pedals for lead.

Often wondered about these low wattage valve amps. Would it be worth getting one for the valve tone and outputting to a bigger amp for gigs. Answers on a virtual postcard please. silk cut - trainer cigarettes

You could always mike it up.
Valves are the way to go though.

If you ever come across a Peavey Bravo 1x12 snap it up. Little amp, massive sound.

Silk Cut, same as all the rest, bad. Got to mix with something

Westcoaster - cheers.

Westbone - those amps are the $h^t. Beautiful each in their own way.

Elpico beauty = akin to a favourite wicker chair. Two-knob heaven.
Selmer beauty = pick any one of the ships in that great 60's kids' show (the one with the marionettes).. uh... having a senior moment here..Thunderbirds!!!!! TB-1, TB-2, etc... the Selmer reminds me of that.

Thunderbirds:

https://www.youtube.com/watch?v=BfIAKj3Gl1E

Funny enough we call the Selmer 'sick bay' from the original Star Trek

...which also nails the vibe.

Have you tried the amp with the new valves :?:

Yes. I started with the easiest to find and swapped out the 12ax7 preamp for several new ones... not much difference. The power valve and rectifier tests fine, but I swapped them out just to see - no audible difference in the noise.

The circuit has a multi-stage filter capacitor near the preamp tube that may be faulty. I have a hunch that the noise is being generated via that capacitor. It likely needs replacing - a buddy of mine who knows about these things has found one, and so we will soon see.

Capacitors are the first to go. They're hard working little gits.

The 'sick bay' Selmer is in for a total refurb. All these old bits are tired.
Take mine to this good guy.
http://www.tube-electronics.co.uk/

Westbone wrote:Capacitors are the first to go.

In an amp that old the capacitors "dry out" and become useless not only that the resistors are probaly carbon tubes with metal end caps, if so they could well need replacing as well as they start to fall apart.

I fixed up an old 50s tube amp for a friend and ended up replacing all the caps and resistors not to mention rewiring a lot of the earthing and putting in Hoax's favourite, a Faraday cage. Came out nice and quiet with a lovely tone. Some of the old amps are bordering on lethal with regard to safety.

grogg wrote:...Some of the old amps are bordering on lethal with regard to safety.

I have a '65 Daneletro that's in good but original condition, i.e., original tubes (valves) and wiring, and no ground lug! I seldom play it but I have spoken to the chap we use at the shop to repair tube amps and I shall be giving her the once over for safety's sake!

Ya know, it's a bloody miracle we didn't all die "back in the day". I can remember cavalierly sticking my grubby little hands into the back of our television, and stereo for that matter, to yank out the tubes and test them at the local shop. I should be glowing in the dark at least.

The one I fixed relied on the signal ground to protect the player, well dodgy and is probably common practice back in the day. I recommend anyone using these old amps checks them out and modifies the grounding for safety.

On the point John made it became quite fashionable for pro guitarists to use small boutique valve amp combos that were then mic'd up to a PA.

Good stuff grogg. With regard to lethality and these old amps... Some from the late 50's and early 60's that feature tube rectification do not have a power transformer, so that they are essentially running line voltage from the mains. In some of these designs, there is very little in the circuit to protect the player in the event of a fault. Not cool.

One of the first things to do would be to add a power transformer.

This amp has a decent working PT.

Digging in the case of the Symphonic something quite magical emerged: a circuit diagram. (Thank you, Len).

Behold :!:



I love an old dusty circuit diagram.

Kewl!
Appeals to the old draftsman in me.

Thats cracking, love the simplicity.

On the safety thing I wouldnt rely on the mains transformer, the lethal voltages that valves require to operate are normally not isolated from the mains earth so a fault can translate these voltages to your guitar, you then grab an earthed microphone ....

The amp I fixed up had very weak earthing to protect the player, just the signal path which because these amps work off lots of volts and little current the connection path doesnt need to be strong for the amp to work. I strongly urge anyone using these old amps to have them checked out.

PS I have 2 modern valve amps which I imported from China and the first thing I did with them was check this out, no problems at all from a safety point.

Yes indeed. Swapping the old power cord (2 prong) for a properly earthed three prong would help. :idea: :idea: :idea:

anaerobe wrote:Yes indeed. Swapping the old power cord (2 prong) for a properly earthed three prong would help. :idea: :idea: :idea:

Oh well, just take care.

Grogg, sorry - I didn't mean to be glib. I'm just happy to finally get my paws on such a nice old amp. If you have any other advice I am happy to hear it.

No problemo, for me these things have just got to be taken apart and made good before trying.

Most of our era run scared of these old amps and rightly so, but when they are all wired up right then theye safe - the warmth of tone through to pleasant even distortion is a pleasure. Enjoy your new treasure anearobe.