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stancor williamson?

M

musicamex

New Member
hi, i am a tube nut but have mostly played around with guitar and bass amps. i just snagged an old chassis on ebay, mostly for the 2 old british coke bottle 6l6 output tubes. those broke in transit due to bad packing (a cannon ball and a lightbulb should never meet in transit). the seller refunded a small amt and i guess in my sadness for the lost tubes i had some relief.

not being a hi fi guy, i was really impressed albeit somewhat confused with the iron. the pt is super clean, huge almost new looking stancor pc8413 and the ot is an acrosound ultra linear to300. there are what appear to be 2 chokes, one mounted under the chassis and the other, a real honker (as big as some guitar pt's but with only on pair of black wires so i guessed a choke or inductor of sorts) mounted on top. in the ebay photo i thought the big one might be a driver like on old gibsons at first.

the tube compliment is 2 tungsol sn7gt, 1 radio sun coke bottle(?) 5u4, and the 2 broken 6l6 (british but not mullards). after a bit of snooping on the wonderful internet, i think this might be a "stancor williamson ultra linear circuit". being of the guitar amp world i could use a little help in identifying this amp. the chassis is aluminum with no holes to mount it to something else. it has one pot on the front and one on the top of the chassis like a bias pot. there is the speaker connections and an rca for the input on top. i think it is a factory build since the wires are all tied with bits of string throughout. it is very clean for it's suspected age and i'm pretty sure this thing is all original except for the power plug. so i plan to replace the filters and anything else suspect.

i play guitar synth and this might be the ticket for getting tube sound without the pitfalls of coloring/changing what i build using a headset like a guitar amp does.

i'd appreciate any ideas or help. i can send photos. i have had it for just a few hours. thanks amigos.
 
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thank you for the replies. i had found the acrosound literature and the schematic to290 to300 it is possibly what i have. i'll look at the amp a bit closer today. neither amp has more than a vol control. were these amps to be run with another preamp section? what would have been connected to the acrosound input? a turntable i would suspect? thanks.
 
also are there any thoughts or opinions on the williamson circuit as to pros or cons? i am wondering if i should restore the chassis or just part it out. the transformers seem to be pretty substantial for a 2 6l6 amp.

thanks.
 
They sound nice, but there are some revisions to it that help with stability. Google for Williamson Amplifier and you'll get a pile of returns. http://www.r-type.org/articles/art-107c.htm is one such that goes over some of the tweaks to improve it.

Not sure that one is really suitable for 6L6G tubes based on the voltages it ran. The original Stancor version ran an 807 tube, which is pretty doggone close to a 6L6GC as far as the specs go. It runs pretty high voltage and pushes the tubes decently hard enough that a lesser spec tube won't survive very well. With the right tube though, especially with that UL transformer, its a pretty solid powerhouse. You'd need a twin to make it stereo, or I bet it would make a pretty nice instrument amp. Myself, I'd probably change the sockets to run 807's again just because big coke bottle tubes with plate caps look very badass. They are also not particularly expensive, certainly less pricey than vintage US produced 6L6GC tubes are.
 
gadget73 said:
They sound nice, but there are some revisions to it that help with stability. Google for Williamson Amplifier and you'll get a pile of returns. http://www.r-type.org/articles/art-107c.htm is one such that goes over some of the tweaks to improve it.

Not sure that one is really suitable for 6L6G tubes based on the voltages it ran. The original Stancor version ran an 807 tube, which is pretty doggone close to a 6L6GC as far as the specs go. It runs pretty high voltage and pushes the tubes decently hard enough that a lesser spec tube won't survive very well. With the right tube though, especially with that UL transformer, its a pretty solid powerhouse. You'd need a twin to make it stereo, or I bet it would make a pretty nice instrument amp. Myself, I'd probably change the sockets to run 807's again just because big coke bottle tubes with plate caps look very badass. They are also not particularly expensive, certainly less pricey than vintage US produced 6L6GC tubes are.
Click to expand...

1625s are even cheaper if you don't mind adding a fil. TX.
 
true, but if the amp is what I suspect it is, space is very much at a premium on that chassis. I used to have one of those two chassis Stancor Williamson amps and off the top of my head I have no idea where you'd stick a 12v transformer that didn't look goofy.
 
