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seanww69 11th July 2007 10:31 AM

Armstrong 521 Amplifier
Hope someone can help, I have just acquired an Armstrong 521 Amplifier but i am stuck to find out what spear plugs i need for it.
Can anyone help.

AndrewT 11th July 2007 12:04 PM

what is a spear plug?
What are you trying to connect?
The 521 is getting quite old, it may help to post a pic of the rear panel.

As far as I know the 521 is not a chipamp.
ask the mods to move this to solid state.

seanww69 11th July 2007 02:06 PM

Armstrong 521 Amplifier
2 Attachment(s)
Hi Andrew Thanks for your reply I have enclosed pic of back of amp, I am trying to connect speakers to the unit.
Many Thanks for your help

AndrewT 11th July 2007 02:24 PM

don't recognise those sockets.
I guess they are about 2mm diameter, two pole plugs.

It might be easier to replace the sockets with others that fit the spaces available.

Gordy 11th July 2007 02:37 PM

I have seen sockets such as those on old commercial valve amplifiers.

If you have no luck here I would suggest starting a thread on the valve amp section of the forum and include your socket picture in the first post. Don't mention the amp name in the thread title as it is not important, instead call the thread something like "Please help identify which plug I need for this socket". The valve amp crowd are nicely enthusiastic, and someone will surely know the answer...

Good luck.

seanww69 11th July 2007 02:50 PM

Re: Armstrong 521 Speaker Connections
Hi Guys

Thanks for your help, i'll repost and see where i go from there.

Again Thanks

sreten 11th July 2007 02:51 PM


The sockets are very old, the pins have different diameters for phasing.

You need a special plug or two types of old split plugs similar to
banana plugs but smaller diameter. I have not seen either of
these for a long time, used to be fairly common.

Split plugs looked like short cotter pins

With a threaded ring with cutouts for the loop on the shaft.
You threaded your cable through and then screwed the
plastic covers onto the ring.

Simplest idea is probably to fit a pair of these, on the left (Maplin) :

edit : or find someone with a good old spare parts bin.


poynton 11th July 2007 04:39 PM

2 Attachment(s)

As posted on your other thread....



sreten 11th July 2007 05:44 PM

make sure you do not use these ......... ;)/sreten.

Gordy 11th July 2007 10:13 PM

...and for general info on the amp try here...

(Link checked and live at time of posting)

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