btw, in these photos, the amp looks allot dirtier than it really is. what looks like rust on the transformers is actually the factory coating with dust on it. same underneath the chassis. the cloth covered wire is dirty but still very sound. two of the 22k 2w resistors on one of the 6l6 tubes look like they got pretty hot but the condition of the cathode of the smashed tube looks like it was "rode hard" anyway. probably 50 yrs old i'd guess. the other looked good by comparison---all a nice even grey like a virgin rca grey plate tube, albeit with no glass.
i am glad you are interested in helping me decide if it should be restored or made into something different. if it was a marshall jtm 45 or a 5f6a bassman chassis i'd know in a heartbeat not to mess with the originality of the circuit or at least not to change it so it couldn't be put back to how it was. when when gigging musicians bring me recap jobs on old classics i am careful to photograph and save all unsoldered components (not snipped out) for future collector restorations. even then, making it look like it came from the factory when putting back in the worn out parts is tough.

on the ot of this amp i was able to see letteing under the paint and an old trick of rubbing graphite on it i was able to clearly read acro sound to300.

unlike the stancor williamson (acrosound) this is all on one chassis. better imho than having the HV through a cable. maybe having the power supply apart makes for a quieter output.
 
jaymanaa said:
1625s are even cheaper if you don't mind adding a fil. TX.
Click to expand...

how would the 1625's be in a guitar amp? looks like different sockets, plate v on top, and you mentioned a different fil xformer? i always like experiments that don't get too costly or time consuming.
 
Ah, thats not the Stancor-produced amp kit that I was thinking of. Those were a 2 chassis arrangement with a cord between the power supply and the amp. Thinking you have a kit or homebrew though. THe screws holding the tube sockets in place are sort of a giveaway. Factory produced stuff is typically riveted together. Also, those look sort of like KT66 tubes to me, not 6L6G's. The KT66 is a more appropriate tube for that circuit anyway.


1625 is basically a 12 volt 807 tube. The 807 tube is pretty much a 6L6GC with a 5 pin socket and a plate cap. To run a 1625, you'd need a 12v heater transformer, the 5 pin sockets and the plate cap setup. Not terribly involved to retrofit an amp with those things if you can fit the transformer in. The sockets usually fit in the same chassis hole as an octal does, and its not much to punch a hole to feed some silicone wire up through for the cap. They are kind of big physically though, so you'd have to make sure they would actually fit first. The 6BG6 is another similar option, but it uses an octal base and a plate cap. 6v heater too, so no external transformer needed.
 
The 1625 uses a seven pin socket that was extinct for years before the Chinese started to reproduce them a decade or so ago. That helped to keep the price of the 1625 almost free for decades. I bought piles of them in the early days of epay for next to nothing. I don't know what they go for now. I still need to get around to my PPP 1625 amp.
 
In the for what it's worth column, ALL of the tubes are in the wrong position in the pic provided:

1. The rectifier belongs up near the front right mounted choke (hope there's enough clearance! The proper tube is a smaller 5V4GA, while it looks like a larger 5U4G has been provided, as installed in the wrong socket),

2. The two KT66 output tubes belong in the front and back tube sockets in the middle of the chassis, and

3. The two 6SN7's belong in the left most two sockets.

Based on the underside shot of the wiring, it is definitely the original Acrosound Ultra-Linear version of the Williamson amplifier (1952). It was originally published using the new (at the time) 5881 output tubes, but indicated that KT66s would certainly work.

Dave

Dave
 
the tubes if you look really closely at one of the photos show 6l6. i verified that with seller. i like this single chassis over the double chassis especially for a gig setup. simple/compact is the key. if i were to restore it i have both kt66 and a bunch of 6l6 tubes. it looks like el34's would work with the plate voltage available. i have zip experience with an 807. is it more of an audiophile tube?

since i play around a base of guitar synth (often 4 or 5 sounds/patches at once) i often split my signals and run the synth through a roland keyboard amp or a traynor tube pa amp and the guitar through my home brew 18 watt, loosely based on the marshall 18 but with a parallel triode first stage and cathode biased pp el84's. for the clean sound i like the tube over the ss roland. everything is routed through the guitar's 13 pin cable. the guitar is home brew too.

i have always been interested in the bargains out there for plate cap tubes but living in the tropics i have zip as a well to draw from and forget customs being king inspecting glass. any suggestions as to good sources for octal tubes that would work well in guitar applications in lieu of 6v6, 6l6, el84 etc so i can stick with more conventional iron?

thanks. this is a very interesting site with allot to be learned. the tubebooks.org link someone used in this thread was worth it's weight in mullards. i won't read what i downloaded in the next several years. no such a thing as a library here for maybe 25 miles and then it is mostly fiction.

thanks to all for sharing info. as there a similar schematics site? i am especially interested in very simple circuits that perform well. less is more in my book especially for guitar amps.
 
dcgillespie said:
In the for what it's worth column, ALL of the tubes are in the wrong position in the pic provided:


Dave
Click to expand...

Nonsense. All the holes are the same size, therefore it doesn't matter where the tubes go. They're all really the same anyway. You can't fool me with these fancy numbers and such :no:
 
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